Research On Mechanical Behavior And Seismic Performance Of Concrete Structure Under The Freeze-thaw Cycles

Freeze-thaw resistance is an important aspect of durability of concrete structures in cold region.Through experimental study,theoretical model deduction as well as data regression analysis,nonlinear dynamical behavior and seismic performance evaluations of existing concrete structure under the freeze-thaw cycles are studied.Specifically,this paper has carried on the following work:1.To study the compressive stress-strain curve of concrete subjected to freeze-thaw cycles,four groups of concrete prism specimens with dimensions of100mm×100mm×300mm were exposed to rapid freeze-thaw cycles.The parameters of the specimens were cubic strength of concrete,air entrained or not and freeze-thaw cycle numbers.Then,all specimens were tested under uni-axial compressive and repeated compression loading.After the test,the times of freeze-thaw cycle,the strength of concrete,air entrained or not were discussed.Based on the test results,the stochastic damage constitutive relationship of frozen-thawed concrete were established.2.To research the bond behaviour between concrete and plain steel bar after freeze-thaw cycles,three series of center short buried specimens were subject to rapid freeze-thaw cycle test.The parameters of the specimens were cubic strength of concrete and freeze-thaw cycle numbers.Then,experiments were taken on to analyze the effect of freeze-thaw cycles as well as the strength of concrete on the bond behaviour under monotonic and cyclic loading.Finally,the bond-slip relationship between concrete and steel was obtained.3.An experimental investigation on the seismic behavior is presented in this paper,which included 6 freezing-thawing damaged reinforced concrete columns and 2un-damaged reinforced concrete columns.The effect of frost-thaw cycle times and axial compression ratio on the seismic behavior of the freezing-thawing damaged reinforcedconcrete columns were considered.The research showed that the seismic indexes of the specimens,such as stiffness,displacement ductility and energy dissipation,rapidly decreased with the increase of axial compression ratio and frost-thaw cycle times.4.Based on the concrete elastoplastic damage model which has been suggested in this paper,a numerical simulation calculation was carried out for the experimental specimens by using the finite element software ABAQUS,the degradation mechanism of the seismic behavior of reinforced concrete column under low cyclic loading after freez-thaw cycles is studied.5.Based on the low cyclic test results,“sentinel point” trilinear restoring force model has been established for the freezing-thawing damaged reinforced concrete columns.The formula of feature points and the corresponding hysteretic rules were given.It showed that the results of test coincided with the calculation,which could provide a reference for elastoplastic seismic response analysis of concrete structures in freezing and thawing environment.