Progressive Collapse Analysis Of Reinforced Concrete Frames Using Opensees

It has been a tendency of the earthquake engineering to conducting progressive collapse analysis of the important engineering structures under strong earthquake and establishing the corresponding appropriate method for structural design as well as control. However, the definition of the structural critical collapse, structural anti-collapse performance and collapse mechanism evaluation methods in the current seismic design code can not meet the requirements for the development of performance-based structural design theory as well as the increasing complexity of building environment. Structural progressive collapse analysis is a complex process considering both dynamics and kinematics of structures. At present, most researches on progressive collapse of structures under abnormal load are terminated in the establishment of the initial collapse criterion of the structures, because of numerical difficulties. What’s worse, there is hardly any research on monitoring damage status in structural or components’level, and modifying of analysis model during the analyzing process.Based on OpenSees Beam with Hinges Element, the element with salve nodes at the ends is constructed. And a static condensation method is adopted to deal with constraints of the slave nodes. By control of OpenSees analyzing process using Tool Command Language (Tel for short), four criterions including flexure failure of the beam and the column, ultimate capacity of the beam, shear failure of the column and axial failure of the column are introduced. The damage status of the structure or the components is checked, and the constraints of the failure elements’are modified according to the method of constraint handling as well as static condensation to achieve modification of the structural model. Internal force release and its dynamic redistribution due to failure of the beams or the columns are discussed in detail.A more practical scene of gradually failure of the elements and progressive collapse of the whole structure can be reflected by modifying of the structural model during the analyzing process. Internal force release and its dynamic redistribution are the major factors, which are too important to be ignored during the structural progressive collapse analysis, affect the actual collapse mechanism, collapse mode and the evolution of structural damage under abnormal load.