This paper presents a novel configuration of high strength U-shaped steel-encased concrete composite beam (HUCB) in which shear studs connect concrete and U-shaped steel at top flanges and bottom plate. The junction surface of upper slab and lower portion is strengthened by evenly distributed inserted circular rebar. Two steel reinforcements are arranged in the composite beam along the longitudinal direction to reduce the deformation of encased concrete and provide adequate bending capacity under fire condition. Based on the flexural experiments of five specimens, the test failure pattern, load-deflection relation curves, sectional strain distribution at different height and ultimate flexural performance of the HUCB were obtained and are reported in this research. The experimental results show that the HUCB has high ductility and excellent flexural performance. According to test results of five specimens, new calculation formulae were presented to theoretically analyze the flexural capacity of the HUCB. The theoretical analysis values of flexural capacity according to the proposed calculation formulae are consistent with the test results of all specimens. A three-dimensional finite element model is also established to investigate structural performance of the proposed novel composite beam. Test results of five specimens verify the accuracy and validity of finite element analysis results. Parametric studies of the HUCB under positive bending moment are carried out to further analyse the influence of concrete compressive strength, yield strength of U-shaped steel plate and flange width of concrete slab on the flexural performance of the proposed new composite beam.

本文提出了一种新型的高强度U型钢包裹混凝土复合梁（HUCB）的配置，其中抗剪栓钉在顶部法兰和底板处连接混凝土和U型钢。上部平板和下部的接合面通过均匀分布的插入圆形钢筋得到加强。在组合梁中沿纵向方向布置了两个钢筋，以减少包裹混凝土的变形并在火灾条件下提供足够的弯曲能力。在五个试样的弯曲试验的基础上，获得了HUCB的试验失效模式，载荷-挠度关系曲线，不同高度的截面应变分布以及极限弯曲性能，并进行了报道。实验结果表明，HUCB具有较高的延展性和优异的抗弯性能。根据5个试件的试验结果，提出了新的计算公式，从理论上分析了HUCB的抗弯承载力。根据提出的计算公式得出的抗弯承载力的理论分析值与所有试样的测试结果一致。还建立了三维有限元模型，以研究所提出的新型复合梁的结构性能。五个样本的测试结果验证了有限元分析结果的准确性和有效性。为了进一步分析混凝土抗压强度的影响，对正弯矩下的HUCB进行了参数研究，