Experimental and Numerical Investigation on the Anchorage Zone of Prestressed UHPC Box-Girder Bridge

Abstract

The structural behavior of the anchorage zone is a key issue in prestressed ultra-high performance concrete (UHPC) box-girder bridges. This study investigates the mechanical behavior of a diaphragm–blister integrated anchorage system (DBIAS) used in UHPC box-girder bridges through the full-scale model test. Parametric analyses were also conducted using test-validated finite-element models. Experimental results show that no visible cracks have emerged when the applied load reaches 4,700 kN, which is 1.36 times the design value. Although the strain in some local areas has entered into the tensile strain-hardening domain of UHPC under the prestressing force, the whole structure still works well. The contribution of strain-hardening behavior of UHPC to the loading capacity of anchorage blister is 8.7%, based on nonlinear finite-element analysis. Therefore, the tensile strain capacity of UHPC may be taken into consideration in the design so as to fully make use of the material strength. Compared with the conventional independent blister anchorage system, the local effects on the anchorage zone are significantly reduced by setting anchorage diaphragms and transverse ribs in a DBIAS. The increase in the width and longitudinal spacing of adjacent diaphragms shows effectiveness in relieving the stress concentration in the anchorage zone. However, local effects will not be continuously reduced when the width of the diaphragm is more than six times that of the anchorage blister or the spacing between the diaphragm and the transverse rib exceeds a certain distance (2 m in the present study case).