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Re: earthquake in STAAD-III

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Mr. Boris

1- your earthquake record is too short (1.26 sec), so the exciting load is
near to impulse load.

2- the intervals of the earthquake record are big and can't give good
interpolation for the rest of records.

3- As Mr.Mark Gilligan said, you can't use the same records for the
response spectrum analysis.

4- Even if you have enough records you will not necessarily have the same
results as the UBC, because you have to use a design earthquake not any
earthquake (you can review the discussion of Mistreatment of Seismology
Issues).



A.M.Zaki



At 05:04 ã 12/12/98 +0100, you wrote:
>-----Original Message-----
>From: Vincenzo Valerio <enmar(--nospam--at)etheron.net>
>To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
>Date: sobota, december 12, 1998 1:08
>Subject: RE: earthquake in STAAD-III
>
>
>>What you did is OK.
>>If you have got different loads is also OK. Remember that a time history
>>analysis and response spectrum are dynamic analysis and UBC does a static
>>analysis.
>>UBC should be more conservative and also more expensive.
>
>
>No, it can't be OK. I've tested everything on this simple example:
>
>  ------------------
>  |                     |
>  |                     |
>  ------------------
>  |                     |
>  |                     |
>  ------------------
>  |                     |
>  |                     |
>----                 ----
>////                  ////
>
>When I compare UBC and SPECTRUM results, absolute values are similar, but
>diagram shapes are different. In SPECTRUM moments are constant along
>members, and in UBC moments are changing sign - in the middle of every
>member value is 0 (that's OK. I think - cracks are always close to joints).
>
>With GROUND MOTION moments are 4-5 times greater then with UBC or SPECTRUM,
>and moments are constant (like in SPECTRUM).
>
>Here is input file (to perform time history analysis remove * from load 3):
>
>STAAD PLANE QUAKE TEST
>UNIT METER KNS
>JOINT COORDINATES
>1 0. 0.; 2 0. 2.; 3 0. 4.; 4 0. 6.
>5 4. 0.; 6 4. 2.; 7 4. 4.; 8 4. 6.
>MEMBER INCIDENCES
>1 2 6; 2 3 7; 3 4 8
>4 1 2; 5 2 3; 6 3 4
>7 5 6; 8 6 7; 9 7 8
>MEMBER PROPERTY EUROPEAN
>4 TO 9 PRI YD .3 ZD .3
>1 2 3 PRI YD .5 ZD .3
>CONSTANT
>E CONCRETE ALL
>SUPPORT
>1 5 FIXED
>DEFINE UBC LOAD
>ZONE 0.4 I 1. RWX 12. S 1.2
>MEMBER WEIGHT
>1 2 3 UNI -5.
>DEFINE TIME HISTORY
>TYPE 1 ACCELERATION
>*EARTHQUAKE IN PETROVAC
>0. 0. 0.08 -1.733 0.2 0. 0.38 2.6 0.52 -2. 0.58 -0.75 0.72 -2.362
>0.8 0.5 0.88 -0.981 1.04 4.019 1.16 -2.348 1.26 -2.64
>LOAD 1 UBC
>UBC LOAD X
>LOAD 2 SPECTRUM
>MEMBER LOAD
>1 2 3 UNI GY -5.
>1 2 3 UNI GX 5.
>SPECTRUM CQC X 1. ACC DAMP .05
>*PETROVAC
>0. 0.; 0.08 -1.733; 0.2 0.; 0.38 2.6; 0.52 -2.; 0.58 -0.75; 0.72 -2.362;
>0.8 0.5; 0.88 -0.981; 1.04 4.019; 1.16 -2.348; 1.26 -2.64
>*LOAD 3 GROUND MOTION
>*MEMBER LOAD
>*1 2 3 UNI GY -5.
>*1 2 3 UNI GX 5.
>*GROUND MOTION  X  1  1
>PERFORM ANALYSIS
>PRINT MEMBER FORCES ALL
>FINISH
>
>
>
>