多困难度几何规划法设计组合工字形钢梁

船舶构架中，在设计骨材时要考虑船体板的影响，一般考虑将板的影响看作骨材的带板，因此T型材设计按工字型梁来设计。提出了多困难度几何规划问题的线性迭代法，在困难度较大、几何规划问题在用对偶规划求解时，由于其计算式比较复杂，因而计算量也很大。通过将目标函数和约束函数都缩并成单项正定式，在降低困难度的同时也将约束正定几何规划问题换成线性规划问题，并结合MATLAB求解。此方法不仅计算量小，而且收敛也很快，并已通过设计工字型钢梁验证了此方法。

Design of Built-up Steel I-section Beam Through Geometric Programming with Degree of Multiple Difficulties

The effect of hull plate is to be taken into account in the design of frame. Hull plate is usually considered band plate of the frame, hence T-section beam can be designed as I-section beam. A linear-iterative method for solving the problem of geometric programming with degree of multiple difficulties is given. It is complex to transform geometric programming into dual programming in the case of larger degree of multiple difficulties, thus the calculation become difficult. First, using Duffin formula and a method for reducing intension, the geometric programming with degree of multiple difficulties is transformed into linear geometric programming, and the degree of difficulty can be reduced, then the problem is solved in combination with MATLAB. This calculation method is simple and the convergence is acceptable, which has been validated by the design of I-section beam.