Study On Shear Stress Distribution Detection Technology For Hinge Joints Of Assembled Beam Bridges Based On Acoustic Emission

The prefabricated concrete beam/slab bridge is one of the major forms of highway Bridges in China,and therefore maintain their safety and enhancing their structural performance is critical.In precast concrete beam/slab Bridges,concrete joints are primary details for transferring live load between precast members and ensuring structural integrity.The cracking and failure of concrete joints will cause serious damage such as the overloading of a single beam or slab which will lead to the reduction of bridge performance or even catastrophic accidents.Therefore,it is of great theoretical and engineering value to evaluate the stress state of concrete joints for the safety of the prefabricated beam/slab Bridges.However,at present,there is still a lack of effective technical means for the measurement and detection of shear forces or stresses--the most important internal forces(stresses)in concrete joints.Acoustic Emission(AE)technology is a non-invasive passive nondestructive testing method,which is widely used throughout various fields of civil engineering.Based on the acoustic emission phenomenon,this thesis studied and proposed a method to re-construct the distribution of shear stresses/forces in concrete joints.The main contents of this paper are as follows.(1)the theoretical calculation method of shear stress in concrete joints of prefabricated structures was investigated and studied in depth.The model of shear stress distribution in the concrete joints under different stress states was calculated by using the method of hinged plate.(2)common techniques used to measure stresses were analyzed to reveal the general research direction of the shear stress measurement in concrete joints and the important characteristics of the required techniques.The Acoustic Emission phenomenon and its physical mechanism were briefly introduced to lay a basic physical foundation for evaluating the stress distribution of the concrete joints via AE signal analysis.(3)the principle,mathematical model and the latest research progress of AE source positioning technology was analyzed to form a theoretical support for subsequent research.Based on the theories and methods of AE theory and the random damage mechanics of concrete,a quantitative relationship model between stress and acoustic emission parameters was constructed.Based on the theory of time series analysis and mathematical models,a method,mathematical model and flow chart were presented to re-construct the distribution of shear stress in the concrete joints using AE signals.(4)the model experiment was carried out,and the re-construction method of shear force distribution in concrete joints based on AE signal was verified with the experimental data.Reinforced concrete T-beam and slab girder were selected as the experimental objects,and the load testing was carried out on the reinforced concrete beam Bridges in the form of five-point method to simulate the half-wave sinusoidal load and the form of one single concentrated load,respectively,and AE equipment was used to collect AE signals emitted from the joints.Using the experimental data,the re-construction method of the shear force distributions in concrete joints was validated based on AE signal.The outcomes of this work will provide technical support for the safety evaluation and the service performance maintenance of prefabricated concrete beam/slab bridges,and has important theoretical impact and engineering value in civil engineering.