Hi All,

The client is not sure about the 'g' value for the site. Only info availalble is that the site falls in seismic Zone #2B-UBC.

Client asking to consider some conservative value for the said seismic zone.

Please guide. The CAESAR mannual give the following. Suggest.

Seismic Zone -- "g" Load
4 -------------- 0.28
3 -------------- 0.21
2 -------------- 0.105
1 -------------- 0.0525
0 -------------- 0.035

Thanks,

This is a consulting question. I doubt that anybody will adress it. This question must be adressed by you, your firm, and your client.

John,

U r right !! We are addressing the issue. In the mean while I just wished to know as to what is given in CAESAR manuals are the conservative max or what?

Thanks anyways....

Kalpesh,

May be you should check the building code for the project site.

The CAESAR II manual contains an excerpt from the ASCE7 code. There are numerous codes in force all around the world.

I would suggest that there may be a code in force for this locale?

Kalpesh,

You are asking a question where you want a number which is " conservative" and for which you don't need any technical justification.

To answer your question: Take a horizontal value of 0.5g and a vertical value of 0.4g.

As required by you, I am not offering any technical justification as to how these numbers are arrived.Only thing: in my personal opinion, they are "conservative".
Regards

For seismic analysis in dynamic mode, seismic spectrum in vertical is 0.667 of horizontal values.

1. For static seismic analysis, vertical g'loads are normally not consired. Any explanation please?

2. For static seismic analysis, g'loads as U1,U2,.... and restraint friction coeff. (mu) are normally not consired simultaneously. Any explanation please?

Hope to get valuable explanation/ suggetions. Thanks in advance.

I think to be "conservative" you should use 2g's Vertical and horizontal...

This is the problem with picking numbers out of the air.

Find out what code is in force... one way of doing this is to go talk to the structural people designing the building structures.

As for the last post from ABIR c/o Calcutta India I have not the slightest idea what he is trying to say or ask.

My guesses as to what he is asking....
#1 why are vertical loads not normally considered?? It depends on the code requirements which are based on science and risk calculations.

#2 Mu is not used and in some building codes specifically prohibited as a restraining mechanism for seismic loads because static mu does not exist in an earthquake.

The science of designing things to withstand earthquakes is well defined by the codes and buildings etc. should not collapse when designed and constructed appropriately. The unfortunate deaths you see in the 3rd world as a result of seismic events occur because of ....

Lack of Money for adequate design and construction.

Ignorance, people do not apply themselves to learn what is appropriate (kind of like the opening question)

Or simply a coarse disregard for the publics safety at large (lives are cheaper than proper design and construction)

I fully agree with John.We should not look forward to answers in air that is why I mentioned in my reply " w/o technical justification".

It might be slightly painstaking but there is no substitute to learning the hard way. There are ample no. of text books on Structural Dynamics (by Clough and Penzien for example), materials available on the net, COADE newsletters, which , if someone wants to, will help them understand the basic of STATIC AND DYNAMIC analysis of earthquake.

As for ABIR,the value 0.667 for vertical is not a "SACROSANCT" value. It is a recommendation by the UBC code. In 1995 ( I think that was the year) the KOBE earthquake in JAPAN had vertical components exceeding the horizontal one.

Please read the codes,go through materials available on the net( there are excellent articles available on www.skghoshassociates.com )for the code explanations ( you will get ample information , particularly about IBC 2000 code), go through an excellent newsletter by Dave Diehl of COADE . Only then one will stop asking for answers in air.I think availability of engineering software is making the youngstars forget/overlook the basic engineering theories and do a GIGO ( garbage-in ,garbage-out).

Regards

anindya

I'm not sure how to spell this in English but Shukria or thank you

A very good summation!

Its a nice explanation on unfortunate death in 3rd world. Thanks.