301 N Broadway - Shell & Core - Plan

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3rd & Broadway, Santa Ana, CA Volume 2 - Structural Calculations June 17, 2024 | Project # S21043.00 pg. 7 4.2 DESCRIPTION OF THE ETABS MODELS CSI ETABS (a structural analysis software program) is utilized to analyze the linear elastic response of the structural system for gravity and seismic loading. The ETABS model includes all components which are directly related to the gravity and lateral load resisting systems of the superstructure including the slabs, columns, shear walls, coupling beams, and the floor diaphragms. The diaphragms and shear walls are modeled using shell elements and the diaphragms are modeled using “semi-rigid” properties to accurately capture diaphragm flexibility. The columns and the coupling beams are modeled using frame elements. The top of the foundation (at Level P01) is selected as the seismic base and all structural elements which attach to this level are “pinned” with the translational degrees of freedom (DOF) restrained but rotational DOF unrestrained. The design of the tower structural framing begins with the ETABS linear-elastic structural analysis model which has properties which reflect the overall mass and geometry of the project. The wall thicknesses, core layout, member sizes, and structural properties are established based on the demands from the analysis model in order to meet strength and performance criteria. The core wall dimensions are a function of the shear forces and the flexural demands in the tower. As the design progresses, various core wall thicknesses and core wall layouts were analyzed to most efficiently meet all design criteria while fitting within the architectural program. The coupling beam width always matches the core wall width throughout the height of the tower.