Fatigue life assessment of a tack welded high-strength wire mesh for reinforcement of precast concrete bridge girders

Abstract

The research provides experimental data and assesses the effect of tack welding on the fatigue life of a high-strength electro-welded wire reinforcement (WWR) mesh used as reinforcement of precast concrete girders for bridge construction. The experiments were performed on samples obtained from one girder dismantled when ready for service. Tack welding is a controversial construction technique that entails structural risks for the WWR meshes consisting of substantial loss of strength, local embrittlement and fatigue life shortening. Hence, fatigue tests of specimens containing two types of cruciform joints, respectively obtained by electro-welding and by tack welding, were carried out and interrupted in case of surpassing the endurance limit. The experiments were followed by tensile tests of the survival specimens in order to detect the damage effects from the tensile failure of the main mesh reinforcement. Micro fractographic analysis revealed the physical mechanisms of fatigue damage induced by tack welding. Fatigue testing and fractography showed that adequate designed and executed tack welds can bear fatigue loads higher than the fatigue resistance of WWR specified by technical codes, since the type of damage that might be generated does not affect the fatigue life nor the tensile loading capacity of the WWR.