Tuesday, January 04, 2011
Back in Design Office on 17th: the nature of engineering calculation.
First projects to do, involve assessment of timber framed decking already built, and assessment of existing scaffolding system needin assessment to new codes. Suggested we use limit state version of Aluminium structures code rather than the permissible stress version which we have already. With limit state can calculate resistance of tubes, and set up some tables to limit assembly usage. With permissible stress code, not dealing with resistance of tube since factored to allow for variance in load. With limit state have design factors for resistance and for loading, so that can accomodate variability in resistance and loading more realistically.
So until back in the office have time to write, setup Excel workbooks for calculations and generation of drawings, and modify website. Plus get out and about which tend not to beable to do once work starts. Tend to get stuck in office all day everyday. When get home keep working, reading some design manual or textbook, or writing Excel workbooks: so as to be able to get on with solving problems the next day. A never ending process of learning. Formal education only covers part of what need to know. Exercising duty-of-care then requires researching the literature and getting upto speed with the established science about an established technology. This has to be done otherwise will invent an inferior version of the wheel, which will fail in an unexpected and unacceptable manner.
So that the majority of time is not spent on an individual project but developing knowledge and experience which is applicable across many more projects. Thus whilst able to tackle a project doesn't mean immediately upto speed with the technical requirements of the technology involved. If upto speed with technology, then maybe able to solve problem in a few minutes, whilst several hours maybe required to formally document. But this situation is only so, if have a high degree of reptition and have developed to tools to complete task in a few minutes (eg. Excel workbook), otherwise if problem not repetitive yet problem well understood then it can take several hours to days to calculate out the required solution. If not familar with the technology then can take a day, to weeks to get upto speed with that technology, which may involve finding worked examples of similar problems and working through such, developing a feel for the procedure, and checking that can replicate results, and have confidence that have understood the science and concepts involved.
It is not like choosing between using a screwdriver or a hammer. It is more like using such tools to build other tools, before get on with the task at hand. For example cannot use a metal lathe before built one. Once such tool exists, other tools can be built using the more advanced capabilities of the lathe. The same goes for engineering calculations, simple elements or building blocks are used to build larger mathematical models of complex systems, so that the bahaviour of one element influences the behaviour of another. Most of time stick to simple procedural approach, simply applying reaction from one element as action on another. But occassionally build full mathematical system of equations and solve the system, this is the approach taken by structural analysis software (eg. MicroStran, MultiFrame). However such models are not actually full models, they only model part of the behaviour of the system, and not altogether accurately. Whilst the system of equations may be solved accurately by the available software, the mathematical model of the physical system is not an accurate representation of the real system. The results thus have to be assessed qualitatively to determine what value if any the quantitive results have. Typically may have to solve several mathematical models each dealing with opposing idealistic extremes, the real behaviour of the system lying some where in between. The designer then makes a judgement accordingly on the size of structural components.
It is thus not very helpful, if people go building things and then receive a notification from council to get an engineers report and apply for development approval or remove the structure. It can take some where in the order of 5 times longer to assess an existing structure than it does to design a structure. And then all we are saying, after much research to get the best models to reflect what has been done, is that the existing structure is barely compliant with the Building code of Australia. That is the existing construction has little reserve capacity and is not very robust. We have simply done our best to avoid the users having to demolish. It is not what we would design, and not what we would recommend. Demolition however is wasteful of materials, so if the construction is acceptable to the owners, which typically is, they built it, then primary issue is does it pose an hazard to the community. If with a great deal of extra analysis effort can demonstrate the risk of retaining is acceptable, then let it remain.
However proof for the existing does take a great deal more effort, and not all existing construction can be demonstrated adequate, and strengthening can be difficult requiring dissassembly. Thus far we have been amicable and not charged the real cost of time expended on such activity. But really cost benefit wise should get structures designed before construct them. Because the real cost of assessing existing structure and strengthing required can cost a lot more than saved by avoiding get the design and building youself. Noting that owner builders tend to use any materials they have lying around their property, not always suitable for the structure desired. Should note that jumping up and down on the structure does not test the strength of the structure the wind load is many times greater than your own impact weight.
So once work starts back in the office, probably won't beble to sustain any writing. Last year held back from writing posts to SEAint, because previous year spent far too much time writing posts, mant of which did not send. Also my posts tended to be too long. So the alternative is to try an approach where by I respond to the questions by posting to my own blog. Amongst other things this would make my own posts easier to find than in the SEAint archives, and so I could reference from elsewhere. Especially my own website.
The idea for my website is to build a resource for training engineering technicians the traditional way: from tracer, through drafter, to designer. Such approach should also keep with the original approach not fully implemented of providing a resource for owner builders.
Why am I still writing at this time. I know I could stay awake for 36 hours, including cycling around everywhere. But not sure I can still do that.
