| With the development of the cause of the traffic, as well as to speed up the pace of urbanization, a bridge in the increasingly busy roads and traffic in the city is even more important. However, along with the growing traffic and the bridge structure to extend the period of military service, a considerable part of the aging structure of the bridge, damaged, the performance of its functions to meet the current requirements, if the injury surveillance of detection and poor, could cause the collapse of the bridge and people getting killed The accident, or even to the country's huge economic losses.The structure of the bridge, reconstruction or replacement of structural components, have affected the normal traffic, which requires engineers to strengthen the existing bridge structural damage diagnosis, assessment of reliability, maintenance and reinforcement of a comprehensive study of the technology to tap the existing bridge structure The carrying capacity, to extend the service life of existing bridge structure, so as to achieve the purpose of saving funds for construction and assessment of the state of the bridge, reinforcement and maintenance programs should be a bridge to the testing data.Traditional methods of detection of the main bridges, including the appearance of detection, no damage or micro-damage detection, on-site load testing, as well as in special circumstances, to carry out destructive sampling tests and so on. In general, the traditional methods of detection difficult to obtain comprehensive information on the structure, particularly the structure of the hidden parts, and the results are often dependent on the accuracy of the testing work experience and subjective judgments, it is difficult for the safety of the structure of reserves and the degradation of the way to do A systematic assessment. At present, generally recognized as a most promising approach is to combine identification system, vibration theory, vibration testing technology, signal acquisition and analysis, intelligent sensor technology such as multi-disciplinary dynamic load law.As of the end of 2006, China Road and Bridge nearly 340,000, of which small and medium-sized bridge span of about 310,000, accounting for more than 90%, and the simply-supported bridge also account for a considerable number of small and medium-sized long-span bridges.Therefore, to carry out simple beam bridge Experimental Study significant momentum, and the method of exciting and dynamic parameters to identify the level of accuracy has a direct impact on a bridge to the dynamic test results, this should be carried out simply supported highway bridge excitation of the methods and parameters of power Recognition technology is essential.The traditional method of bridge excitation can be divided into environmental incentives (pulse), and incentives to force the three major types of natural law.The above discussion of the bridge excitation method, we can see that a bridge dynamic load test methods commonly used excitation pulse of law, and the pilot jumped off the sports car of the three tests. Law excitation pulse without any equipment, this exciting method of large-span bridges flexible structure can play good exciting results, but on the pulse of the structure of the input energy in small, medium and small for the span of the bridge excitation is often not up to Expected to exciting effect. As long as the speed of the car and vehicle dynamic characteristics of the combined effects, the sports car test in order to stimulate the necessary dynamic characteristics of the bridge. Belonging to the pilot jumped off the impact of pulse incentives to stimulate the bridge vibration, but the role of the vehicles will change the frequency of the bridge, a bridge makes the measured frequency of errors will have. The role of a bridge so that traffic measured the frequency of error how to achieve what extent, the need for analysis of the study.The traditional power structure identifiable parameters need to be exciting and dynamic response to the points of time history, the use of modal analysis, to strike a driving force for all points between the exciting force and frequency response functions, from the frequency domain data Analysis of the structure of power parameters (mode, the natural frequency and damping ratio). Or to strike a driving force for all measuring points with the exciting force between the impulse response function, from the number of domain analysis of the data structure of the power parameters.Dynamic parameters of the traditional methods of identification are: (1) based on the frequency response function of the single-state recognition law and the amendments to the identification of single-mode state law; (2) Klosterman iterative identification method; (3) Levy Act; (4) is Polynomial fitting to pay; (5) frequency identification method optimization; (6) time-domain complex exponential fitting; (9) Ibrahim time-domain law; (10) characteristics of the system algorithm (ERA), and so on.Based on vibration theory and dynamic parameters of the traditional recognition technology, and scholars of output only in response to the dynamic parameters of the data recognition technology is studied. Can be used only in response to the output data to identify the parameters of the dynamic method: pick up the peak law, Ibrahim Improved time-domain method, random subspace (SSI), the levy system to improve the algorithm, based on the single-mode output in response to state law, such as identification.In this paper, the bridge dynamic load test commonly used incentives Pulsation and exciting sports car test methods conducted in-depth analysis and research; through the theoretical approach, given the jump in the trials, the quality of vehicles on the bridge between the measured frequency and extent of the impact of Impact of the law. Used in the bridge for the lack of exciting ways, a road suitable for simple beam bridge across the obstacles of roadster of the incentive approach.In theory derived from a time-domain least square method to identify the structure of the bridge's natural frequency and damping ratio. To determine the initial damping ratio and frequency as time-domain least square method of initial value, which identified the bridge damping ratio and natural frequency. Freedom from the structure of the free vibration attenuation equations and modal analysis theory, derived more freedom to identify modes of the formula. Based on the measured response to the displacement of free decay time-domain data and least-squares method to identify the natural frequency and damping ratio using this formula, the number of points from the free decay displacement data can be analyzed in the structure of the bridge vibration mode.A selection of simply supported reinforced concrete beams as a numerical simulation of the target, calculated this simple beam of the former third-order vibration mode. According to the vibration mode shape to determine the location of the barrier and the corresponding height, and calculate the excitation of such circumstances the whole process of power-term response to the bridge.In response to the data were not random error and random error of 5% of the cases, the use of time-domain least square method to identify the structure of the bridge vibration-damping and over, and precision analysis. In this paper, the use of methods to identify modes of simply-supported bridge vibration mode of simulated identification. And the use of orthogonal modes of vibration mode to identify the quality of the evaluation. |
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