Random Vehicle Load Research Articles

Bridge Damage Identification Using Rotation Influence Line Under Random Vehicle Loads

As a critical characteristic curve of bridge structures, the influence line (IL) is effective in evaluating the bridge damage and bearing capacity. Contrary to conventional methods using static loading to obtain IL, this study proposes a methodology to determine the rotation influence line (RIL) based on the vehicle–bridge interaction (VBI) under random traffic loads. A key feature is the employment of the machine learning algorithm to determine the RIL from the upper and lower bridge response data induced by traffic flow, which is simulated using the cellular automata (CA) approach. Subsequently, by establishing a relationship between the RIL difference and the structural damage coefficient, this study identifies the bridge damage location and degree effectively. The numerical example results validate the accuracy in identifying both single- and multi-damage cases. The parameter analysis indicates that larger vehicle speed induces higher errors in identifying the RIL and the bridge damage.

Analysis of dynamic response of three-span bridge using vehicle load data from Road Administration Department IV in Vietnam

In many studies, the dynamic response of bridges is influenced by various factors. Multiple factors, such as vehicle loads, road roughness, vehicle-bridge interactions, and travel speed, impact the dynamics of a three-span bridge on highways. Because the mass of the vehicle, including the cargo, fluctuates randomly, a probabilistic methodology based on the Monte Carlo method is utilized to produce random anomalies for dynamic analysis. To examine the Song Gieng bridge, data from the Road Administration Department IV on heavy vehicle loads and overloaded vehicles are utilized to produce random vehicle loads. The analytical results indicate that there is a discrepancy in the probability distribution rules between the vehicle load (input random variable) and the dynamic impact factor (output random variable). This implies that their mapping connection is not monotone. Compared with the threshold values specified in the bridge design standards of Vietnam and the United States, the dynamic impact factor obtained in this study is significantly different. These findings can provide additional guidance for practicing engineers.

Fatigue life evaluation on wire rope suspenders of the suspension bridge based on a time-varying degradation process

Suspenders are critical force transmission components of a suspension bridge and may be more prone to fatigue damage due to environmental aggression and repetitive live loads. To evaluate the safety of the suspender more accurately, a fatigue life evaluation framework of the rope suspender was proposed, where a time-varying fretting-corrosion-fatigue degradation process of the rope wire and probabilistic critical limit states based on failure area were integrated. A case study on the rope suspenders of a prototype suspension bridge was performed under the random vehicle and wind loads, and the reliability indices and fatigue life of the rope suspender were obtained. Results show that the fretting wear had an obvious effect on the degradation process of the wire rope in conjunction with corrosion fatigue, and the fatigue life of the rope suspender would be less than its design life. The proposed method can comprehensively evaluate the service life of wire rope suspenders and provide replacement suggestions more timely, ensuring the safety of the bridge operation.

Random vibration analysis of the maglev vehicle-guideway system using a probability density evolution method with uncertain parameters

Random dynamic analyses of maglev vehicle-guideway coupled systems are of significant interest but have yet been comprehensively performed. This paper presents a time-dependent coupled random model of a maglev vehicle-controller-guideway-pier to investigate random vibration characteristics of the dynamic system. In the study, a 12-degree-of-freedom vehicle model is considered, a three-dimensional detailed guideway model is established using the finite element method, and the electromagnetic levitation force is controlled with a current feedback controller. Then, the generalized F-discrepancy representative point set selection strategy and probability density evolution method, which can consider multiple random parameters, are combined to analyze the dynamic system. Random vehicle parameters and irregularity are introduced and the mean value, standard deviation, limits satisfying different probability guarantee rates, and probabilistic information are calculated. The model was validated with field measurement data from an electromagnetic suspension (EMS) maglev line. In addition, the Monte Carlo method was used to assess the accuracy and efficiency of the proposed method. The results demonstrate that the proposed method has good accuracy and efficiency. The effects of vehicle running speed, random irregularity, and random vehicle loads on the dynamic vibration of the system are discussed.

