Contents lists available at ScienceDirect Structures journal homepage: www.elsevier.com/locate/structures Macro modeling of steel-concrete composite shear walls Nakisa Haghi a , Siamak Epackachi b, ⁎ , Mohammad Taghi Kazemi c a Dept. of Civil Engineering, University of Science and Culture, Tehran, Iran b Dept. of Civil Engineering, Amirkabir University of Technology, Tehran, Iran c Dept. of Civil Engineering, Sharif University of Technology, Tehran, Iran ARTICLEINFO Keywords: Steel-plate concrete composite shear walls PERFORM-3D Macro model Fiber-based element ABSTRACT To date, many researchers have developed various types of macro models to simulate the general response of conventional steel plate and reinforced concrete shear walls. Although extensive numerical and experimental studieshavebeenconductedtoassesstheseismicresponseofsteel-plateconcretecompositeshearwalls,arobust macro-model for simulation of the cyclic response of such systems has not been developed yet. Herein, a fber-based model is proposed to simulate the nonlinear seismic response of SC walls using PERFORM-3D program. The details of the proposed model, including material properties, element type, and boundary condition, are presented. The proposed model is validated using the available test data of seventeen SC wall specimens with and without boundary elements. Based on the analysis results, this novel approach can capturetheglobalresponseofSCshearwallsincludinginitialstifness, peak shear strength and its corresponding displacement, stifness and strength degradation, and pinching behavior accurately. The proposed macro model for SC shear walls can be considered as a reliable tool to extend the engineering application of SC walls in the building industry. 1. Introduction The application of steel-concrete (SC) composite shear walls as a lateral resisting system for tall buildings has been increased (e.g., [1–3]) due to their high energy dissipation and load-carrying capacity compared to traditional concrete shear walls (RC) and steel plate (SP) shear walls. The SC shear walls, considered in this study, comprise two steel faceplates flled with concrete. The steel faceplates connected with the tie bars and attached to the concrete with the headed studs. Like RC shear walls, the use of boundary elements (BEs) consisting of steel section column (e.g., [4]) or steel tube flled with concrete (e.g., [5])at two ends of the walls enhances the energy dissipation capacity and ductility of SC walls signifcantly. The nonlinear simulation of SC walls can be accomplished either by using micro fnite element or macro analytical modeling approach (e.g., [6–9]). The micro fnite element modeling provides detailed inter- pretations of the localized behavior of such walls, and the macro ana- lytical modeling simulates the overall behavior of the wall with rea- sonable accuracy. The high resolution nonlinear fnite element analysis is known as a powerful tool to simulate the nonlinear response of structural elements. However, its application in engineering practice has signifcantly limited due to the time-consuming analysis and nu- merical complexities, fully three-dimensional modeling of the concrete element, considering the contact stresses and interfacial friction be- tween steel faceplates and concrete panel, and the reliability of the concrete and steel material models. Macro modeling approach, on the other hand, representing the overall behavior of the structural element, is an efcient and practical analytical tool. It does not require high computational eforts, making it suitable for engineering applications. The accuracy of macro models signifcantly depends on the simplifying assumptions and the idealized material models, upon which the model is developed. To date, the analytical modeling of SC walls has been limited to simplifed empirical equations to predict the strength and stifnessofSC walls (e.g., [10–18]). These formulations were derived either using limited test data available in the literature or theoretical concepts, which are based on many simplifying assumptions. Using these em- pirical equations, the user is unable to simulate the nonlinear response of SC walls subjected to monotonic and cyclic loadings. Given a lack of reliable macro model for SC walls, there is a signifcant need to develop a robust analytical tool, which is able to simulate the monotonic and cyclic nonlinear response of SC walls. The model needs to be easily implemented in an engineering computational platform for practical analyses of buildings and infrastructures incorporating SC walls as a lateral force-resisting system. Herein, a fber-based macro model is developed using PERFORM-3D https://doi.org/10.1016/j.istruc.2019.10.018 Received 8 August 2019; Received in revised form 10 October 2019; Accepted 25 October 2019 ⁎ Corresponding author. E-mail addresses: n.haghi@usc.ac.ir (N. Haghi), epackachis@aut.ac.ir, siamakep@bufalo.edu (S. Epackachi), Kazemi@sharif.edu (M. Taghi Kazemi). Structures 23 (2020) 383–406 2352-0124/ © 2019 Institution of Structural Engineers. Published by Elsevier Ltd. All rights reserved. T