P-delta effects per 97 UBC 1630.1.3

[DriveThru]

In order to include the P-delta effects per the 1997 UBC Section 1630.1.3, you need to multiply the story shears by an amplification factor. I am studying dynamic analysis with Alan Williams book - Seismic Design of Buildings and Bridges and his example uses the maximum nodal forces from a response spectrum nodal analyses. It seems to me that the forces used for p-delta should be the design forces from a distribution of the base shear, not the maximum nodal forces. The maximum nodal forces do not add up to the base shear. I cannot find an example in any other book that uses a dynamic analysis. The reason for all this is because this type of problem has been on the California S.E. Exam. Anyone's help in finding another example or who has studied from this book would be appreciated.

 

[BryanStein]

You are correct. The amplification factor should be applied to the story shears. A response spectrum analysis would use a modal superposition to determine the forces. I believe the IBC will actually tell you that a response spectrum analysis should not be mixed with P-Delta amplification factors.