Seismic performance of concrete walls for housing subjected to shaking table excitations Julian Carrillo a,b,⇑ , Sergio M. Alcocer b a Departamento de Ingeniería Civil, Universidad Militar Nueva Granada, UMNG, Cra. 11, No. 101-80, Bogotá, Colombia b Instituto de Ingeniería, Universidad Nacional Autónoma de México, UNAM, Ciudad Universitaria, Coyoacán 04510, DF, Mexico article info Article history: Received 29 August 2011 Revised 5 February 2012 Accepted 9 March 2012 Keywords: Concrete walls Shear behavior Low-rise housing Shaking table tests Lightweight concrete Welded-wire mesh abstract Aimed at better understanding the seismic behavior of reinforced concrete (RC) walls, typically used in one-to-two stories housing in several Latin American countries, a large investigation project has been car- ried out. Previous experimental programs considered the behavior of walls subjected to monotonically and cyclically increased loads. This paper compares and discusses displacement and shear strength capacities, as well as the dynamic characteristics of six RC walls tested under shaking table excitations. Variables studied were the wall geometry (solid walls and walls with openings), type of concrete (nor- malweight and lightweight), web steel reinforcement ratio (0.125% and 0.25%) and type of web reinforce- ment (deformed bars and welded-wire mesh). Shaking table tests were essential for assessing dynamic characteristics, such as changes in fundamental frequencies and damping factors of RC walls for low-rise housing. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Because of their potential lateral stiffness and strength, one- to-two stories high concrete wall structures are subjected to small demands of lateral displacements and seismic forces. This phe- nomenon has prompted housing designers and contractors to use concrete compressive strengths of 15–20 MPa, as well as 100- mm thick walls. Also, in zones where seismic demands are low, such that design controlled by vertical actions, the minimum web shear reinforcement prescribed by ACI-318 building code [1] appears to be excessive for controlling diagonal tension cracking. Moreover, application of such a code commonly leads to an unjus- tifiable excessive cost of the housing unit. As a result, web steel reinforcement ratios smaller than the minimum ratio prescribed by ACI-318 building code and web shear reinforcement made of welded-wire meshes are frequently used. All these features are a direct consequence of attaining speed of construction and econ- omy in a very competitive housing market. However, the effect and adequacy of such structural characteristics on seismic behav- ior have not been assessed experimentally. In a first stage of the testing program, reinforced concrete (RC) walls tested under monotonic and cyclic loading, and reinforced with 50% of the minimum code-prescribed web shear reinforce- ment [2,3], exhibited comparable shear strength capacity to that of walls reinforced with 100% of the minimum steel reinforcement ratio. Nevertheless, walls with 50% of the minimum code pre- scribed web shear reinforcement and reinforced with welded-wire mesh exhibited limited displacement capacity as compared to walls reinforced with 100% of the minimum amount. When correlating earthquake demand to structural capacity, it is essential that capacity be evaluated under conditions closely approximating those representing the true dynamic conditions [4]. Up to date, shaking table testing is recognized as the most suit- able experimental method for reproducing the real dynamic effects of earthquakes on buildings, structures or components. Thus, this study aims at evaluating the effect of wall geometry, type of con- crete, web steel reinforcement ratio and type of web reinforcement on the shear strength, displacement capacity, and dynamic charac- teristics of RC walls for low-rise housing subjected to shaking table excitations. Most representative wall models tested in previous phases were selected for studying the structural behavior under actual seismic actions. Dynamic tests included four solid walls with height-to-length ratio equal to 1.0, as well as two walls with door and window openings. Wall properties were those obtained from current design and construction practice found in typical low-rise housing in several Latin American countries. Walls were designed to fail in shear to better understand the strength mecha- nism that take place during shear failures observed in RC walls for low-rise housing. 0141-0296/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.engstruct.2012.03.025 ⇑ Corresponding author at: Departamento de Ingeniería Civil, Universidad Militar Nueva Granada, UMNG, Cra. 11, No. 101-80, Bogotá, Colombia. Tel.: +57 1 6500000x1268; fax: +57 1 6370557. E-mail address: wjcarrillo@gmail.com (J. Carrillo). Engineering Structures 41 (2012) 98–107 Contents lists available at SciVerse ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct