Lateral forces in multistorey and portal buildings

[Joslaz]

Hi, i have just started in structural design.
My doubts consist in:
1. where do i aply lateral forces (wind) in multistorey buildings,in outter columns or directly in the resistant elements (such as shear-wall, St. Andrew´s cross, etc.)due to the floor rigid diaphragm?
2. In portal frames with flexible diaphragm in roof, if i design a longitudinal wind girder at the top of the column to transmit wind reactions to the gable-end portals, do i must aply wind forces in columns or in the wind girder chord?
Thanks

 

[csd72]

Joslaz,

These are all very good questions to ask your supervising engineer.

We all have a lot to learn when we start off, so these questions should definately be expected. If I was your supervising engineer, I would be worried if you didnt ask questions.

I would advise you to get a good solid notebook to write the answers down so that you dont have to ask the same questions twice.

usually your wind loads on the wall transfer to the floor/roof diaphragms and then to the frames, but there are some exceptions such as large concrete panels that will transfer some load directly to columns.

A few references on load paths:

http://timber.ce.wsu.edu/Supplements/WindDesign/load_paths.html

http://www.atcouncil.org/pdfs/bp1d.pdf

csd

 

[shin25]

joslaz,

As csd2 has mentioned, the lateral forces should be applied to the diaphragms (because most of the mass of the building is usually concentrated at this level), from there the load will be shared by the shear walls based on their relative stiffness. You may opt to have your columns perticipate in the lateral force transfer, but sometimes they are not included. But as the building will go thru lateral deformation due to lateral load, the columns need to be detailed to handle this deformation.

 

[csd72]

A few more references:

http://www.kuleuven.be/bwk/materials/Teaching/master/wg01b/l0710.htm

 

[Joslaz]

Thanks for the responses.
i used to design industrial building with either flexible cladding with side rail purlins or rigid cladding (horizontal precast concrete panels), in which wind action is taken by the columns.
you all have respond me about rigid claddind such as brick, vertical precast concrete or block masonry which transmit lateral forces (w) to the floor diaphragms as 1/2w+1/2w and columns are only designed both for vertical loads and lateral displacement due to lateral forces,that´s right?
sorry for my english. it´s quite forgotten.

 

[shin25]

You have to first figure out if your building will transfer lateral forces thru a moment frame or shear walls or combination of both. If the transfer is thru shear wall action and beams to column connections are pinned (or pinned by assumption and detailed as such) then your above statement is right.