Seismic performance of slender RC U-shaped walls with a single-layer of reinforcement

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.

Nonlinear dynamic seismic analysis of a modern concrete core wall building in Los Angeles using the BTM‐shell methodology

“…The seismic behavior of ductile RC structural walls (RCSWs) is governed by a variety of mechanisms and damage patterns, such as flexural and shear cracking (Figure 1A), vertical bar buckling and rupture (Figure 1A), horizontal bar rupture, web diagonal tension failure or crushing (Figure 1B,C), vertical crushing of boundary elements (Figure 1D), and sliding shear (Figure 1E) as well as out-of-plane global inelastic buckling. These damage patterns have been observed in experimental testing 7,[9][10][11][12][13][14][15][16][17] and earthquake-damaged buildings. 18 Numerous experimental studies have investigated the hysteretic seismic response and damage of RCSW over the last 40 years (e.g., [9][10][11]13,14,19,20 ).…”

Core versus Surface Sensors for Reinforced Concrete Structures: A Comparison of Fiber-Optic Strain Sensing to Conventional Instrumentation

“…The wall thickness ( t w ), flange length ( L f ), and web length ( L w ) of all units was 100 mm, 1050 mm, and 1300 mm, respectively. These notations of the wall segments, ‘web’ and ‘flange’, correspond to that in Figure 1 a, and are synonymous with the segments of other U-shaped wall tests [ 23 , 24 , 25 , 26 ].…”

Tests on reinforced concrete U-shaped walls subjected to torsion and flexure

“…The resulting dimensions of the two half-scale U-shaped wall specimens, denoted UW1 and UW2, are 100, 1300, and 1050 mm for t w , L w , and L f , respectively. These test units have the same cross-sectional dimensions of the U-shaped wall specimens TUB (Beyer et al, 2008), TUC/TUD (Constantin and Beyer, 2016), and TUE/TUF (Hoult et al, 2020), but vary, sometimes considerably with respect to the latter specimens, with regard to the reinforcement detailing. The design of the test units followed a similar approach to others (e.g.…”

“…Core wall specimens with H-shaped cross-sections were tested for torsion (Maruta et al, 2000), but a highly contentious scale factor of 1:12 was employed. While there has also recently been some experimental testing on RC U-shaped core walls (Beyer et al, 2008; Constantin and Beyer, 2016; Hoult et al, 2020), only a small twist was applied to these specimens at different loading stages, with the aim of providing information on the degradation of the torsional stiffness rather than the torsional performance or capacity. Even though non-planar RC walls are abundantly embedded within the RC building stock internationally, there is currently no experimental evidence for the performance and capacity of non-planar RC walls subjected to either torsion or a combination of flexure and torsion.…”