STRENGTH ESTIMATION OF SLENDER STEEL CONCRETE COMPOSITE COLUMNS

1.提出了无支撑对称框架柱计算长度系数的计算公式。利用能量法得到了柱的计算长度公式，并对公式进行了修正，以补偿不安全的估算。计算结果表明，用该公式计算的有效长度与正确值吻合较好.采用两种不同的方法计算了不同截面形式的钢-混凝土组合柱的屈曲荷载。一种是采用切线模量理论，将钢筋部分和混凝土部分视为一体;第二种是强度叠加法，将钢柱和混凝土柱分别计算的屈曲荷载之和作为屈曲荷载。通过两种强度的对比，验证了强度叠加的准确性，并在此基础上提出了钢-混凝土组合柱屈曲承载力的简化设计方法。3.进行了方钢管混凝土柱的轴心受压和双向偏压试验。选取屈曲长深比、偏心量和偏心荷载角作为试验参数。检查强度和行为。研究结果表明：本文提出的单轴偏心受压柱的强度公式能够预测双向偏心受压柱的最大承载力。

1. A formula for evaluating an effective length factor of column in unbrased symmetrical frame is proposed. An equation for an effective length of column is obtained by using the energy method, and it is modified to compensate for unsafe estimation. It is shown that the effective length obtained by proposed formula agrees well with the correct value.2. Buckling load of steel concrete composite columns with various steel sections is calculated in two different ways. One is performed using the tangent modulus theory, considering steel portion and concrete portion behave as a one body. The second one is the method of superposed strength in which a simple sum of separately computed buckling load of steel and concrete columns is regarded as a buckling load. By comparing with two strengths, accuracy of superposed strengths are examined, and simple design method for evaluating the buckling strength for steel concrete composite columns is proposed on the superposed strength method.3.Concrete filled square steel tubular columns were tested under concentric and biaxially eccentric load. As the experimental parameters, the buckling length-section depth ratio, magnitude of eccentricity and angle of eccentric load are selected. Strength and behavior are examined. It is the conclusion that : the maximum strength of columns under biaxially eccentric load are able to predict by the previously proposed strength formula of columns under uniaxially eccentric load.