Study On Damage Identification Based On Dynamic Parameters And Self-monitoring And Self-repairing Of Rc Structure Of Near Surface Mounted Sma

Structural health monitoring (SHM) is an emerging applied new technology in recent years, dealing with continuous health monitoring of structure online, test and damage identification, the ultimate goal is to increase and improve the reliability, safety and durability, and to ensure the structure can finish the design life and reduce the maintenance costs. The technology is applied to monitor the large scale engineering, such as bridges, dams and so on. The timely repairing without influencing traffic is concerned when the damage identification can be realized at the same time.The research of the dissertation sums up a large number of references of the curvature mode, flexibility mode and intelligent material at home and abroad, makes a relatively comprehensive discussion on its theoretical significance, study application, research achievements and existing problems, studies the health monitoring methods based on the curvature mode, flexibility mode and SMA. Main research works can be summed up in five aspects.A beam with vertical bending vibration is taken as the research object, and general formula of differential equation was solved in any supported conditions. According to the modal theory, Solution of the differential equation was expressed as mode superposition of each mode, substituted into the differential equations and considering orthogonally of mode shapes, curvature FRF was obtained. Based on the characteristics of curvature FRF, after the displacement mode of the structure was measured by experimental test, curvature mode of the structure can be obtained. Dynamic test of a simple support beam was finished before and after damage, the corresponding curve of curvature mode was calculated by test result, the result of the finite element analysis and experimental result were compared, it is shown that mode curvature can be used to identify the damage of structure. The influence and sensitivity of the damage location, modal order, and damage degree were discussed to the accuracy of identification result.In order to use the modal curvature in one of concrete-filled steel tube (CFST) engineering, the theory difference of damage identification between straight and curve beam were analyzed, the modal curvature formula of curve beam curvature is derived. A CFST model was designed in the labratory, the difference mode curvature was calculated by finite element program of different damage condition of the arch rib, the theoretical result shows that modal curvature can be used to damage identification of arch ribs; dynamic experimental tests was carried out to get the acceleration response of the structure of various conditions, and modal curvature was transformed, the results of experiment and finite element analysis were compared, it is shown that modal curvature changes at the node arch ribs were injured. The result illustrate that the method can identify single damage and multiple damages of arch rib.In order to identify the complex structure in low order frequency, damage identification theory of the modal flexibilityis analyzed, the damage identification parameter was put forward based on modal flexibility matrix theory, a sensitivity parameter of difference flexibility matrix was used to identify the damage of a steel beam, extract the frequency and the corresponding structural vibration model after finite element simulation, the result shows the proposed damage identification sensitivity parameter can locate the damage position of single damage or multiple damages of the beam obviously; The dynamic test of the steel beam was carried out in the laboratory, and collected the structural dynamic parameters with single injury and multiple injuries in various conditions, structural frequency, corresponding mode shapes and modal flexibility were extracted sensitivity parameter curve were drawn, it is shown that the experimental sensitivity parameter can identify the damage easily. The compared result of finite element calculation and experiment illustrated that the sensitivity parameter can be applied to structural damage identification.In order to research or realize the self-monitoring and emergency self-repairing of structure,3 groups reinforced concrete beam embedded with SMA were made in the laboratory, shape memory alloy (SMA) was used to self-monitoring and self-repairing emergency as sensing and actuating element. The SMA were heated by electricity, the low-voltage DC power was developed; the function of sensitivity and mechanics of SMA were tested by supplying electricity heating SMA line; bond-slip between the SMA and concrete were analyzed and tested; it is shown from the experiment when the width of concrete beam crack is less than 0.3mm,there are very good linear relationship between SMA resistance rate and concrete crack width, and when the width is within the 1.5mm the SMA resistance rate and concrete crack width is linear relationship, it is shown that it is possible for the SMA to be used as sensing element in structural health monitoring. When the width of concrete beam is more than 2mm, SMA drive effect take places and can make the crack of concrete healing by heating the SMA, During the test experiment of SMA sensitivity, the resistance is very sensitive to the length change of SMA; In the self-healing properties experiment, it is found that it is suitable to control the pre-tensioned SMA at ultimate tensile strain of 20%-30%.At last, one of CFST arch bridge was analyzed by finite element program, and comprehensive dynamic test was carried out under ambient excitation. incentive to conduct a, first order vertical, reverse mode of the main and sub-span, first order transverse mode of full-span were tested and analyzed comprehensively, it is found that test result is consistent with the finite element result; The vertical vibration of arch rib and deck are synchronization, vertical vibration frequency of arch rib is slightly greater than deck frequency; it is shown it can identify the vibration mode under the full environment excitation; The first order mode is the transverse vibration mode of the deck, seismic response analysis of bridge deck have to be pay special attention to transverse seismic response. The torsion vibration model is higher than other mode, it illustrate that the torsion rigidity of structure is strong that it is favorable to against wind; The measured frequency of bridge is greater than the calculated frequency, it is shown that the bridge stiffness is better. The test results of main span of the bridge and the experimental results in the chapter 4 were compared,there are very good consistency.