Research On Health Monitoring And Numerical Simulation Of Concrete Structures Based On Smart Materials

Cracks in reinforced concrete beams are the main cause of many engineering accidents.The causes of cracks are mostly caused by various factors such as high-strength external loads,fatigue loads and secondary stresses.The cracks will cause air and moisture to enter the interior of the reinforced concrete,corrode the steel,cause rust to swell and damage the strength of the beam,and the fatigue durability of reinforced concrete bridges in service will be greatly reduced,resulting in increased chance of collapse accidents.Therefore,it is very important for crack monitoring of concrete beams.A composite material made of fiber,also known as FRP,can be a substitute for reinforced concrete structures.Since FRP materials are non-magnetic and corrosion resistant,the use of FRP can avoid electromagnetic interference and corrosion problems.FRP materials have high tensile strength,light weight,corrosion resistance,fatigue resistance,diamagnetic resistance,electrical insulation,small creep,low modulus of elasticity,etc.,making FRP reinforced concrete structures increasingly being applied to civil engineering.Engineering.(1)In this paper,the characteristics of the location and depth of cracks in the bending section of a concrete beam with FRP material as the main tendon are studied.The real-time crack monitoring is conducted with the piezoelectric ceramic smart aggregate as a monitoring tool to study the crack monitoring method.feasibility.The concrete beams with FRP bars as main reinforcements and ordinary steel bars as main beams were taken as the research objects.Intelligent aggregates based on piezoelectric ceramic materials were embedded at both ends of the bending-resistant sections of beams.Using piezoelectric materials with both piezoelectric and inverse piezoelectric effects,two pairs of smart aggregates,one pair as a driver and the other as a sensor,are respectively embedded in different depths,and applied external static loads under different conditions.A sweep excitation signal is given to the driver and the received signal is collected from the sensor.The wavelet packet energy and damage indices of the received signals were analyzed.The locations and depths of the cracks observed in the concrete beams were compared.The results show that when the cracks occur,the received wavelet packet energy will be significantly smaller,and the damage index will increase.It shows that the crack detection method based on piezoelectric ceramics can effectively monitor the occurrence of cracks.(2)In order to further study the crack monitoring of concrete beams based on piezoelectric ceramics,this paper used ABAQUS finite element software to conduct numerical simulation analysis of crack monitoring experiments to explore the width,depth(depth)and quantity of cracks in the cracks in the bending section of concrete beams.The effect of the change on the energy and damage indicators of the signal received by the pre-embedded sensor.By designing various conditional variables,the effect of controlling a single crack variable on the signal is achieved.It can be seen from the calculation results that the depth and number of cracks are the two factors that affect the signal energy,but the width of the cracks is less affected when the depth and number are determined.In the simulation test,it was found that the embedded height of the sensor can effectively monitor the crack depth.The numerical simulation experiment provides a good theoretical basis for the monitoring method of concrete beam cracks based on piezoelectric ceramics.(3)Prestressed corrugated pipe grouting technology is one of the key processes in the construction of prestressed concrete bridges,due to the blocked pores,improper grouting methods,poor control over the expansion rate and consistency of cement slurry,and the fluidity and excretion of sizing slurry.The water rate has not reached the design requirements and other issues,inevitably lead to pre-stressed hole grouting is not dense,and even holes and other phenomena.The corrugated pipe grouting simulation experiment was designed in this paper.Piezoelectric ceramics were embedded in the upper and lower sides of the corrugated pipe in the design concrete grouting experiment as receivers.The center of the corrugated pipe was fixed with smart aggregate as a driver and the grouting degree was 0%.At 50%,90%,and 100%,the difference in amplitude of the two sensor signal amplitudes was used to evaluate the grouting condition of the bellows.ANSYS finite element analysis software was used to establish a two-dimensional simulation model of the experiment to study the stress wave propagation path of bellows with different grouting degree.In the grouting condition of 0%,50%and 90%grouting,the signal received by the piezoceramic sensor above the bellows is much smaller than the signal amplitude received by the lower driver.When the grouting is 100%,the two sensors accept the signal amplitude.By observing the displacement cloud diagram of the two-dimensional finite element model,it can be found that when the corrugated tube is not fully grouted,the stress wave emitted by the intelligent aggregate cannot be completely propagated to the upper part of the corrugated tube,and the only signal at the key node follows.The stress wave propagation path and distance change,and the displacement amplitude changes accordingly.The results show that this method can effectively monitor the compactness of prestressed bellows.