在船舶设计与强度评估中，为更加真实地了解船体结构的安全极限，要求计算船体梁的极限强度。逐步破坏法由于其计算效率高，结果比较可靠，被广泛运用于大型海船设计，但在内河船舶设计规范中，至今尚无有关极限强度的条款。通过非线性有限元程序计算得到加筋板单元平均应力应变关系，并与 Rahman 法、CSR法以及 ISUM 方法计算得到的应力应变关系曲线进行对比，以验证其可靠性。然后，按照一定的规律建立符合内河船舶构造的加筋板单元应力应变关系数据库，并编写逐步破坏法计算程序，在计算过程中，其能根据加筋板单元尺寸自动选取对应的关系曲线；对参数超出数据库的情况，则通过插值实现。% During the modern structural design process and the subsequent strength assessment of ships, the conventional linear elastic theory is no longer appropriate in estimating the maximum working loads. In⁃stead,the progressive collapse method has been widely used for its high computational efficiency and reli⁃ability. This method,also known as the Smith Method or the incremental iterative method,is established based on the average stress-strain relationship of stiffened plate units. However,the application of the Smith Method on inland vessels has been hardly investigated. This paper employs the FEM to execute a se⁃ries of calculations of stiffened plate elements,incorporating the material nonlinearity and the initial defor⁃mation of structures due to welding. The slenderness ratio of plates and stiffeners is chosen to be the main variable,and the Istopt software is used to fit each curve with the average stress-strain relationship for in⁃land vessels so that a function database can be established. Also,this paper describes the detailed calcula⁃tion procedure of the progressive collapse method and discusses the particular technique of variable interpo⁃lation.
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