UC San Diego

High-rise buildings have seen a considerable increase in numbers in recent years, with the number of buildings taller than two-hundred meters doubling since the year 2015. One of the most widely used lateral force resisting systems in high-rise buildings are reinforced concrete coupled core wall piers. Assessing the stiffness, strength, and force-distribution characteristics of this system is difficult, mainly because of the interaction between the internal forces and the uncertainty and simplifications used to account for the elements not defined as part of the main lateral force resisting system. Typically, regular geometries and ideal loading conditions are considered in research of core walls, not quite representative of real structures. There is still a need to evaluate the seismic performance of buildings representative of current practice with refined methodologies. Vertical and horizontal irregularities, torsional effects, the effect of higher modes, the flexibility of the diaphragm and the effect of soil-structure interaction are some aspects that require further evaluation. Current design practice separates the design of the structure's components into several models: a model to assess the performance of the main lateral force resisting system, a separate model to analyze the diaphragms, and a separate model to design the foundation. This may not give an adequate assessment of the performance, as the global behavior of the structure is sensitive to the response of each component. It is also unclear if separating the models results in an adequate design of the diaphragms and foundation.This research focuses on the nonlinear dynamic seismic response of a thirty-six-story reinforced concrete U-shaped couple core wall building. The building has three basements, eight podiums, and twenty-five tower levels, with eccentricities on every floor. The modeling strategy used for the walls is the beam-truss model, which has been extensively validated. The stringer-panel model, a design-oriented methodology, is used to capture the in-plane force distribution and stiffness of the diaphragm. Furthermore, the mat foundation is modeled using a grillage of elastic beam-column elements with no torsional stiffness over distributed elastic springs and dashpots. The entire structure is included in a single model, which is used to assess the performance of the lateral force resisting system, and to obtain the design forces for the diaphragms and mat foundation.