双向渐进结构优化法（BESO ）是近年来兴起的一种解决各类结构优化问题的数值方法。其原理是通过同时删除和增补单元，使剩下的结构逐渐趋于优化。(Bidirectional Evolutionary Structural Optimization (BESO) is a numerical method which has been developed in recent years to solve various structural optimization problems. Its principle is to optimize the remaining structure by deleting and adding elements at the same time.)