负载下外包钢筋混凝土加固轴压钢柱的承载性能研究

发布时间：2019-05-23 23:08

【摘要】：外包钢筋混凝土加固钢柱近年来得到越来越广泛的应用。这种加固方式解决了钢结构的防火、防腐问题,提高了纯钢柱的整体、局部稳定性,但我国钢结构加固规范并没有给出这种加固方式的计算方法和构造要求(打栓钉、加强柱脚)。世界各国(地区)规范中型钢混凝土正截面承载力的计算模式主要有四种：基于数值计算结果的经验公式、将型钢视为等效的钢筋,按照混凝土柱的承载力计算模式计算、将混凝土转化为等效型钢,按照纯钢柱的承载力计算模式计算以及采用强度叠加理论的型钢混凝土柱计算方法。强度叠加理论简单,安全,并且符合我国设计人员的习惯。比较了各国(各地区)规范中型钢保护层厚度、钢筋保护层厚度、型钢和钢筋间距、型钢含钢率、纵筋直径、间距、配筋率,箍筋直径、加密区间距、配筋率,翼缘宽厚比、腹板高厚比等构造要求,为我国新钢结构加固规范提供建议。开展轴心压力下的外包混凝土加固钢柱的试验研究,根据试验数据,分析了叠合柱截面的应力分布,以及叠合柱的传力方式。后浇混凝土与内部型钢共同工作机理研究,加固形成的型钢混凝土叠合柱是二次受力结构,加固前原结构未卸载的荷载为第一次受力；后浇钢筋混凝土在加固后并未立即产生应力重分布,而是共同分担第二次受力新增的荷载。第二次受力过程中,后浇钢筋混凝土中的应变滞后于原来钢柱的应变,钢柱的累计应变始终高于后浇钢筋混凝土部分的应变。钢柱达到极限状态时,后浇钢筋混凝土部分的应变还很低,材料强度没有得到充分发挥,应予以折减。叠合柱中原钢柱和后浇混凝土能否共同工作,取决于接触面的构造处理和施工做法,如加焊栓钉。运用Abaqus对加固后叠合柱进行模拟分析,混凝土材料采用塑性损伤本构,钢筋选择等向强化本构,钢筋内置区域植入混凝土之中,原钢柱与混凝土之间的粘结滑移采用型钢混凝土粘结滑移公式,为了准确模拟组合板的二阶段制造和二次受力,引入了生死单元。初应力使得外包钢筋混凝土加固的钢柱荷载-变形位移曲线后移,轴力集中于钢骨,初应力系数和型钢材料强度对其承载力折减影响显著。建立基于叠加原理的外包钢筋混凝土加固钢柱的承载力计算公式以及折减系数,与试验值吻合较好。
[Abstract]:Steel columns strengthened with reinforced concrete have been more and more widely used in recent years. This reinforcement method solves the problem of fire prevention and anticorrosion of steel structure, and improves the overall and local stability of pure steel column. However, the calculation method and structural requirements of this reinforcement method are not given in the reinforcement code of steel structure in our country. Strengthen the foot of the column). There are four main calculation modes of normal section bearing capacity of medium-sized steel concrete in codes all over the world: based on the empirical formula of numerical calculation results, section steel is regarded as equivalent steel bar, and the bearing capacity of concrete columns is calculated according to the calculation model of bearing capacity of concrete columns. The concrete is transformed into equivalent section steel, and the bearing capacity of pure steel column is calculated according to the calculation mode of bearing capacity of pure steel column and the calculation method of steel reinforced concrete column based on strength superposition theory. The theory of strength superposition is simple, safe and in line with the habits of designers in our country. The thickness of medium steel protective layer, the thickness of steel bar protective layer, the spacing between section steel and steel bar, the steel content, longitudinal bar diameter, spacing, reinforcement ratio, hoop diameter, reinforcement area spacing, reinforcement ratio and flange width to thickness ratio are compared in different countries (regions). The structural requirements such as web height to thickness ratio provide suggestions for the reinforcement code of new steel structures in China. The experimental study on steel columns strengthened with external concrete under axial pressure is carried out. according to the test data, the stress distribution of the section of the composite columns and the force transfer mode of the composite columns are analyzed. The working mechanism of post-pouring concrete and internal section steel is studied. The steel reinforced concrete composite columns formed by reinforcement are secondary stress structures, and the ununloaded load of the original structure before reinforcement is the first load. The stress redistribution of post-pouring reinforced concrete does not occur immediately after reinforcement, but the additional load added to the second force is shared. In the second stress process, the strain in the post-cast reinforced concrete lags behind that of the original steel column, and the cumulative strain of the steel column is always higher than that of the post-cast reinforced concrete part. When the steel column reaches the limit state, the strain of the post-cast reinforced concrete part is still very low, and the material strength has not been brought into full play, so it should be reduced. Whether the original steel column and post-pouring concrete can work together in the superimposed column depends on the structural treatment and construction method of the contact surface, such as adding welding bolt nail. Abaqus is used to simulate and analyze the superimposed columns after reinforcement. The plastic damage constitution is adopted in the concrete material, the isotropic strengthening constitution is selected for the steel bar, and the built-in area of the steel bar is embedded in the concrete. The bond slip between the original steel column and concrete adopts the bond slip formula of section steel concrete. In order to accurately simulate the two-stage manufacture and secondary force of the composite slab, the life and death element is introduced. The initial stress makes the load-deformation displacement curve of the steel column strengthened with reinforced concrete move back, and the axial force is concentrated on the steel bone. The initial stress coefficient and the strength of the section steel material have a significant effect on the reduction of the bearing capacity of the steel column. The calculation formula and reduction coefficient of bearing capacity of steel columns strengthened with reinforced concrete based on superposition principle are established, which are in good agreement with the experimental values.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU391

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