Design Methods: Quality Robust Design and Limit State Design

Soft Conversion of Permissible Stress Design to Limit State Design.

Some time around 1989, Australia started to convert their structural codes from permissible/allowable stress design to limit state design. Such conversions had apparently been tried many times before in the past, but always eventually scrapped, and this was the general view again, that the idea would be shorted lived. However by 2000 all relevant structural codes had been converted to limit state methodology, and the permissible stress codes scrapped. The one exception I know of, being the aluminium structures code for which there is both a permissible stress version and limit state version: the limit state version does not conform with any of the other limit state version codes.

Limit state theory is based on the concept that every product has multiple states-of-nature in which it operates, for each state-of-nature there are unique acceptable criteria for acceptance. A car for example may be fuel efficient for city driving but extremely inefficient for long cross country trips, another car may be the exact opposite. The end-user selects the vehicle which is optimum for their most frequent type of journey and accepts the inefficiency for the other type of journey. Alternatively if frequently make both types of journey, a vehicle which is optimum across both types of journey, but less than optimum on any individual type of journey compared to those vehicles optimised for one type of journey only. As a vehicle ages it also becomes less fuel efficient. As a vehicle ages, the brakes also become less effective, and stopping distances increase. Another concept known as quality robust design (QRD) aims to ensure that whilst there is high variability in the operating conditions, there is minimum variability in the performance. This also takes into consideration the variability in the production process, and the capability to produce an end-product with the required performance.

For example in a region where there is a high demand for housing, and a scarcity of steel, and where clearly the steel is not required in the concrete to prevent the building collapsing during construction or day to day usage, then the steel is not going to be installed in the reinforced concrete structure no matter how much inspection is implemented. The steel will be seen as an unwarranted and unnecessary expense and if not available it cannot be installed. The need for the steel will not become apparent until its too late, during an earthquake or hurricane. Traditional quality control (QC) would place the responsibility with the builder for not following the specifications. Modern quality assurance (QA) places the responsibility with the designer, for not designing a product which can be constructed from the available resources: labour skills, materials and equipment.

A product experiences differing states-of-nature during its fabrication and construction, handling and transportation, in-service usage, maintenance and repair and during and after future modifications and renovations. Structurally these states-of-nature are classified into 3 large groups:

1. Stability
2. Strength
3. Serviceability

{As is usual I got side stepped from my original train of thought}. Limit state design and quality robust design are both dependent on statistics and probability to allow for the variability in operating condition of the product and the environment. The ultimate strength limit state, can be a state of collapse of a member or assembly or the fracture of materials. Most traditional design has been based on keeping materials in the linear elastic range, so that when a load is removed the deflection caused by that load is also removed: elastic recovery. The end of the linear elastic range is typically marked by the yield strength of the material if the material has one. Above the yield strength materials deform plastically: that is when the load causing deformation is removed the deformation remains. This is important for manufacturing where a large slab of steel is to be rolled into a a thin sheet or the I-section of a universal beam, or coiled sheet steel roll formed into a c-section. In these cases once the section has been formed, it is not desired that the material spring back to its original condition. Once these formed sections are put to use in the structure of a building or machine then any further permanent deformation would typically be considered end-of-life for the structure. Collapse or fracture of the structure is thus an important limit state, and the operating and environmental conditions under which this is acceptable need to be determined.

Risk analysis, failure mode, effect and criticality analysis (FMECA) can involve some highly qualitative reasoning before anything is quantitified, if at all. Probability concepts can also be relatively complex. Design for collapse involving probabilities of events can also be fairly daunting and scary, coming from a tradition of designing for operation and concept of safety. However it is this latter concept of safety, that wish to remove. In my mechanical engineering studies we were explicitly advised against making reference to factors-of-safety, or margins of safety, we were reprimanded if we used such terms. The preference was design factor or factor of ignorance. These numbers can in general be fairly arbitrary and give a false sense of safety which is not present.

For example a cable may be broken a certain load (N), and we choose to use the cable only for situations where the operating load is 50% of the load (0.5N). It is a mistake to assume that the cable is twice as strong as it needs to be. The cable may well break at a load less than 0.5N, it just as a lower probability of occurring than breakage at a load N, or 0.9N or 0.75N or what ever higher load chosen. The higher the load to N, the higher the probability of the cable breaking, the further away the lower the probability of failure so 0.1N may be good choice, but there is still a probability of failure. It is not safe from breaking. Further more we cannot be certain that the operating environment will not exceed N, or the 0.5N, or the 0.1N that we choose. All we know is that the strength of the cable can vary and that the load applied can vary, and we need to accomodate this variability in design. Whilst permissible stress design hides the probability and reliability concepts behind the scenes in the derivation of a design factor, limit state design wants to make these risk concepts foremost in the designers mind. But tradition is in the way, so a soft conversion of the permissible stress codes was carried out, to set a path in place towards a more risk based probabalistic approach to design.

With respect to bending the permissible stress formula for hot-rolled steel design was something of the form:

M <= 0.6.fy.Z

Where
M = applied bending moment
fy = yield strength
Z = elastic section modulus {S=plastic section modulus. Though some countries may reverse these notations.}

{NB: actually not the exact form since code was based on permissible stresses, however much of the steel was designed using the Australian Institute of Steel Construction (AISC) safe load tables. Now the Australian Steel Institute (ASI) and design capacity tables (DCT's)}

The problem with the permissible stress equation is that it gets rearranged:

1.67M <= fy.Z

Thus inferring that the structure is 67% stronger than it needs to be. This however is incorrect, for it fails to allow for variability in the strength of the material (fy), and variability in the dimensions of the section used to calculate elastic section modulus (Z). It also fails to allow for variability in the actual design action-effect (M). Given that we can have fairly tight control on the strength of materials and the dimensions of the sections, the strength or resistance (fy.Z) has little variability (or small standard deviation), whilst the magnitude of the loading has significantly greater variability, the design factor (1.67) can be split into two parts to accommodate variability on both sides of the expression and remain calibrated against the old code and provide a step towards a new philosophy. Thus the expression becomes:

1.5M <= 0.9fy.Z

This can be expressed more generally as:

psi.M <= phi.fy.Z

where:

psi = partial load factor
phi = capacity reduction factor

The fundamental requirement of the building code of Australia (BCA) is that the resistance in this case (phi.fy.Z) is the 5th percentile resistance of the part. The value of phi can therefore be adjusted to suit the origins of the values of fy and Z. In general fy should be the 5th percentile yield strength of the material, so that phi mostly applies to the variability in Z. So that phi is a simple way to allow for variability present in the dimensions of the section which go into calculating the elastic section modulus. The derivation of the value of phi=0.9 is something hidden behind the scenes of the code, but it is something which can be questioned and brought more into the open. Anycase it reflects an expected low variability in the resistance of the structural member. None the less there is variability and there is a 5% probability that this strength will not be achieved in practice.

Our code has no explicit reference on the probability of exceedance for the design load (psi.M), however in the 1989 version of the wind loading code, the 1000 year mean return period used back then was derived from a 5% probability of exceedance for a 50 year life expectancy. Currently wind loading is based on wind speed with a 1/500 annual probability of exceedance for buildings of normal importance, this relates to a 500 year mean return period. So unless otherwise noted the basic principle is that the design action and/or design action-effect should have a 5% probability of exceedance for a given life expectancy: or is otherwise the 95th percentile load.

So when we work with wind loads we do not use the psi=1.5, instead we use the design action (psi.M) which has the required probability of exceedance. So that the most generic version of limit state structural design is:

95th percentile action-effect <= 5th percentile member resistance

There is no safety as such, there is always some probability of failure. We could choose the 99th percentile action-effect, but there would still be some probability of it being exceeded. We cannot choose the 100th percentile action-effect because we don't know what it is: everything we measure has variability. Whilst statistical assessment of manufacturing output can control resistance fairly tightly, the statistical estimates of loading is fairly crude and in some instances possibly highly unreliable.

Engineers Australia in 1990 issued to its members a booklet titled :"Are you at risk! Managing expectations". Part of the exercise was to get engineers and other technical professionals away from declarring things to be safe. When something is declared as "safe" the public tends not to perceive that it will fail no matter what the conditions. Little seems to have changed: there are still engineers declaring buildings to be earthquake resistant, hurricane resistant and flood proof: and as to be expected they continue to fail. The response is make the design load bigger will make it safer. Keep making design loads bigger, just makes more expensive, uses more materials, and limits supply to fewer and fewer people.

The magnitude of the design load is not the issue. The real issue is the qualitative consideration of the modes of failure and the consequences, consideration of the full continuous spectrum of limit states.

Some of the poorest regions of the world, are also prone to seismic activity, and they have been making use of steel reinforced concrete. Whilst the concrete is obviously abundant, the investigations after destructive earthquakes, indicates the steel is obviously not so abundant.

Since the design load can always be exceeded, making the design load bigger is of little real benefit, it just makes the structures less affordable. Reading about the 2008 Sichuan earthquake, it reinforced the perspective that consequences of failure are the issue. Traditional Mongolian yurts may not have resisted the earthquake, but their collapse would have caused fewer deaths, less severe injuries, and further more could have been replaced rapidly. Far from being a disaster, would have been more like an inconvenience. Our ancestors were mobile, that is the benefit of being an animal rather than a plant. Plants are stuck in the paths of earthquakes, hurricanes and floods, animals are not. Architects and civil/structural engineers are turning us into plants, and many of our modern world problems are associated with us being more like static plants than mobile animals: not least of which is concentration of pollutants and waste of fuel. Sure there is an issue of travel: work/home/work/home etc... which is a major waste. But brought about because the city is a giant plant with massive global root system. If going to use concrete in a structure in these regions because it is abundant then make it a compression only structure, so that doesn't require the steel: get creative. However, if the design load is exceeded still going to get crushed. Tension membranes and cable-nets can certainly cover large areas: but back to issues of availability of suitable materials. Also what is housing for, protection from the environment or privacy? A large membrane structure could protect a village, but not provide privacy to the individuals within.

