Experimental Study of the Post-tensioned Unbonded Prestressing UHPC Prefabricated Retaining Blocks for Highway Bridges

Abstract

Abstract The traditional sacrificial concrete shear keys are generally employed in practical bridges to restrain the excessive transverse displacements of the superstructures and protect the substructures from being seriously damaged under the earthquakes. However, the post-earthquake rehabilitations or reconstructions of the conventional concrete shear keys are difficult and inconvenient. To this end, this paper proposed and designed a novel modified post-tensioned unbonded prestressed ultra-high-performance-concrete (UHPC) prefabricated retaining block (UHPC-PRB) structure with the straight joint connection. The novel UHPC-PRB structure is composed of the prefabricated UHPC retaining block, the prestressing anchorage system, and the cast-in-situ cap beam. The prefabricated UHPC retaining block was installed to the cast-in-situ cap beam using the unbonded prestressing tendons. The proposed UHPC-PRB structure is supposed to be effective in not only providing the same functionality as the traditional concrete shear keys, but also is expected of simplifying the retrofit process and reducing the rehabilitation expense. To investigate the seismic behavior of the proposed UHPC-PRB structure, four specimens were designed and the pseudo-static tests were carried out. The damage process, displacements, strains, and stress states of specimens were studied. In addition, influences of the loading height, thickness of the UHPC retaining block, and the initial prestresses of the prestressing tendons on the seismic performance of the proposed UHPC-PRB structure were also studied. The experimental results indicated that, (i) the proposed UHPC-PRB structures had excellent lateral deformation ability and self-resetting capacity; (ii) the initial prestresses of the prestressing tendons had significant effects on the lateral displacement, critical rotational load, and horizontal bearing capacity of UHPC retaining blocks; (iii) prestress loss of the prestressing tendons had certain effect on the development of the bilinear analytical model of UHPC retaining blocks, but this effect could be ignored in practical bridges; and (iv) increasing the horizontal loading height would reduce the critical rotational load and bearing capacity of UHPC retaining blocks.