T-Shaped RC Structural Walls Subjected to Multidirectional Loading: Test Results and Design Recommendations Beth L. Brueggen, M.ASCE 1 ; Catherine E. French, M.ASCE 2 ; and Sri Sritharan, M.ASCE 3 Abstract: Two T-shaped reinforced concrete wall specimens were subjected to reversed cyclic loading quasi-statically to failure. Both represented half-scale wall assemblages of a 6-story prototype building. Modifications to the wall detailing were incorporated to study the effects of longitudinal reinforcement distribution and splicing, shear lag, increased amounts of shear reinforcement, and increased di- mensions of the boundary elements beyond original code-based requirements. In addition, the minimum number of stories required to capture important aspects of multi-story wall behavior through physical experiments was investigated. Distributing the longitudinal reinforcement across the flange, rather than concentrating it within the boundary elements, was found to reduce crack widths, damage to the wall, and shear sliding across the wall panel. Concentrating large amounts of reinforcement in the flange tips tended to increase shear lag effects in the web- direction loading, but led to moderate increases in the in-plane strength and deformation capacity in the flange direction. Locating the lap splices at the second-story level avoided problems with localized damage observed in cases where lap splices are located at the wall-flange interface. Increasing the amount of shear reinforcement and dimensions of the boundary elements did not have a significant impact on behavior. A minimum of two stories was found to be necessary to characterize the behavior of this 6-story prototype structure; it was sufficient to capture the height over which plasticity occurred. DOI: 10.1061/(ASCE)ST.1943-541X.0001719. © 2017 American Society of Civil Engineers. Author keywords: Reinforced concrete; Nonrectangular walls; Earthquake-resistant design; Multidirectional loading; Experiments; T-shaped wall; Seismic; Testing; Concrete and masonry structures. Introduction Tests of two reinforced concrete T-shaped walls were conducted using the National Science Foundation (NSF) Network for Earth- quake Engineering Simulation (NEES) Multi-Axial Subassem- blage Testing (MAST) system at the University of Minnesota. These tests were some of the first of their kind used to subject large-scale reinforced concrete wall assemblages to quasi-static multidirectional loading. Walls of this type are often used to resist lateral loads in multiple directions, whereas planar wall systems are assumed to resist only in-plane lateral loads. Previous tests of nonrectangular RC structural walls had been limited to unidi- rectional and bidirectional loading histories through the (geometric or shear) center. Grammatikou et al. (2015) evaluated an extensive database that included 497 tests on walls with nonrectangular sections (I-, U-, T-, L-, and box-shaped sections), all of which were subjected to unidirectional loading. Ile and Reynouard (2005) tested U-shaped walls under uniaxial and biaxial cyclic lateral load- ing. More recently, Constantin and Beyer (2016) have published their work on tests of U-shaped walls under quasi-static cyclic diagonal loading. Prior to these works, detailing provisions had not been validated for nonrectangular walls under multidirectional load histories. In particular, a concern existed that compression de- mands due to some nonorthogonal loading may exceed the de- mands associated with orthogonal loading or that damage from prior loading in one direction would significantly impair the re- sponse in another direction. Additionally, most wall tests had been conducted using continuous reinforcement that extends from the foundation, which is not a common construction practice in the United States. This project compared the effect of continuous ver- tical reinforcement to the use of lap splices located out of the po- tential plastic hinge region based on companion tests of rectangular walls that investigated the effects of continuous reinforcement, mechanical couplers, and lap-splice details located at the wall- foundation intersection (Aaleti et al. 2013). Other issues investigated in the study included the effect of distributed longitudinal reinforce- ment versus concentrating it in the boundary elements, which has been noted to be of a concern in light of recent earthquake damage to walls (Sritharan et al. 2014); horizontal extension of boundary elements and anchorage of boundary element hoop reinforcement; increased horizontal reinforcement; minimum assemblage height to model the 6 story prototype wall; the quantification of flexure, shear, and strain penetration deformation components; shear lag effects (i.e., reduction in longitudinal flexural strain in the flange as the distance from the web increases during web-direction loading); and the type and distribution of damage incurred. Description of the Test Structures The half-scale specimens identified as NTW1 and NTW2 repre- sented subassemblages from the wall system in a 6-story, prototype 1 Senior Associate, Wiss, Janney, Elstner Associates, Inc., 6363 North State Highway 161, Suite 550, Irving, TX 75038. 2 Professor, Dept. of Civil Engineering, Univ. of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455 (corresponding author). E-mail: cfrench@umn.edu 3 Professor, Dept. of Civil, Construction, and Environmental Engineer- ing, Iowa State Univ., 394 Town Engineering, Ames, IA 55011. Note. This manuscript was submitted on June 10, 2015; approved on October 5, 2016; published online on March 1, 2017. Discussion period open until August 1, 2017; separate discussions must be submitted for individual papers. This paper is part of the Journal of Structural Engineer- ing, © ASCE, ISSN 0733-9445. © ASCE 04017040-1 J. Struct. Eng. J. Struct. 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