Fatigue behaviour of concrete bridge deck slabs reinforced with glass FRP bars
El Ragaby, Amr
Bridge deck slabs are one of the most corrosion-vulnerable bridge components due to the direct exposure to de-icing chemicals and severe weathering conditions. The use of fibre-reinforced polymer (FRP) as reinforcement for bridge deck slabs is a promising solution to corrosion-related problems. Recently, glass FRP (GFRP) bars have been widely used as internal reinforcement for concrete bridge deck slabs since they are less expensive compared to the other kinds of FRPs (Carbon and Aramid). Since bridge deck slabs directly sustain repeated moving wheel loads, they are one of the most bridge elements susceptible to fatigue failure. However, the performance of FRP-reinforced concrete elements subjected to cyclic fatigue loading, which is a critical design limit for bridge decks, has not been fully explored. This research is designed to investigate, analytically and experimentally, the fatigue behaviour and fatigue life of concrete bridge deck slabs reinforced with glass FRP bars. The experimental program includes construction and testing of ten full-size deck slabs. The test parameters include reinforcement type, reinforcement ratio in the bottom and top layers, and the scheme of fatigue loading. The experimental program was carried out in two phases each with five deck slab prototypes. The first phase investigated the behaviour of deck slabs under accelerated, variable amplitude, fatigue loads till failure. The second phase investigated the behaviour of test prototypes, loaded till failure, under monotonic loading conditions preceded by a specified number of fatigue load cycles representing different life-time loadings. Phase two helped to verify the residual static capacity as well as the performance and durability of the GFRP reinforcement under service loading conditions. The analytical study was conducted in two parts. The first part included developing a new fatigue life model, P-N curve, to predict the fatigue life of such slabs. This model was extended to evaluate equivalent damage relationships between different wheel load cycles and amplitudes. It was also used to calculate the fatigue damage accumulated to a bridge deck along its service life. The second part of the analytical study included finite element modeling (FEM) to analyze and predict the behaviour of bridge decks under static and cyclic fatigue loads. The FEM was carried out using commercially available software, ANACAP. The analytical model was verified against the test results and then was used to investigate the effect of different parameters such as concrete compressive strength and wheel loads in tandem on the fatigue performance of such structural elements. Results are presented in terms of deflections, strains in concrete and GFRP bars, mode of failure and crack widths at different levels of cyclic loading. The results showed the superior fatigue performance and longer fatigue life of concrete bridge deck slabs reinforced with glass FRP composite bars. The proposed fatigue life model and equivalent damage rules are in good agreement with test results. The FEM was able to predict the behaviour of FRP-reinforced concrete bridge decks with high accuracy. Based on the performed experimental and analytical study, useful conclusions and recommendations for bridge deck slab design were provided.
- Génie – Thèses