This study investigates the cumulative damage of a 20-story high-rise steel building equipped with buckling-restrained braces (BRB) under the likely occurrence of earthquake and wind events in the design life of the building. The objective of this research is to introduce a method for evaluating the cumulative damage of BRBs under multi-hazard events that are expected to occur during the service life of a high-rise building in order to achieve a safer building. A methodology is proposed using a Poisson point process to estimate the timeline of earthquake and wind events, wherein the events are assumed to be independent in nature. The 20-story high-rise steel building with BRBs is designed according to the Japanese standard and analyzed using the finite element approach, considering nonlinearities in the structural elements and BRBs. The building is analyzed consecutively using the timeline of earthquakes and winds, and the results are compared with those under individual earthquakes and winds. In addition to the responses of the frame such as the floor displacement and acceleration, the damage of BRBs in terms of the damage index, the energy absorption, the plastic strain energy, and the maximum and cumulative ductility factor are evaluated. It is observed that the BRB’s fatigue life under multi-hazard scenarios is a multi-criteria issue that requires more precise investigation. Moreover, the overall building’s performance and BRB’s cumulative damage induced by the sequence of events in the design life of the building is significantly larger than that under an individual event.
This study proposes a capacity spectrum Method (CSM)-based procedure to estimate the maximum seismic performance of steel buildings passively controlled with bilinear oil dampers. In the proposed CSM, the maximum seismic response of a building was estimated, in the acceleration-displacement response spectrum, as the intersection between the capacity curve and the damping-adjusted demand curves, using the equivalent linearization method. The building equivalent damping ratio was determined by the sum of the inherent damping, and the square root of sum of squares (SRSS) of the hysteretic damping and the viscous damping of the supplemental oil devices. The calculation steps of the proposed CSM are explained in detail based on the equivalent single degree of freedom (ESDOF) system, and its accuracy was examined by comparison with time history analysis (THA) results. Two model steel buildings of 4 and 10 stories, uniformly equipped with oil dampers along the height, were subjected to six selected earthquake ground motions scaled to be compatible with Level-2 earthquakes, as defined in the Japanese Building Standard Law. The seismic performance of the buildings was estimated by the proposed CSM procedure and compared with the results of nonlinear THA in terms of the maximum story displacements and the shear forces. It was observed that the proposed CSM scheme provided a satisfactory accuracy to assess the maximum nonlinear response of steel buildings passively controlled with oil dampers.
Reinforced Concrete (RC) frame structures are designed and constructed in the major parts of Afghanistan. Meanwhile, the brick masonry wall is one of the most common material that is used as internal and external walls inside the reinforced concrete frame for the building construction. The brick masonry infill wall is defined as a non-structural element for the common structural design software, where only weight is considered, not its strength or stiffness. The Hindu-Kush earthquake, October 2015 that happened in Afghanistan showed that, the buildings with brick masonry walls had less damage or small cracks on the walls. While the buildings without brick masonry walls (bare frames) had serious damage or shear failure on columns. Therefore, the current research aims to find out the effects of brick masonry walls to the seismic performance of RC frame structures by conducting earthquake response analyses of the frame models with and without brick masonry walls. The structural model is based on an actual school building (the 24-classroom school building project that has been designed as a special moment resisting frame with three-stories and constructed in Kabul, Afghanistan). Input earthquake ground motions are generated artificially based on the Afghanistan design spectrum and the phase spectrum of actual earthquake records, such as 1940 El Centro earthquake, 1995 Kobe earthquake and 2003 Bamearthquake. The nonlinear frame analysis program, STERA 3D, developed by one of the authors is used for the analysis, where the backbone curve of the masonry element is defined including the deterioration of the bearing capacity after yielding. The performance of the frame model is examined to verify the effects of masonry elements from the natural period, the story drift and the damage of the frame and brick masonry walls.
High-rise buildings in the regions with multi-hazard (MH) events, such as wind and earthquake, are exposed to more than one type of lateral excitations which act in consecutive manner. Conventionally, in such regions, the maximum of each MH event is used separately to evaluate the performance of buildings while the contribution of preceding event is neglected. When using vibration control devices such as steel dampers, which are effective against both earthquake and wind, accumulation of damage due to continuous input may become a problem. Thus, the current research work aims to investigate the contribution of preceding MH event to the performance of buildings. In this regard, a 20-story RC frame with supplemented buckling-restrained brace (BRB) is designed to satisfy the criteria under the Level-2 earthquake ground motions recommended in Japanese design standard. Then, a total of 16 sets of MH scenarios are created by combining four sets of preceding wind loads with different intensities (17, 20, 25 & 31 m/s of mean speed) and four sets of succeeding earthquake loads of Level-2 intensity. The performance of the RC frame is evaluated in terms of global parameters (such as, natural periods, mode shapes, inter-story drifts, roof displacement profiles, and residual displacements) and BRBs parameters (such as, ductility demands, cumulative plastic deformations, and force-deformation relations). It is observed that the performance of the building with BRB is significantly affected under the successive application of wind-earthquake scenarios in comparison to the application of the single hazard. This result suggests the importance of considering multi-hazard events in the design of buildings.
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