Abstract
Reinforced concrete walls are commonly used to resist the lateral loading induced by wind and earthquake actions. While most walls include two vertical reinforcement layers, some regions of the world construct slender, non-rectangular concrete walls with a single vertical layer of reinforcement. The seismic performance of such elements is largely unknown given the paucity of experimental research. This paper presents the results of two slender reinforced concrete U-shaped walls tested at the Earthquake Engineering and Structural Dynamics Laboratory (EESD Lab), École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. Both wall specimens, designed similar to construction practice in Colombia, were tested using quasi-static cyclic loading to observe if out-of-plane instability would develop when deformations were limited to prevent the flange boundary ends crushing. Initial failure of both wall specimens corresponded with local out-of-plane buckling in the boundary ends of the flanges occurring on load reversal. The buckling lengths were approximately 700–800 mm, which corresponded to 44–50 bar diameters. The crack patterns were observed to be steepest in the web of the walls, demonstrating the increased shear demand in comparison to that of a rectangular wall. Both wall specimens reached ultimate drifts larger than 2.5–3.0% before global failure occurring in the web-flange intersection due to crushing. A small twist was subjected to one of the walls when centered and loaded diagonally, which showed that the decay in torsional stiffness is proportional to the decay in translational stiffness.
Highlights
Reinforced Concrete (RC) walls are commonly used as the primary lateral force-resisting elements in RC buildings, where core walls resist wind and earthquake loading in both horizontal directions
Dynamics Laboratory (EESD Lab), École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. Both wall specimens, designed similar to construction practice in Colombia, were tested using quasi-static cyclic loading to observe if out-of-plane instability would develop when deformations were limited to prevent the flange boundary ends crushing. Initial failure of both wall specimens corresponded with local out-of-plane buckling in the boundary ends of the flanges occurring on load reversal
This paper presented results from the experimental tests of two slender RC U-shaped walls with a single layer of vertical reinforcement
Summary
Reinforced Concrete (RC) walls are commonly used as the primary lateral force-resisting elements in RC buildings, where core walls resist wind and earthquake loading in both horizontal directions. No special transverse reinforcement to confine the boundary ends of RC walls is required by some building codes in Latin American (Massone et al, a). Concentrating reinforcement in the boundary ends of the wall is practiced in Latin America if higher flexural demands are required (Blandón et al, 2018). RC walls (or cores) are often non-rectangular due to architectural and structural requirements (Belletti et al, 2013; Smyrou et al, 2013, Blandón et al, 2018). The behavior of U-shaped walls differs from rectangular walls with regards to the lateral strength and stiffness of the wall (Paulay and Priestley, 1992). U-shaped walls have three primary inplane modes of bending in comparison to rectangular walls, which only have one; a U-shaped wall can bend about its major (strong) axis and about its minor (weak) axis with web-in-compression and web-in-tension
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