How can I perform progressive collapse analysis (e.g. remove column and get dynamic response) in SAP2000?
SAP2000 can be used to model progressive collapse in the sense of studying how removing certain elements affects the structure. You can simulate this type of progressive collapse analysis with dynamic effects by running time history analysis as follows:
(1) Create "Model A" that contains the entire structure, including the column to be removed. Analyze Model A to obtain internal forces for the column to be removed.
(2) Create a "Model B" that does not contain the column to be removed. However, simulate the presence of column to be removed by applying end column forces obtained from Model A to the appropriate joints of the model.
(3) Run time history analysis with a load applied at time = 0. The load would be opposite to that applied in step 2 and it would effectively simulate removing the column. You would need to use a ramp function to reduce the loads applied in the time history analysis to zero values in a short time. How short (or long) the time should be would depend on how quickly the column is removed and you should use your judgment to decide this.
It is however important to remember that this type of progressive collapse analysis has certain assumptions and limitations. For example, it is not possible to model the effect of the collapsing structure hitting the structure that is still standing.
- Analytical Tools for Progressive Collapse Analysis by Robert Smilowitz
- Dynamic Analysis Procedure for Progressive Collapse by Elizabeth Agnew, and Shalva Marjanishvili; STRUCTURE Magazine, April 2006 - provides some SAP2000 specific information