Research on the external prestressing steering devices of steel inner core‐ultra high performance concrete composite box girder

Abstract The steel inner core‐ultra high performance concrete (UHPC) composite box girder is characterized by thin plates and lightweight. For engineering applications, it is recommended to use the external prestressing system in combination. Therefore, an external prestressing steering and anchorage design scheme was proposed in this paper. In the scheme, holes were pre‐drilled in the steel core, allowing the anchored steel web with steel tenons at the ends to pass through the holes and embed into the UHPC. Then, the steel diaphragms were used to assist in load‐bearing. The global calculations were conducted for the background engineering, clarifying the value of steering forces generated by the external prestressing. To investigate the anchorage performance at the connection between the steering device and main girder, three sets of static pull‐out tests were designed. The results indicated that all specimens failed by pull‐out. The addition of steel diaphragms can significantly improve the ultimate bearing capacity and pull‐out stiffness. Compared with headed stud connectors, using steel tenon connectors can better limit the initial interface separation displacement. For Scheme C, under the action of the designed steering force, the maximum separation displacement does not exceed 0.20 mm. It can meet the force requirements under the normal service limit states. The study provides engineering reference for the design of external prestressing steering devices.