Pushover analysis

[s_saranya]

I am doing pushover analysis of a RC frame in ABAQUS.

i) Modelling of confined and unconfined concrete in the same cross section (eg. RC column, concrete cover area is considered as unconfined and remaining area is confined) is possible in ABAQUS like in PERFORM 3D or SAP?

ii) Also the structure should be pushed in proportion of the mode shape using displacement controlled boundary condition. How can it be done?

iii) How to determine the mass participation factor in each mode from ABAQUS?

 

[FEA way]

1) It depends on which type of finite element you are using. For beam elements, the rebar *REBAR keyword can be used to specify the location of each rebar.

2) You can find mode shapes using eigenfrequency extraction. In a nonlinear static analysis, you have to define the prescribed displacement manually but you can try to do it in such a way that the deformation corresponds to the first mode shape, if that’s what you mean.

3) Participation factors are automatically written to the .dat file.

 

[s_saranya]

Thank you, I am getting effective mass participation in ABAQUS as 57% . But in SAP2000 it is 80%. What could be the error?

 

[FEA way]

First of all, make sure that all settings of the analysis are the same in both programs. Then check how these variables are defined in Abaqus and SAP2000. For definition used in Abaqus, check the documentation chapter "Theory --> Procedures --> Modal dynamics --> Variables associated with the natural modes of a model".