Seismic performance evaluation of reinforced concrete wall-frame mixed building systems

Abstract

Bangladesh is located in a seismically active region that a history of devastating earthquakes. Therefore, seismic design of buildings by Bangladesh National Building Code (BNBC) has been subjected to rapid developments to ensure ductile behavior and safe performance of the designed structures under possible future earthquakes. Different structural systems are available in draft BCBC-2017 to resist seismic loads. In this thesis, three different wall-frame mixed building systems such as building frame, dual frame and general wall system with three different plan configurations were designed as per draft BNBC-2017 to evaluate seismic performance in terms of global pushover curve and response reduction factor (R). A total of 36 building models were considered with three different plan and story configurations located in seismic zoning -2 having seismic design category C as per draft BNBC. Nonlinear static analysis (pushover analysis) was carried out for all the building models using finite element software. Initially, FE model was validated with the result available in the literature. Different techniques for simulation of shear wall in a mixed building system were studied. From the analysis, it is shown that auto wall hinge properties may provide better correlation with the failure pattern of the wall. Building frame system demands higher shear force and bending moment values under the same gravity and earthquake loads than other two systems. These values increase as the eccentricity of the plan is increased. Response reduction factor, R values show conservative for low-rise (5-storied) and seems underestimated for mid-rise (10-storied) and high-rise (15-storied) buildings for the considered plan configurations. It decreases as the height of the building is increased. Commercially available structural analysis programs can be used directly for general wall system without separating the walls and frames or assigning any particular required strength to different elements up to five storied building only. For mid-rise and high-rise mixed building systems, it cannot be used directly as it returns numerically different value of R for the same seismic event.