Combination of Codes of Practice

[eeedesign]

Hi to all Structural experts,

I just need to ask if in the analysis and design, is it allowed to use multiple code of practice. Say, Analyzed the structure in seismic using UBC97 but design it with BS 8110-97 is it possible to do that? Because i notice that BS Code does not include seismic provisions, only ACI-318 has.Please enlighten me.

Thanks a lot

 

[Ron]

In general, no. In practicality sometimes, particularly if you have a valid reason for doing so, such as yours.

The code writers want to prevent a design engineer from picking and choosing code provisions from multiple codes that would result is a substandard design.

 

[JAE]

It seems to me that in most area there would be a specific, required, and adopted code for a building that you would use....as opposed to you just selecting one.

There might be some areas of the world where there is no valid, governing body that mandates the code, provides inspection, etc., so in those cases you would use your own judgement and get buy-in by your client before using one.

Selecting different code, specification, or guide resources can be dangerous as sometimes the mix of loads and mandated load factors or safety factors don't mix.....an example would be using the older "fastest mile" wind maps with the current 1.6W factor on winds, which are intended to be used with 3 second gust winds instead.

 

[hokie66]

This is an area which requires a lot of engineering judgment. The major code bodies do pay attention to the others, and there is often a time lag between coordination of the codes. For instance, the ACI Code may make a revision based on research, and the Australian Code or British Code may agree, but the actual implementation takes some time. Australian Standards typically allow the use of alternative methods, with the Engineer and often the Building Authority needing to approve.

 

[CELinOttawa]

Agree with Ron in principle, however note that:

There is a concrete code which UBC expects to be applied, and you've named it: ACI 318. You should not go use BS-8110 without good reason, and simply wanting to is not a good reason. I don't agree with Ron that you have a practical reason in this case, but I agree that with a practical reason such an approach can be justified as being made with good engineering judgement. Some examples follow.

Note that I'll be tackling your question from a Historical/Restorative Engineering point of view, my primary field of practice...

- Occassionally a code will have removed a type of work, such as lattice built up steel columns. In such a case I apply the whole of the old code wherever possible, and do not mix and match unless I must.

- There are many, MANY, correlations, approximations, assumptions, etc, involved in preparing a set of codes and there are a great number of points of interaction. A great example of this is Concrete where the compressive strength can only be used as an indicator of other physical properties (shear strength, tension strength, creep properties, etc) within a particular bounded range (typically 20MPa to 45MPa).

BUT (isn't there always a but?) with respect to gravity loading most load code requirements could be satisfied by most material codes... The real exceptions are for the "other" loads, ie: Wind, Seismic, Vibration, etc. Those have particular approaches which are ballanced between loading and material resistance codes/standards.

 

[bkal]

One thing you might want to consider is a combination of load and material partial factors of safety. It is likely that use of single-source codes would give you a certain (acceptable) probability of 'failure', while using a combination of codes from various sources this might not be the case.

 

[steellion]

Is there still a jurisdiction that uses UBC97? That's almost 20 years old.