If we can get back to the qualitative issues instead of thinking we are smart because we can do some complex mathematics, then we can find better design solutions to the problems that we encounter. There are different states-of-nature, a great deal of variability and uncertainty to be accounted for, and differing criteria for acceptable performance.

At the moment the community has little to say on the performance requirements imposed in the built environment, yet it is the people who have to pay one way of another. The BCA talks about loss of amenity: at the present point in time the primary loss of amenity is not getting it in the first place. Further more most houses do not comply with current code requirements.

So first here is an opportunity to knock down the price of an established house because it is not compliant with current codes. Second an opportunity to assess when these established houses will fail, what the consequences of failure are, and then use this as a basis for BCA alternate-solutions, which will provide more affordable housing and less hazard to life when they actually collapse. Note the building doesn't have to be made of cotton wool so that when it collapses it cause minimum injury: rather the structure should provide adequate warning of its impending collapse. A warning from a government department not adequate because that may relate to current codes of practice, not the capability of existing structures. So need an early warning system which alerts occupants before they hear the loud cracking sound of the members of the structure failing.

Earlier Attempt at Describing Probabilistic Structural Design

An Earlier attempt at describing Probabilistic Structural Design:

Metamorphs Journal on Scribd

Basically involves testing of a cable, then considering selection of a suitable cable for a baggage handling department where do not know the maximum weight of the baggage handled. Same principle could be applied to selection of suitable scales so that do know weight of baggage handled: but not the weight of that which arrives.

NB: Whilst the probabilities for independent events may generally be multiplied together, the approach taken in the above essay, is over simplistic. For more detail on reliability refer to Mechanical Engineering design by Shigley, or to Reinforced Concrete by Warner, Rangan and Hall.

Structural Engineering

The art of moulding materials we do not really understand
into shapes we cannot really analyze,
so as to withstand forces we cannot really assess,
in such a way that the public does not really suspect.

Professor E. H Brown, (1967), Structural Analysis, Vol 1, Longmans, Green & Co.

Manufactured Structural Products And Simplified Wind Classification

Manufactured products are typically classified into size ranges and/or performance grades. It is generally not practical or economical to have infinite variety of product offerings. Further more it is generally not economical to base the size ranges on an arithemetic series, and therefore size ranges are typically based on a geometric series usually a Renard series.

Buildings and other structures are typically designed and constructed one-off, rather than purchased off-the-shelf. However there is an increasing number of off-the-shelf buildings becoming available, the primary reason is that people want buildings not pictures of buildings. Unfortunately the industry is poorly served by consulting civil engineers, who are focused on one-off construction, and the need for consideration of site specific features. Whilst there are site specific features to consider it would be nice if the output of civil engineers actually reflected such custom consideration: rather than implementation of some routine solution and calculation of some point-value. Structural sections, bolts and a variety of other components all have standardised sizes and performance grades. All such components have critical characteristics for which minimum and/or maximum values can be determined for a specific generic application: there is no need to keep calculating from one project to the next: its a waste of time and paper. Simple selection criteria are required based on the controlling characteritics of the product. One such characteristic is the wind load.

To the wind loading code AS1170.2, a regional wind speed (VR) is selected: this is typically the wind speed experienced 10m of the ground, over terrain of category 2 (M[z,cat]=1): typically a local airport. This regional wind speed is then adjusted to match the site specific features, by the use of multipliers for terrain category (M[z,cat]), topography (Mt), shielding (Ms), and direction (Md), to give the site specific design wind speed (V[sit,beta])at a given reference height (z).

V[sit,beta] = VR Md (M[z,cat] Ms Mt)

The maximum from several different directions then becomes the design wind speed (V[des,theta])

This can then be converted into a reference pressure (qzu) as follows:

qzu = (0.5 rho[air]) V[des,theta]^2

The design pressure (p) on a given surface then obtained from:

p = qzu. Cfig Cdyn

{Example  Calculation sheet can be found at ExcelCalcs: schWindAssessment}

Where Cfig is a pressure coefficient dependent on the location of a given surface with in a given shape and configuration of building, and Cdyn is a dynamic response factor. From these formulae it can be seen that there are potentially an infinite number of pressures that a range of products need to be designed: not very practical. However for a generic application the values of Cfig and Cdyn are more or less lock in by AS1170.2, so the main variable is qzu, from one site to another. Whilst there are several factors which go into calculating qzu, the same value of qzu can be determined from a variety of differing inputs. Therefore wind load classes can be defined by the maximum value of qzu permitted in the class. And given that there is a minimum ultimate strength design wind speed of 30m/s, there is also a minimum value of qzu, which for the sake of argument could be called wind class N0. From the minimum then need a method of defining other classes. The basic principle adopted for AS4055, barring some historical anomalies and rounding, is that each wind class applies a pressure 1.5 times greater than the lower class. However due to the anomalies that doesn't quite hold true. Anycase 6 wind classes are defined N1 to N6, defined by ultimate strength design wind pressures (qzu), or otherwise by the associated design wind speed Vzu=V[des,theta]. Since tropical cyclones also impose fatigue issues, for the same wind speeds there are 4 cyclonic classifications C1 to C4.

Note that AS4055 is simplified wind loading for housing. The wind classification system itself does not have anything to do with houses, nor the dimensional constraints in AS4055 nor the pressure coefficients in AS4055: it would be far better if removed from AS4055 and placed in AS1170.2. For anything other than housing: AS1170.2 should be used to determine Vzu or qzu, and assign a wind class.

When defining a product, design to qzu determined from AS1170.2, then assign nearest lowest wind class. When selecting a product, assess the site to AS1170.2 and assign the nearest highest wind class. It should be noted that local government authorities (LGA's) produce wind speed maps for housing, a site classed as N1 for a house may not be classed as N1 for some other structure. A site can only be classified with respect to the reference height (z) of the structure. A three storey house is likely to fall outside the scope of the wind speed maps and the simplified tables in AS4055. Also the wind speed maps are roughly derived, so that it is beneficial to get a site specific wind load assessment.

For many N1 sites on the maps are at the lower end of wind class N2, and difficult to prove the full shielding which puts them into the lower class. However many of the N3 sites are near the upper end of wind class N2. In terms of timber framed housing to AS1684.2, this doesn't make much of a difference for there are only combined span tables for wind classes N1 and N2, member size largely controlled by live loading requirements rather than wind loading. However, the wind classification affects the requirements for lateral bracing and tie-down systems. The tie-down system mostly affects the connections, and that can be a matter of personal design philosophy. Not connecting the members to achieve the full capacity of the installed members, may be considered extremely wasteful. For eaxmple connections in a wind class N1 house have little to no reserve capacity for additional wind load, as may be imposed if a carport or verandah is attached to the house at some future date. {Contrary to popular opinion: you cannot attach any size carport or verandah you wish to a house structure in wind class N1. There is no reserve capacity, and chances are cannot attach one at all.}

Anycase the wind classification system permits simple selection, for a variety of manufactured structural products (sheds, carports, verandahs, houses, fences, windows, doors), however, determination of wind class should be by using AS1170.2 not AS4055. Alternatively additional design aids should be created to further simplify the assessment.

More importantly manufacturers should produce full technical specifications. Saying to AS1170.2, to AS4055, or to AS1684 is meaningless. The specific's of these codes should be identified in technical specifications for the product. In particular the internal and external pressure coefficients, or nett pressure coefficient used should be identified in the specification. Pressure coefficients do not vary between cyclonic and non-cyclonic regions. Those hanging baskets swinging from the pergola can equally well be thrown through the window in a cyclonic or non-cyclonic region. Determinining internal pressure coefficients is a complicated matter of assessing the risks associated with various states-of-nature that a building may experience. Assesssing all the states-of-nature is time consuming, so the simplest approach is to assume the building envelope is breached and that high internal pressures are generated. This is not however always conservative, since for a framed structure, it results in zero loading to the wind ward face. On the otherhand if high internal pressures do produce the maximum stresses in the frame it is not necessarily economical. The purpose of manufactured structural products is to be economical and provide fast supply.

The building code of Australia (BCA) requires consideration of the hazard to life, as well as the loss of amenity. Not having the amenity in the first place, may be fast becoming the major concept of loss. The magnitude of load has very little to do with the hazard to life. The design load always has a probability of being exceeded. so considering Tropical Cyclone Tracy, steel roof cladding was ripped from building and its sharp edges became lethal. All the cyclone testing of cladding and the cyclone washers, and the increased design loads, have failed to remove the sharp edges from the cladding. When the design load is exceeded as it will be one day, the hazard remains. But the population is going to become complacent about us having cyclone proof buildings, which we don't have: they will believe they are safe when they are not.

Safety is not a quantitative issue, it is a qualitative issue. When and how the structure fails when the design load is exceeded is the primary issue of design which is currently neglected. The current magnitude of design loads are largely determined by insurance councils and government with respect to the cost of replacing structure, not the hazard to life. Wind borne debris is a problem, but as indicated when the design loads are exceeded, it is still going to be there. The exercise is partly one of balancing inconvenience against disaster. Disaster arises when the community is not able to recover without external assistance. It should not be necessary for all parts of a building to have the same resistance nor to survive the same event. Many buildings, and many rooms within buildings are non-essential, and loss of such is not a major hardship. There are certain core facilities within houses which contribute to the quality of life in a modern city, these are primarily kitchens, bathrooms and laundries. Most other rooms in a house can be lost. More over buildings can be designed with weatherlocks which control the internal environment.

