چكيده به لاتين
Recent studies on seismically active regions highlights the importance of seismic sequence phenomena and its influence on increasing the amount of structural damage on buildings. On the other hand, the current approach which is being utilized on modern seismic codes only considers the collapse risk under the effect of single seismic event as a design criterion and does not explicitly address the effect of aftershocks on increasing the risk of structural collapse. This would indicate the vulnerability of current buildings and constructed structures against mainshock-aftershock (MS-AS) seismic scenarios. Therefore, such sequential seismic events should be taken into account to investigate the performance of various systems. The current study assesses the collapse risk of the newly introduced linked-column frame (LCF) systems, taking into account the MS-AS seismic sequence phenomenon and the associated uncertainties.
The LCF systems were introduced as an additional lateral resisting system to improve the drifts and strength features of moment resisting frames, as well as its resilience characteristics. This is achieved by using the concept of structural fuse, which designates some sacrificial structural elements in the buildings that can be easily replaced after strong seismic events. The system consists of dual columns connected by replaceable link beams and an adjacent moment frame. Due to the energy dissipation of link beams, the formation of plastic hinges in the adjacent moment frame elements would be delayed. As a result, the moment frame elements would remain elastic while the link beams go through inelastic deformations and dissipate the seismic energy. Therefore, the residual drifts of the structure could be addressed and the building would return to its original state within a short time.
This study evaluates the annual probability of collapse as a seismic risk measure and compares the results for LCF systems and steel moment frame. For this purpose, using the OpenSEES software package, the 3-story frame model is developed with concentrated plasticity approach. Incremental dynamic analysis is implemented for analysis and after extraction of the fragility curves under the effect of the mainshocks and aftershocks, the annual collapse probability is calculated, based on the site hazard curve. The results indicate a significant reduction in the collapse risk for the linked-column frame, as compared to the moment frame. Also, the annual probability of collapse is witnessed to be slightly increased, by taking into account the effects of aftershocks as compared to the single seismic event.
Keywords: Moment Frame, linked-column frame, seismic sequence, aftershock, resilience, seismic risk
