Expert: Arshad Khan - 12/15/2008

Question
QUESTION: after running the e-tabs model including all factors like, type of soil, zone factors, ca & cv. i wanted to know the major heads of checks from the analysis point of view after running the entire model succesfully.

ANSWER: Hi Syed,

The checks you should do are:

1. Check the last run log file for any errors, then correct those.
2. Check the deflected shapes to see if anything looks wrong.
3. Check the mode periods- 1st mode should be around n/10 seconds where n is number of storeys.
4. Check support reactions and compare against hand calculations.
5. Do animations of the deformed shapes to see any members that may not have correct connectivity.
6. Check the BM and shear diagrams against hand calculations.
7. Check column axial loads against hand calculations from loading down due to tributary areas.

---------- FOLLOW-UP ----------

QUESTION: DEAR ARSHAD: THESE ARE THE BASIC STEPS...
I MEAN TO SAY THAT HOW THE DRIFT & WHAT ITS MAXIMUM ALLOWABLE VALUE, THE VALUES OF STATIC SEISMIC MOMENT AS WELL AS DYNAMIC SEISMIC MOMENT, ITS PROBALBLE RATIO BETWEEN THE TWO AND ANY OTHER FACTORS GOVERNING THE STABILITY OF THE BUILDING.

Answer
Hi Syed,

The aspects you ask about depend on the shape and aspect ratio of the building and also location, so it is difficult to give any specific answers.

Regarding drift- for medium rise buildings (20-40 storeys)the overall drift due to lateral loading should be below H/500; for taller buildings this can be H/400, but you need to check the inter-storey drifts to ensure they do not adversly affect your finishes, curtain walling, etc. (<10mm for service wind loading, and in accordance with UBC-97 clause 1630.10 for seismic storey drifts).

For buildings with aspect ration greater than 5-6, you will also need to check dynamic response and comfort criteria due to acceleration- usual limts for these are between 15-18 mg (0.15 to 0.18 m/s2)for a 10-year return wind loading.