Another important issue to understand is that the BCA structural provisions are largely based on ultimate strength. That is stresses are permitted to exceed yield strength, and enter into the plastic behaviour zone of the material. This can be identified in the codes by the change from elastic modulus(Z) and use of plastic modulus (S), and the change from yield strength (fy) and the use of ultimate strength or fracture strength (fu). Materials are not expected to under go elastic recovery when the load is removed, they will remain permantly deformed even fractured. Probabilistic design permits less than or equal to the breaking load, it does not have to be strictly less than. The breaking load itself is an uncertain quantity which may be greater than the value used. The BCA uses 5th percentile characteristic strengths. After the structure has experienced its ultimate strength load it may have collapsed and ceased to be serviceable. This is important, a building is not designed to provide safe shelter during a hurricane, unless it is a post-disaster facility which is to remain serviceable after the event. After a design level event a normal building is expected to be no longer serviceable and to need replacement. The primary concern for the design level event is keeping the building anchored to the site, preventing it from becoming airborne debris. It is not the intent to keep it in service and operating.

For many years now the shed and garage industry has had members complaining about not being able to compete because there are those using internal pressure coefficients lower than the standard AS1170.2 specifies. Problem is AS1170.2 doesn't specify a value, it specifies a methodology for determining an appropriate pressure coefficient. That individual businesses in the industry cannot compete is largely because they rely on external consulting civil engineers, and otherwise know very little about structures and manufacturing or industrial engineering. Put simply they are mainly poorly designed businesses with poorly designed and even more poorly specified products. The businesses are also over loaded by sales people who get paid commissions to sell a product they of which they have zero understanding. A properly designed business could use significantly larger structural sections than most are using and wipe the majority of the suppliers off the map. The size of structual section has little to do with whether can compete or not.

So the Australian Steel Institute (ASI) shed group publishing documentation opposing the use of the wind classification system merely compounds the problems in the industry. The wind classification system is specifically for these types of manufactured products, and is far better to refer to wind class N1 or N2, than to refer to TC3 or TC2. The latter only gives consideration to one of the site characteristics whilst the wind class considers all the wind critical characteristics. To reiterate, AS4055 is for housing the wind classification system it defines is not limited to housing: but AS4055 can only be used to determine the wind class for housing, it is necessary to use AS1170.2 for other structures.

Damage to sheds during tropical cyclone Larry, and tropical cyclone Yasi, is not all together indicative of low quality non-compliant buildings. Many of the photos show the sheds collapsed, but it also shows the sheds still anchored to the original site: basic objective achieved. The BCA does not specify serviceability requirements, that is left as a subjective judgment for the designers and end-users, relative to the specific application.

One major problem with the shed industry is it runs around declaring their product complies with the BCA. Who cares? The product is required to comply with the BCA, so just provide the BCA evidence-of-suitability which demonstrates it complies. If it merely complies with the BCA then it is the lowest quality product permitted in the market. So forget about marketing BCA compliance, market how the product exceeds the BCA and provides higher levels of serviveability. We may not have tropical cyclones in South Australia, but we do experience tornadoes in the remote outback. Tornadoes are typically outside the scope of the BCA, but still need to be designed for. Design is not about code compliance it is about making the product fit-for-function, whilst giving due consideration to uncertainty and variability in its use and manufacture.

Now part of the problem is a failure to understand, that the fundamental law governing all supply is that for fair trading which requires goods are suitable for purpose. Once a product is released to the market or into the environment it will be used for all manner of purposes beyond the intentions of the designers. Technical specifications and product literature therefore need to make explicit the suitability of the product and the evidence-of-suitability. Shed manufacturers compete on price because one piece of junk is the same as any other, there is no added value for the higher price.

The building industry is not serious about the quality and performance of its products, it is largely why it is regulated. Buildings are failing because the component parts are not up to specification, and that is largely because the specifications of the major product itself is lacking.  Australia's relative isolation, and often monopolistic enterprises has seemingly resulted in many specifications being based on assumption. For example steel always from BHP, therefore don't really need to specify in detail. Coldformed steel sections always from Lysaght, so similarly don't need to specify in detail. This however is no longer the case, and those cheap c-sections are probably half the price because they are made from steel with half the strength. It is not the internal pressure coefficients that the ASI shed group should be concerning itself with. The products supplied need proper technical specicifications. Part of which requires putting  wind class N2 windows, along with wind class N2 doors, in a wind class N2 shed, on a wind class N2 site.

All the manufacturers need to get up to speed with the wind classification system, and the ASI shed group shouldn't be advising, near mandating that the wind classification system should not be used. Doing so makes te ASI shed group part of the problem. Door and window manufacturers need to provide their products with proper technical specifications. Due to the requirements of the glazing code, windows likely to be compliant, but door manufacturers do not yet appear to be paying any attention to the BCA. The doors to your house as well as the doors to your shed are highly likely non-compliant with the BCA. Consequently doors can be blown of their supports at less than design wind loads and lead to the development of high internal pressures not otherwise accounted for. Basically the economical design of the building is not taking into consideration the failure of the industry's ability to supply doors to a technical specification.

For a simple analogy. The walls to sheds have frames at 3m centres, with girts spanning 3m metres typically spaced less than 1.2m, the ribs in the wall cladding span the 1.2 m between girts. The roller doors are typically 6m wide, no frame behind, the ribs of the door cladding span 6m. The door clearly has no where near the resistance as the adjacent wall: the door is the weakest point on the wall. The wind will push the door in, causing it to balloon, until it stretches so much it slips from the door guides and is then torn from the building, at which point high internal pressures occur in the building and will end up loosing more than just the door. Make sure the doors are compatible with the specification of the shed.

Complacency is another problem in the building industry. People don't want any hassle, they go to shed manufacturers because there is an expectation that all design problems have properly resolved in the past. So delays because this door not compliant are typically over looked with, just get it finished: a doors a door. This is a suppliers problem. The supplier is supposed to have designed the product and be ahead of the local council and regulating authorities, not behind. There will always be delays experienced during development approval, if rely on the council to advise what regulations have to be complied with. The designers task is to assert which regulations are relevant and that they have been complied with. Sales people are not designers, and custom manufacture does not equate to custom design. If the shed supplier does not employ design personnel on staff, then buyers should seek the services of an independent consultant. Suppliers should seek to inform and educate the public.

Anycase I will essay shed design in more detail at a later date, along with design-for-failure. Other writings on wind loading to AS1170.2 with comparisons to ASCE7-05 can be found in the SEAint archives.

SEAint Archives:

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Pricing Labour and/or Services

Prices are not absolute, they are only ever relative to a given point in time and set of circumstances, and therefore related costs are also relative. In Australia we have state and federal industrial awards which set minimum working conditions for various occupations, including minimum wages. These awards have embodied within them wage relativities which are typically sustained. It creates something of a new age aristocracy, with ranking being based on academic ranking and some groups perceived importance of the occupation. For an otherwise equitable society this is inappropriate. The flaw with such state or national ranking is that its says engineers for example are always worth more than tradespeople: such is nonsense.  Whilst people do get paid over the award rates and therefore there is scope for variability in the market, the occupational representatives will appeal to the industrial courts and commissions to have the relativities reinstated, that is adjust minimum wages in the awards to market rates to keep one occupation ranked higher than another. The nonsense with such scheme is that it is applied across industries and across the state and/or nation, when relativities should vary between businesses dependent on staff and line functions. An engineer in a consultancy has a line function and is more important to business operations than a carpenter who looks after the buildings. An engineer who works for a building company has a staff function and is less important than the carpenters who fullfill the line function. Staff can be terminated and contracted on an as needs basis, line personnel cannot be contracted on an as needs basis for they are the point and purpose of the organisation.

Giving consideration to a sole proprietor, if they contracted the line function, then effectively handing the work over to someone else who gets paid for the job, and so the  sole proprietor doesn't make anything except maybe a small commission for having the work to handover. However tend to get paid more for doing the work than simply attracting it and handing over to others, so if going to hand the work over to others to do, then need to find a lot more work to do. A modern trend in business is to do exactly that: find work and get others to do it. Some engineering consultancies for example have a small core of personnel, they tender for work, and once they have the contract they then seek out personnel who can actually do the work: that is they don't have the expertise nor the labour capacity in house. But this not really any different than other businesses, builders contract to build, but subcontract to drafters, engineers, carpenters, plumbers, electricians, concreter's: a sole proprietor builder with no personnel at all. So what price, what value the effort of those who distribute work, what commission should they be paid? Should there be an industrial award for such activity, and should there be an occupational title for those who carry out such activity? My feeling is no! The industrial awards whilst useful for new startups, otherwise tend to distort the market. It may be beneficial to set a minimum wage to impose a minimum standard of living, but even that is questionable.

Some 95% of all businesses are small business, and account for some 48% of employment: small business employs less than 20 people in non-manufacturing and less than 100 in manufacturing. Some 80% of Architects, Surveyors and Engineers practices are very small business employing less than 5 people. Whilst industrial awards are imposed on employers, they are not imposed on sole proprietors: some industries are dominated by sole practitioner businesses. There are many activities where by individuals consider that they get a greater share of the potential income if they work for themselves rather than as an employee. For whilst it is possible to be paid over the award rates as an employee, something has to happen in the market place before that will happen. Changes in the market may only affect a few businesses and/or employees. If the market does not provide the desired increase in wages for employees then pressure is applied to bring about changes to the awards. This can impose on all businesses to increase wages even though the individual business has experienced no increase in sales or increase in productivity. Potential exists for big business and/or their employees to manipulate the system to grab a greater share of the market, at the same time as award wages are increased beyond capacity of small employers. Small employers tend to retract to being sole practitioners again. Sole practitioners are not bound by industrial awards, only need to cover cost of living.

