Linear and Nonlinear Seismic Analysis Ofreinforced Concrete Special Moment Frames Subjected to Strong Ground Accelerations
This paper represents the static and dynamic analysis results of a 20-story reinforced concrete special moment frame building excited by strong ground motions. The method used in this research is based on recommendations from FEMA, 2012 and ASCE7-10 and Japanese codes. For this research work, three different analysis methods were conducted. Firstly, Static Equivalent Lateral Force method was used for the preliminary analysis and scaling up the values obtained by dynamic analysis. Secondly, dynamic Modal Response Spectrum Analysis (MRSA) method was used as the main analysis method due to its simplicity and general usage by designers to find the maximum base shear, story drifts and member forces. Lastly, the seismically designed building was evaluated by nonlinear Modal Time History Analysis (MTHA) for safety against strong earthquakes. The main objective of this study was to propose a step by step guidance on safe seismic design of tall reinforced concrete buildings subjected to strong ground accelerations. To fulfill this task, firstly the story drifts and base shear force were obtained by MRSA which were within the allowable range. Furthermore, the member forces were determined and sections were proposed with adequate reinforcement accordingly. Finally, three different types of ground motion accelerations (El Centro 1940, Kobe 1995 and Taft 1952) with different velocity levels (25, 50 and 75 kine) were applied into the building by ETABS structural analysis software to know the response of the dynamically designed building against strong ground motions. Consequently, the building showed a satisfactory response in case of medium earthquake of 25 kine and strong earthquake of 50 kine while the allowable drift limit was exceeded in case of 75 kine which is a mega-strong earthquake and is unlikely to happen.
This paper can be a useful source of information for other researchers to understand seismic design procedure for reinforced concrete buildings using recommendations from FEMA, 2012 and ASCE7-10 and Japanese codes.
Key words – Seismic design, Equivalent Lateral Force, Modal Response Spectrum, Modal Time History, Special Moment Frame