The shear behavior of reinforced concrete wide beams was investigated. The experimental program consisted of nine beams of 29 MPa concrete strength tested with a shear span-depth ratio equal to 3.0. One of the tested beams had no web reinforcement as a control specimen. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure.The key parameters covered in this investigation are the effect of the existence, spacing, amount and yield stress of the vertical stirrups on the shear capacity and ductility of the tested wide beams. The study shows that the contribution of web reinforcement to the shear capacity is significant and directly proportional to the amount and spacing of the shear reinforcement. The increase in the shear capacity ranged from 32% to 132% for the range of the tested beams compared with the control beam. High grade steel was more effective in the contribution of the shear strength of wide beams. Also, test results demonstrate that the shear reinforcement significantly enhances the ductility of the wide beams. In addition, shear resistances at failure recorded in this study are compared to the analytical strengths calculated according to the current Egyptian Code and the available international codes. The current study highlights the need to include the contribution of shear reinforcement in the Egyptian Code requirements for shear capacity of wide beams. 陋 2013 Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center.
Prestressed, precast hollow-core slabs are used extensively for floor and roofing systems in precast concrete construction in Saudi Arabia. Design of these precast structural units is based on ultimate load-carrying capacity of these members. Full-scale load tests were conducted on prestressed precast hollow-core slabs with different shear span to depth (a/d) ratio, which were loaded to failure to ascertain the ultimate load-carrying capacity of these slabs. A total of 15 slab specimens, 5 and 2.5 m in span and having three different depths, 200, 250 and 300 mm were tested to failure using four-point load test. It was interesting to note that the failure mode of hollow-core slabs changed from pure flexure mode to flexure-shear mode for slabs with depth greater than 200 mm. The web shear cracking strength of PPHC slabs decreased with an increase in depth of the slab. A transition from flexure-shear to web shear failure as a function of a/d was noted in the load tests. The analysis of the experimental results showed that the existing ACI code equations underestimated the flexure-shear strength of these hollow-core slabs. Based on regression analysis of experimental data, a modification is proposed in the existing ACI code equation which can capture accurately the mode of failure and ultimate load-carrying capacity of these slabs.
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