For a business enterprise, sole proprietor or otherwise, income is what ever they are able to get, there is no industrial award which sets minimum income levels. The industrial awards however do provide a basis for minimum costs to be covered by the income. Business however is a real world experiment, and just because industrial awards set minimum wages for employees, it does not mean that the business is capable of recovering such costs from its sales and operations. The sales which can be achieved at any point in time are uncertain, therefore total income generated is uncertain. Possibly more importantly is that not all costs are visible, tangible, measurable and allocatable. It is a matter of emergence or synergy: the whole is different than the sum of the parts. For example calculate the visibile costs, release a product to market and it only sells for less than the sum of costs. Release another product to market and it sells for significantly more than the sum of costs. Labour, mind and body, is no different than any other product: it can be bought and sold for what ever price the market is willing to support. Sole practitioners don't allow the industrial aristocracy dictate wages to them, they leave it to the market place to determine their income. For some who quit their stable jobs in hopes of making more money than the industrial awards grant them, this may be a bad move. For those who lost their jobs because of changes in the economy, "recessions we had to have", then owner/operator of a small business may represent income not otherwise available: less than the award but more than unemployment benefits. Cities may represent a different kind of environment than our ancient hunter/gatherer ancestors, but it is still a wilderness and a we are still fighting for survival. Cities, and modern technologies do not gaurantee comfort and luxuries, no matter how hard you work. Further more hard work does not give right to such things.

PRICING
The basic guide for pricing labour as a owner/operator, is to divide desired income by the number of hours expect to work. Desired income has to cover minimum cost of living to survive, but can otherwise reflect desired lifestyle. The expected hours of work, can reflect the available hours willing to work, having spent time on other activities.Hence it is beneficial if can get paid to do what you like to do, spending as many hours as are able to do so.

Labour rate = Desired Income / Expected Hours of Work  [$/hour]

This only represents the cost of owner/operators labour to a project, also have to cover costs, and determine chargeout rate. For contractors, with little expenses, the typical guidelines reduce the expected hours to account for such things as: public holidays, sick days, vacations, and long service leave. This calculation is some what important to full time employees on industrial awards: for they get paid for more hours than they actually work. For example consider award wage group C14, last I looked $522.15/week, for a 38 hour week, and a 52 week year. Therefore annual income $27,151.80, for total of 38x52=1976 hours per year, leading to hourly rate of $13.74. But allowing some 47 days at 7.6 hrs/day, paid without work, that removes 357 hours, leaves only 1618 hours actually worked. Thus have to recover the costs of labour at rate of  $16.78/hour labour charged out, before additional expenses are added.

How to cover the additional expenses if not easy to directly allocate, or would otherwise cost more to track than the effort is worth. The simplest approach is to take expenses as a proportion of total revenue and otherwise assume zero profit.

P = R - E
if P = 0 then R = E

E = L + OH
Let OH = fR therefore E = L + fR

Therefore : R = L + fR
Or

R = L / (1-f)

Where P= Profit, R=Revenue, E=Expense, OH=Over Heads, L=Labour, f=OH/R

The fraction 'f' may be available in industry surveys, from historical sales data if business already operating, or otherwise some reasonable number adopted, that is guessed. For example if f=0.4, then: R = 1.67L., and so the $16.78/hr becomes $27.97/hr.

Having calculated a labour rate, by the preceding method it doesn't mean that going to get any work. The hours for a project multiplied by the labour rate may produce a price that the market doesn't like: and note the potential customers in the market are not caluclating costs, they are just guessing or have a gut feeling about what they believe to be a fair and reasonable price. If the customer can do this, then so also can the supplier, at the end of the day the price is what both buyer and seller are willing to accept.

"The successful producer of an article sells it for more than it cost him to make, and that's profit. But the customer buys it only because it is worth more to him than he pays for it, and that's his profit. No one can long make a profit producing anything unless the customer makes a profit using it. " [Samuel B. Pettengill]

In the building industry many businesses over value what they sell, from builders, to manufacturers, to designers and engineers. There contribution to a project is low value and unimportant. Many engineers would find themselves unemployed if regulations which imposed their presence was removed. You don't pay an engineer $1000 to remove and save $1000 worth of concrete, better to have the resistance of the concrete than some scribble that says not required. Too many engineers seem to make the mistake that they protect public safety and stuff would be hazardous without an engineers presence: not so. They neither impart real cost savings nor achieve safety. The issue is that the safe economical system has already been provided by heritage, and therefore current batch of engineers contributing little. Part of the problem is the wage relativity nonsense of the industrial awards: choosing to be an engineer because expect to get paid more than trades person. Engineers are being produced because we can produce them, just like we can produce cars we don't need. Having produced them have to make up reasons to need them, to sell them, or create legislation to impose them. Having a degree does not give a person a right to a high salary, nor to public recognition. Far too many modern professional engineers are relying far too much on the contributions of ancestors to conclude the value and importance of engineers. Those ancestors however do not however have the skills to match the modern specification of professional engineer nor did they have the same attitude. Business requires that can generate revenue, society requires that contribute benefit. To gain recognition modern professionals who want the recognition have to do the contributing. Much of the technology provided is not all that important, and people since the dawn of industrial society have questioned its real value, and still question its value. The survival of populations in cities is dependent on water pumped into them: no power supply, then no operational pump and no water, and if no water then no people can be supported in the city. Finite resources consumed to support a growing population, with no real thought to the future. One possible future is population catastrophically wiped out as it runs out of power. Another possibility is that population will simply age and die out without replenishing itself, leaving a ghost city. The future is uncertain and business is trying to predict future income from todays actions. Rather than engineers complaining about their status, and their incomes, they should better understand the nature of business, the environment and uncertainty. Problem is too many engineers worked for the government in the past building infrastructure to herd the population: they consequently have something of a more dictatorial attitude towards the people and sense of own self importance. Such attitude not going to get them very far in the new modern world of privatisation. The businesses the engineers work for have to provide real value at the right time. The infrastructure that engineers provided whilst working for the government is not seen as a benefit by all: though the engineers see it as a benefit. In business, think you have a good idea then pursue at own expense, not the peoples expense. Then again, the business has to get the money for research, design and development from somewhere, and that somewhere is the customers who pay more than the cost of the product they buy. People don't so much object to profits, but to what the profits are used for. Profits used for expensive suites, expensive cars, expensive houses, holidays, world trips, expensive offices, and typically an expensive lifestyle are objected to most especially if the quality of the service provided is low.

So for example there is a lot of DIY because people can cost the materials, and have spare time in which they can do the work. Without getting into complications of comparitive labour rates and opportunity costs, the individuals simply perceive that the cost difference between supply price and material cost is too high, and therefore choose to DIY. So to get the work have to demonstrate the value in service supplied. Builders cannot get the work, drafters cannot get the work because of DIY, but engineering practitioners get the work because legislation imposes a need for calculations that most people cannot DIY. But cannot rely on such captive audience remaining: also having a captive audience diminishes the recognition get from such audience. It is therefore necessary to build real value, and demonstrate that value to potential customers. That is recognition from customers not the population.

Part of that added value is having the solution before the customer turns up. Things can be designed once and made many times, or if a service carried out many times. Car manufacturers build cars with features that the market hopefully wants. Whilst buildings are typically built to customer requirements, and are thus not available when the customer turns up. On the other hand established buildings dominate the available supply, but typically can only buy an established building if it is not in use. However there are market builders who have stock plans, the house isn't available when the customer shows up, but they do have a choice of designs to choose from. Design and engineering are additional costs, new buildings represent delays in supply, and they also have teething problems, all compared to an established building. An established building may however have problems that need resolving. The value of available supplies thus determines decisions made and directions taken. Such decisions are not necessarily taken using any direct costing, or cost-benefit or value-analysis. At the end of the day these are just sophisicated methods to justify a guess. Using such tools the parts maybe weighted and valued, but the sum of these parts doesn't represent the value of the whole. So the opinion relative to the whole is no worst nor better than that based on the sum of opinions relating to the parts. A guess is a guess no matter how sophisticated. In the modern world there are far too many mathematical models which are given unwarranted credence, and yet there is only garbage to feed into them and consequently only get garbage out off them.

Costing methods can be made increasingly complex as can pricing methods, but at the end of the day, acceptance in the market is left to personal opinion or subjective judgement. Business is an experiment, and getting the price right is part of that experiment. The business has to be dynamic, adaptive, and responsive to feedback from its operating environment.

Not suggesting avoid sophisticated costing and pricing methods, just that they have to be appropriate to the age and nature of a business activity. The older an activity, the mre likely all its associated costs can be determined including those intangibles such as allowance for future needs. Further it can be determined whether detailed tracking is required, and the level of detail required. Often tracking costs more than the benefit obtained.

Time Is Life, Time is Not Money!
One problem with the previous rate is that it gives rise to the believe that time is money, and the concept that some engineers have that they sell time. Hourly rates are problematic. Contractors are likely to drag a contract out so that they don't have to find another contract, and so get the most from one contract. One recommendation for calculating contract labour hire rate is to allow 20% loss of time looking for work. This gives rise to different recommended rates for short contracts and long term contracts. Lower hourly rates are charged for longer contracts. The acceptable labour rates determines how long can be spent looking for work, so that more than 20% may be possible: since also dependent on what it costs the individual whilst they look for work. Also don't have to look for work, can spend the time in other activities, such as developing solutions, so that have available when a customer turns up looking for. Got to change mindset away from the 9 to 5 work time mentality. The difference between working on the business, versus working in the business. Most people who give up their job and start a business, are still locked into the employee mentality: do the work that flows in and pay no attention to where it comes from or why? A few years later no work, no business and no income. Firefighters are paid to be on stand by, there can be no doing something else when on stand by, they have to be available for fighting fires. Part of being in business means being available, even if not doing any work, and so there is a cost associated with such availability. For example a cost of not doing any work this week, so that can start work next week: if choose to do work this week may have to spend many more weeks without work. Hourly rates therefore have to be increased to account for reduced hours actually working.

Another issue to consider with hourly rates is that not every hour worked is worth the same value. With extensive division of labour within an organisation lower value tasks are carried out by persons on lower pay rates. But even then not everything that these people do is worth the same value, however the average value of their work is less than the average value of someone elses typical work. By distributing work to a collection of people on different labour rates a lower over all fee for a job can be determined, compared to fee worked out on the basis of the cost of the top level skills required on the project. For example internal to an engineering consultancy an engineer gets paid more than a drafter, the bulk of the work tends to be drafting, and fees worked out with costs distributed between drafter and engineer. As sole practitioners however the fees of the engineer are too high, the work flows to the drafter who subcontracts the engineer on an as needs basis. Further more the engineer typically cannot relate well to the customer, so subcontracting to the drafter, is the wrong direction for the customer, even if preferred direction for the engineer. The engineer has to be doing the drafting work if to relate to the customer, and needs to be charging a lower fee for such work. Since such engineer is doing both drafting and engineering, their average rate is lower than those just doing engineering, but still higher than the drafter. The net fee however may still be too high, however there will be less delay compared to the engineer and drafter combination. So there is a premium for the faster delivery time.

