Expert: Babak Esmailzadeh Hakimi - 2/5/2012

Question
1st step : To model the structure completely and to load it totally according to codes of practice including lateral loads.

2nd step: To remove the shear walls and load the frames laterally for 20 to 25 % of standard seismic loading.

This procedure ensure the structure to get equipped with dual structural system which is suitable to confront earthquakes.

Asslam o w, sir

I need some clearence above your previous answers

1. According to above two models which one is taken as to design frame sections and shearwalls means shearwall frome first one and beams and columns/frame design from second one by removing shearwalls and applied lateral loading. Iam bit confusing.

2. 20 to 25% lateral load is applied at diaphram of each slab.

3. If it possible to design frame section for total vertical load and total lateral load by shear walls. If so , I modelled without shearwalls because at some locations shearwall also act as column to support beams and slab. Then how remove shearwall and check for frame only elements for both vertical and 25% lateral load.

3. At shear wall n nodes give moment on both directions,both direction horizontal and vetical at each node. If want to design it foundation as srip footing then how I take load mean sum each on each direction and applied load as single load fx,fy,mz,my,p at centre of strip footing. Please clarify. When sum the moments of all nodes and appled at center of strip footing it gives more width of footing.

Answer
Dear RS

1- It means that your frame has to be able to resist about 20% of earthquake loading alone without any help from shear walls . You need 2 models and you cant do both analyses using a single computer model (file).

2- Yes you apply seismic loads on diaphragms

3- You need to consider vertical forces ( z direction) and moment around lateral direction of your strip footing. Don't be confused by a lot of data resulting from your analyses. I don't suggest to sum all forces on the center of strip because it is far from reality.


Please let me know about any further question you would have.

Regards
Babak E Hakimi