Static Seismic Analysis

Dear

Question 1

Normally the seismic load combinations(static or dynamic) should be absolute sum with other load cases(OPE, SUS). But CAESAR II result output is printed out with direction force( + , - ). We want to get the load case like as below.

W+T1+P1 + / - U1
:
:

How to get the absolute sum using Uniform Loads function.

Question 2

How to create the load combinations(for nonlinear restraints).

If uniform loads is applied both directions concurrently, our load combinations are as bellows;

CASE 1 (OPE) W+T1+P1
CASE 2 (OPE) W+T1+P1+U1
CASE 3 (SUS) W+P1
CASE 4 (OCC) W+P1+U1
CASE 5 (EXP) DS1-DS3
CASE 6 (OCC) DS2-DS1
CASE 7 (OCC) ST3+ST6

If uniform loads is not applied both directions concurrently, our load combinations are as bellows;

CASE 1 (OPE) W+T1+P1
CASE 2 (OPE) W+T1+P1+U1
CASE 3 (OPE) W+T1+P1+U2
CASE 4 (SUS) W+T1
CASE 5 (OCC) W+P1+U1
CASE 6 (OCC) W+P1+U2
CASE 7 (EXP) DS1-DS4
CASE 6 (OCC) DS2-DS1
CASE 7 (OCC) DS3-DS1
CASE 8 (OCC) ST4+ST5
CASE 9 (OCC) ST4+ST6

But result of CASE 8 and CASE 9 are same, so we think we can use only one case (case 8 or case 9)

In above case, U1 is positive direction of g¡¯s and U2 is negative direction of g¡¯s in X, Y, Z.

There really isn't an easy way to get what you want. The current version of CAESAR II isn't setup to do this directly in a static analysis.

For linear jobs, you can do this in the dynamics module. Setup your uniform load cases as independant loads, and use the "static/dynamic" option to combine two static cases absolutely.

Alternatively, you could send you static output to an MS Access (ODBC) database and post-process the results.

We are adding this capability into the static modules for Version 4.30. This version should be released in January 2001.


I really don't understand the later half of your second question. Your load case #4 consists of "W + T1", this is not "Sustained". Furhtermore, the only way cases 8 and 9 could yield the same results would be if ST5 and ST6 are the same, which could only happen if U1 and U2 are the same.

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Regards,
Richard Ay (COADE, Inc.)




[This message has been edited by rich_ay (edited October 05, 2000).]

Dear
I think you must not only look for the sign
-U and +U. You must also look for the direction U (Y direction) U (X direction) and
U (Z direction)in the static seismic analysis. And you must found the max. forces and moments for the restraints.
Look, the horizontial acceleration gives a load in a Guide restraint. When calculate
only U vertikal, then you becom no load
in horizontioal restraint!

Dear Mr.rovern,

I think, your load combination may have some mistakes. CAESAR II recommend the load and stress combinations for nonlinear case as below;

For non linear case with two vector(X,Z uniform loads are applied simultaneously);

CASE 1 (OPE) W+T1+P1
CASE 2 (SUS) W+P1
CASE 3 (OPE) W+T1+P1+U1 ----total load
CASE 4 (OCC) DS3-DS1
CASE 5 (EXP) DS1-DS2
CASE 6 (OCC) ST2+ST4 ------code stress

For non linear case with each vectors(X-vector 1,Z-vector 2 uniform loads are applied separately);

CASE 1 (OPE) W+T1+P1
CASE 2 (SUS) W+P1
CASE 3 (OPE) W+T1+P1+U1 ----total load
CASE 4 (OPE) W+T1+P1+U2 ----total load
CASE 5 (OCC) DS3-DS1
CASE 6 (OCC) DS4-DS1
CASE 7 (EXP) DS1-DS2
CASE 8 (OCC) ST2+ST5 ------code stress
CASE 9 (OCC) ST2+ST6 ------code stress

I think the sign of dynamic load is not important since it is OK if we just consider the maximum absolute load for dynamic load.
If you want to separate the seismic load only to inform that to civil group, you can add additional load combination, for example (OCC) U1.

For the stress the sign U must have the same as W , but for the restraint load the sign from U is imported.
The load case (T+W) (+U) or (-U) must be summed for the restraint load (load case HS in german)