ABSTRACT
The prestressed concrete (PC) box-girder are widely used as the main girders in the medium-span and large-span concrete bridges. However, excessive deflections and cracking in the girder, are commonly accrued in the traditional PC box-girder bridges, especially in China. The innovative UHPC box-girder structure was proposed to deal with these problems in the traditional bridges on the basis of the excellent properties of ultra high performance concrete (UHPC). In the proposed bridge structure, the vertical prestressing tendons are removed while the diaphragms are provided to strengthen the thin-walled webs. Based on these conceptual ideas, a trial design scheme of three-span continuous UHPC box-girder bridge with the main span of 400m is presented. Moreover, the UHPC slab I-beam with double cantilevers was designed to test the shear performance of the stiffened web in the UHPC box girder. In the shear test, the load-deflection curves, concrete strain profiles, cracking behavior and shear failure mode of the web are studied. Results indicates that the cracking load is increased by 30% and the development of shearing cracks could be effectively limited by arranging the dense diaphragms.
