Mechanical Study On Piezoelectric Smart Beam

With the development of society,people individually realize the importance of environment protection and energy conservation.As a type of self-diagnostic,self-adaptive,and self-healing structures,smart structure is a new way to green civil engineering,which has the functions of sensor,processing information,and actuation.Since piezoelectric material can realize the transformation between mechanical energy and electric energy,it can transform mechanical energy from engineering structures and activate engineering structures,which individually provides sensing and actuating function for civil structures.Also,power technology based on piezoelectric material has become a research hotspot.Based on piezoelectric material's energy transformation properties which involve actuating and powering functions of engineer structures,a smart self-recirculating bridge is conceived.Inverse piezoelectric effect underlying the first function of this bridge,the piezoelectric actuators are set in the tensile zone of the cross section of beams to provide variable prestress by regulating volt.The function protects bridges from cracking due to adapt different load situations.This function can strengthen bridges and avoid costs of repair and recreation.The second function is based on piezoelectric effect.Mechanical energy from traffic loads is transferred to electric energy to power bridge lighting,signals and so on.In order to explore feasibility of the new piezoelectric bridge and get reference data for design,two main parts are included in the paper.The first part is the study of the mechanical properties of bending beams actuated by piezoelectric actuators.The other part is evaluating the efficiency of piezoelectric powering and the influence of piezoelectric transducers.Study on mechanical characteristics of piezoelectric pre-stressed beams started from forming the relation between volt and actuating force.After that,piezoelectric actuator loaded at the tensile zone of the beam ends by the steel frame.Under different pre-stresses,test specimens' cracking ended with different loads and deflections.By the experimental data,we found that prestress increased cracking loads and decreased deflections,which means that pre-stress can delay cracking and increase cracking loads.The specimens' solid models were formed by Ansys 14.5 to simulate the experiment.It is indicated that simulating outcomes are consistent with experimental data.Since the accuracy of the models has been validated,we conduct numerical tests on them.The impact of ratio of reinforcement,contact stiffness and span-depth ratio on deflection and cracking loads were researched in this numerical test.At the end,we found that the rank of impact of the three factors is:span-depth ratio is the most prominent factor,and contact stiffness is smaller than it.Ratio of reinforcement influenced very slightly.Referring to technology of piezoelectric powering pavement,piezoelectric transducers were intended to be set in bridge deck pavement.The research started from piezoelectric vibrators,the core component of piezoelectric transducers.Analysis of the vibrators' dynamic properties helps in evaluating powering efficiency of themselves.Based on reasonable assumption of traffic condition and transducers' structure,a bridge with span of 200m was took as an example to estimate its powering efficiency,indicating that improvement is necessary aue to low efficiency.increasing the humber of transaucers can increase power generation,however,too many transducers certainly will influence stress condition of bridge deck,so the impact on bridge deck pavement was quantified by finite element analysis.The outcome showed that embedding piezoelectric transducers increases the stress on bridge deck,while the stress on the pavement lying on transducers decreases.In this thesis,a new conception about piezoelectric material application in bridge engineering was come up with and researched successfully.This thesis can provide useful data and design proposals for piezoelectric structure design.