Shear Transfer in Cracked Reinforced Concrete Under Monotonic and Repeated Load

[摘要] This thesis presents an experimental and analytical study of the behaviour of shear transfer across cracked reinforced concrete subject to monotonic and repeated loading. The experiments used push off specimens to produce pure shear forces along a shear plane which had a total area of 45000 mm2. The experimental program consisted of two main test series which evaluated the transfer of shear forces by (a) dowel action alone, and (b) the combination of interface shear transfer and dowel action mechanisms. The average shear displacement, crack width, and reinforcement strains were measured for all load increments. The reinforcement ratios provided across the shear plane, the initial crack width, the type of transverse reinforcement, and the type of shear load were the main variables studied. Assessments were also made of (a) the relative contribution of the interface shear transfer and dowel action mechanisms to the total shear, (b) shear transfer design presented in British standard BS:8110 and American Code ACI 318-83, and (c) the representation of shear transfer in nonlinear finite element analysis of structural concrete. The research concluded that shear transfer is significantly influenced by initial crack width, reinforcement ratio and repeated load. Shear forces can be efficiently transferred across cracked surfaces by the combination of the interface shear transfer and dowel action mechanisms. The interface shear transfer mechanism sustained between 70% to 82% of the total applied shear, while the dowel action was responsible for 30% to 18% of the total shear. The shear stiffnesses of cracked reinforced concrete degrades nonlinearly when the load is first applied and depend on both lateral and shear strains. The current methods of BS:8110 and ACI 318-83 gave a too conservative shear transfer strength for design purpose in monotonic case of loading. An alternative formulation derived from the test results of this study agreed reasonably well with other available experimental data. The ultimate shear transfer under repeated load can be taken as 0.7-0.9 of the shear transfer strength under monotonic load. Also formulation derived from the test results under repeated load showed safe prediction for the other experimental results under reversed cyclic load .

[发布机构] University:University of Glasgow

[关键词] Civil engineering