Seismic Performance Assessment of a 24-Story Building With Composite Moment Resisting Frames (Cft-Mrfs) and Composite Buckling-Restrained Braced Frames (Cft-Brbfs)

Abstract eng:
Reinforced concrete is the preferred material used in Ecuador for most buildings. Moment Resisting Frames (MRFs) is the most common structural system chosen for reinforced concrete construction. However, steel construction has gained some popularity during the last 15 years in Ecuador. Most of the steel buildings constructed in this period are low-rise structures composed mainly of MRFs. This paper presents the initial steps of a research program that aims to provide the local steel industry with other alternatives for structural systems of taller buildings. Composite Moments Frames (CMRFs) consisting of concrete-filled steel tube columns and I-shaped steel beams (CFT-MRFs) as well as Buckling-Restrained Braced Frames (BRBFs) are the structural systems that are proposed in this paper to be considered in the seismic design of mid-rise and high-rise buildings. Ecuadorian seismic code (NEC 2015) does not include design provisions for the CFT-MRFs or the BRBFs due to a lack of knowledge relative to the analysis, design, construction and behavior of buildings using this type of structural systems. Therefore, there is a need to carry out both analytical and experimental research on these systems in order to make feasible their application in future projects. This work addresses the analytical studies of the proposed research program. The main objective of this investigation is to evaluate the global seismic response of a prototype building composed of CFT-MRFs and CFT-BRBFs. The first part of the paper provides a review of the most relevant aspects related to the design of a 24-story prototype building where CFT-MRFs and CFT-BRBFs constitute the main lateral load resisting system. This design was based on the seismic provisions from American codes and recommendations from related research. The second part of the paper describes the analytical modelling of the prototype building and the calibration that was done for every structural component (beams, CFT columns, beam-to-column connections and BRBs) pertaining to both structural systems. Two types of nonlinear analyses were conducted: static pushover analyses; and time-history analyses with several ground motions. Finally, the results of the nonlinear static and dynamic analyses performed on the prototype building are presented. The results of the seismic evaluation of the prototype building show that both systems, the CFT-MRFs and the CFT-BRBFs, have an adequate seismic performance and consequently represent an interesting alternative for the construction of mid-rise and high-rise buildings in Ecuador.

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