The stringent requirements on dimensions, ductility, energy absorption, strength and stiffness of coupling beams have resulted in much research on various alternative coupling beam designs, which include the use of diagonal reinforcement, rhombic arrangement of main bars and steel composites. Experimental results showed that each of these designs offered better performance than the conventional type but had its own limitations. A new embedded steel composite coupling beam design is therefore proposed. This paper presents the findings from the experimental tests of a coupling beam fabricated with this proposed design and a conventionally reinforced coupling beam, which serves as the reference. The preliminary test results showed that the embedded steel coupling beam with relatively large span-to-depth ratio ( l/h = 2.5) had excellent shear capacity (∼10MPa) and very good energy absorption.
The shear strength of concrete does not increase in proportion with the concrete grade. Thus, when high-strength concrete is used in place of normal-strength concrete, the shear capacity of the structure could become critical. In the study presented, the effect of concrete strength on the shear capacity of concrete beams was investigated. As previous research on normal-strength concrete beams has shown that the presence of an inflection point within the shear span can significantly influence the shear capacity, particular effort was made to study this influence in the case of high-strength concrete beams. The results indicate that, as the concrete strength increases, the shear capacity of the beam also increases, but the shear capacity is proportional to the cube-root rather than the square-root of the concrete compressive strength. It is also revealed that the presence of an inflection point can increase the shear capacity by as much as 100%, regardless of whether normal-strength or high-strength concrete is used. Finally, the test results were analysed by comparing them with the predicted strength values calculated using the formulae given in the various codes and Aoyagi's equation.
Experimental studies on the newly proposed design of plate-reinforced composite (PRC) coupling beams have been carried out. Previous results have demonstrated the useful application of this design in coupling beams of medium span-to-depth ratios (l/ h) under both inelastic seismic and elastic wind loading. This paper presents further experimental studies on five PRC coupling beams, which investigated the importance of shear connectors on plate/reinforced concrete composite action. Three medium-length (l/ h = 2.5) and two short (l/ h = 1.17) PRC coupling beams, each containing a vertically embedded steel plate, were tested under reversed cyclic loading. While one short beam was welded with expanded metal meshes on the plate surfaces, others were welded with shear studs on the plates in the wall regions and/or the beam spans. Results showed that the expanded metal meshes did not work effectively, and while the shear studs in the beam span only slightly increased the beam capacity, those in the wall regions contributed considerably in improving inelastic beam performance.
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