Stress Redistribution in Prestressed Concrete Bridges Built with Ultra-Thin Precast Girders

Abstract

The balanced lift method for bridge construction proposes to build the bridge girders in a vertical position and to rotate them into the final horizontal position with the aid of compression struts. During the construction process, when the bridge girders are rotated from the initial vertical position into the final horizontal position, it is of utmost importance for an economic application of the balanced lift method that the structural members are as light as possible. In a test beam (length = 30.02 m, height = 1.44 m, width = 0.7 m) the actual filling process with concrete was carried out. Subsequently, the longitudinal strains on the outside of the beam were monitored over a period of four years in order to investigate the creep behaviour. Due to creep, the initially high stresses in the prefabricated outer shell are gradually reduced and the in-fill concrete is subjected to axial compressive stresses.