Nonlinear Finite Element Analysis of FRP-strengthened Concrete Slabs under Static and Traffic Loads

摘要

Fibre-reinforced polymers (FRP) are commonly used in reinforced concrete (RC) structures as externally bonded materials for retrofitting. A number of researches on the FRP-strengthened RC slabs have been conducted in recent years. However, investigations of overall performance and the bond-slip behaviour between FRP and concrete of FRP-strengthened RC slabs under traffic load are very limited. In this thesis, simple and efficient layered composite plate elements including bond-slip are developed so as to model the structure behaviour of FRP-strengthened RC slabs under static load effectively and accurately. A new layered composite plate element with perfect bond assumption is firstly developed for analyses of FRP-strengthened RC slabs under static load. Then based on this element, two new composite plate elements considering bond-slip effect between FRP and concrete are developed by introducing a zero-thickness bond element and debonding layer concept. Timoshenko’s composite beam functions are used to construct the new elements and by employing layered method the developed elements are presented as integrated elements with the concrete, reinforcing rebars, FRPs and adhesive modelled using the integrated elements. Both geometric and material nonlinearity have been included in these finite element models. After numerical validation, extensive parametric studies have been conducted using the new composite plate elements to study the effects of various parameters on the structural response of FRP strengthened RC slabs, such as types of FRPs and adhesive, strengthening scheme. The other focus of the thesis is the investigation of the structural behaviour of FRP-strengthened RC slabs under traffic load using commercial finite element analysis software ANSYS. The structural behaviour of the FRP-strengthened RC slabs under transient moving, fixed-point cyclic and moving-wheel cyclic loads has been studied. Nonlinear finite element models and finite element analysis procedures are developed for these investigations. For the structural performance of FRP-strengthened RC slabs under fixed-point cyclic load, both perfect bond assumption and bond-slip effect are taken into account. The structural behaviour of FRP-strengthened RC slabs under static loading, fixed-point cyclic loading and moving-wheel cyclic loading are compared. Parametric studies are carried out to investigate the influencing factors on the structure behaviour of FRP-strengthened RC slabs under cyclic load.