Monitoring And Analysis Of The Impact Stress Of Concrete Filled Steel Tubular Column Based On Piezoelectric Smart Material

The concrete-filled steel tubular(CFST)structure is widely used in large structures because of its convenient construction,good seismic performance,high bearing capacity and good economic efficiency.In the service period,in addition to carry its own gravity load,it is inevitable to be affected by other loads,such as impact load,seismic load,wind load,etc.These sudden dynamic loads may cause greater damage to building structure,or even collapse.Therefore,it is of great significance to improve the ability of disaster prevention and mitigation by developing a smart sensor to monitor the internal time-varying stress of concrete and study dynamic process of concrete filled steel tube structure based on microcosmic level.PVDF piezoelectric film has much advantages like good piezoelectric characteristics,wide frequency response,wide dynamic range,high sensitivity,fast response,low energy consumption,low cost easy processing,etc.It has been widely studied in the field of civil engineering and has a good application prospect.Based on its good piezoelectric properties,a high strength PVDF piezoelectric sensor is developed to monitor the internal time-varying stress in CFST columns under impact load in this paper.The specific work of the main contents include the following aspects:(1)Based on the characteristics of existing piezoelectric materials,a PVDF piezoelectric sensor with high stress was developed,and the sensitivity of PVDF piezoelectric sensor was calibrated by drop hammer impact test machine.(2)Embedded the developed piezoelectric sensor in the CFST column,the time-varying stress test of concrete was carried out based on the drop hammer impact test,and the local stress monitoring method of concrete-filled steel tubular column was put forward.According to the process of elastic-plastic stress development of concrete in column,the relationship between time-varying stress and strength and stiffness degradation were analyzed,the characteristics and laws of concrete stress evolution were revealed.(3)According to the uniaxial stress-strain relationship of steel tube core concrete had already proposed,using the concrete plasticity damage model within ABAQUS,considering the effect of strain rate,material non-linearity,cracking effect of concrete and other factors,the damage development process and performance evolution law of the structure under the impact was simulated.The reliability of the finite element model was verified by comparing with the numerical simulation results and experimental results.The dynamic catastrophe process of the CFST column was analyzed and revealed.(4)According to the impact force time history curve of CFST under different impact loads,the maximum value of impact force,the time of impact force and the variation of displacement with impact energy were analyzed.Compared the maximum value of the impact force obtained by numerical simulation with experimental results,the bearing capacity change laws under different parameters were analyzed.And based on the calculation method of static bearing,the maximum value of impact force calculation method of circular and rectangular CFST columns under impact load was proposed.