Leaderboard

First , I am Very Happy to Participate in Forum Such As This Forum , I need to Make Engineering Discussion With These Questions 1. Why We Make Scale Factor Between Static And Dynamic Seismic Analysis ? 2. After Scale Factor We Design By Load Combinations Included Dynamic Cases Only Or Static Load Only Or Dynamic And Static ? 3. What is Diaphragm And What is Importance of Diaphragm In Seismic And Wind? 4. When We Define Diaphragm? And We Define As Rigid Or Semi Rigid And What is the Different Between Them? 5. Different Between Displacement And Drift Due to Seismic ? 6. Displacement Due to Seismic Results From Etabs We Multiply it X 0.70 X R ,Why And What About Drift ? 7. We Make 3 Cases For Each Case ( X AND Y ) in Static Analysis What About Dynamic Same Or Not Static Analysis Ex Ex With + Eccentricity Ex With – Eccentricity Ey Ey With + Eccentricity Ey With – Eccentricity 8. Why We Don't Combine Seismic And Wind in Load Combinations? 9. In Dynamic Analysis , Forces Cause Mode Shapes Or Mode Shapes Cause Forces? 10. Difference Between Response Spectrum ( Dynamic ) And Time History , Which Best? 11. What is the Effect of Seismic in Slabs And Beams? 12. Design Of Slabs And Beams By Load Combination Included Seismic Right Or Wrong? 13. After Finishing 3D Model , What are the Checks For Seismic? 14. Slab On Grade , I Put In Etabs Or Not ? 15. How Building Make Damping For Seismic ,What is Factors Damping Depend on? 16. Different Between Point Drift – Story Drift – Diaphragm Drift ?

Firstl I would like to thank you because you are very active and writing in details.

These members act as tension, or compression members; they act like a brace. I think, they shouldn't be assigned as diaphragm.

Dear Mohammad Shaker I do not know about this and also did not hear about this at all . In my point of view, frame element can be converted to shell elements where there are large transfer of forces at the joints. For example, in case of Transfer Girders (the girders which transfer shear force from shear wall to adjacent columns) must be or can be modeled as shell element as these are directly attached to the member(shearwall) which is transferring heavy shear. The same is the case under Pile Cap. The connection between pile cap and top of pile is critical. You may have seen that the pile near pile cap shows heavily reinforced because we model it node to node so some portion of pile must be inside the pile cap. But when you model frame element it will not catch this effect. So to have this effect we model top portion of pile as shell element. As far as what you are saying is concerned, in my point of view, the absorption/collection of forces is stiffness based. If you model a s column of 300x1500 as frame element then you need to design it as bi axial bending as it will take inplane as well as out of plane bending. The shear reinf. you need to provide must be both sides. But of you provide this 300x1500 member as shell element then you need to skip out of plane bending because we normally neglect the out of plane stiffness of shear wall. So if shell element with proper modifiers it will not absorb the lateral force in out of plane direction. But if you use as frame element it will give you inplane as well as out of plane stiffness and then you need to design as for both biaxial bending. I am not sure I make a proper reply to your question or not......... Thanks Muneeb