Higher prices have either premiums or penalties incorporated. A premium because there is benefit to the customer, penalties because there is some disadvantage to the supplier. Higher prices do not mean higher value or increased quality. Prices are relative things.High prices may just mean that the supplier doesn't want to do the work. So having found someone who can supply at lower price is no loss or detriment to the supplier with the higher price: they achieved what they set out to do, not be hassled with such work. Its not always a race to drop fees and grab work. Often greater benefit in pushing fees up and pushing the work away, ultimately the price gets high enough that the work no longer seen as a hassle and the work is accepted.

Whilst a project fee may be worked out on the basis of an hourly rate and an estimated time duration to complete with possibly material costs included. The final fee is subject to the nature of the market and may need to be dropped, or it may be possible to increase it. It is not necessary to have calculated detail as to where the fee came from. It is only really necessary for the business to have an accumulative income which stays ahead of the accumulated expenses: not for the individual project. Some projects are a loss, others a gain, on average the business achieves a nett gain. There should be no drop in quality due to a loss on the project, the business still has the resources to do properly, the project is just not self funding, and there is no reason why all projects should be. The problem is owners who extract excessive profits from the business to fund exorbitant lifestyles. Profits have to be retained in the business to fund future uncertainties.

Projects which make a loss are indicating something about the market. Like we are tired of paying large fees to be told what we already know, so if such "service" must be imposed on us, please do so at lower fee. Which means figure out what is really required, what value it has and charge an appropriate fee for. When it comes to engineering there is a perception that it means supply calculations: which is a low quality service to provide. Relevant calculations can now be done by computer in a few seconds, a mere fraction of the time taken by engineers calculating by hand. Selling time thus becomes silly. Further it is what happens prior to and after the calculations that is important not the process of calculation itself, such calculation process is an hindrance and delay. These "fore" and "after" actions are where the value lies. So let other than engineers use the computer programs and play around with the models, it is better than them building the real things and having the real systems fail. They still need some one to validate and certify the final design and a fee to be charged for. The playing around with design concepts however is where it belongs in the hands of end-users and/or makers, getting familar with a concept and experimenting with its benefits and detriments, and otherwise checking the consequence of variations. Designers do not have to be qualified, they do not have to understand scientific laws, they can build prototypes and understand the real thing. If they can build computer based virtual prototypes then they can save time and possibly expense: they get to find out for themselves why some part of a proposal is a bad idea.

Point is things become established, and technologies change, so there is an expectation that supply prices change, and typically that means decrease. What engineers complaining about declining fees fail to understand is that the value of their contribution to projects has been steadily declining, as their output becomes more and more routine, predictable and expected because variants already exist in the technological environment. It may be possible to sell each car produced at similar price because each one takes similar effort to build. But this does not hold true for specifications of a car, or anything else. The first specifications take a great deal of time and effort to create, copying however is a considerably simpler and less time demanding activity. Even variants are less demanding than the original. Heritage diminishes value of future endeavours, it provides a foundation on which to build. So cannot expect to keep charging same price for design work. Experience both diminsihes and adds value. Experience adds value because know the answer now whilst someone else has to work it out. The cost of someone else working it out basically matches the cost of knowing the answer. But once all know the answer, the value starts to decline. So all this hourly rate, time is money, selling time stuff is misleading, as is having national industrial awards. Prices, labour rates, fees are all highly variable and uncertain. Start with something, anything, monitor feedback and then change accordingly. Small business, sole practitioners are typically better able to respond quickly to the market, than large businesses. Larger business more into controlling the market than responding to. There are no certain answers, just got to get good at experimenting and predicting the right response, the desired response from a complex system.

Business, TelCo's, and Power companies

When studying quality assurance it was pointed out that quality cannot be acheived by constantly changing suppliers. If suppliers don't have a stable market then there is no incentive to invest in productivity or quality improvements, for there is too much uncertainty in the environment and may not gain a return on the investment. Therefore suppliers need a certain amount of loyalty from their customers.  On the other hand the customer needs the supplier to invest in quality and productivity and not just invest profits in luxurious lifestyle. To achieve this large corporate buyers can impose discounts and penalties on their suppliers, that is the buyer can can control the terms of supply rather than the supplier. For example a 5 year contract, on condition of a 5% discount each year: this actually justified on the basis that the buyer helped the supplier improve quality and reduce waste: and the buyer wants to share the benefit they helped achieve.

So enter the government privatising and deregulating everything, like telecommunications companies and electrical power supply. On top of which we have a competition watchdog, which is there to prevent monopolies and protect competition. Though given the subtle difference between the common perception of competition and the economists definitions, it may be better to protect diversity rather than competition. The theory is that by deregulating and protecting competition efficiency is produced and this benefits the buyers by lower prices and higher quality. Its all rubbish. Competition produces chaos, and annoyance and inconvenience.

Every 3 to 6 months, some telecommunications company phones up and tries to get the receiver of the call to change service provider: and typically calling from overseas, like from India to Australia. The benefit of changing supplier is discounted service for some time frame. Changing does not make these interrupting phone calls go away, and the new contracts may lock in for 1 to 2 years and impose a penalty if drop out earlier. The service providers are mostly retailers, they do not own the telecommunications infrastructure, they do not build it, and they neither maintain nor operate it. They are basically paper shufflers who play around with money on paper.

Similar situation arises for electrical power retailers. They come around knock on door, asking to see last bill, and some number on the form: because they are discounting in the area, and if have right number on form win the lottery or something and get the discount. Once again the majority are just retailers, they don't own power stations, or fuel supplies, they don't build, operate or maintain any of the infrastructure: just paper shufflers.

Some how these companies can buy the resource direct from the actual producers and sell to the public at lower price than the public can buy themselves direct from producer. Probably end up similar situation to that of the farmers pressured by the supermarkets. The supermarkets for that matter tend to impose the same contracts and discounts on all suppliers. Depending on what is being supplied to the supermakets can simply increase fee to allow for discount so that get fee normally get: not like they provide enough work to deserve a discount and certainly not providing any services to assist improvement of productivity or quality. But that's another story.

The point here is that just because these retailers are offering lower fees at the moment doesn't mean that the customer will benefit in the long term: financially or otherwise. The "otherwise" is probably the more critical issue, because as pointed out above, the retailers are just measuring things in terms of money and shuffling numbers on paper: the result is that the actual infrastructure can be placed at risk. Due to such risks, some regulation is required to control the retailers: so not actually deregulated market just a different set of regulations.

Price is not an absolute measure of anything: it is always relative to a time and set of circumstances. One retailer offering lower fees is just a stimulus in the environment, it is not a guarantee that prices will drop across the board, nor an indicator that prices can be maintained at that level. All the retailers have to buy from the same producers, they have to pay all the people doing the paper shuflling, making phones calls and running door to door making the sales, and otherwise make a profit to keep shareholders happy. Put simply costs that were not present in the previous government/people owned system. Admittedly the previous system may have had public servants employed not doing much of anything: for example plans for power stations not built, or simply attending pointless meeting after meeting making out to be involved in productive administration. A privatised bureaucracy is no more efficient than a government bureaucracy: so no real benefit to privatisation: just a shift in ownership and control. Fundamentally the minimum cost of everything is zero: don't do it. If choose to do it, then it costs what it costs. The objective of business is not to minimise costs, but to maximise profits: and having locked the costs: the only way to maximise profits is increase sales and prices. The exercise is therefore to redistribute the associated costs, to achieve higher benefit or added-value.
Competition does not lower prices nor produce efficiency. Diversity of suppliers merely offers variety in the quality of service and prices. A given total profit can be achieved by low prices and high volume, or high pr ices and low volume. Business is a real world experiment and each enterprise aims to see what works for them. If other players can ask high prices, then so can everybody else. Business pushes prices up in an attempt to get similar income and lifestyle to those with the higher prices: don't generally or sensibly want to be the one with the lowest price. Only drop prices if expectations of higher sales volume, and thus greater nett profit.

In terms of telecomunications and power supply, the market has been deregulated and the retailers are all out to get some share of a market not previously available. So to get a share of that market they all offer lower prices: what else can they do? They don't have anything or do anything, so price structures is all that they can play around with. So the lower prices is actually questionable, because the price constructs are not altogether comparable: except maybe on a fixed period: say the 1 or 2 years of a contract lock in. To provide the lowest rate need to know what rates everybody else in the market is offering. If it is truly unregulated then can only guess what the lowest rate in the market is going to be before publishing figures. Once figures published, then know real position in the market, but still a guess for next release of new prices: because do not know what the other players are going to do: raise or lower their prices relative to which other player. So at any point in time its anybodies guess which player offers the lowest price rate.

So for many consumers, there is no value to them in switching from the original producer/retailer to one of the new retailer only companies: its just an inconvenience and interruption to their day. Its similar to discount vouchers and end of season sales. For busy people collecting the discount vouchers is more effort than the discount is worth, for other people they have the time to get the maximum possible value from the vouchers: its a matter of opportunity cost to the individual. Stores making discount vouchers available understand these opportunity costs, and some what hoping that not everyone takes advantage of all the vouchers released.

The sales people for the telecommunications and power companies however, don't appear to understand such opportunity costs: for that matter many appear to have just stepped off the ship and can only just speak English. They seem to think that everybody would appreciate having their day interrupted to get a discount. No! If we didn't call the supplier chances are we are not interested. Also if people are locked into 2 year contracts and cannot change without paying a penalty, then there is also reluctance to change. But it does seem like the retailers may know, which households have never changed from the original producers, and therefore, who is not currently locked into a 1 or 2 year contract.

