Rapid Testing Method Of Bridge And Theoretical Innovation Through Impact Vibration

China is in the period of rapid development of industrialization, information technology, smart city as well as infrastructure construction growing vigorously. Meanwhile, during the long-term service, bridge is subjected to some kinds of influence, such as environmental erosion, material deterioration, sunken foundation, daily traffic load and so on, which induced the gradual degradation of structural performance, and other risk of accident such as ship collision, overloading and hazardous articles leakage, natural and geological disasters etc., which shorten the service life of the bridge, also causing serious damage for life and property security. Therefore, how to maintain and manage a large number of bridge facilities, and find the early damage or hidden danger of the structure that are an urgent problem to be solved at home and abroad. At present, the regular inspection of the bridge is still based on manual testing which is time-consuming and laborious. Because of the complexity of system of the health detection technology with high cost,it is difficult to be widely applied in large numbers of small and medium bridge. The research and development of automatic testing is gradually applied to tunnel, road, rail and bridge (cable, bridge deck and underwater pile foundation), which greatly improves the detection efficiency,unfortunately, at present there is no equipment and technical method to evaluate the overall safety performance of the bridge. Therefore, the purpose and significance of the paper is to develop a rapid test and security investigation for the majority of bridges on the road network in China. The research contents and innovations of this paper are as follows:(1) General idea and framework. This paper proposed a bridge quick test method and developed integrated device based on impact vibration test. Basic thought: a quick test vehicle with integrated impact system, sensor layout system, integrated control system, and the whole data analysis system carries out to identify the comprehensive parameters of the bridge (including deep parameters of flexibility) for achieving the rapid testing and evaluation. Unique advantages: Impact vibration test data from impact force and structure response can evaluate and resolve the Structure frequency response function and more completed structure characteristics, getting more realistic and detailed information on structure characteristics. Effective results: rapid test method based on bridge impact vibration can further identify the structural flexibility. Flexibility (corresponding to inverse of stiffness) directly reflect the carrying capacity of structure. After identified flexibility,the structural deflection will be predicted under static loads. So, as to realize the rapid test and evaluation of the small and medium bridge by using the rapid detection vehicle.(2) In order to study the potential theoretical advantage of impact vibration, firstly structure information which come from between impact vibration and ambient vibration was proved to be have essentially different. The structure of frequency response function(FRF) from impact vibration test data for calculation is true, and the amplitude of frequency response function and the theoretical value is consistent. The frequency response function from ambient vibration have the same shape as the theoretical value (so, it just identifies the basic parameters, such as frequency,vibration mode) but different in amplitude (a certain proportion exists ?roi), so the structural deep parameters can't be estimated by ambient vibration data. Furthermore, it is proved that it is a fundamental advantage to use the impact vibration test data (impact force and structural impact response) to identify the structural deep parameters.(3) Study on the theory of the displacement flexibility identification based on impact vibration test. The traditional flexibility identification extracts the mass information by means of finite element model, achieving flexibility identification by displacement mode shape of the mass normalized. Obviously, this reliability degree of flexibility identification method with known mass is restricted by the accurate degree of finite element model, which does not meet the rapid test idea presented in this paper. This paper write the displacement flexibility for complex modal format ,which solves the displacement flexibility through identifying displacement shape, modal scaling factor, and system pole, avoiding the problem of structural mass information, of which modal scaling factor is the core of flexibility identification. This paper introduced the enhanced frequency response function in single degree of freedom to identify natural frequency and damping ratio by orthogonality of the vibration modal vector using dimensionality reduction and decouple of No ×Ni frequency response function. Finally, identifying the Modal Scaling Factor Qr by the identified system pole at the rth.(4) The method of impact vibration test based on blocks is studied. The traditional test methods aim at the whole structure measurement, demanding to layout a large number of sensors,high test cost, long time-consuming for bridge closed, which do not meet the requirements of rapid test presented in this paper. In order to solve these problem, this paper proposed the impact vibration test method based on blocks, of which the bridge surface is divided into various sub structure, and then carrying out test on each sub structure to get the integrated parameters of the whole structure come from the vibration test data of each sub structure to identify the structural displacement flexibility matrix of the overall bridge structure. The key point is how to solve the integration of displacement mode shape of each sub structure. Because the structural mode shape only shows the natural frequency form of each stage, not the real vibration amplitude. So,displacement mode shape at different stage of each sub structure can be randomly scaling, and vibration direction is not fixed. This results induced the different amplitude of displacement mode shape at different stage and wrong direction of vibration. The paper proposed the impact vibration test on multi-reference points and impact vibration test on single reference point, through combining the mode type continuity and frequency response function curve to respectively solve the problem of structure integration between multiple reference points and single reference point.(5) Integrated hardware development and engineering application. For bridge impact vibration test, this paper develops a kind of impact load device suitable for medium and small bridge safety diagnosis. The device can produce impact force consisting of large amplitude, wide frequency and single amplitude value. It can fully excite the real dynamic characteristics without damage to the bridge. At the same time, a sensor automatic layout vehicle with flexible bracket was invented. The device uses a small number of accelerometers to measure quickly on the deck along with the movement of the measuring vehicle, which solve the problems of traditional accelerometers by gluing, magnet to fixed on the bridge deck, which is not easy to be disassembled and reused, labour intensive, long time-consuming and so on. At last, the accuracy and .practicability of the proposed method are verified by field test.(6) Based on the temperature load (input) and structure temperature response (output), the evaluation method of long-span bridge is proposed. In this paper, the theory of impact vibration and the rapid test method can be used to test and evaluate medium and small bridge on highway network,but there are some deficiencies in long-span bridges. This paper based on impact vibration theory is first proposed evaluation method according to temperature load (input) and temperature induced strain (output) of long-span bridge, the advantage of this method based on the temperature load and temperature response to reveal relation of the structural innate. According to this relationship, a long-span suspension bridge is analyzed and evaluated on line.