Title: Effect of Axial Restraint and Loading History on the Behavior of Short Reinforced Concrete Coupling Beams

Author(s): Boyan Mihaylov, Alexandru Trandafir, Xenofon Palios, Elias Strepelias, and Stathis Bousias

Publication: Structural Journal

Volume: 118

Issue: 4

Appears on pages(s): 71-82

Keywords: axial restraint; coupling beams; loading history; shear strength; strut-and-tie model

DOI: 10.14359/51732644

Date: 7/1/2021

Abstract:
Short reinforced concrete (RC) coupling beams are key for the adequate behavior of coupled-wall structures, while at the same time are susceptible to brittle shear failures. Particularly vulnerable are existing pre-1970s coupling beams in seismic zones that feature orthogonal reinforcement with low amounts of stirrups. However, while the shear behavior of such members is influenced by the axial restraint provided by the stiff shear walls, lab tests have neglected this effect. In addition, lab tests typically feature a symmetrical cyclic loading history, while in reality, large inelastic pulses in one direction may affect the behavior of the beam in the opposite loading direction. Therefore, this paper presents an experimental program consisting of four large-scale coupling beams with variable levels of axial restraint and different types of loading. Load-displacement curves, crack diagrams, deformed shapes, steel strain measurements, photographs, and advanced strut-and-tie models are used to establish a comprehensive picture of the behavior of the beams. It is shown that the axial restraint generates large compression in the beams and significantly alters their crack pattern and shear strength. Large inelastic pulses have a limited effect on the strength, but significantly influence the drift capacity of coupling beams.