Hi,
I have a question regarding column deflection and sway in STAAD. The below picture shows the deformed shape of a column subjected to lateral forces in a frame. I know the maximum sway/drift in STAAD is gotten from the node displacement value (translation) at the top node in any direction needed (please correct me if I'm wrong) but my confusion is in obtaining the deflection value of the column member itself.
I have used the DFF parameter for deflection check and have set the DJ1 and DJ2 parameters to the top node and bottom nodes.
I'd like to know if the deflection value given by STAAD design output considers or includes the lateral translation of the top node or is it based on the assumption that the top and bottom nodes did not move (similar to beam bending). What is the best value to use for the column deflection? The STAAD output value or the nodal displacement close to the middle of the column?
Thanks.
By default any member has 2- Nodes, and the nodes are the part of the member. Thus the displacement of the nodes either translation or rotation is referring the member only. There is also another option in staad i.e section displacement . The section displacement values gives the displacement values of the member i.e column in this case ,between the top and bottom nodes. You can also insert a node midway between the column and check the displacement of the node. But Short columns or long columns fail due to buckling and staad is designing the column according to the Euler's Equation. The allowable limit of sway for wind load is H/500 as per IS 456 , for seismic loads you may refer IS 1893
Thanks for your answer