MECHANICAL BEHAVIOUR OF DAMAGED REINFORCED CONCRETE PIPES REPAIRED WITH LAYERED SANDWICH FIBER COMPOSITES

Abstract

Trenchless pipe repair can offer time and cost savings over traditional excavation and replacement of damaged pipes. Conventional repair methods using prefabricated steel liners are not effective due to significant loss of discharge capacity, especially for non-circular cross-sections. The objective of this thesis is to introduce a novel layered sandwich system composed of fiber-reinforced polymer (FRP) composites. Concrete pipes with a length of 500 mm and inner diameter of 380 mm are stressed to simulate damage; cracks at the crown, invert and springline are produced by loading via the three-edge-bearing (TEB) test setup (ASTM C497). The damaged pipes are repaired with multiple layers of FRPs sandwiching thin layers of a syntactic foam core. The sandwich system will save FRP materials and provide the required stiffness based on the mechanics of sandwich composites. The sandwich system is applied with epoxy resin to the entire length of the inner diameter of the pipes. The repaired specimens are then loaded to failure via the three-edge-bearing test. The highest load was achieved by a hybrid sandwich liner composed of Glass Fibre Reinforced Polymer (GFRP), syntactic foam, and Carbon Fibre Reinforced Polymer (CFRP). Finite Element Analysis (FEA) was performed in ABAQUS and results were compared to experimental results. The load versus strain plots of FEA and experimental results were in agreement and had an average test/model ratio of 1.00 and COV of 47.88%. A parametric study was performed in ABAQUS of a pipe model had an inner diameter of 762mm, a wall thickness of 152.4mm, and a length of 1000mm with varying layers of GFRP, Syntactic foam, and CFRP. Results from the parametric study showed that the most effective way to increase stiffness is to increase the number of GFRP and CFRP plies as the syntactic foam plies offer a marginal increase in stiffness.