The Extension Service Life Assessment By Earthquake Action Of Old Reinforced Concrete Frame Structures

Reinforce concrete frame structure is one of important structure in present. In our country the number of reinforced concrete frame structure is large, and the distribution is also very broad. Due to action of some factors, the RC structure would have aging materials and damage of buildings. For example, the concrete carbonation and concrete cover cracking for steel bar corrosion. The damage leads to deteriorating of resistance. Resistance of structure is declined in some degree at the end of design working life in earthquake fortification zone. The old reinforced concrete structure is still appropriate to meet the seismic requirements and can also be used security. People are very concerned about this issue. This paper focus on the seismic behavior of the old reinforced concrete frame structures. The research is as follows.The paper summarizes the domestic and international research condition and results of reinforced concrete structure durability and the seismic performance of existing buildings. Introducing the non-line finite element analysis method for the reinforced concrete structure or members and the choice of the element in ANSYS software and the process of building the model.After the steel bar corroded, the bond strength between steel bar and concrete is reduced. It leads to the change on reinforce concrete members of mechanical properties. Using the batch of APDL, the finite model of corrosion reinforced concrete column and beam is built and low-cycle reversed loading is applied on the finite model. At the same time, the paper considered the concrete carbonation, the steel bar section losing and the descending of bond strength. The hysteretic and skeleton curves for the corrosion members are obtained. The calculated hysteretic curves show the properties of column. The parameters of hysteretic model are given. The conclusion is agreed well with the experiments in other paper.Nowadays, many works have been done about the seismic behavior of RC frame members in many countries by theoretical studies and pseudo dynamic testing and quasi-static testing. However, the research on the working performance of RC frame has seldom been investigated. The time-history seismic analysis can truly reflect the seismic behavior of structures and find out the earthquake response when earthquake happens, so it is the precise method at present. In order to access the seismic capacity of old RC structure in earthquake fortification zone, author takes the teaching building example. Based on the studies of the damage of buildings, the ratio of steel bar corrosion is calculated at the end of design working life. The finite model of corrosion reinforced concrete column and beam is built. The time-history seismic analysis of frequently occurred earthquake and seldom-occurred earthquake is carried on. The conclusion shows the change of seismic behavior of the structure. It must be helpful for the life forecast of structure and seismic strengthening of building.