Overlap of Splitting in Slabs with Closely Spaced Intermediate Anchorages

Slab splitting, resulting from the dispersion of a number of intermediate loads arranged in a line, is a common problem in such engineering structures as steel–concrete composite girders and pylon anchorages of cable-stayed bridges. Previous studies on intermediate anchorages have two major limitations: improper adoption of results obtained from studies on end anchorages and neglecting to account for the beneficial effect from lateral stress overlapping. Through load path modeling, finite-element modeling, and experimental testing, this study provides new insight into this common problem. For the single-load case, a load path model is established to capture the flow of forces in the intermediate anchorage zone, from which an explicit equation for the distribution of transverse stresses is derived. For the multiple-load case, an analytical method is proposed to evaluate the splitting effects in slabs with different load spacings. The analytical method is applied to predict slab splitting in prefabricated composite beams. Four prefabricated composite box girders with different spacings of stud clusters were tested and used to verify the proposed analytical method. Furthermore, the analytical method was applied to predict the splitting effect in pylon anchorages of cable-stayed bridges, and the results compared with results of finite-element analysis using shell elements. It is found that the splitting force equation for the end anchorage zone would significantly overestimate the splitting effect in slabs with closely spaced intermediate loads. In composite girders with precast concrete deck, only the front halves of transverse rebars in intervals between shear pockets are effective to protect the slab from longitudinal splitting failure.