Bridge Dynamic Tests Research Articles

Research on dynamic detection method of bridge vehicle load based on optimization algorithm

Abstract In recent years, accidents causing casualties and losses to people and property have occurred frequently throughout the country due to bridge safety problems, causing huge losses to the country and people’s property. To prevent the recurrence of such incidents and effectively maintain the safety and interests of the people, this paper intends to use the optimization algorithm as the technical support to study the optimal method for dynamic detection of vehicle loads on bridges. The gradient descent method is used to obtain the deflection influence line of the bridge dynamic test structure and the overall vibration frequency of the structure. The bridge test area is then selected by the stochastic gradient descent method, and the measured strain and deflection influence lines are used to modify the initial finite element model of the bridge so that the finite element model can truly reflect the actual mechanical behavior of the bridge structure. According to the survey, as of the end of 2019, there were 878,300 highway bridges with a total mileage of 6063.46 m, which was 26,800 more than in 2018, and the mileage increased by 4,948,600 m. Among them, mega bridges accounted for 5716 bridges with a mileage of 10,323,300 m, and bridges accounted for 108,344 bridges with a mileage of 29,237,500 m. Many bridges in service provide convenience for people’s life and travel but also bring great challenges to bridge management and maintenance, bridge appraisal, and assessment. Monitoring the bridge load condition helps to grasp the actual working condition of bridges in a timely and accurate manner and to warn and repair the safety hazards that appear on bridges in time to prevent accidents.

Methodology For Calculation Of Bridge Safety Factor In Lithuania

The paper reviews the United States and Slovenian safety factor calculation methodologies and proposes a method for more accurate estimation of residual strength of bridges designed and built in Lithuania. For more detailed analysis, the main parameters and defects directly affecting the strength of the bridges were analysed in detail, and the flows of heavy vehicles, which have significantly increased for previously designed bridges, were assessed.This article proposes to calculate the dynamic factor of bridges, not according to the empirical formulas used in the United States and Slovenian safety factor calculation methodologies, but after performing the bridge dynamic test, because the results of Lithuanian bridge dynamic tests show that the parameter strongly depends on smoothness and damage of carriageway wearing surface. In order to evaluate the suitability of the Lithuanian bridge safety factor calculation methodology proposed in this article, a real bridge was selected, and its safety factors calculated according to the above mentioned and proposed methodology and the results obtained were compared.

Novel tensor subspace system identification algorithm to identify time-varying modal parameters of bridge structures

Subspace-based system identification algorithms have been developed as an advanced technique for performing modal analysis. We introduce a novel tensor subspace-based algorithm to identify the time-varying modal parameters of bridge structures. A new time dimension is introduced in the traditional Hankel matrix, and a mathematical model of tensor subspace decomposition is established. Combined with the stabilization diagram, tensor parallel factor decomposition is used to estimate the frequencies, mode shapes, and modal damping ratios. The effectiveness of the proposed algorithm is validated by comparing it with the classical sliding-window–based stochastic subspace algorithm on a model cable-stayed bridge dynamic test. The proposed algorithm is further applied to process the dynamic responses of a real bridge health monitoring system to identify its time-varying modal frequencies. Our results demonstrated that the proposed algorithm significantly reduces computational efforts and extends the range of solution ideas for future out-only time-varying system identification problems.

Prediction method of bridge static deformation based on dynamic test

AbstractTo solve the high cost of bridge load tests, considerable influence on traffic, and damage to bridge structure in the process of problem detection and maintenance of existing bridges, we use the method of improved Gaussian process response surface to explore the prediction of the rigidity and unit weight of existing bridges to produce high‐precision predictions of the existing bridge static test. The Gaussian process response surface method in Bayesian principle is adopted to optimize and correct the model. Because Gaussian process is a non‐parameter model with high sensitivity, reliable accuracy, and small calculation, it avoids repeatedly using finite element model. This makes the efficiency of finite element correction improve significantly. A continuous beam bridge is adopted as a study case. In sample selection, an improved uniform design method based on weighting is designed to improve the learning efficiency and prediction accuracy of the model while using ANSYS to analyze and predict the typical bridge. The analysis of the date of the bridge dynamic test is used to correct the finite element model, obtain the actual parameters of the bridge structure, and predict the measured data of the bridge static load test based on the modified finite element model.

