圆钢管混凝土轴心受压构件稳定性直接设计法

Direct design method for concrete filled steel tube column

现行钢管混凝土设计规范所提供的稳定性设计计算公式,在一个方程中有截面面积和稳定系数这两个未知数。在设计过程中,传统的方法是采用迭代法求解该方程以获得截面面积设计值。通过引入材料力学中一个表示截面面积的公式,与规范中的稳定性设计计算公式组成一组方程组,通过求解方程组得到构件合理长细比和一个无量纲参数П的函数关系,这个无量纲参数П取决于截面特征参数β和一般设计已知量(包括材料强度、含钢率、轴压力设计值等)。给出了圆形截面的截面特征表达式。在设计截面时,首先通过设计已知量和截面特征参数直接得到构件的合理长细比λ,然后通过该长细比计算截面的主要尺寸。最后通过一个算例说明,该直接设计法计算结果可靠,较传统迭代法更简便,是稳定性设计的一种实用算法。

In the current design code for concrete filled steel tubular members,the stability design formula for CFST columns subjected to longitudinal force comprises two unknown parameters,which are cross-section area of the column and stability coefficient.The equation with two unknowns is solved using traditional iterative method.In this paper,the cross-section area formula from material mechanics was introduced,which coupled with the stability design formula for CFST columns in the current design code.The two simultaneous equations with two unknowns were solved,the functional relation with slenderness ratio and nondimensional parameter Π,which is determined by the characteristic parameter β of the columns cross-section and general design parameters such as material strength,steel ratio and axial compressive force etc.,can be obtained.The characteristic expression for circular cross-section is given here.In the design process for the cross section of concrete filled steel tubular columns,the rational slenderness ratio should be determined from characteristic parameter β and known design parameters at first,then the general dimensions of cross section can be derived from it.A calculating example given here indicates that the given method is reliable,and it is simpler than the traditional iterative method.Therefore,it is a practical calculation method for stability design.