On the other hand I do have paper journals where by I would wite my thoughts down in the early hours of the morning, especially when I was at university. Couldn't get to sleep, start writing at 1:00 AM for four hours or so. Lots of essays criticising education.
I didn't want to go to uni, to study engineering. I wanted to study. I thought the idea was to get away from teachers, and seek knowledge. So when found out I had to pick a study programme, I choose science as first option. But have this crazy points system in place, and got may third choice B.Eng in mechanical engineering at the South Australian Institute of Technology. I failed to get past 2nd year mathematics and dropped back to associate diploma, I could use the mathematics, but the school of mathematics exams, were biased towards theoretical proof's most of which appeared to me as circular proofs and no proof at all. To me the school of mathematics has to sell their theories to engineers, by providing real evidence of the suitability of the theory for engineering applications. If the mathematics is invalid then peoples lives are placed at risk. Navier did not validate Euler's theories and his own extensions in a safe manner, he built bridges which failed during construction.
Which is the other issue that I had. From an early age (that would be around time of Flowery Field Junior school), I new what architects and engineers did. But clearly my technological environment could not have been designed and built by people who knew what they were doing. And adults constantly complaining about defects here and there. Therefore my teachers had to be wong. Adults do not know better, and jobs are not carried out only by qualified people. If work is only done by qualified people, then the people teaching and qualifying them, clearly do not know what they are doing.
The knowledge required to design a beam is relatively established and clear. The knowledge to design a bridge is also relatively well established and certain. But the knowledge required to assess if a bridge is really required is not so certain. Further more at the end of the day, the real characteritics of an engineered system are dependent on subjective judgement. Two different people, gets two different judgements. One may consider design effective, and other consider it defective. The voice that the existing technological environment is defective is louder than that considering it is acceptable. Largely because those who think it is defective are seeking change, those that find acceptable have no need for change. With every system however, there are always defects that have to be accepted along with the benefits, or at least accepted until such time as they can be removed or diminished in influence. There is no perfect system and always have to accept the dark and the light, all shades of grey. (Yes I know there are theories indicating all is finite integer quanta, but if infinitesimal then on a macro scale it is a continuous spectrum.)
Which poses a problem for designers. Once they have placed something in the environment, or the market, then the product will be put to a multitude of uses way beyond the expectations of the designer. The end-users will then blame the designer for the failings of the product, rather than accept responsibility for their poor selection of a product with characteristics better suited to their needs. Making something comply with a code does not make it safe, nor perfect, or even desirable. Blind compliance with codes of practice can produce extremely dangerous products.
It should also be noted that bigger is not alway stronger. Bigger bolts maybe stronger than smaller bolts if made from the same material. However the holes in the timber they are being used to bolt together will also be bigger than expected for specified bolts, therefore the carpenters choice of bigger bolts cause got some spare and readily available doesn't always make it better. Such choice would make the timbers weaker.
The timber framing code for example is not written to provide for solar panels attached to rafters. (Or at least not the version I have: I don't use, so no rush to update: Australian Standards are extortionately expensive). Thus whilst a rafter can selected from the timber framing code in a minute or less. The assessment of the rafter to carry the extra loading from the solar panel, and the holes for any connecting frame would change it to a hour or so calculation exercise.
Which does also raise other issues. Do we really need to be producing so many calculations for council approval. Much of the calculation task has been done once or more times before. It therefore does not serve any real purpose to do the calculations again. That is the reason we have the likes of the timber framing code. Wasteful to keep producing pages of calculations to check common elements like wall studs and common rafters. Also don't want different engineers coming up with what appear to be different answers for the same stucture: as far as builders can tell. So the span tables and similar in the timber framing code achieve some level of consistency. Not altogether though because Building Surveyors are typically not all that conversant with mechanics and not fully qualified to identify if a proposed house structure is within the scope of the timber framing code. I hazard a guess and same some 80% of houses are outside the scope of the code. If it has a hipped roof probably outside the scope of the code. The code contains no structural model for a hip rafter. The hip rafter is only sized as a connnection board like the ridge board, this situation only exists when the hip rafter has no overhang. Further more common rafters are required to have backspans at least twice the overhang. Jack rafters in the hip corner have overhangs greater than the backspan, and the fascia board is no longer behaving as a simple board but now more like a beam. The timber framing code also ignores the magnifying effects of the eaves overhang when sizing tie downs. There are various issues. Some may be acceptable simplifications others may not. But I would rather have a structure checked by a 2 year qualified engineering associate, than by a 3 year qualified Building Surveyor. Most especially given that the structure is typically sized up by a timber estimator: the only training being use of timber framing code. Thus with timber estimator and building surveyor have two people involved with project only conversant with timber framing code and not conversant with structural mechanics and the limitations of the structural models presented in AS1684.1 the part of the code they never use, and probably never seen.
