Seismic Performance of Post-Tensioned Steel Frames With Hysteretic Dissipaters

Abstract eng:
A comparison of the structural performance of Post-Tensioned Steel Frames (PTSF) and Steel Frames with Welded Connections (rigid) (SFWC) under seismic action is presented. A set of eight steel frames are used for this purpose, four correspond to PTSF with semi-rigid connections and hysteretic dissipaters, which consist of 4, 6, 8 and 10 stories; the other four are SFWC with the same number of stories. Global response parameters, as maximum inter-story drift (γ), residual drift (γ R ), hysteretic energy (E H ), base shear force (V b ) and local response parameters as force and bending moment in beams and columns are compared. The responses were estimated using incremental nonlinear dynamic analysis. For this aim, the building frame models were subjected to a set of 30 narrow-band earthquake ground motions, which were scaled at different values of the seismic intensity in terms of spectral acceleration at first mode of vibration of the structure (Sa(T 1 )). The selected seismic intensity values range from 0.1g to 2.0g with increments of 0.1g. In order to compare the performance, the average results obtained for each frame subject to the action of the 30 earthquakes is calculated. Results show that: the hysteretic energy dissipated in the PTSF is smaller than that dissipated in the corresponding SFWC. Under the action of severe earthquakes, plastic deformations in PTSF focus on the dissipater elements, preventing damage in beams and columns which remain in the elastic range. In all cases, inter-story drift and residual inter-story drift were smaller in the PTSF. Furthermore, in all PTSF γ R was smaller than 0.005. The demand of strength in columns, such as axial force, bending moment, and shear is smaller in the PTSF too; this is more evident for the exterior columns. The shear and bending moment in beams are smaller in PTSF, but in the case of axial force higher values are observed in the PTST, this is caused by the additional post-tensioning force. In general, it can be concluded that PTSF are efficient to withstand seismic actions as they experience smaller distortion and resistance demands than their counterparts of frames with welded connections. The implication of this is that lighter sections could be used, reducing the total weight of the structure.

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