STUDY ON LOCAL COMPRESSIVE PERFORMANCE FOR ANCHORAGE ZONE OF UHPC BOX-GIRDER WITH DENSELY DISTRIBUTED DIAPHRAGMS

In order to obtain the mechanical behavior and local bearing capacity of the diaphragm-anchor block integrated anchorage system (DABIAS) in a UHPC continuous box-girder with densely distributed diaphragms, the mechanical behavior analysis of the UHPC box-girder anchorage zone was carried out by a large-tonnage tension test and an non-linear finite element method, taking a newly built UHPC box-girder bridge as the engineering background. The conclusions were as follows:the local compressive cracking in a UHPC anchorage zone is controlled by the tensile stress of UHPC. The local bending effect and radial-force effect of the DABIAS are insignificant, but the bursting-force effect and diaphragm-bending effect are prominent, and it is amajor factor leading to the bearing failure of anchorage zone. When the prestressed load was stretched to 4700 kN, there is no risk of cracking for the small-sized anchor block of the DABIAS in the engineering background. Similarly, the prestressing tendon with twenty-five steel strands can meet the bearing capacity of the anchor block well. It can be widely adopted in pertinent engineering. The UHPC anchorage zone can be used in normal even when the tensile strains of UHPC enter the strain-hardening domain. Thus, in order to reduce the project cast, the strain-hardening characteristic of UHPC should be utilized in design. In addition, the calculation results of the local compressive bearing capacity of UHPC anchorage zone based on different formulas are quite different (the maximum difference reaches 40.9%), among which the results based on Kim's formula, "Technical Specification for Reactive Powder Concrete Structures" and "Technical Standards for Highway Ultra-high Performance Concrete (UHPC) Bridge (Exposure Draft)" are close to those of FEA.