Study On ECC Link Slabs Of Simply Surpported Girder Bridges

To solve the problem of cracking of conventional reinforced concrete link slabs on the multi-span simply supported girder bridge joints,which causes water penetration and endangers the safety of the bridge structure,link slabs made of Engineered Cemetitious Composites(ECC)is proposed in this paper,taking full advantage of high ductility of ECC to adapt to the rotation and shrinkage of the bridge girder and solve the problem of water penetration and enhance the continuity of the deck,which is significant for engineering application.Considering the lack of systematic research on the performance and design of the ECC link slab,this paper studies the design of ECC material,the elastic mechanical analysis,the design and the finite element numerical simulation of ECC link slab.First,the material design of ECC is carried out.According to the performance requirements of bridge deck,the basic performance evaluation indexes and the corresponding test methods are determined.Based on this,the influences of main compositions of ECC on its performance are analyzed,and finally the recommended ratio of ECC compositions is proposed.And the mixing and molding process of ECC are determined.Second,the stress and deformation of the ECC link slab are analyzed by linear elastic mechanical analysis method.The calculation formula of stress and strain under the influence of vehicle load,the uneven settlement of the bridge supports,the braking force of vehicle and the shrinkage of the girder are given.Based on the conclusion of elastic mechanical analysis,finite element model of ECC link slab and the whole bridge is established by ABAQUS softwar,and then the mechanical response of ECC link slab under various load conditions are analyzed.The mechanical responses under moving wheel load and the sensitivity analysis of the slab structural parameters are analyzed as well.Finally the mechanical responses of ECC link slab when laminated rubber bearings are installed are analyzed.Then,the determination methods and reasonable value of the length,the thickness and the reinforcement ratio are put forward by theoretical analysis and reference to the existing design experience.Then the design of detail structures was discussed,and finally the design method and processes of link slabs was proposed.And two improved structures of ECC link slab are proposed,and the effectiveness of the improved structures is verified by the finite element analysis.Finally,the scale model of ECC link slab is designed to simulate the influence of negative moment.The static load test proved that the mechanical performance of ECC link slab meet the requirements.In this paper,focused on the mechanic performance and design of the ECC link slab of the simply supported girder bridge,the basic performance control indexes are put forward and the optimal ratio of ECC compositions with ultimate tensile strain of 2.1%is obtained by laboratory test.And the design method,reasonable values of design parameters and optimized structures of ECC link slab are proposed by means of theoretical and finite element analysis,which provide the theoretical basis and reference for application.