FRP Materials for Rehabilitation of Buried Pipes

Abstract

Over time, pipes tend to deteriorate due to various physical and chemical parameters. Therefore, they necessitate rehabilitation to improve the service life of structure. Bonding a fiber-reinforced polymer (FRP) liner inside the pipe, is an effective rehabilitation technique to increase the strength and stiffness of deteriorated pipes. To do so, it is very important to know the structural behavior and mechanical properties of the FRP liner under applied loads. This paper discusses the results of solid wall FRP liners with four layers of fabric, subjected to compressive transverse loading. A customized compression testing machine with string potentiometers to measure the diametrical change was set up to test the liners under parallel plate loading test method. Four specimens of glass fiber-reinforced polymer (GFRP) and two specimens of carbon fiber-reinforced polymer (CFRP) liners, having an average internal diameter of 330 mm and 336 mm respectively, were tested to find the diametrical change, stiffness factor (SF) and pipe stiffness (PS) at 5% and 10% diametrical change. Based on experimental results it was evident that, due to changing stiffness and large deformations under loading, the specimens experienced geometric non-linearity. An analytical model was developed to find diametrical deflections both in vertical and horizontal directions and their corresponding strains at springline and crown/invert to elucidate the elliptical ring deflection causing the geometric non-linearity. The model seemed to be in good agreement with the test results.