Point is many are not interested in the lower prices for a variety of reasons, not the least of which is that the sales person interrupted and wouldn't quickly accept no: the harder they try the more locked the answer "no" becomes. Also of importance is the perception that the over all quality of service is declining due to poor maintenance of the infrastructure, and that it will get worst. Its not lower fees people want, its more reliable service, and the paper shufflers cannot provide. If these retailers can affect the quality of service they do not mention so or explain how: they only ever present the option of lower prices. They are not creative enough with their paper work, nor do they explain how they get the resource they sell in the first place. In other retail, aware that local stores gets discount for buying in bulk from wholesaler, and wholesaler gets discount for buying in bulk from manufacturer/producer. So assume that this is what the telecommunications and power retailers are able to do: buy in bulk from the producers. This however also infers a need to push consumption: not really good for the power industry. {NB: most modern phones require a power point, whilst traditional phones didn't: want to lower costs put the traditional phone back.}

That is the retailers have to sell what they buy: whether the product is considered perishable or not depends on the terms of their contract. Like internet service providers, buy so many gigabytes or hours of activity for a month: if don't use it then loose it, it doesn't roll over to the next month with most suppliers. So if power retailers buy so many kWhrs for a year, and cannot sell them to consumers, it becomes like perishable fruit if have to sell with in a given period of time. That perished then becomes a cost to be recovered in price of next batch of power sold, and so the price goes up. But what are they actually selling? Its like the mobile phone companies, $600 for $50: next time I'm short of money I will just go mobile phone shop and exchange a $1 for $2. The problem is the only measure they have for what ever it is they are selling is dollars: the monetary value only. But not really measured: the original price really pulled out of thin air. The power companies seem to be moving in similar direction.

The power companies can only buy potential kWhr's, whilst consumers typically buy KWhr's actually used: though may be averaged and bill based on estimated yearly usage and every so often brought into alignment with actual usage. So retailer has a problem if consumers use more power than the "potential" the retailers bought: for which the producer may impose a penalty on the retailer. So irrespective of whether consumers use more or less power the price can climb: it all depends on how well the retailers can balance their requirements.

Prices are not absolute and all depends on what the individual considers reasonable. The more of a resource a consumer uses, the lower the price they want, however reliability of supply is also important, and they will not opt for lower at the cost of loss of supply. For example no power and the refrigerators don't work, and the fruit perishes and so do medical supplies: this represents losses to businesses and also potential loss of life. Reliability of a resource supplier is therefore important. If lower prices appear to be resulting in reduction in reliability people are not going to switch to lower price and reinforce lack of supply.

Also in terms of power reduction, no benefit can arise unless an entire generator/turbine can be shutdown. So if local power station has 5 turbines, there can be no real reduction in cost of supply, until only need to operate 4 turbines. Also with urban sprawl, there is likely to be increasing energy losses getting power from station to the outer suburbs. An option is to build a power station closer to the outer suburbs, but then got problem of transportation of the fuel supplies, and also the minimum size of power station that is practical to build and operate. It is a problem concerning the economics of geography and location: power station where the coal is, the water is, or where the usage is? The answer is typically only valid at a single point in time: and thus invalid once the power station is built and operational: because prices are not absolutes. For example power generated using coal is becoming an increasing environmental issue: basically been an issue since first used. Original issue was visible particulate matter, now it is invisible gases: but no one said gases have to be exhausted to the atmosphere. The exhaust gases are a resource currently wasted. The carbon tax may be an increasing issue of concern, but in the main both business and individuals are extremely wasteful. Its not lower priced power retailers that need to be looking for, nor suppliers of ever so questionable green power: rather use less power, pay less.

The way to use less power is to increase the real benefit required from the power used: so not a cost cutting exercise, but a quality, productivity improving, waste reduction exercise. For example achieve light without electricity, heating and cooling without electricity, and cooking without electricity. And rechargeable batteries are they a problem or a means of buffering peak demands. We primarily use the electricity we do because it is convenient and there is a lack of diversity in alternative systems. Similarly people mostly use mobile phones because of convenience not necessity: lets many in business be relatively incompetent: instead of paying attention during a meeting they sort it out afterwards with a phone: so could have saved the fuel travelling to a meeting. Which is another issue, all the houses and buildings empty during the day, whilst people out at work in other buildings. All this travelling back and forth, stuck in traffic jambs, to sit at a desk using a computer all very wasteful. Further how much energy used in houses occupied by one person during the day? Also we have mulitstory buildings for carparks to feed offices: we could be using the cars as workstations and the carparks as the office blocks. Some of the buildings we have are highly questionable. Like supermarkets with oceans of carparks: could just have a market with goods sold direct from vehicles. Then there is all the street lighting and the comercial buildings lit up during the night: is it all really necessary? Similarly offices that require lights on during the day, more poor design. The need for hi-rise buildings themselves are questionable. Geographical economics may imply the formation of central business district (CBD): but the construction of hi-rises buildings more create the CBD rather than a consequence of. That is the CBD is developed at the expense of more localised centres of business: and so unnecessary travel is imposed. Urban sprawl is largely sprawl because of the CBD: build and develop more local centres and have less concentration of pollutants, more built in redundancy and improved security of supply.

We have moved from population mostly engaged in agricultural work, to manufacturing onto service sector. Telecommunications and power retailers are a sign of modern society. Our problems are not so much those of production: we can produce what we need with few people: our problem is acceptable means of distribution to those that need. A lot more paper shuffling is going to be taking place, selling ever stranger financial products, to bring about transformations in the infrastructure, the heritage, we already have. As long as people are content with what they have they are unlikely to change behaviour. Its like the frog: throw into hot water it will immediately jump out, place in warm water and slowly bring to the boil the frog won't move and will be boiled to death. People in industrial society basically have all the material comforts they could possibly want: they are not overly certain however that is what they really need or wanted. Service sector is keeping people occupied, and finding alternative ways to buy and sell stuff., and pump money round the economy: this is necessary because we have more people than is required to physically produce stuff: on top of which got a decreasing population actually interested in producing stuff.

So it all becomes about buying and selling abstract somethings, which may turn out to be nothing, and get the likes of the global financial crisis (GFC).

Another Thought on Popper: Structural/Mechanical Design

DanQuo's applied science: Another Thought on Popper: Popper’s idea of falsifying rather than verifying a hypothesis is essentially what structural engineers do during the design process. The...


I believe the preceding article describes exactly the process which was criticised by Popper.

The whole structural/mechanical design process described concerns accumulating supporting evidence of suitability. Suitability is determined by comparison with some predefined acceptance criteria: increasingly some code of practice. The proposed structure once assessed against the acceptance criteria and found compliant is then approved for construction. Once constructed it becomes a real world experiment. Once it eventually fails, the acceptance criteria in the codes of practice are revised. {The alternate hypothesis that the beam will fail holds true.}

What I believe Popper was arguing is that need to deliberately go looking for the evidence which will falsify the proposed hypothesis, not wait for it to turn up. The evidence collected in Europe suggests that all swans are white, the evidence in Australia suggests swans are black. What ever the evidence supports it is necessary to go looking for the complement, opposite, alternative or challenging hypothesis. The evidence to date suggests that swans are either black or white: but what evidence is there to support that they cannot be blue, green, yellow or red? Other birds have these colours so what prevents swans from having these colours?

From statistics have the null hypothesis and the alternative hypothesis. The null hypothesis is that the structure is fit-for-function or suitable for purpose. The alternative hypothesis is that the structure is not fit-for-function and it will failure. Quality robust design does not seek to minimize the probability of the failure event but rather deal with the failure.

Traditional structural design was primarily concerned with gravity loads and preventing the structure from sinking into the ground or collapsing under its own self-weight. Real world failures have resulted in increasing requirements for consideration of wind loading, seismic loading and live loading.

The Ronan point disaster, was the consequence of failing to consider a potential failure event. The gas explosion lifted the floor up, and blew the wall out, and the floor then had no wall to sit on. Having a mechanical and manufacturing engineering background, I have always found the structural codes to be some what deficient when it comes to loading considered. I believe there are typically considered to be 6 degrees of freedom, though I have a tool design handbook which identifies 12. There are three axes of translation, and 2 directions along these axes, and three axes of rotation and 2 directions of rotation about.

Structural codes have a tendency to only consider a given axis and only consider movement in one direction relative to. So tradition check gravity loads and prevent movement towards the ground, but otherwise ignore upward wind loading, or ignore upward loading from an explosion. A failure event occurs and codes revised to consider the other direction: thus now consider wind uplift. As I understand recent discussions on SEAint listserver, the international building code (IBC) ignores vertical seismic actions and only considers horizontal, whilst the nuclear industry apparently considers the vertical. However requirements for robustness in structural are starting to introduce more consideration of qualitative acceptance criteria into structural design, if not explicitly identified in the codes. As I understand it good seismic design is more to do with detailing than altogether resisting the magnitude of the forces involved.

Resisting forces is a problem. The alternative hypothesis that the structure is not fit-for-function and will fail holds true: the structure will fail. It is not possible to design earthquake resistant buildings, or hurricane resistant or flood proof buildings. The so called earthquake resistant buildings will be destroyed by earthquake, the hurricane resistant buildings will be destroyed by hurricane, and the flood proof buildings will be damaged by flood. Because structural design is based on supporting evidence rather than falsification these failure events are not considered.

The BP oil rig was always going to fail, and it was always going to leak oil into the Gulf of Mexico. Good design is not to make its failure a low probability event, but to design for the failure event. If failure events are made low probability then people become complacent about the hazards, and emergency services are otherwise cut. What could just be an inconvenience escalates into a disaster. It has been suggested that earthquakes and floods in undeveloped countries are less of a problem than in developed countries. The argument being that the people in the undeveloped countries have less to loose and also consequently less to recover. Whilst the developed countries have highly integrated and interdependent systems of supply: life style and life support is entirely dependent on the infrastructure of the city: loose the infrastructure and life is severely affected. If struggling to survive in the first place, then life after the earthquake, is still the same struggle for survival.

