I recorded the periods before and after time history analysis respectively during IDA.
Who could give me the reason that the initial period is higher than that after THA?
Thanks!
before analysis
#Dynamic Analysis Parameters:
# gamma value for newmark integration: 0.5
# beta value for newmark integration : 0.25
# damping ratio (0.02-0.05-typical): 0.02
# period (sec.) : 1.2267221416400451
# stiffness-prop. RAYLEIGH damping parameter; D = alphaM*M : 0
# stiffness proportional damping; +beatK*KCurrent : 0
# mass-prop. RAYLEIGH damping parameter; +betaKcomm*KlastCommitt : 0.007809555705691575
# initial-stiffness proportional damping +beatKinit*Kini : 0
after the analsis
1.2110905780430474
1.2110905780430474
1.2110905780430474
1.2110905780430474
1.2110905780430474
1.3589346320652633
1.2137205643773135
1.2110905780430474
1.2110905780430474
1.2396251479253928
1.2110905780430474
1.2472346769718976
1.2959294432927149
1.2562258404016369
1.6442130174628098
1.890571367411808
1.9458452729578186
1.2705502953148529
1.836261872022902
1.9364574628645292
1.304938344876924
1.9667545858952133
1.8188620889208282
1.9370794623925365
1.9801088744338338
2.0269076867196096
1.9782893664261498
1.9619335723189049
1.941594904314906
1.8558450358638097
1.670138136820399
1.4564661011530338