The stiffness matrix is kept constant in all incremental loadings and each iteration.Only force vector is changed.So, the efficiency of computing is approved dramatically.

• 由于采用了常刚度法，则在所有荷载增量与每次迭代中刚度阵均不变动，只需改变右端荷载向量即可，因而显著地提高了计算效率。