Structure Dynamic Responses Under Long-duration And Multi-wave Packets Ground Motion

The current code for aseismic design of buildings in China applies response spectrum theory to design aseismic structures while the duration of strong motion is excluded, which is also one of the three major characteristics (the other two are amplitude and spectrum) of strong ground motion causing structure damage. In order to clarify the effect of strong ground motion duration on reinforced concrete (RC) frame structures, this paper applied finite element software named ANSYS to establish the models for typical RC frame structures, and simulate their dynamic response under the accelerations with long-duration and multi-wave packets that obtained in Whenchuan earthquake.The objects and corresponding conclusions studied in this paper are as follows:1. based on the definitions for strong motion duration used currently, the durations of acceleration records in Whenchuan earthquake were calculated, and the best definition was chosen, by which the rupture directivity effect on seismic duration in Whenchuan earthquake was verified.2. the average period and predominant frequency of Fourier spectrum were calculated for acceleration records on hanging wall as well as the footwall. The result indicated that the predominant frequency of the acceleration records on hanging wall was significantly larger than that on the footwall.3. the distribution characteristics of acceleration records with multi-wave packets were analyzed, and the cause of this phenomenon was discussed. Besides, the typical acceleration records with multi-wave packets were divided into several single packets.4. two finite element models for typical RC frame structures were established, and their dynamic responses under accelerations with the same peak ground acceleration, similar response spectrum but different durations were simulated by numerical calculation. The conclusion was that strong motion duration had some impact both on elastic dynamic response and on elastoplastic dynamic response of structures which should be considered, especially under strong ground motion with rather long-duration.