Shear Strength of Joints in Precast Concrete Segmental Bridges

摘要

The behavior of precast concrete segmental box girder bridges at both serviceability and ultimate strength conditions is dependent on the behavior of the joints between the segments. To accurately predict the bridge response throughout the complete range of loading, knowledge of joint behavior is essential. In this study, a series of full-scale joints, flat and keyed, dry and epoxied, single-keyed and multiple-keyed, have been tested under different confining stress levels and epoxy thicknesses. The shear behavior, shear capacity, and shear transfer mechanisms of these different kinds of joints have been studied. It was determined that the shear capacity of joints increased as confining pressure increased, and epoxied joints had consistently higher shear strength than dry joints; however, the failure was more brittle than dry joints. The average shear strength for a key in multiple-keyed dry joints was always found to be less than those in single-keyed dry joints due to imperfections in fitting of keys. The shear strength of keys in multiple-keyed epoxied joints, however, was similar to those in single-keyed joints, indicating epoxy mitigated the fixing imperfections and permitted the shear load to be uniformly distributed. The experimental results obtained in these tests were compared with the MSHTO and other design criterion. It was seen that these relationships tended to underestimate the shear strength of single-keyed joints and multiple-keyed epoxied joints by a value up to 40%, but they always greatly overestimated the shear capacity of dry multiple-keyed joints. Hence, the results indicate that some strength reduction factors should be introduced to the design relationships when applied to multiple-keyed dry joints.