Numerical study on the creep behaviour of Fiber-Reinforced Polymer sandwich structures considering traffic loading

Abstract

Ageing of infrastructure leads to an increasing demand for new technologies and design solutions in current bridge engineering. Over the last decades the traffic intensity has grown tremendously, while design codes and regulations have become stricter. Many current steel bridges realised in The Netherlands suffer from fatigue problems. Replacement of the bridges can be expensive, and thus engineers are asked to provide design solutions that can extend the lifetime of these structures. Rehabilitation through the replacement of steel orthotropic decks with Glass Fiber-Reinforced Polymer (GFRP) sandwich deck panels is considered as one of the few possible solution strategies. FRP's are considered a viable option, due to their versatility, high strength-to-weight ratio, fast installation possibilities, low maintenance costs and their resistance against both corrosion and fatigue. The increasing amount of bridges containing FRP structural elements demonstrates the high potential of the material. However, many engineering consultancies address to face difficult challenges when working with FRP. The main concern in the construction and design field is about the long-term performance of the material. Due to the viscoelastic nature of the polymeric matrix, FRP structural elements show complex creep and recovery behaviour under variable traffic loading. Current standards account for this traffic load by conservatively assuming that 40% of this traffic load should be accounted for in creep calculations, which originates from experience with concrete bridges. However, due to the fast recovery behaviour of FRP compared to concrete, this value might be too conservative. Based on current knowledge and experimental results, a numerical model was created that is able to predict the long-term creep deformation including both creep and recovery behaviour. The model uses experimental results based on UD-plies, which enables the model to calculate the long-term deformation of laminates with a wide variety of layups. The Finite Element Analysis (FEA) software package Abaqus has been used to model a FRP sandwich deck panel and calculate the time-dependent response under traffic loading. Finally, a FRP sandwich deck panel has been analysed by both the numerical model and according to the procedure prescribed by current standards. Results have shown that the amount of traffic load that is currently considered as permanent static load for creep calculations could be reduced. However, it is recommended for future research to improve the numerical model by using more accurate creep prediction models supported with profound experimental work. It is expected that this would lead to an even higher reduction of the amount of traffic load that is currently considered in design recommendations.