Dynamic Tests in Bridge Health Monitoring

Abstract Dynamic tests are one of the most significant diagnostic procedures applied in Bridge Health Monitoring in many countries. The paper presents a proposal of unified classification of the bridge dynamic tests together with review of the testing methods, including tests under designed and controlled loads, arranged short-term tests under normal traffic loads as well as permanent dynamic monitoring by means of built-in gauges mounted on a structure. Classification of bridge dynamic tests is proposed taking into account various types of vibration excitation methods, measured parameters and possible applications of obtained results in the Bridge Health Monitoring. General rules and procedures of bridge dynamic tests are described and discussed.

Continuous force excited bridge dynamic test and structural flexibility identification theory

Compared to the ambient vibration test mainly identifying the structural modal parameters, such as frequency, damping and mode shapes, the impact testing, which benefits from measuring both impacting forces and structural responses, has the merit to identify not only the structural modal parameters but also more detailed structural parameters, in particular flexibility. However, in traditional impact tests, an impacting hammer or artificial excitation device is employed, which restricts the efficiency of tests on various bridge structures. To resolve this problem, we propose a new method whereby a moving vehicle is taken as a continuous exciter and develop a corresponding flexibility identification theory, in which the continuous wheel forces induced by the moving vehicle is considered as structural input and the acceleration response of the bridge as the output, thus a structural flexibility matrix can be identified and then structural deflections of the bridge under arbitrary static loads can be predicted. The proposed method is more convenient, time-saving and cost-effective compared with traditional impact tests. However, because the proposed test produces a spatially continuous force while classical impact forces are spatially discrete, a new flexibility identification theory is required, and a novel structural identification method involving with equivalent load distribution, the enhanced Frequency Response Function (eFRFs) construction and modal scaling factor identification is proposed to make use of the continuous excitation force to identify the basic modal parameters as well as the structural flexibility. Laboratory and numerical examples are given, which validate the effectiveness of the proposed method. Furthermore, parametric analysis including road roughness, vehicle speed, vehicle weight, vehicle\'s stiffness and damping are conducted and the results obtained demonstrate that the developed method has strong robustness except that the relative error increases with the increase of measurement noise.

A Novel Testing System for Mechanics Properties of the Thin-Walled Micro Components in Inertial System

In this paper, micro tensile method was combined with micro bridge dynamic test method as a new testing method for mechanics performance to be put forward, and a novel testing system for mechanics properties of the thin-walled micro components was established. The micro testing specimen were designed and manufactured. And related mechanics performance tests were carried on to verify the feasibility and reliability of the test system. The experimental results show that displacements of the testing system are measured with 0.01μm resolution and axial loads are measured with 0.005N resolution.

Modal shape identification of the vibration data of bridge dynamic test using fuzzy clustering

The transmission of vibration to the adjacent buildings due to the traffic passing over Ghalemorghi Bridge in Tehran, has caused disruption to the inhabitants of the buildings. In order to investigate the vibration condition of the bridge, a dynamic loading test was performed and the output was analyzed using a non-parametric modal identification approach. In this article, the non-parametric modal identification algorithm from output measurement has been interpreted corresponding the clustering algorithm by subset relation with complex exponential basis functions on basis of soft computing paradigm. Moreover, the free vibration of bridge acceleration under the loading of a passing truck is processed by this identification method, and the acceleration vibration data integration in frequency region is performed by fuzzy clustering in order to determine the modal shape. Finally, vibration of the bridge elastic bearings and the similarity of the deck natural frequency to the vibration frequency of “Deck-Elastic bearing” system are recognized as two major problems of the bridge.

Bridge Dynamic Tests: Implications for Seismic Design

A five span, 400 ft (120m) long, reinforced concrete box girder bridge supported on single column piers, which are pile founded, was subjected to extensive dynamic tests. The pullback and quick release method of excitation was used. Two D-8 crawler tractors were used to apply total release loads which had a magnitude of about one-quarter of the earthquake design loads. System identification techniques were used to extract the experimental in situ dynamic stiffness of the pier pile group foundations from the suite of field data. An independent geotechnical analysis of the bridge's pile foundations yielded pile group stiffness which were in acceptable to good agreement with the experimentally determined values. Moreover, this analysis indicated that for design level seismic loadings the pile group stiffnesses are quite deflection dependent. It was further shown that it is essential to include the soil-structure interaction effect in the analytical model if correct distributions of seismic loads are to be obtained.