Engineers are sued and/or prosecuted because they put forward false propositions, such as the building is safe or that the building is earthquake resistant, when the building is no such thing, and cannot be made so. The point of moving towards limit state probabilistic design is so as to avoid such false propositions, to be more explicit that the design is based on low probability of failure, not zero probability of failure. What is the probability that a US ship will be boarded by the enemy: until the USS Pueblo was boarded it was zero, afterwards increased to one. The failure event needs to be dealt with, not ignored because of low probability. Good design does not involve increasing the design loads every time a structural failure occurs: it requires consideration of the mode of failure and the response to failure. {NB: not suggesting buildings be designed to resist meteor impacts or aircraft flying into them: the cause of the failure is a different issue.  The issue here is that failure has occurred by what ever cause.}

When the multi story buildings in a crowded city collapse, there is no clear space to escape to, there is little clear space where a person can stand and a collapsing building will not fall on them. Increasing the resistance of the structure doesn't provide protection from the failure level event. There is little merit in strengthening existing hospitals to new higher magnitude loads, if the day after strengthening is complete, an earthquake of greater magnitude occurs and destroys the strengthened buildings. Far better to consider the response for the failure event in the first place. Cities have more buildings not compliant with current codes than are compliant, buildings are typically compliant with older now obsolete codes. Strengthening existing buildings may satisfy insurance companies who do not wish to pay out for replacement and therefore want to minimize such pay out, but it does little to really address safety.

Consider the operation of a submarine without instrumentation, all that the captain knows is that there is a 5% probability that he will operate the submarine at a depth which will collapse the submarine: the magnitude of the collapse depth is unknown, and the operating depth is unknown. The captain is unlikely to operate the submarine. When it comes to buildings people either believe their buildings are resistant to extreme events, or aware that there is potential for failure but not under what circumstances. People are poorly informed relative to the decisions they have to make. It would be preferable that people know that a structure is going to collapse before they start hearing the creaking and feeling the movement. When to shelter in the building and when to evacuate the building or when to evacuate the area altogether? If know when the building or other structure is at risk it is not necessary to strengthen to comply with current codes: simply respond accordingly to the current state of the dynamic environment.

Similarly design structures themselves to respond accordingly to loading events. For example a Mongolian Yurt is unlikely to crush its occuppants if collapsed by an earthquake, whilst a concrete apartment block will. Whilst a yurt unlikely to resist a hurricane, it can be packed up and occupants and dwelling evacuated together.

Additionally to be quality robust the structures need to be fabricated and constructed using processes which have low variability, maintained by processes that have low variability, and otherwise designed to have acceptable performance no matter what the variability of the operating environment. Acceptable performance does not mean equal performance no matter what the operating conditions, but some type and level of performance which is considered acceptable for the operating conditions.

Designing and constructing reinforced concrete apartment block in a region where steel is in short  supply is not quality robust. No matter how much inspection is provided the required steel is not going to get into the structure if it is not available. A welded steel structure is not going to be fabricated by certified welders if none are available. The null hypothesis is that the structure can and will be constructed to the specification, the alternate hypothesis is that it will not. If not built to the specification how defective and hazardous will the structure be when placed into use?

Normal design process is largely built around supporting evidence that the proposal is fit-for-function and can be made to specification. Design is a justification process, not a process of falsifiability or refutability. Interpreting Popper as business as usual for the design process, misses the point, we have to deliberately search for that evidence which refutes the hypothesis that our final design is fit-for-function, and further more design for the failure event. Failure of the production process, failure of the product in service and failure of the maintenance process. Whilst the failure event is not possible to avoid, an appropriate response can be determined: and we return to square one: the null hypothesis that the structure is fit-for-function backed up by our supporting evidence of suitability for our predefined acceptance criteria. At some point have to decide that have done all that is practical with respect to supporting and refuting evidence.

When a decision is made it shouldn't just be on the basis of the benefits obtained but also the detriments incurred. Politicians put forward supporting evidence for the benefits of a proposal but leave out the detriments, the opposing politicians present only the evidence supporting the presence of the detriments. In a court of law the coroner and prosecution will accumulate the supporting evidence that a design was defective, the defence will have to provide evidence supporting fitness-for-function in the face of evidence to the contrary.

As far as I am aware thus far no designer has been held responsible for a design which could not be made fit-for-function using the resources available. Thus far manufacturers and builders are held responsible for not making and supplying to specification: for thus far few have put forth the alternate hypothesis that the specification was not fit-for-manufacture, not fit-for-fabrication and not fit-for-construction.

So to recap: null hypothesis structure or design is fit-for-function. The alternate hypothesis the design is not fit-for-function and will fail. How will it fail, what is an appropriate response? When consider resolved this issue, then have returned back to the null hypothesis so reconsider the alternate hypothesis once again. Repeat whilst practical and refuting ideas available.

{NB:
The difference between DanQuo's article and what I describe, is subtle. I took DanQuo's description to be the stock standard structural design process, which reaches a predetermined conclusion of fitness-for-function. That is the process is iterated until a design-solution which meets the existing acceptance criteria is met. I am suggesting this process does not involve the falsification process, it is all justification. I am saying that when this conclusion from the routine process has been reached, that is the point at which the alternate hypothesis should be addressed, and should attempt to prove the conclusion is false and the design is not fit-for-function. Further more it can always be proven not fit-for-function, and therefore helpful to be aware of those situations. Failures are important.

TEDxYYC - David Damberger - Learning from Failure - YouTube

}

Karl Popper, Design, Regulations and the Fallacy of Evidence-of-Suitability

DanQuo's applied science: Encountering Popper: “We have to admit that, strictly speaking, scientific laws cannot be proved and are therefore not certain.”[1] I have just recently beco...



Karl Popper, remember reading about in New Scientist magazine in the 1980's, never read his books, but often refer to the classic example of the white and black swans, and the problems of collecting evidence. Whilst I otherwise refer to Edward de Bono's idea of proto-truth. The refinement of language can cause all sorts of problems in communication, the meanings of words is not always clear: most especially in engineering. Engineering involves transforming objects and creating new objects, and what names to give these derivatives and new creations? When is a table, not a table? When does an object belong to a particular class of objects and when does it not? Where are the boundaries and where are the overlaps, what is contained within what? Each new instance of an object within a class, is it a repetition of something which forms a subclass, or is the start of a new subclass?

Sometimes the role of designer seems to be more one of technical lawyer, than one of dealing with the physics or mechanics of a system. When is a wall a partition? When is a partition a barrier? When is a barrier a partition? When is a veneer not a veneer? What is cladding? What is a buildings fabric? What is fabric and when is fabric not a textile? When is the proof load in the code inappropriate for testing? Is a destructive testing requirement appropriate for testing existing construction? What is structural failure? What is fitness-for-function, or suitability-of-purpose?

If think have an answer for these questions chances are, someone else will have a different answer. Design and acceptability of the design is a matter of subjective judgment. In an attempt to minimize the variation in judgments we have regulations and codes of practice: but these are open to interpretation. The actual written word in the code versus the intent and meaning behind the code, magnified by the views of different people. To obtain approval from the authority having jurisdiction (AHJ) there is a requirement to present evidence-of-suitability. Thus a building is not considered compliant with the performance based requirements of the building code of Australia (BCA), unless adequate evidence-of-suitability is presented. Many people in the industry haven't quite got a grasp of this requirement: they think that all that is required is to provide a description of the proposal then approval will be granted.

There are two basic options, only one of which is desirable:

1) Supply evidence to a court after failure.
2) Supply evidence to an AHJ before implemented.

Supplying evidence to a court is not a good option. If something ends up in court, then already have some one who is piling up evidence that the product is defective and is not suitable for purpose: the prosecution. The defence, is thus going to have difficulty demonstrating fitness-for-function, when there is already a case of failure before them.

All products, once released to the environment, to the market, will be put to all manner of uses beyond the intents of the designer. So after failure, the issue is not so much as whether the product was fit-for-function, but rather was if suitable for the end-users purpose, and was there anything misleading which indicated that it was suitable. This all leads to more and more disclaimers on products, all explicitly expressing what the product is not suitable for, rather than indicating what it is suitable for. But often times these appear silly: for example hammer with notice not suitable for hardened nails. What is a hardened nail, how would you know if using one? If a carpenters claw hammer, then expect to use with nails driven into wood, rather than nails driven into masonry. But if driving nails into masonry then preferable that are wearing safety glasses in the first place. If nail ends up in hammer rather than wall, did the manufacturer really need to have listed all areas that it is not suitable for? Would a user, use a wooden mallet or rubber mallet to drive nails? If chips fly of the head of the hammer and damage someone's eyes, is it really the manufacturers responsibility. A lack of common sense and personal responsibility wastes a great deal of designers and manufacturers time in court.

The result is more an more legislation and regulation, with increased requirements to seek approval from an appointed authority having jurisdiction (AHJ) before implementing anything. The problem with regulation however is confusion over the purpose of the approval. For example I often get clients who are unhappy with local councils (AHJ) and some engineer. Especially builders, but occasionally owner-builders, the usual complaint is something is over-engineered and otherwise unbuildable, and everyone (council and engineer) are idiots, especially council for approving. The council however is not concerned with the buildability of a proposal, the councils concern is whether the proposal imposes inconvenience or hazard on the community. If the proposal does not pose an inconvenience or hazard, then can go ahead and build, if the building proponent did not figure out how to build it then that is their problem.

As for being over-engineered, that is a silly term. Something is either over-sized due to a lack of engineering, or under-sized due to a lack of engineering. The problem is only going to be resolved by providing more engineering. The issue to resolve is: to stop the builder leaving their drawings, requesting calcs-for-council and then clearing off. Got to get the builder to sit down and think about what they actually want to do, are willing to do, have the resources to do. This is planning and design, not the crunching off numbers. It is important, because if check the numbers then the first design is most likely to turn out compliant, and not over-engineered as they say. The problem is that whilst the structural numbers may be correct, it is not a design-solution to the real problem. As they say 2/3rds of the solution lies in putting the question correctly, running into a consultants and requesting calcs-for-council, was not putting the question correctly: they got what they asked for, but it is not what they needed.

