Experiment Research On Bearing Capacity Ability Of Expansive Confined Concrete

Concrete-filled steel tubes (CFT) have widely developmental foreground due to their excellent properties such as high strength, high ductility, light weight and construction convenience. The first part in the dissertation proposes expansive concrete-filled steel tubes by using the expansive concrete instead of the ordinary concrete to produce an initial confinement. The second part proposes expansive concrete-filled PVC pressure tubes by using the expansive concrete. Through the experiments and the theoretical analysis, the behaviors of the new style expansive constrained concrete structures were investigated. The results may supply significant theoretical basis for the expansive constrained concrete structure in practical applications, and provide useful information for the further research. The main work in the dissertation includes:Firstly, Mixture proportions of the expansive concrete used suitably to fill in steel tubes and PVC pressure tubes are determined, through the laboratory tests of expansive concrete. At the same time, the influences of the expansion agent addition and fly ash on the mechanical properties, compressive strength and free expansion ratio of expansive concrete have been discussed and studied, and the free expansive model of expansive concrete is investigated. The results supply theoretical basis for the study on the behavior of expansive constrained concrete members.Secondly, the expansive constrained concrete members were cured indoors; the period of curing was 28 days. Observe the effect on members from tube wall and centre concrete when concrete released heat. Experimental results indicate that the hydration heats of concrete have extreme impact on members, under triaxial compression confined by steel tube, the concrete with expansive, which works well together with the tube wall, do not lead to deviating between tube wall and centre concrete because of the self-stress. Expansive agent and shrinkage affect the concrete self-stress together.Thirdly, the expansive concrete-filled steel tube members under axial compression were tested. Observe the effect on members from the different expansive agent and different tube diameter, and comparing the theoretic numerical value with the experiment result. Experimental results indicate that the concrete-filled steel tube members which have more expansive agent have higher bearing capacity. Comparing the ANSYS value with the experiment result of the members, the displacement and strain calculated from ANSYS are in accordance well with trial result when import the contact between concrete and steel tube wall.Finally, the expansive concrete-filled PVC pressure tube members under axial compression were tested. Observe the effect on members from the different expansive agent and different tube diameter, the formula of concrete-filled steel tube is not well in the bearing capacity of expansive concrete-filled PVC pressure tube. Comparing the ANSYS value with the experiment result of the members, the displacement and strain calculated from ANSYS are in accordance well with trial result.