A new-type prestressed composite girder bridge

Abstract

There has been a strong demand on more economic and lower depth girder bridges for short and medium span range in Korea. A new type steel-concrete composite girder has been developed to realize a more economic bridge system with a lower depth girder. In the girder bridge, a steel plate girder is simply supported and then concrete form is hung to the girder. Thus, the self-weight of the concrete is loaded to the steel girder. To increase the resistance of concrete in the lower casing against tensile stress, compressive force is introduced by prestressing tendons without preflexion processes as the main processes for PREFLEX girders. Conventional prestressed concrete girders cannot be transported to a separate worksite from where they are cast due to the concrete's self weight unless they are prestressed. However, the new method in this paper enables easier transport and piling since the concrete in the lower casing is maintained in a non-stress state. Likewise, losses of compressive stress in the lower casing concrete due to its long-term behavior can be minimized, since prestressing work is carried out immediately before placing the girders on the piers. To evaluate the manufacturability and performances of the completed bridge, three 15-m girders and a bridge specimen with two 20-m girders were constructed. The camber during the construction and introduction of an appropriate compressive force was evaluated. Static loading test was also conducted to examine cracking and to evaluate the decrease in stiffness and failure behavior under extreme conditions. © 2007 Taylor & Francis Group.