Lateral force distribution of Storey Shear derived from ELF method

[Ratsvein]

Hi!

I am a new to structural engineering and currently trying design to a four story RC building (Special moment resisting frame) following the provisions from ASCE 7-10 ch 12 for seismic design requirements using Equivalent Lateral Force method in determining the seismic loads. However, the ASCE doesnt seem to recommend methods on how to determine member forces for columns and beams from the lateral forces (storey shear) obtained from ELF method. I will use STAAD.PRO to analyze the structure but I would like to be able to manually check the results. Can you recommend references for frame analysis guides on how to approach this? or should i use matrix analysis for it?


Thank you very much!

 

[JAE]

ASCE 7 is a document only focused on providing the appropriate loads for buildings. It doesn't directly get involved in the means of analysis.

Performing a full frame analysis of a multistory building using hand calculations would be quite a task. One can do it but it takes a lot of time (and paper!).

A rough portal analysis might be attempted in a series of 2D frames perhaps.

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[Ratsvein]

I was planning to use spreadsheets for manual computations.

Considering that the building is L-shaped causing re-entrant corner horizontal irregularity and will most likely develop Torsional irregularity (possibly extreme torsional irregularity due to length and width ratio being @ 0.25), how accurate would you say a portal analysis be for this situation?

Thanks!!

 

[JAE]

Probably not too accurate.

With that kind of building you'd have to make a lot of assumptions to derive load paths and load distribution based on building torsion, etc. to "set up" some 2D portal checks.
Not sure you'd match your STAAD analysis very closely but I'd have to think through the challenges a bit.


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[Ratsvein]

Okay! Thanks for your input!

 

[Shu Jiang PEng SE]

Permitted analytical procedures are determined by the structure "Seismic design category" and "Structural characteristics. Refer to "Table 12.6-1 Permitted Analytical Procedures" in ASCE 7-10 for details.