A DIC-based Study On Mechanical Properties Of Concrete After Exposure To Elevated Temperature

Concrete is the main load-bearing structural material,and its fire performance research is hot point of building fire safety research.At present,the experimental research on the mechanical properties of concrete after exposure to elevated temperature mainly adopts traditional measurement methods,such as displacement meter,strain gauge and so on,which can only get the data of local or average deformation.In this paper,the mechanical performance of concrete and concrete confined by stirrup after exposure to elevated temperature was investigated,and DIC was used to monitor the deformation and cracks development of the specimens.The main tasks are as follow:(1)The applicability of DIC in the axial compression test of concrete materials after exposure to elevated temperature is analyzed from the working principle,advantages,and applicable range.Pre-experiments were performed to determine the relevant parameters of DIC,and the conclusions that DIC can be considered as date acquisition equipment and analyzing software are obtained.(2)Experimental study on the axial mechanical behavior of 36 concrete specimens,including 9 specimens at room temperature and 27 specimens after entire period of heating and cooling process,was carried out.The effect of temperature and water-cement ratio on residual bearing capacity,elastic modulus and peak strain of specimens after exposure to elevated temperature were analyzed.The DIC technology was used to monitor the deformation of whole concrete specimens,and the entire process of crack development was obtained.(3)Experimental study on the axial mechanical behavior of 20 concrete confined by stirrup specimens,including 4 specimens at room temperature and 16 specimens after entire period of heating and cooling process,was carried out.The effect of temperature and volume stirrup ratio on residual bearing capacity,elastic modulus and stress-strain curve of specimens after exposure to elevated temperature were analyzed.At the same time,the DIC technology is also used in this test.(4)Based on the previous research,several finite element models were established by using ABAQUS,and the temperature field of concrete confined by stirrups was studied.The effects of elevated temperature,heating rate and the number of exposed fire side on the temperature fields distribution of the specimens are analyzed.The temperature variation at different positions of the cross-section are analyzed.In general,the application of DIC to the axial compression test of concrete after exposure to elevated temperature has achieved good results,reflecting its advantages of enabling non-contact full-field deformation measurement,the success of this test can further promote the application of DIC in the research of brittle materials such as concrete and lay a foundation for its application in practical engineering.