NSM CFRP Strengthening and Failure Loading of a Posttensioned Concrete Bridge

Abstract

Two carbon-fiber-reinforced polymer (CFRP) systems developed as possible means to strengthen existing concrete structures have been applied to a bridge at Kiruna (Sweden). The bridge was no longer in service and was thus used in extensive tests to failure. It was a posttensioned five-span bridge consisting of three longitudinal main girders topped with a concrete slab. The program reported here consisted of a series of three tests of the girders in the second span: loading each girder up to 2.0 MN before strengthening, loading each girder up to 2.0 MN after strengthening, and loading to failure after strengthening. One of the girders was strengthened by installing three 10×10 mm2 near-surface mounted (NSM) CFRP bars on the soffits, and another by installing three prestressed 1.4×80 mm2 CFRP laminates. This paper focuses on the NSM-strengthened girder, which failed at a maximum load of 6.1 MN, with a corresponding midspan deflection of 159 mm. The failure was a combination of flexure and shear, and the strain in the NSM bars at the ULS was 1.2%.