Certificates of Structural Adequacy – Origin

When we refer to a Certificate of Structural Adequacy (CSA) we are not referring to a formal certificate meeting some requirements of local regulation.

Here in South Australia the formal certificate is a Certificate of an Independent Technical Expert (CITE), and the person issuing such certificate has to be a chartered professional engineer (CP.Eng). The formal certificate is typically issued by an engineer checking calculations either directly for city council or for a private certifier (building surveyor).

No member of the public should need to get a CITE when seeking development approval, as the development application fees are for an independent assessment of the development proposal. The main reason for a need to submit a CITE is if the proposal is for something unusual, for example: radio mast, radar dish, tall chimney stack, cooling tower. Basically a structure which is not a habitable building.

However building surveying technicians are limited in the type of development they are permitted to approve, whilst private certifiers want to cut costs and avoid paying an engineer. If they can get the building applicant to pay for a CITE directly then the private certifiers, or council, get to keep more of the development application fee.

Working for Private Certifier

For a short time the Roy Harrison & Associates was providing engineering checks for a private certifier (eg. issuing CITE). The private certifier gained new management which required we sign a contract effectively guaranteeing we could do more work and do it faster.

Don’t need to be a lawyer to know a contract imposed by one party on a second party is typically to the disadvantage of the second party. They weren’t guaranteeing a steady supply of work. So we weren’t about to become an employing business, for their benefit, with no reliable supply of work for such employees. The attitude of the new management indicated it would be a poor choice to sign the contract: so we didn’t and the work went away.

The work couldn’t be done faster because the work submitted for development approval wasn’t good enough: and the work was done by people who lacked adequate experience and clearly lacked supervision by persons with adequate experience.

Also not entirely about adequate experience it is also about curiosity and questioning attitude, not taking anything for granted. About a desire to understand rather than blindly follow routine.

To do the work faster therefore required more complete documentation, and such documents to contain a specification which is compliant. If the proposal not compliant then potentially becomes an education exercise as attempt to educate the designers.

Educating designers during the development approval process is time consuming and inefficient.

Review Process

Often the defects were qualitative. That is the numbers weren’t right, because qualitative aspects of the design would make the design defective. For example in one case didn’t want the designers to put more steel reinforcement in the joint, it already had too much steel to allow concrete to be installed. It was a practicality, buildability issue which would prevent the fixed end moment from being developed, in which case the beam would behave as simply supported and be inadequately reinforced. In other words it could not be built to provide the required performance.

So whilst assessment for development approval is not about checking buildability, such issues may influence the functionality which is being assessed.

It isn’t always clear what needs to be assessed for development approval, however, the basic test is: if the issue is covered by an Australian standard then the assessment needs to be submitted for approval.

For example may consider that the simple splicing of a beam is a construction need and whilst it needs designing, it doesn’t need submitting as part of development approval. However the assessment needs to demonstrate compliance with a materials code such as AS4100 steel structures code. Therefore the assessment needs to be submitted for approval. So for example if spans are greater than 12m then qualitatively expect to see some splices: if not present then a potential flaw with the design.

Now whilst I didn’t have the chartered engineer credentials to issue a CITE, I otherwise was able to assist reviewing proposals which were in the scope of the structural experience I had acquired thus far.

I reviewed the proposals and wrote down issues I found. I often complained that I couldn’t read the calculations, couldn’t follow the calculations, that I disagreed with the interpretation of codes, or considered the calculation sequence flawed.

That is when moved to the next stage. Rejecting proposal because I disagreed with the calculations wasn’t and isn’t acceptable. The proposal can only be rejected because it fails to comply with the NCC/BCA.

So the question changed to: “if I was doing the calculations would I consider the proposal fit-for-purpose?”. Since I had spreadsheets with which I could do the calculations in much less time than had been taken to produce the design in the first instance, I could ignore the design-calculations and do my own proof-calculations.

So now could check faster. If I considered the proposal defective, I could check the design-calculations to see if there was any fancy theory to prove me wrong. If not I identified the flaws I found.

Builders and Manufacturers

With the work for private certifiers dried up we could concentrate on work for manufacturers of structural products and associated builders. These people started wanting certificates of an independent technical expert.

These certificates caused two kinds of problems:

  1. Certificates by Roy were rejected due to lack of independence. This I believe to be largely because he didn’t properly certify the actual proposal, as he often recommended the minimum size sections suitable: rather than declaring the proposal to be adequate. Thus he became designer, and was clearly designer. Also anything bigger than the minimum suitable section isn’t necessarily suitable, as bigger isn’t better: especially for C-sections where shallower thicker sections maybe stronger, whilst deeper thinner sections are weaker. Therefore the certified sections weren’t proof that the original specification was adequate. I believe the concept of the certificate was flawed in such cases.
  2. I had to wait for Roy to review my calculations and sign the certificate.

