This question may sound a little confusing if you read the title alone. There are several codes used for design and there are several countries too that have their own structural design criteria and consulting practices. In fact, this blog is the result of a question asked by a student in civilera forum.
This structural engineering student is from a country in Africa and he was doing a project using ETABS 2019 and all of a sudden realised that his version of ETABS do not support UBC or IBC for seismic analysis and design.
The fact is that his country is not having a code and his country don’t even have a seismic guideline or zoning for him to even know that a seismic analysis is needed or not for the building structural design. So, he thought International Building code or the Unified Building code would be a good choice and started the structural design work, only to realise that ETABS 2019 version do not support these codes and supports only ACI or Indian codes or other popular country codes like Euro codes.
What to do if there is no code of Practice?
Before answering this, let me quote the exact question the structural engineering student had.
‘’Hi structural engineers, I want to know something very important in structural design. There are 2 questions. One is related to etabs.
- I want to know if Etabs v19 has IBC or UBC codes in it. I’m using v18 but it doesn’t have it. I really need help with this ASCE seismic load and wind load calculation. How to calculate for all these values in etabs.
- What if your country does not have a building code or seismic code and you want to design a building? What are the considerations you will take into account?
Example Liberia does not have her own building codes so if I’m from Liberia and I’m working in etabs which code can I used and how can I go about design it. Secondly, Liberia does not experience Earthquake I’m not saying Liberia is earthquake resistant. So, in this case which category can I put Liberia in using others building codes?’’
I will try to answer this question. There are many things to address in this structural design doubt.
ETABS new versions do not support UBC. In fact, many don’t use this code of practice now and hence CSI might have thought to remove it or add it later after the release of the new version.
The second question is more a legal and regulation related than structural. I can only answer it with some conditions as explained below.
Does the country have any rules on which code to be adopted? If yes, you have to use the same code to protect yourself from any future legal issues that may arise in case of any incident or accident due to design considerations. Or else there should be strong justifiable reason to adopt a different code than that specified by the regulatory authorities or the building control in that country.
One also need to know if Liberia is in a seismic zone. Has there been any major or minor seismic activities or earth quakes in the country in the near past?
If yes, you have to design for seismic resistance. The seismic zones and the seismic parameters to be chosen depends on the extent and severity of the seismic activities.
If not a seismic zone, then, there is no need to design for earth quake. But in spite of being in a non-seismic zone, you want to design for minor seismic you can choose any reputed code – Indian or American codes or any other seismic code of practice. This is a structural Engineers discretionary decision. In the absence of a structural guideline, this is the best that one can do.
You can also discuss with other practicing structural engineers and civil design consultants and understand the general practice in the country.
Is a Notional Load adequate?
If the region is not seismically active, then probably a notional horizontal load may be adequate to be considered. Codes like BS 8110 recommends a minimum notional horizontal load to go in to the analysis. Even if you consider a wind load, in most cases it provides for more than a notional load and hence bring in certain amount of lateral load resistance. This might be adequate to take care of some seismic resistance when there is a very mild seismic activity.
Is it ok to use any other country code?
In the absence of a code of practice and if you want to consider more lateral load than notional, then yes considering another country code is a good idea. However, which country is a question. You can consider a country similar to the region under consideration or a neighbouring country where the practice and the seismic probability is similar. However, it is needed to ensure that the code of practice for the design is one that is reputed and accepted all over the structural world
Is it ok to use Indian code?
IS 1893, the code of practice for seismic resistance and IS 13920, the code of practice for ductile detailing and design is a widely popular code for structural design of buildings. Both of these are amended recently and is quite advanced. It is quite ok to use the Indian codes for seismic analysis, design and ductile detailing.
Summary
Civil & structural Engineering is not just analysis and design or limited to software like ETABS or staad pro. It is also about taking discretionary decisions like these. Over all success of a structural engineer or a consultant is much more than analysis and design. Taking decisions, choosing options, analysing site conditions and interpreting code all comes as a need for succeeding. The early you are independent to take decisions on your own on these additional aspects than pure structures, the earlier you will succeed in your structural consulting profession.
