Study On Seismic Performance Of In-service Multi-aging Reinforced Concrete Columns

Because people have thought that the durability of concrete is a good materials for long while ignoring the durability of concrete who impacts on the durability of concrete structure, the progress of study on properties of structure who infects durability has been slower. On the other hand, because of the durability , the direct and indirect losses have far exceeded expectations, and bringed the world a very serious financial burden. Form the investigations of Yushu earthquake and Wenchuan earthquake in China,we can find that the seismic performance of multi-aging reinforced concrete decreases than the modern architecture, mainly attributable to multi-age, durability who has been affected, the relationship of stress-strain and concrete strength properties, and the connections and properties between rebar and concrete who have been undergoned great changes .There are more and more buildings coming to aging even over-age period of time.But our present study has still been limited in seismic performance analysis and reliability assessment in the new structure and pays less attention to the aging of existing multi-age structure. The issues such as concrete carbonation, rebar corrosion and seismic performance of multi-age structure are described and studied as follows.Rebar corrosion accounts for the first reason in many factors about damage of concrete structure. Corrosion will directly affect the structure of the utility and safety.By cyclic loading tests of the old columns in different axial compression ratio, hysteresis curves,hysteresis curves and characteristics of crack and damage are measured, at the same time, A simple analysis of seismic impact is maked about axial compression ratio.It have been found that, crack generates and develops along the vertical interface in reinforced concrete protective layer because of lower strength, rebar corrosion and degradation of bond-slip, energy-consuming capacity and ductility of components are reduced and the brittleness is more cleared.We can find that the longer the period of concrete carbonation of concrete the greater peak stress, and the line segment accounts for the greater increase in the proportion of segment, the curve of peak stress is larger, the decline is more steep in the test of the stress-strain relationship with different carbonating years.Based on the geometry and material parameters of components in experiment, reinforced concrete uses friction coefficient to reflect the relationship of bond-slip, at the same time uses attenuation coefficient to reflect the stiffness degradation under different axial loading.By the using finite element analysis software ABAQUS, this model hysteresis curve of the simulation software in good agreement with the experimental results.From the mises of rebar and concrete,we can study the failure mechanism and the characteristics of force under cyclic loading.