To resolve issue (1), Roy started issuing certificates of structural adequacy. Though eventually he changed back to issuing CITE’s with the full calculations. The CITE is most likely ignored and therefore doesn’t provide any productivity in getting approval faster.

On a design project for which council requested further information. When I spoke to the councils engineer on the phone, they indicated that they didn’t need full calculations, and that a simple letter with my calculated value of the critical property would suffice.

I took this concept and adapted it to my certificate of structural adequacy. In my certificates, I have a disclaimer at the top, making it clear that there is no attempt to provide a certificate to comply with any regulations. That the purpose of the certificate is the building proponents assertion that there has been deliberate intent to make the structure fit-for-function, and that any additional review would therefore be independent. The certificate then describes my assessment process, and tabulates maximum design-action-effects and provides tables of resistance. I sign the certificate and therefore no delay waiting for Roy’s signature.

My tables of resistances are only slightly different than if I presented calculations. If I do calculations I typically print out moment diagrams and then annotate with other action-effects, and then write the member capacities along side. I may provide some additional information as to the inputs required to check the capacity (eg. Lx=Ly=Lz=????). I may have a page of calculations, showing steps for calculations for capacity check of a primary member: but often don’t.

I rarely show the mathematical expressions. This is because software like Microstran and Multiframe do not, and cannot, show the calculation formulae used. If I calculate moments along span of a beam, I show the calculated moments but not the formula, I may or may not plot the curve.

In short with computers we can now compress a lot of the calculation sequence and produce the minimum useful printout. The person doing an independent check can use their preferred tools to carry out their own calculations.

If I was requested to provide documented calculations I would have several hours additional work to do, as much of the original assessment comprises of calculating on computer using quick calculators then documenting the result directly in the certificate.

To provide detailed documented calculations, I would need to rework the calculations through a spreadsheet better suited towards presenting a report. Though in some cases I could just provide the Multiframe model, or export to Microstran.

An independent review can be conducted quickly if data is available in appropriate data files which can transfer to alternative software. I do not consider it a valid independent review if both the design and review are conducted using the same software. Thus if the design is done using say Multiframe then the review should use something different like MicroStran.

Similarly it is not acceptable for all steel design to be done using Limsteel. We need to check that we haven’t hit a design case for which a given piece of software has a defect.

Conclusion

So the certificate of structural adequacy is to meet a need. It is for those situations where no structural calculations have been produced, and there is no one who can otherwise defend compliance with codes of practice.

If no structural calculations have been carried out, then no defendable structural assessment has been made. If there is no defendable structural assessment, then the assertion that the structure is fit-for-function is not defendable. Therefore the review of such a proposal by a chartered engineer would be the first defendable assessment made, such an assessment would be neither a review nor independent. Therefore either council or a private certifier are unable to complete their task.

A builder or drafter doesn’t want a certificate which declares their proposal structurally inadequate, they want to know the changes to make it structurally adequate, and thus allow them to get development approval.

A certificate of structural adequacy allows us to make an assessment, specify changes to make the structure adequate if necessary, assert that the structure is considered to be fit-for-function, and that such assertion is defendable. Thus allowing council or a private certifier to move forward with independent assessment and certification.

Simple structures suitable for certifying typically take less than 1 day to assess and certify. Though if something unusual is present it may take 1 to 2 weeks to assess. The unusual may be identified during initial qualitative assessment, or it may not become apparent until the calculations are under way. So something which initially seems straightforward may become complicated.

Variable terrain, and topographical features can complicate determining wind speed. A simple 1 minute calculation turns into hours: mostly tracking down suitable information. Unusual building shapes can complicate determining wind pressure coefficients: once again a few minutes turns into hours.

In such situations a more formal report maybe more suitable than a certificate. Not the least of which is that the longer report takes less time than attempting to compress such writing into a shorter certificate.

So we will generally adapt the certificate of structural adequacy to suit the nature of the project, and provide report where such is more suitable.

A CITE however is not adaptable, its general format/style and when it can be issued is determined by regulation. In most cases where a private certifier or council has sent you to get such certificate you cannot legitimately get one. In which case need to seek a structural assessment, which will either be documented in the format of a report, or a certificate of structural adequacy.

{NB: Sometimes a certificate of an independent technical expert is referred to as a Regulation 88 certificate. Either way it is the final approving certificate, so if you don’t have any structural assessment to review then cannot legitimately get such certification.}