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Master of Science in Civil Engineering (M.S.C.E.)
Year Degree Awarded
Month Degree Awarded
Roughness, Precast, Prestressed, composite, slabs, horizontal shear
The horizontal shear strength of the interface between prestressed concrete hollow core slabs and cast-in-place concrete topping slabs was evaluated through a set of 24 push-off experiments. The push-off test specimens featured segments of dry-mix and wet-mix hollow core slabs with a variety of surface treatments including machine finished, sandblasted, broom roughened, rake roughened and grouted. A cast-in-place slab was poured on top of the hollow core specimens to form a 15 inch by 15 inch interface between the two materials. Results indicate the average horizontal shear strength of the push-off specimens was 227 psi. Higher shear strength and slip capacity was observed in specimens that were broom roughened in the direction transverse to the applied shear force and in grouted dry-mix specimens. Specimens with machine finished surfaces had lower average horizontal shear strength than those with intentionally roughened surfaces, but still exceeded the shear strength of 80 psi specified in the ACI 318-08 code. A method to comparatively quantify the surface roughness of the hollow core slabs with different surface treatments was adapted from an existing ASTM standard for pavements. This standard specifies the procedure to determine mean texture depth that can be correlated to horizontal shear strength of the push-off specimens. Analytical studies were also performed to estimate the maximum horizontal shear stresses that can be expected in composite hollow core slabs under normal construction conditions. A finite element model was developed to observe the behavior of the horizontal shear failure mode for composite hollow core slabs.
Sergio F Breña