See I don't really diverge. At school a topic was presented and I simplified into a set of abstract rules and concepts. Then when I wrote assignments got told I should provide concrete examples of what I was discussing. Back then I made everything too abstract. No I interrupt with divergent topics, jumping from one thing to another. But clearly there must be a path, a chain joing all these things together. Edward De Bono, in lateral thinking or one of his books, suggests picking a word at random as a seed, to generate alternative ideas, and free up thoughts. It is also like simulated annealing algorithms. Normal optimising routines may fail to find the true minimum value of a function, they get stuck in the valleys of a mathematical curve and cannot jump out. Simulated annealing provides an oracle I think, in the form Boltzmann probability for a gas, which energises a conceptual particle following the mathematical curve and jumps it out of the valley, so that can continue the search for the mathematical minimum elsewhere. Or something like that.
Originally university education brought new perspective to industry, that was because what was being learnt had little to do with industry. The graduate had to determine whether their education brought value to what they were employed to do. Occupational degrees however exist for a different purpose. We know what the required knowledge base is, and in the main it only needs to be at the 2 year Associate Degree level. Things have become distorted, most people with a MBA, have inadequate knowledge of business and management at the undergraduate level they have no real right to a masters degree. Due to lack of knowledge at the lower level they make poor managers. Degrees now reflect more breadth than depth, and that means that required depth is being lost.
It is better to train people for industry at the associate degree level in multiple degrees than a single bachelor degree containing breadth. The required and necessary breadth for a given industry, business enterprise or job position, cannot be determined with certainty. It is necessary to adapt to the changing environment, and the environment changes with our very presence in it. Each action we take changes the environment we operate in, we thus have to respond to these changes and adapt our behaviour accordingly. People with AQF Associate degrees who are able to get the job done are important to sustaining acceptable levels of performance for our technological society. For example an engineering associate with an Associate Degree in Steel Design, should conduct the detail design of steel structures. The person with the Bachelor degree in Civil Engineering, typically does not have specialist knowledge in steel design, their bias will typically be reinforced concrete, and more importantly advanced structural analysis. It is part of the problem a B.Eng doesn't make a person and engineer, but more of an engineering analyst.
Robert Stephenson for example was engineer of the Britannia bridge. Fairbairn provided the applied science and Hodgkinson applied mathematics, but Stephenson is the one who had to decide if all the science and mathematics was valid and go ahead and build the bridge. Science and mathematics can take place in isolation from any actual construction. However, I contend that real engineers operate at the frontiers of science and technology. So simply building a bridge does not make an engineer, nor does crunching some numbers about its structural adequacy. But what is in a title? Very little, for there is no real need to use titles. On the other hand has become clear that engineering associates and engineering technologists cannot turn round to so called engineers and acquire the expertise and experience they are looking for because the universities and silly industrial relations systems have fast tracked the graduate into position of engineer, and they are barely competent technicians.
We need to stop educating people to the B.Eng level, and train more people with Associate Degrees and lower. Further more understand the difference between education and training. Education provides enabling competence, training develops competence, profiency and over all fitness for the task. University exams and qualifications, therefore do not represent assessment of an adequate level of practice: further traning is required before fit for the needs of industry. And industry is typically only interested in a single area of structures, thus whilst the major engineering disciplines typicall have at least 5 major areas of practice, graduates only practice in a single area. Thus only need train and develop proficiency in a single area: therefore with respect to that single area the duration of a study programme can be reduced, and an additional vocational practice certificate training programme added in.
The problem of employment. Well already have that problem. Chose mechanical engineering, should have chosen structural engineering. However I am suggesting bringing the problem forward, and having a properly articulated education and qualification system. Instead of choosing civil engineering, choose stormwater and drainage design, obviously a major area for growth in Australia at the current point in time. Assuming that is that some party is going to fund design and construction of the appropriate infrastructure to mitigate future large scale flooding. At any point in time a multitude of people studying across all major areas of practice. There is still the potential to have too many graduates in one area and not enough in another. However, the graduates that are surplus, can choose an alternative direction. Further more if all is dependent on a common 1 year Diploma in Engineering Science, then they can change engineering discipline and area of practice. Further more they can change a lot more quickly at any future point in their career. Because the reality is those with say a B.Eng in civil engineering once they have specialised in say structures there is little possibility that they can move over into stormwater drainage. This is because they lack adequate depth of knowledge in the specialist area, and industry not all that willing to retrain. But If have vocational certificates of practice, they can enrol in a training programme and gain the experience and develop profiency.
Individuals are no different to businesses, it is necessary to keep upto date with the market: what knowledge and skills does the market need now, what will it require tomorrow?
Simple IE process: Observe, Measure, Record, Design and Implement.
Do this with respect to the environment in which you live. And hey if wanted independence of parents, why so many people want the parental assistance of government. Be prepared and look after own interests. Don't go with the flow, you will be in same trouble as everyone else, take own direction, and make own pathway. Either you are a cog in the current machine, or the next generation machine of your own making.
PO: An array of ideas to develop further.