Performance Based Seismic Design: Challenges of Application for a Tall Building in a High Seismic Zone

Abstract eng:
This work aims to present the challenges of Performance Based Seismic Design (PBSD) method with an application to a real tall building project in a high seismic area in Beirut, Lebanon. The paper describes the motivations for implementing the PBSD as an alternative method to a code prescriptive approach (i.e. IBC/ASCE 7). Due to the code limitations on common seismic load resisting systems (SLRS) for high seismicity and building height, only a frame or a dual system (frame-wall) was permitted according to the code. The resulting structural design was both uneconomic and not compatible with the architectural aspirations for an iconic structure. As an alternative, a coupled wall system was selected to resist the seismic load and justified by PBSD. However, a more sophisticated type of approach and analysis is not without it’s practical challenges, ranging from the extremely laborious data input procedure within the non-linear model for a complex geometry to actually getting the PBSD approach approved by the local Authority. PBSD has been never adopted for building seismic design within Lebanon. Thus the work required to obtain approval were higher than normal. In order to persuade the authorities having jurisdiction to accept the use of PBSD, extensive documentation through publications, scientific papers and guidelines were required to confirm the validity and reliability of the proposed methodology. As always the choice of the correct seismic input for performing the analyses was important: the ground motion selection needed the correct identification of the target earthquake scenario for different hazard levels. This task was undertaken by a local seismologist who performed a hazard analysis based on the knowledge of the actual seismicity of the local area, assessing correctly the seismic area source and faults as addressed in recent scientific publications. The 3D mathematical models were developed in Etabs for SLE and Perform3D for MCE. The paper highlights the modelling strategies and implementation, in particular for MCE simulation, inside the software Perform3D. The evolution of the energy dissipated is reported to measure the amount of non-recoverable damage and investigate the compliance with the expected and desired plastic mechanism for the selected coupled-wall system.

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