Study On Uniaxial Compressive Performance Of Preloaded Steel Reinforced Concrete Rectangular Short Column Confined By Carbon Fiber Composite Sheets

Based on the state of the behavior of the compressive performance of pre-loaded concrete confined with carbon fiber reinforced polymer (CFRP) sheets, the performance of axially compressed pre-loaded SRC rectangular short columns confined with CFRP sheets was studied by experimental investigation and numerical simulation. Fourteen concrete rectangular short columns were confined and loaded, the failure modes and mechanism of confined columns were studied through the experiments. The influence of steel, pre-loaded level and CFRP layers were analyzed and discussed. The peak load and deformability after column yield of confined column increase obviously. Conbined with RC column, the amount of peak load for SRC column confined with CFRP increse slow down. With the improvement of pre-loaded level, the effective tensile strain coefficient of CFRP gradually reduce. The yield load, peak load and ductility also gradually reduce. All confined columns failed under the mode of the breaking of CFRP sheets after the yielding of steel and rebar, the ductility of the specimens are increased obvious as the CFRP layer increase from two to three. According to the data from experiments of columns, a suitable numerical model to simulate the whole process of pre-loaded SRC rectangular short columns confined with CFRP sheets was proposed. The techniques of deactivate and reactivate element was applied to simulate the whole process of pre-loading, strengthening and formal loading of columns. By defining damage factor in CDP model to consider the influence of pre-loading to concrete. The calculation results fit well with the experimental results, it indicate that the finite element simulation is accurate. Using the numerical model to analyze the influence of pre-load level on the stress distribution(the ratio of first and third principal stress) of middle section concrete, the results showed that pre-load limit the stress increase of confined concrete, and then resulted in the peak load of pre-loaded columns were less than formal columns which were all confined with CFRP sheets.