Response of an open-plane frame to multiple support horizontal seismic excitations with soil–structure interaction

The problem of seismic structural design reduces ultimately to estimating the response of the structure to an assumed forced motion imposed on the ground. For multiple supported structures, in most cases, it is generally sufficient to assume that the arrival time of each component of the base motion is the same for each support point, making the transmission time zero (i.e., uniform or rigid base excitation). The inappropriateness of this assumption has been established for long structures like bridge spans. In the current study, the effect of wave passage on the response of an open-plane frame building structure on isolated column bases has been examined for a few selected horizontal accelerograms. Soil–structure interaction has also been considered. The results indicated that a multiple supported excitation approach yields significantly different peak column shear compared to uniform base excitation. Further, the peak column shear mobilized is affected by soil–structure interaction. The pseudo-static contribution to the peak response was seen to be very significant (>90%) particularly for low wave velocities even though the span was only 6.0 m for the non-interactive structure. When soil–structure interaction was considered, the pseudostatic contribution was found to be (for certain accelerograms depending on the ground displacement record) in excess of 25% for the structure founded on hard soil. These results suggest that is prudent to consider wave passage effects when determining the response to seismic excitations even of open plane frames with short spans.