Impact of bi-directional loading on the seismic performance of C-shaped piers of core walls

Abstract

Reinforced concrete structural walls are commonly used as the primary lateral load resisting system in modern buildings constructed in high seismic regions. Most walls in high-rise buildings are C-shaped to accommodate elevators or other architectural features. C-shaped walls have complex loading and response including: (1) symmetric response in the direction of the web, (2) asymmetric response in the direction of the flange and (3) high compression and shear demands when used as a pier in a coupled-wall configuration. A research study was conducted on C-shaped walls tested under (1) uni-directional and (2) bi-directional loading of an isolated walls and (3) bi-directional loading of a c-shaped pier in a coupled wall system. Each of the walls failed in flexure with strength loss resulting from low-cycle fatigue of the boundary element longitudinal reinforcement with buckling followed by fracture. The damage progression was as follows: (1) cracking at the wall-foundation interface, (2) concrete spalling in the web, (3) buckling and fracture of web reinforcement, (4) spalling in the flanges, (5) buckling and fracture of the bars in the boundary elements. Concrete spalling and steel bar damage occurred at lower strong-axis drift levels for the bi-directionally loaded, resulting in lower drift capacities for these loading protocols. However, for the strong-axis direction, bi-directional loading does not reduce flexural or shear effective stiffness values suggesting that current values are appropriate for design and evaluation of buildings with c-shaped walls.

Experimental study on the effects of bi‐directional loading pattern on rectangular reinforced concrete walls

“…Several experimental studies have been reported on nonplanar (flanged) RC walls under bi‐directional loading 2–11 . In their experimental study on U‐shaped walls, Ile and Reynouard 4 observed up to 33% reduction of displacement capacity due to bi‐directional loading effect.…”

“…F I G U R E 1 Unexpected failure modes observed in RC walls, (A, B) lateral instability in Chile 13 and (C) New Zealand, 14 (D) concrete spalling at web to boundary element interface, 15 (E) out-of-plane shear-axial failure of a slender wall, 16 and (F) diagonal web crushing of a slender wall 14 Several experimental studies have been reported on nonplanar (flanged) RC walls under bi-directional loading. [2][3][4][5][6][7][8][9][10][11] In their experimental study on U-shaped walls, Ile and Reynouard 4 observed up to 33% reduction of displacement capacity due to bi-directional loading effect. They concluded that a pre-existing displacement in the transverse direction reduces the maximum attainable strength in U-shaped walls.…”

Bi-axially Loaded RC Beam-Column Joints and Haunch Retrofit

“…the most recent five works, to the Authors' knowledge, are Lucchini et al (2022); Gwalani et al (2021); Salami et al (2021); Zhang and Tao (2021); Opabola et al (2020)), shear walls (e.g. the most recent five works, to the Authors' knowledge, are Wang et al (2023Wang et al ( , 2022; Niroomandi et al (2021); Behrouzi et al (2020); Beyer et al (2008)). Generally, tested specimens were not shear-critical thus similarities with respect to beam-column joints are difficult to be obtained.…”

Study and Numerical Analysis on Seismic Performance of Concrete U-Shaped Shear Wall

“…Te shear wall with a reasonable design of the wall limb section shows good stifness, which can efectively resist winds, earthquakes, and other horizontal efects. Compared with the conventional rectangular section reinforced concrete shear wall, it can only provide one translational stifness [7]. While the U-shaped cross-sectional shear wall can provide the stifness needed for two translational directions of the structure and has excellent seismic performance, it is recognized that it has good marketing in both high-rise buildings and large space buildings.…”

“…Beyer et al [8] performed quasi-static cyclic tests on two U-shaped reinforced concrete walls, which provided a theoretical basis for studying the seismic performance of U-shaped walls and formulating appropriate design guidelines. Behrouzi et al [7] tested three large C-shaped walls under unidirectional and bidirectional loads. It was found that the C-shaped wall has a symmetric response in the web direction and an asymmetric response in the fange direction.…”