Pre-stressed steel-concrete composite beams are widely used in bridges around the world. Loads during the service life of bridges may cause failure in the form of fracture in the studs near the ends of the bridge girders. The effect of stud failure on the residual static capacity and residual fatigue life of composite girders is not well investigated. Therefore, this study presents numerical investigations into the effects of the progressive failure of stud shear connectors on the residual static performance and remaining fatigue life of post-tensioned steel-concrete composite beams. The Finite Element (FE) model was validated using existing experimental work. Moreover, the effects of the progressive failure of stud shear connectors on the steel-concrete interface slippage, shear stress range, and compressive and tensile strains were investigated. The behavior of the composite girders in terms of the estimated fatigue life and residual capacity was inversely affected by the number of fractured studs. The AASHTO theoretical equation conservatively estimated the remaining fatigue life until 15% of the rows were removed and then the FE model predicted fewer remaining fatigue cycles than the theoretical equation. Until 15% of the rows were removed, the strengthened sample had a better response in terms of the stress range, tensile and compressive strains, and residual capacity. After that, both the strengthened and non-strengthened samples exhibited similar responses to the failure of studs. Subsequently, the positive effects of the post-tensioning vanish as the end studs fail. Therefore, designers should pay special attention to the ends of post-tensioned composite beams where the local failure of studs is expected.
Steel-concrete composite (SCC) bridge superstructures are widely used today extensively in highway bridges. Post-tensioning (PT) has been commonly used in this type of structure as a repairing or strengthening technique. As bridges are typically subjected to cyclic loading, understanding their performance under fatigue is vital. In this paper, two specimens were tested to study the performance of SCC beams with external post-tensioning under the effect of fatigue loading. Because the external PT is mostly added to existing bridges as a retrofitting technique, one of the specimens has undergone some damage prior to experiencing fatigue loading. The strains in the shear connectors as well as the midspan deflections were monitored during the fatigue tests. The results show that as the number of fatigue cycles increases, both the deflection and strain in the shear connectors also increase. The pre-existing damage decreased the effectiveness of the PT to enhance the fatigue behavior of the SCC beam. For the pre-damaged specimen, the increase in the shear connector strain and the midspan deflection was 4.5 and 1.4 times those for the undamaged specimen, respectively.
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