Abstract
Test specimens were circular plates of reinforced concrete 80cm in diameter. Experiment factors were: 1) shear span (l_s), 2) concrete strength (F_c), 3) depth to reinforcement (d), 4) steel ratio of shear reinforcement (P_s), 5) steel ratio in radial direction (P_r) and 6) steel ratio in circumferential direction (P_ψ). The total number of test specimens, 108, was decided by grid composition of these factors as follows. (Ref. Text fig. II-3) 2(l_s)×2(F_c)×3(d)×[2(P_s)×(P_ψ)×2(P_γ)+1(P_ψ)]=12×9=108 Loading and supporting materials were circular rings of acrylite located axially symmetricly. Test Results: (Ref. Text fig. V-3 through V-6) 1. The ultimite shear strength is in inverse proportion to log l_s/d. 2. The ultimate shear strength is further increased when shear reinforcement is properly located in position and direction. 3. The ultimate shear strength is apporoximately proportional to concrete strength. 4. The addition of radial steel reinforcing increase the ultimate shear strength only slightly. 5. The ultimate shear strength is not directly related to tho amount of circumferential steel reinforcing but increases when the bending strain in the circumferential direction at the edge of the plate is restraine by heavy circumferential steel reinforcing. This is especially true in the case of thin plate. From these, the following experimental formula has been derived: [numerical formula] in which, P_u is ultimate load γ_0 is radius of circular ring for loading. The scale effect is left as a problem to solve in the future.
