带开孔板连接件的HSS-UHPC组合梁抗弯性能

为探究高强钢(HSS)-超高性能混凝土(UHPC)组合梁的抗弯性能，考虑剪力连接度影响，设计并完成3片设置开孔板连接件的HSS-UHPC组合梁跨中两点对称加载试验；对剪力连接度分别为1.02、0.89和0.76的HSS-UHPC组合梁抗弯刚度、挠度、界面滑移、应变分布规律及钢梁与UHPC板的整体工作性能等进行分析，探讨了该型结构的受弯破坏机理；通过建立HSS-UHPC组合梁的ABAQUS非线性有限元计算模型，分析了混凝土强度、翼板厚度、钢材强度三者间的匹配关系，评估了现有简化塑性理论对该型组合梁抗弯计算的适用性。研究结果表明:设置开孔板连接件的HSS-UHPC组合梁具有较高的抗弯承载能力和良好的塑性变形能力，其抗弯刚度和延性均能满足工程使用要求；UHPC板与HSS梁在弹性受力阶段的界面滑移发展缓慢，最大滑移出现在1/8梁长附近；进入塑性受力阶段，界面滑移迅速增大，且最大滑移断面逐渐外移至梁端；剪力连接度对HSS-UHPC组合梁的抗弯性能影响显著，连接度由1.02分别减小至0.89和0.76时，结构的早期抗弯刚度分别降低了7.0%和8.7%，极限承载力也分别减小了9.2%和14.6%，界面最大滑移则分别增大了15.8%和17.0%；对比试验研究、数值模拟和理论计算结果三者吻合良好，数值结果显示采用Q690取代Q460的组合梁抗弯承载力提高了29.0%，但延性下降了39.7%；提高UHPC强度和增大混凝土翼板厚度均能显著改善HSS-UHPC组合梁延性并增强其抗弯承载力。 

Flexural performance of HSS-UHPC composite beams with perfobond strip connectors

Considering the influence of different shear connection degrees, the mid-span two-point symmetrical loading tests for three pieces of high strength steel (HSS)-ultra-high performance concrete (UHPC) composite beams using perfobond strip (PBL) connectors were conducted to evaluate the flexural performance of HSS-UHPC composite beams. The properties including flexural rigidity, deflection, interfacial slip, and strain distribution laws of HSS-UHPC composite beams were analyzed under the shear connection degree of 1.02, 0.89, and 0.76, and the overall performance of steel beams and UHPC plates was discussed. In addition, the failure mechanisms of the beams subjected to bending moments were analyzed. On the basis of the ABAQUS nonlinear finite element numerical models for the HSS-UHPC composite beams, the matching relationships among concrete strength, plate thickness, and steel strength were investigated, and the feasibility of existing simplified plasticity theory in calculating the flexural performance of the HSS-UHPC composite beams was evaluated. Research results indicate that the HSS-UHPC composite beams using PBL connectors have the favorable flexural capacity and large plastic deformability, and their flexural rigidity and ductility are qualified for engineering applications. For the composite beams in the elastic stage, the relative interfacial slip between UHPC and HSS develops slowly, and the maximum slip occurs near the 1/8 of the beam. In the plastic stage, the interfacial slip rises rapidly, and the maximum slip section gradually moves to the beam ends. The flexural performance of HSS-UHPC composite beams is significantly affected by the shear connection degree. When the connection degree decrease from 1.02 to 0.89 and 0.76, the initial flexural rigidity of the composite beams lowers by 7.0% and 8.7%, respectively, and the corresponding ultimate bearing capacity decreases 9.2% and 14.6%, but the maximum slip grows by 15.8% and 17.0%, respectively. Good agreement is found among the numerical, experimental, and theoretical results. Numerical result demonstrates that after the replacement of Q460 steel with Q690 steel for the composite beams, the flexural capacity sees an increase of 29.0%, but the ductility decreases by 39.7%. The ductility and flexural capacity of the HSS-UHPC composite beams can be improved by higher UHPC strength and thicker concrete plates.