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设计箱形截面梁时可采用四个参变量:梁高h、腹板厚度t及两个系数α和β,根据强度条件、局部稳定条件及刚度条件得出一个求截面积最小的目标函数A,将已知条件(截荷、材料、跨度、支承情况等)代入进行求导即可最终求出四个参变量,截面尺寸即可确定,且其截面积必为最小.然后将截面尺寸园整,布置加劲肋,最后进行截面各方面的总校核,必要时对截面尺寸作些修正,设计即告完成.这种设计法从理论上保证了截面尺寸为最小;即使经过修正,尺寸也必然接近最小.而且设计是一次完成,避免了通常凑截面反复计算的繁琐性和盲目性.
Four parameters can be used to design the box beam: the beam height h, the web thickness t and the two coefficients α and β. According to the strength conditions, the local stability conditions and the stiffness conditions, a minimum objective function A , The known conditions (load, material, span, bearing conditions, etc.) into the derivation can be derived finally four parameters, the cross-sectional size can be determined, and its cross-sectional area will be the minimum. The entire layout of the stiffener, the final cross-section of the total checks of all aspects, if necessary, make some changes to the cross-sectional dimensions, the design will be completed.This design method in theory to ensure that the cross-sectional size is the smallest; even after the amendment, the size Must be close to the minimum, and the design is done in one pass, avoiding the tediousness and blindness of the usual iterative calculations of sectioning.