RESEARCH AND DEVELOPMENT OF THREE NONLINEAR BEAM-COLUMN ELEMENTS

Since the elastoplastic damages occur in concrete structures and components in plastic stage under a severe earthquake, precise prediction of nonlinear behavior of structures in the earthquake is important to assess the seismic safety of the structures. A structural elastoplastic analysis program MEASP which bases on macro elements is compiled with object oriented language and three kinds of nonlinear beam-column elements are implemented in MESAP: stiffness-based fiber element, flexibility-based fiber element and flexibility-based plastic hinge element. Differences between the elements are compared by case study. Four kinds of integration methods for obtaining the flexibility matrix of the plastic hinge element are studied. The results show that a flexibility-based plastic hinge element is an accurate macro element with low computation cost. Only two integration points are required by the Gauss-Radau integration method handling a nonlinear analysis. It is accuracy and its computational efficiency is applicable in the entire structure nonlinear analysis and practical in engineering.