Seismic Behavior and Detailing of High-Performance Fiber-Reinforced Concrete Coupling Beams and Coupled Wall Systems

Abstract

The seismic behavior of coupling beams and walls constructed with tensile strain-hardening, high-performance fiber-reinforced concrete (HPFRC) was studied through tests of large-scale precast coupling beams and coupled walls. A precast coupling beam design was developed to speed up construction and minimize interference with wall reinforcement. Three isolated precast coupling beam specimens with a span-to-depth ratio of 1.75 were tested under large displacement reversals. Test results indicate the use of HPFRC allows a reduction of the reinforcement required to achieve a stable coupling beam response by providing confinement and contributing to beam shear strength. A concrete design shear stress capacity of 0.41√fc', [MPa] (5√fc', [psi]), where fc' is the compressive strength of the concrete, was found to be appropriate. In addition to the coupling beam tests, two four-story coupled wall specimens with precast HPFRC and regular concrete coupling beams were tested under lateral displacement reversals. Besides allowing the evaluation of seismic behavior of coupled walls with HPFRC coupling beams, the use of HPFRC in the plastic hinge regions of the walls as a means of relaxing transverse wall reinforcement was evaluated. The two coupled wall specimens exhibited drift capacities of at least 2.5%. The HPFRC coupling beams were more ductile and damage tolerant than the regular concrete beams. The incorporation of an HPFRC material in the wall allowed the use of a concrete design shear stress capacity of 0.33√fc', [MPa] (4√fc', [psi]) and a wider spacing of transverse reinforcement confining the wall boundary regions.

Experimental study of reinforced concrete and hybrid coupled shear wall systems

“…Based on finite element analysis of a 12-storied hybrid coupled shear wall system, El-Tawil et al [9] recommended a CR range between 30% and 45% as an efficient structural design. For RC coupled shear wall systems, the typical coupling ratio varies between 20% and 55% [10]. A low CR results in inefficient lateral resistance and a high CR leads to reduction of deformation capacity of a coupled shear wall system.…”

“…The V ex,cb -to-V n,cb ratio is essential to account for the significant underestimation of shear capacity using Eq. (1) [10,14]. This magnification factor needs to be evaluated and applied to each wall segment between two consecutive floors.…”

“…For a diagonally RC coupling beam, V ex,cb /V n,cb = 2.0 is suggested based on test results of 25 diagonally RC coupling beam specimens collected in the previous literature [10] and evaluated with tested material properties. Steel coupling beams, on the other hand, may be more rational to use the peak tensile stress instead of the yield stress to evaluate V ex,cb , considering that coupling beams are likely to experience large inelastic deformation under earthquakes.…”

“…http://dx.doi.org/10.1016/j.engstruct.2014. 10.039 0141-0296/Ó 2014 Elsevier Ltd. All rights reserved.…”

Seismic behavior of coupled shear wall structures with various concrete and steel coupling beams

“…[5] However, the arrangement of diagonal reinforcements complicates the construction process. Recently, a new concrete material, called high-performance fiber-reinforced concrete, has been used for CCB-D. [6,7] Ding et al [8] proposed a new ductile coupling beam with a slit in the middle to increase the span-to-depth-ratio, thus avoiding shear failure. Nevertheless, this coupling beam cannot provide enough stiffness and strength and also caused difficulties in construction.…”