Legislation and restriction of service doesn't help resolve this issue, it is those who are currently on the national registers who are largely responsible for just pushing out the numbers: simply meeting the requirements of legislation. At present the national professional engineers register (NPER) is a voluntary thing, and legislation varies between the states which makes reference to such register: some states have their own additional registration and/or licensing schemes. So whilst maybe on the national register, have additional fees to pay in each state. Any case South Australia, does not have any independent registration system, and the there is no restriction of trade: such likely to be opposed on basis of federal fair trading laws. Other states had their systems prior to federal laws, and on review were able to demonstrate retention of: not that the reviews were really open to the public. Those with the authority simply decided to retain such authority, with nonsense about public safety. In South Australia (SA) such policies are typically seen as a grab for work, and opposed. In SA the legislation only restricts with respect to the approval process, the authority having jurisdiction. So anyone can supply design services, if person chooses to employ a drafter instead of a designer, then the buyers problem, if the application for building approval keeps getting bounced back and forth whilst the drafter attempts to supply all the required description of proposal and the required evidence-of-suitability. Whilst all this regulatory compliance is taking place there is little consideration of buildability taking place.

I would like to say that the people should employ an architect or engineer in the first place to ensure design which complies and which is buildable: unfortunately it does not happen to be true. Why? Because all swans are not white. As the advertising goes: oils ain't oils. It is also difficult for the public to know what they need, at the same time for consultants to know what is required. So when people phone consultants up, asking for a fee, its like asking: how long is a piece of string? Consultants really need to see what is involved, for much of engineering, that typically involves drawings produced by others. For large building projects the initial drawings likely produced by architects, and the architect seeks the services of engineers for specialist input. For smaller projects, it is likely the owners or builders who approach the engineers directly. Unfortunately the assumption for the smaller projects is that the design is complete, and calculations are just required from the engineer, to demonstrate compliance of the proposal with the building code: that is the engineer provides evidence-of-suitability in the form of calculations. The assessment of suitability however only gives consideration to the minimum acceptable performance of the end-product in service and at extremes of operation.

The suitability for fabrication, handling and transportation and construction are seldom considered on the smaller projects: massive projects no choice in the matter: all the available equipment and resources of society are pushed to the limits. For structures, when the available steel sections are not large enough, then really have to consider fabrication, when larger than will fit on the back of truck, then transportation has to be considered. However, if a steel beam has to be spliced, that is not just a fabrication issue, it is also an end-product performance issue which requires approval by the AHJ.

If a characteristic is assessable against the building code of Australia (BCA), or other national standards then it has to be disclosed in the development approval or industrial plant licensing application. If it is not assessable then it doesn't need to be disclosed. See the problem: evidence-of-suitability only applies to that which is disclosed, to that which is assessable under the regulations: that which is beyond the scope of the code is ignored by the regulators and all those that supply services solely for gaining approval.

In particular there is much confusion about the requirements for seeking development approval. Development approval in South Australia comprises of two parts:

1) Development Plan consent
2) Building Rules consent

Not all projects require both consents. Internal modifications to a building, may only require building rules consent. There is also a matter of occupational, health safety and welfare (OHS&W) act and regulations. If a space is used as a work space, then it has to be compliant with the building code. When a building is new, then it will comply with the version of the BCA current at the time building permits were granted. The BCA is revised each and every year, to resolve ambiguities and otherwise in an attempt to remove state differences. A developer can get development approval for an empty warehouse (despite lean: there are lots of warehouses being built.). Once built, the tenants move in and fill with industrial racking, this racking can make the building cease to comply with the BCA, the racking gets in the way of access to required exits, increasing travel paths beyond those permitted. The building that was compliant based on submitted evidence-of-suitability is no longer so, and in all probability no approval was sought for the variations.

So another problem have to deal with, is observations of the built environment. Why can I not do that, for they have? Just because something is present in the built environment does not mean it was granted approval, and if it was granted approval it doesn't mean it will be granted approval today. When changes to planning and building rules change, the new rules are typically not imposed on existing. However if an accident occurs in a workplace, the workplace is likely to be assessed against current regulations, not those current at time of development approval. Failure to upgrade the workplace maybe seen as negligent: now compliance may be impractical, and therefore the intent of the code needs to be addressed and alternative solutions implemented, justified by appropriate documented evidence-of-suitability. The real issue is not about going through approval, but about having adequate evidence-of-suitability to defend decisions taken, should those decisions be placed under question. This is a particularly important for OHS&W for there is no formal regulated assessment process, except for a few items of mechanical plant (eg. pressure vessels, cranes). The OHS&W regulators are more likely to prosecute people for breach of relatively generic regulations after some one has been injured rather than go around attempting to impose: employers and employees are typically equally responsible for a safe work place. Collecting evidence-of-suitability after an accident has occurred is the wrong time to be doing so.

Suitability cannot however be based on mere compliance with codes of practice, or observations of what others are doing. For example one situation, all along one road transportation companies, with loose gravel driveways and parking spaces. Apparently the truckies prefer this, it makes it easier to turn, unfortunately it kicks up a lot of dust. The result of this dust is that new transportation businesses in the area cannot have loose gravel surfaces, the result is typical implication of concrete paving. The gravel is permeable and storm water can soak into the ground, typical concrete paving is impermeable and so expensive drainage systems need installing to limit surface run-off and limit drainage to street main to that before the development. This makes it more expensive for new businesses in the area.

The problem with prescriptive based regulations to an apparent problem is that it limits the scope of possible solutions: it hinders innovation. However performance based regulations are more complex to write since need to identify the desired characteristics with out reference to anything specific. Also often times in design required characteristics are often contradictory and conflicting. As far as I know the truck drivers requirements cannot be met by any material which will also meets the regulators requirements. On the other hand the problem seems more like an issue with the trucks: after all the roads and destinations are not surfaced with gravel. Tarmac, asphalt may provide the desired surface the truckies are looking for, but I believe such surfaces abandoned in ports and harbours due to the expense of maintenance. Gravel needs occasional regrading, the asphalt more difficult and expensive to fix.

Suitability has to do more than dig down to the required characteristics, do more than simply collect and compile evidence-of-suitability. The lack of suitability also needs to be addressed. The concrete pavement may be suitable relative to the regulations and public, but it is not suitable relative to the needs of the end-users the people mostly directly affected by the design.

Much of the work that flows through the office where I work, I classify as "nominally existing":

1) Illegal construction for which notice has been issued requiring application for development approval or removal of the construction.

2) Manufactured structural products for which require revised calculations to revised code of practice, or for custom features.

3) Applications in council (AHJ) and awaiting further information.

In all situations there is a lack of available evidence-of-suitability. It is difficult to assess things which cannot be seen. For example how long is the bolt, that disappears into the wall, what fasteners are used inside a wall, and what is buried in the ground? Then there are properties of materials: what strength grade timber as been used, what grade of bolts? For a period steel was relatively simple, it was Australian made by BHP, but no longer can have such certainty. Additionally the strength of steel has varied over the years, and always had different strength grades of hollow sections. So need some non-destructive means of assessing what has gone into a structure. After failure, easy to take test tokens of materials for testing, and dig things up, and get inside. Determining if something should be demolished is not so easy: councils don't want to look bad moving in a demolishing someone's building: engineers don't want to approve something that may be hazardous, on the other hand also don't want to waste materials or effort. Regulations can get in the way: just because something does not comply with codes does not make it a hazard to the community or to other future users. The intents of the codes have to be considered, and also the objects to which they apply.

Pedantic code pushers only approve subject to the exact wording of the codes, those that understand or otherwise contributed to the writing of the code are more likely to refer to the intent rather than the letter of the law. For example the proposed object does not have the characteristics of a swan, therefore does not have to comply with performance criteria for, on the other hand the intent of the code was not limited to swans, and therefore some performance criteria do apply, but the level of performance may be extreme for the object under consideration.

The fundamental requirement is to document the evidence-of-suitability, but also giving due consideration to situations for which is unsuitable, most especially those situations where suitability may be inferred or implied.

Not everything is regulated explicitly. The most fundamental laws are those for fair trading which require goods and services be fit for purpose. Those prosecuting a supplier have to demonstrate that the product supplied was not fit for the purpose that the supplier indicated that it was fit for. That is the end-user cannot simply demonstrate that the product was not fit for their purpose and failed. An end-user has a responsibility to select products suitable for their needs, if they cannot properly specify their needs then they will have difficulty selecting a suitable product. Thus some products require the end-user to appoint someone else to select a suitable product for their needs. But how to select a suitable person to select a suitable product for such needs? Professional qualifications represent a rapid filter for the selection process, but not a reliable filter and not a particularly helpful filter. The end-user still needs to dig below the surface, and get their own evidence-of-suitability as well as check out the lack of suitability.

Most businesses advertise on the basis of suitability, rather than disclose their unsuitability. To start with traditionally architects and engineers were not permitted to advertise: whilst this has been relaxed in recent times: there is a restriction on simply describing projects worked on: no grandiose claims permitted. No architects or engineers would say they are unsuited for monumental type projects, at the very minimum they at least want to be offered such projects. The description of past projects however represents evidence-of-suitability, finding out that a consultant was more of an hindrance on a project is more difficult for the public to find out, unless the project was in the mass media.

Perspective is important. Many consultants seem to think a good idea to promote they were involved with multi-million dollar projects. However from the perspective of others, the response may be, if more competent consultants employed the project would have been off far higher quality for significantly lower cost. More than one way to skin a cat, and more than one perspective on things. Collecting evidence of suitability is one perspective, collecting evidence of unsuitability is the complementary perspective.

Don't just rely on supporting evidence also seek out the contrary.