The innovative precast composite beam consisted of reinforced UHPC beam and inner inverted T-steel shape (forming ITSRU composite beam) is proposed for the marine structures serviced in harsh environment and subjected to complicated loading conditions. The novel composite beam possesses the advantages of lightweight, high strength and ductility, enhanced durability. To study the shear behaviors of ITSRU beams, a shear test program consisted of seven composite beams were conducted to study the effects of shear span-to-depth ratio, steel fiber volume fraction, stirrup ratio and inverted T-steel web thickness. UHPC used in this paper possess compressive strength more than 125 MPa, ultimate tensile strength more than 8.9 MPa and ultimate tensile strain more than 2256με. The inverted T-steel and steel rebar used in this paper have grades of Q355 and HRB400, respectively. A segmented loading control method was used in the shear test, in which a forced-controlled with a rate of 20 kN/min was used before the beam yield and the displacement control was implemented at a rate of 0.5 mm/min after reaching the yield load. The test results revealed that the ITSRU beams exhibited admirable deformation capacity and considerable residual shear capacity even for the composite beam with shear span-to-depth ratio of 1.0. The increasing of stirrup ratio, steel fiber volume fraction and inverted T-steel web thickness could improve the shear resistance and the ductility as well as suppress the appearance of the diagonal shear critical cracks. Based on the test results, an analytical shear model considering the contributions of UHPC in shear compression region, stirrups, steel fibers and inverted steel web was developed to predicted the shear resistance of ITSRU beams. The interaction mechanism of the different components in the ITSRU beams was considered in the analytical shear model. The accuracy of the developed calculation method was verified by the test results.

中文翻译：

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倒T型钢加固新型预制UHPC组合梁剪切性能的实验与理论研究


针对环境恶劣、荷载条件复杂的海洋结构物，提出了由增强UHPC梁和内倒T型钢形状（形成ITSRU组合梁）组成的创新型预制组合梁。新型组合梁具有轻质、高强、高延性、增强耐久性等优点。为了研究ITSRU梁的剪切性能，进行了由七个组合梁组成的剪切试验程序，以研究剪切跨高比、钢纤维体积分数、箍筋比和倒T型钢腹板厚度的影响。本文使用的UHPC的抗压强度大于125 MPa，极限拉伸强度大于8.9 MPa，极限拉伸应变大于2256με。本文使用的倒T型钢和钢筋的牌号分别为Q355和HRB400。剪切试验采用分段加载控制方法，梁屈服前采用20 kN/min的力控制，屈服后采用0.5 mm/min的位移控制。加载。试验结果表明，即使是剪跨高比为1.0的组合梁，ITSRU梁也表现出令人赞叹的变形能力和相当大的残余剪力能力。提高箍筋比、钢纤维体积分数和倒T型钢腹板厚度可以提高抗剪性能和延性，抑制斜剪临界裂纹的出现。根据试验结果，建立了考虑UHPC在剪切压缩区域、箍筋、钢纤维和倒置钢腹板中的贡献的分析剪切模型，以预测ITSRU梁的抗剪强度。 解析剪切模型考虑了 ITSRU 梁中不同组件的相互作用机制。试验结果验证了所开发计算方法的准确性。