Software for Barrier Design Calculations

A simple program for calculating the base reactions for a post forming part of a barrier designed to be compliant with Australian loading code AS1170. It only calculates reactions based on imposed barrier loads to AS1170.1, it doesn't consider wind loads to AS1170.2. The wind loading won't be critical if the wind pressure is less than the imposed barrier pressures.

It can be downloaded here as a zip file.
To install just unzip into any suitable folder, it doesn't touch the windows registry, and can run from a memory stick. The main program file to run is dsgnBarrierPost.exe.

Once the base reaction for the post is known, then a post with equal or greater resistance needs to be selected. Unfortunately the methods of connecting posts to support structure typically have less resistance than the posts, and thus become the critical factor for selecting suitable post spacing and post heights. Additionally the support structure to which the barrier/balustrade is to be connected may be unsuitable, note the barrier is to be loaded along its entire length or otherwise pattern loaded to check the suitability of the support structure.

For example the loads on multiple posts attached to a fascia beam are likely to tear the flimsy cleats and the fascia beam from their support posts. Also if attached to a fascia beam then the barrier post bending moments are transformed into torsional moments in the fascia beam. Torsion is a shear stress issue, not a normal stress issue. Rough rule of thumb is that shear strength is 50% of the tensile yield strength. Therefore generally want to avoid torsion in a structure, and to do that requires careful attention to the perimeter framing of a balcony/decking floor.

The software is made available to assist designers to check the suitability of support structure, by providing the magnitude of the actions the support structure needs to resist. An equivalent horizontal action can be obtained by dividing the base moment by the post height.

Suppliers of barrier/balustrade systems, should preferably have technical specifications stating the resistance of their posts, rails, and connection systems.

The software doesn't produce fancy reports or save data, its a simple design tool. A sample of more detailed calculations can be found here.

Barrier/Balustrade design is also not all that clear cut. AS1170.1 specifies barrier loads to be applied to the top edge of the barrier: this does not make sense for barriers of any height or any structural form. Further commentary on balustrade/barrier design can be found here:

1. Balustrades-pt1
2. Balustrades-pt2
3. Balustrades-pt3
4. Barriers
5. Barrier Design Calculations (Previous mention of the application)

EXPERIMENTAL
The software is primarily experimental. It is a simple program with few features, I can dream up a multitude of additional features for the program. The big question: is it worth developing these features, and should such features all be embodied in the one application?

The display window/form for the application is intentionally small: roughly the size of a smart phone. How features are added for use on a smart phone is entirely different than would be required for a large display monitor. Also the program is written in vb.net, so it would likely need translating into java to port it over to an android compatible smart phone.

Any case the real experimental nature of the application is getting away from all the calculation printouts and all the certification nonsense. The exercise is to develop a box of tools and features which aid the design process, and otherwise aid independent and automated testing of the calculation process. Printing out a calculation report would be a useful aid for checking the calculations: however printing it out and distributing such report shouldn't become a ritual. If I don't provide such report then it cannot become a ritual, and therefore alternative means of validating the calculations buried in the application need to be developed.

DISCLAIMER :
Users of the software must accept this disclaimer of warranty :
The software is supplied as is. The author disclaims all warranties, expressed or implied, including without limitation, the warranties of merchantability and of fitness for any purpose. The author assumes no liability for damages, direct or consequential, which may result from the use of the software.

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Revisions:
[28/11/2013] Original

[23/04/2016] Changed download links to MiScion Pty Ltd Web Store

Barrier Design Calculations

Keep getting asked questions about whether or not a balustrade is suitable or not, when the real issue is whether or not the existing or proposed building is structurally adequate. The architects want balustrades, which is a strange term given there are no real balusters in a glass screen or barrier, with increasingly greater heights and posts spaced as far apart as possible to provide unobstructed views.

Another problem is people pulling 3kN/m crowd load out off a hat, without proper reference to the loading code occupancy type classifications given in AS1170.1. The loading of 3kN/m only relates to occupancy type C5, and the description given seldom relates to the building space involved. Though the code does have a requirement to use 3kN/m if there maybe an issue of crowd loading irrespective of the other loading criteria. But there are other loads to be considered besides the top edge loading, so simply referring to a single load is not acceptable.

To put simply, the architects preferences are not being considered by structural engineers when designing the building, and assumptions being made that the balustrade manufacturers and suppliers have solutions. They don't have solutions: the building structure needs to be designed to accommodate the connection requirements of the selected balustrade system. The requirements of the connection will vary depending on the resultant post reactions: which compared to the past are no longer insignificant. If the balustrade requires a 150mm embedment into a concrete slab, than a ultra thin 100mm thick slab is not going to accommodate the balustrade. If don't want to see base plates and anchor bolts, then will also have to screed over.

The other issue is removal of existing balustrades and replacing with higher balustrades and higher loaded. The existing structure may not be able to accommodate the higher post reactions, and the posts may need to be closer than the previous installation. It is therefore important to employ the services of a structural engineer when designing the space and not rely on the balustrade suppliers. The existing structure may need extensive strengthening before it is suitable for the desired balustrade.

However, realising that there are about 5 load cases to be considered and otherwise need a quick means of assessing the spacing and height requirements for a given loading, I have been working on a simple program with which to calculate the resultant base moment. It is not intended to provide documented calculations, but allow playing with the desired parameters to see what the main building structure needs to be designed for: so that a suitable structure becomes available to the balustrade suppliers to attach to.