Shear rehabilitation of G-girder bridges in Alberta using fibre reinforced polymer sheets

Abstract

Many bridges were built in Alberta after World War II with type G-girder precast concrete elements. Today, there are approximately 1500 G-girder bridges still in service all over the province. These bridges are typical short span (approximately 6 m long), simply supported, and without shear keys between girders. Structural deficiency of the G-girders, especially in shear, plus the economic constraints of the government demand that an economical and efficient method for rehabilitation of these bridges be developed. A research program at the University of Alberta, in collaboration with Alberta Transportation and Utilities and ISIS Canada, has been established to study the feasibility of using fibre reinforced polymers (FRP) to rehabilitate concrete bridge girders deficient in shear. This paper will address the structural deficiency of the G-girders and present eight full-scale test results from four G-girders removed from existing bridges. Carbon and glass FRP sheets and two repair schemes were used in the rehabilitation. Three commonly used shear strength evaluation methods, strut-and-tie model, modified compression field theory, and grid analysis, are investigated. The loads predicted by these three methods are in good agreement with the experimental results. The shear contribution of the FRP sheets at any angle can be accurately accounted for in the analysis. All three methods are found to be consistent.Key words: analysis, beams, bridges, composite materials, design, fibre reinforced polymers, rehabilitation, reinforced concrete, shear strengthening.