In the hollow core beam bridge,the joints in the cast-in-situ parapets are likely to induce stress concentration at the intersection of the parapets and edge beams,and further trigger L-shaped cracks in the edge beams.This study investigates the effect of applying prestressing tendons to control the L-shaped cracks in the edge beams,with the Yangsi Viaduct carrying a section of the Taizhou-Jinhua Expressway as a case bridge,and proposes a method suitable for both the existing bridge retrofit and new bridge design.The finite element models of an existing bridge and a new bridge were developed in Abaqus to examine the stress amplification effect under vehicle loads.The influence of the placement depth and length of prestressing tendons on the stresses in the bottom of edge beams as well as the prestress loss induced by the cast-in-situ parapets with joints in the existing bridge were analyzed.Subsequently,a prestressing approach to control the L-shaped cracks is proposed.It is concluded that the increase of the span lengths and parapet depths lead to the rise of the stress amplification factor of edge beam,and the latter should be between 1.42 and 2.14.For the existing bridge,the lower the placement depth and the shorter the placement length,the bigger the stresses in the midspan bottom of edge beam,while similar effects would not be in the new bridge.Applied with prestress,there will be prestress loss in the existing bridge,instead of new bridge.The stress concentration effect at midspan can be effectively counteracted by applying proper amount of prestress,to avoid the occurrence of L-shaped cracks.
关键词
空心板梁桥/分缝护栏/L型裂缝/裂缝控制/应力放大系数/预应力技术/有限元法
Key words
hollow core beam bridge/cast-in-situ parapet with joint/L-shaped crack/crack control/stress amplification factor/prestress technology/finite element method
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