Experimental Research On Interface Damage Detection Of Steel-concrete Composite Beam Based On Piezoelectric Waves

Steel and concrete composite structures are more and more widely used in engineering with the development of building structure type.Because composite structures can make use of the properties of steel and concrete material,they have the advantages of great stiffness,good seismic performance,saving steel,efficient cost,convenient construction and so on.However,in the process of service,due to the long-term effects of environmental impact and power load,composite structures can produce different types of damage.Composite structure is the structure which can combine different materials together and work together through the interface(called composite interface).As the composite interface generates types of damages such as adhesive failure crack,relative slip and separation,they will severely weaken the combination effect of the composite structure,and even lead to structural collapse and bring huge casualties and economic losses.Therefore,the researches on the composite structure interface damage identification(monitoring)are great of importance.However,research on composite structure interface,especially in the nondestructive detection and health monitoring is still in its infancy,fewer achievements are reported,there are many problems need to be further study,and also have not form a systematic theory and effective method.Piezoelectric-ceramic(PZT)-based structure damage detection(monitoring)technology can play an important role in the composite structure interface state detection(monitoring).The piezoelectric ceramic such as PZT is a kind of intelligent material which has a double function of sensing and actuating.It has a wide application in structural damage detection and health monitoring.In this paper,the piezoelectric ceramics(PZT)are used as transducers to respectively conduct the monitoring experiments on interface bond slip of a concrete filled steel tube column,and interface bond slip and separation of the composite beam,and the goals are to propose an interface damage monitoring model and relevant damage detection innovation method based on the monitoring signals.The proposed method has the properties of strong anti-noise capacity,good monitoring effect,and economical and practical application.Part of the PZT patches are embedded in concrete as "smart aggregates",and another part PZT patches are pasted on the surface of the steel beam flange,forming a sensor array.The research method will combine the ultrasonic techniques,and PZT-based sensing theory,to monitor the signal differences in time and frequency domains,and propose the damage index based on signal feature parameters.The experimental results show that under the action of external loading,the received signal amplitudes will increasingly decrease with the increase of bond slip along the interface,and there is a certain quantitative relationship between the signal amplitudes and interface damage levels.The experiment validates the effectiveness of the proposed interface damage monitoring model,damage index characterizing method,and the damage detection algorithm.Meanwhile,the wave analysis method is used to make the measured signal filtering and spectrum analysis.Finally,the function relation between the composite structure interface stress state and energy loss percentage are established,and a composite structure health monitoring system is developed.The system includes a new type of transducer for inspiring and receiving signal,a high speed and high performance signal generator,a signal amplifier,signal acquisition equipment and other hardware.The system can monitor different structure types of damage at the same time and has a good effect.