| In recent years, the waste concrete is in the largest proportion of construction waste which is from new construction and demolition of old buildings with the rapid development of construction. Concrete contains some or all of the recycled concrete aggregates (RAC) is called recycled concrete, and RAC are produced by breaking, cleaning and classification of the waste concrete particles. Recycled concrete is a kind of green concrete which can protect the environment, save the natural resources and meet the requirements of the sustainable development; however, the use of RAC is still on a low level now. Recycled aggregate concrete-filled steel tubes (RACFST) can effectively promote the use of RAC in building structure and offer the application of recycled concrete an effective way.Currently, the study focuses on the behavior of RACFST at ambient temperature and concrete-filled steel tubes (CFST) after exposed to high temperatures. Based on the work done before, this paper experimentally and theoretically studies the performance of RACFST after exposed to high temperatures, and the main works are as following:(1) The studies on the performance of RAC after exposed to high temperature, RACFST at ambient temperature and CFST after exposed to high temperatures were reviewed.(2) Thirty-two RACFST and eight CFST after exposed to high temperatures were tested while subjected to axially compressive load, and the effects of cross section shape, type of concrete and maximum temperature suffered were investigated.(3) Using the theoretical model based on the software ABAQUS, compressive behavior of RACFST after exposed to high temperatures was modeled, and the results are acceptable. The simplified formulae for mechanical index of RACFST after exposed to high temperature were put forward on the basis of parametric analysis.(4) The complete load-deformation curve of RACFST after exposed to high temperatures was calculated by using the numerical method. The mechanism of RACFST after exposed to high temperatures, such as the law of stress distribution, the interaction between core concrete and steel tube, and etc, was investigated. |
