Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Estimation of in-plane shear capacity of confned masonry walls with and without openings using strut-and-tie analysis D. Tripathy, V. Singhal ⁎ Department of Civil and Environmental Engineering, Indian Institute of Technology Patna, Bihta, Bihar 801103, India ARTICLEINFO Keywords: Confned masonry Strut-and–tie analysis Finite element analysis ABSTRACT Strut-and-tie analysis is popularly used for the design of shear critical structures and can be applicable for the analysis of confned masonry (CM) walls, which often behave as shear walls. Properties of ties in a strut-and-tie model of CM wall can be simply computed from the yield strength of longitudinal reinforcement whereas that of masonry compression strut may depend on various parameters such as its aspect ratio, the strength of masonry and concrete. A non-linear parametric analysis was performed on more than 200 fnite element models to un- derstand the behaviour of masonry strut and a stepwise methodology for the formulation of the strut-and-tie model was proposed for CM walls. The proposed strut-and-tie method was validated by various experimental studies available in the literature. The developed strut-and-tie models consistently provided good predictions for the in-plane capacity of CM walls with and without openings when compared to the experimental results. 1. Introduction The confned masonry (CM) structure consists of load-bearing ma- sonry walls strengthened with nominally reinforced concrete elements at the perimeter and other key locations. The vertical and horizontal reinforced concrete elements are popularly known as tie-column and tie-beam, respectively. This building typology was frst introduced in the reconstruction of buildings destroyed by the 1908 Messina earth- quake [1]. Considering superior seismic performance of CM structure, this type of building typology is included in various building codes like Mexico building code (NTC-M) [2], Argentinean code (Inpres-Cirsoc) [3], Colombian code [4], Chinese code (NSPRC) [5], Chilean code (INN) [6], Peruvian building regulations (SENCICO) [7], and Eurocode 8 [8]. Past experimental research has identifed several failure me- chanisms of CM walls under in-plane loads. Two possible in-plane failure modes for CM walls are shear failure mode and fexural failure mode. However, generally the governing failure mode is a shear failure for CM walls subjected to lateral in-plane loads. Diferent equations have been proposed by various codes and re- searchers for estimating the shear resistance of CM walls. However, these equations are empirical and semi-empirical in nature and based oneitherfrictiontheoryorelementarytheoryofelasticity [9,10].These analytical equations are either highly infuenced by the formulae ori- ginally developed for unreinforced and reinforced masonry walls or are based on the limited number of laboratory tests. To evaluate the accuracy of existing analytical formulation, a repository of 67 test specimens available in the literature was created. This repository con- sists of solid as well as perforated CM walls with a wide range of ma- terial properties, aspect ratios, cross-sectional details of tie-elements and a multiple numbers of panels. Among collected specimens, the numberofsolidCMwallsis53whereastheperforatedCMwallsare14. Ranges of various parameters in the developed repository are listed in Table 1. In total 12 available analytical formulations were used for the predictionofin-planeshearstrengthandthecalculatedvalues(V cal )are compared with the experimental values (V exp ). The accuracy of pre- dictions was evaluated by comparing the average values of V exp /V cal and their respective coefcient of variation (COV) as shown in Fig. 1a and b [1,3,4,11–20]. As depicted in Fig. 1a, the equation proposed by Rai et al. [12] shows the good prediction for the in-plane strength of solid CM wall with an average value of V exp /V cal is 0.9. However, the coefcient of variation (>80%) for this equation is too high. Further, as shown in Fig. 1a and b the equation recently proposed by Gavilan et al. [13] provides a reasonable prediction for the in-plane strength of solid and perforated CM walls with an average value of V exp /V cal as 1.4 (COV=36%) and 1.1 (COV=36%), respectively. It should be noted that the reduction factor as given by Al-Chaar et al. [21] was used for considering the strength reduction due to openings [12]. From this study, it was observed that the available analytical formulations are unable to provide a good and consistent prediction for solid and https://doi.org/10.1016/j.engstruct.2019.03.002 Received 28 August 2018; Received in revised form 30 January 2019; Accepted 1 March 2019 ⁎ Corresponding author. E-mail addresses: dattatreya.pce17@iitp.ac.in (D. Tripathy), singhal@iitp.ac.in (V. Singhal). Engineering Structures 188 (2019) 290–304 0141-0296/ © 2019 Elsevier Ltd. All rights reserved. T