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[kvr karthikeyan]

hi everyone..I have designed a building in staad..but i cannot understand how does staad calculate deflection in beams..there are failed beams in ground floor...please can anyone calculate and show me the calculations whether the beam failed in deflection or not..And also how does staad calculate deflection values

[TYL]

Like majority of the structural analysis software, Staad calculates deflection value using matrix stiffness method.

It depends on what your are modelling in Staad. If it is a steel structure, then I would say the deflection calculated will be pretty accurate (if there is no buckling or stability issues). Hence, for steel structures you need to check the deflection obtained in Staad against the allowable deflection limit.

For concrete structures, this is not so straight forward. This is due to the fact that concrete usually cracks even when subjected to service loadings. As Staad calculates the deflection assuming uncracked section, the deflection values shown is not accurate. Hence, for RC structures, deflections are not checked directly but they are usually check INDIRECTLY by satisfying the permissible span/depth ratio prescribed in design code.