Shear behavior of anchor blocks in externally prestressed concrete bridges

Abstract

In externally prestressed concrete bridge structures, the prestressed tendons are connected with prestressed concrete bridges by anchors and deviators, which are prone to be destroyed by the extremely complex stress concentration, resulting in prestress loss. Therefore, reasonable and safe design of anchors and deviators is very important for externally prestressed concrete bridges. In this paper, six inverted T-shaped specimens that represent the anchor blocks are tested to evaluate the effect of shear span–depth ratio and longitudinal reinforcement ratio on the shear behaviour of anchor blocks. The crack patterns, relative displacement, strain of steel and concrete, ultimate loads and failure modes are investigated. The experimental ultimate loads are compared with the calculated results from two design methods. Results indicate that the shear-friction model of AASHTO LRFD can predict the ultimate load very well when the shear span–depth ratio is less than 0·5. Meanwhile, in predicting the yielding load of the ties, the strut-and-tie model of ACI shows agreement with tested values at relatively large shear span–depth ratio of 0·57 and 0·93.