圆高强钢管UHPC梁抗弯性能研究

STUDY ON BENDING BEHAVIOR OF CIRCULAR UHPC FILLED HIGH STRENGTH STEEL TUBE BEAMS

以含钢率和套箍系数为参数,开展5根圆高强钢管超高性能混凝土(UHPC)梁和2根圆普通钢管UHPC对比梁的纯弯试验;而后,采用已验证的有限元模型,对套箍系数进行了参数分析。试验研究表明,高强钢管UHPC梁发生延性破坏,组合截面满足平截面假定,受压区高强钢管对核心UHPC的套箍作用应被考虑。较普通强度的钢管,高强钢管能更及时地约束UHPC的横向膨胀。随着套箍系数的增加,钢管混凝土梁达抗弯承载力时,中性轴趋近截面中线,受拉区钢管应力减小,受压区钢管和混凝土的应力则增大。承载力计算分析发现,对于高强钢管UHPC梁而言,现有中国规范GB50936−2014的实用计算方法存在不准确且离散性较大等问题,为此该文提出了新实用计算方法。

Taking the steel content and hoop coefficient as test parameters,the pure bending tests of 5 circular ultra-high performance concrete(UHPC)filled high strength steel tube(UFHST)beams and 2 circular UHPC filled normal strength steel tube(UFST)beams were carried out to investigate their bending behaviors.The experimental results show that UFHST beams failed in ductile.The composite section satisfied the assumption of plane cross-section.The hoop action of the high strength steel tube on UHPC should be considered in the compression zone.Compared with the normal strength steel tube,high strength steel tube can restrain the transverse expansion of UHPC more effectively.The finite element model verified by test results was used to conduct parameter analysis of the hoop coefficient.When the concrete-filled steel tube beam reaches its bending bearing capacity,the corresponding neutral axis and the stresses of steel and concrete are related to the hoop coefficient.With the increase of the hoop coefficient,the neutral axis keeps moving toward the section centerline;there is a decrease in the steel stress in the tensile zone,and an increase in the steel stress and concrete stress in the compressive zone.It was inaccurate and discrete to use Chinese code GB50936−2014 for predicting the bending bearing capacity of UFHST beams.Consequently,a new calculation method was proposed.