Experimental Study On Bearing Behavior Of C40Concrete Columns At Early Age

ABSTRACT:The early age of concrete refers to the period that has a significant impact on the performance of concrete (such as strength, shrinkage, creep, etc.), usually within7days. Early-age concrete structures can refer to the structures which are influenced by the age of concrete, and which is usually for7days. Reinforced building construction usually costs7days to9days for a layer. When the strength conditions meet the requirements of code, next layer construction will continue. Building structures during construction which belongs to early-age concrete structures restrict the construction progress and the safety of structure severely. Study on mechanical behavior of early-age concrete structural members has important theoretical and practical value to the reinforced concrete construction and durability of existing structures. This paper focuses on the subject of columns. C40reinforced concrete columns (RC) and steel reinforce concrete columns (SRC) are systematically studied through experimental and theoretical research. This article mainly contains:(1) Bending and compressive tests on5RC columns and8SRC columns were conducted. The important experimental data such as the deflection of specimens, the axial deformation, the rotational deformation and the cross-section strain distribution were measured. The pictures of cracking distribution under static monotonic load were plotted, and the failure modes were obtained.(2) Based on the data of tests, the results of test were analysed, including deformation characteristics, cross-section strain etc. The influence of curing age on the bearing capacity, deformation characteristics and early-loading on SRC specimens were analyzed.According to the uniaxial press stress-strain curve of the same age concrete, ABAQUS software was used to analyze the distribution of stress on section.The comparison between the numerical and experimental results show a good agreement.(3) The calculation formula of cracking load for early-age RC and SRC columns section was derived. Based on the proposed and modified plane assumption method, practical formulas for calculating the normal section bearing capacity of early-age concrete eccentric columns were proposed. The comparison of calculated results between the formulas in this paper, calculation method of the JGJ138-2001, the YB9082-2006calculation method were conducted, and comparison analyses between calculated results and test results are also conducted. As a result, calculation method in this paper has a good agreement with the test result.