D8.E.4 Slenderness Effects and Analysis Consideration
STAAD.Pro uses of the first option. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS. The P-Delta analysis will accommodate all requirements of the second- order analysis described by IS:456, except for the effects of the duration of the loads. It is felt that this effect may be safely ignored because experts believe that the effects of the duration of loads are negligible in a normal structural configuration.
Although ignoring load duration effects is somewhat of an approximation, it must be realized that the approximate evaluation of slenderness effects is also an approximate method. In this method, additional moments are calculated based on empirical formula and assumptions on sidesway (Clause 39.7.1 and 188.8.131.52,IS: 456 - 2000). The rules of Clause 39.7.1 have been implemented in STAAD.Pro. They will be checked if the ELY and ELZ parameters are specified.
Considering all these information, a P-Delta analysis, as performed by STAAD.Pro may be used for the design of concrete members.