Experimental Studies of Membrane Shear Transfer

The transfer of shear in cracked concrete by the mechanism of surface roughness interlock (aggregate interlock) is examined by tests in 16 large concrete specimens. The blocks were designed to simulate segments of the wall of a nuclear containment vessel carrying seismic membrane shear. Each specimen is precracked and the two halves are separated by a given crack width (0.762 mm) and held in position with four external restraint rods. Cyclic, reversing shear stress is applied for 25 to 55 cycles. For specimens with 240 sq in. (1,550 cm²) of shearing area, with a preset crack width of 0.030-in. (0.762 mm), and made with ASTM No. 467 aggregate, the amount of shear plane slip after 25 cycles of shear loading of ±τ is δ x 10⁻⁴ in./psi (7.36τ x 10⁻⁴ cm/N/cm² for 1.375-in. (3.50 cm) restraint rods (for τ±160 psi (110 N/cm²)), and δ=3.2τ x 10⁻⁴ in./psi (11.8 FGt x 10⁻⁴ cm/N/cm²) for 1-in. (2.54 cm) rods (for τ±120 psi (83 N/cm²)).