Dynamic Response of Multitower Suspension Bridge Deck Pavement under Random Vehicle Load

Recently, the multitower suspension bridge has been widely used in long‐span bridge construction. However, the dynamic response of the deck and pavement system of the multitower suspension bridge under random vehicle load is still not clear, which is of great significance to steel‐bridge deck pavement (SBDP) design and construction. To reveal the mechanical mechanism of the steel‐bridge deck pavement of the multitower suspension bridge under traffic load, this paper analyzed the mechanical response of the pavement based on case study through the multiscale numerical approach and experimental program. Firstly, considering the full‐bridge effect of the multitower suspension bridge, the finite element model (FEM) of the SBDP composite structure was established to obtain key girder segments. Secondly, the influences of pavement layer, bending moment and torque, random traffic flow, and bridge structure on the stress of the girder segment were analyzed. Thirdly, the mechanical response of the pavement layer to the orthotropic plate under random vehicle load was studied. Finally, a full‐scale model of the experimental program was established to verify the numerical results. Results show that (1) the pavement layer reduced the stress of the steel‐box girder roof by about 10%. In the case of adverse bending moment and torque, the longitudinal and transverse stresses of the pavement layer were mainly concentrated in the stress concentration area near the suspender. Under the action of the random vehicle flow, the stress response of the pavement layer was increased by 40% compared with that under standard load. (2) Three‐tower and two‐span bridge structures have a great influence on the vertical deformation of the pavement layer under the action of vehicle load. Thus, the pavement material needs to have great deformation capacity. (3) The full‐bridge effect has a significant influence on the longitudinal stress of the local orthotropic plate, but a small influence on the transverse stress. (4) There is a good correlation between the experimental measurement results of the full‐size model and that of the numerical model. The research results can provide guidance for SBDP design and construction of the multitower suspension bridge.

Method of Calculating Life-Cycle Fatigue Damage of Orthotropic Steel Bridge Decks under the Combined Actions of Vehicle Loads and Pavement Temperature

The fatigue analysis on orthotropic steel bridge decks is a hot topic in bridge engineering field. This study provides one method for fatigue analysis under the combined actions of vehicle loads and pavement temperature. To be specific, taking the steel bridge deck of one cable-stayed bridge as a research object, this study proposes a method of calculating life-cycle fatigue damage of orthotropic steel deck under the combined actions of vehicle loads and pavement temperature. First, a finite element model of steel bridge deck with asphalt pavement is built to analyze the influence of pavement temperature on the fatigue stress of steel bridge deck. Second, a simulation method of fatigue stress caused by random vehicle loads is proposed. Finally, a method of calculating the life-cycle fatigue damage of welded joints under the combined actions of vehicle loads and temperature is proposed. The results show that temperature has a significant effect on fatigue damage, and the cumulative fatigue damage in the rib-to-rib welded joint is significantly greater than that in the deck-to-rib welded joint. The results can provide meaningful references for bridge engineers to carry out fatigue analysis on orthotropic steel bridge decks.

Stochastic Analysis of Vehicle-Bridge Coupled Interaction and Uncertainty Bounds of Random Responses in Heavy Haul Railways

The systematic running safety assessment of railway bridges presents lots of challenges, one of which is estimating the uncertainty bounds of the structural responses of bridges under vehicle loads with multisource randomness. In this study, a probability safety assessment method is proposed for evaluating the uncertainty bounds of random time-history responses for the stochastic train-bridge coupled system. First, a refined probabilistic model for the train-bridge coupled system (TBS) in heavy haul railway is established with the multi-excitations of random track irregularities, random vehicle loads and stochastic structural parameters. The probability density evolution method (PDEM) is employed to obtain the solution of the time-varying probability transferred between the stochastic excitations and the output of the dynamic responses. Then, to establish a rapid and straightforward approach for the systematic running safety assessment of the TBS, the quantiles of the probability distribution are used to estimate the time-history uncertainty bounds of random responses of interest distributed in real probability functions. Case studies by the field test and numerical simulation are presented to verify and investigate the accuracy and reliability of the proposed method. The results show that the quantiles of the probability distribution proposed are suitable for the systematic running safety assessment of the TBS.

Dynamic response of a bridge deck pavement

A three-dimensional finite-element vehicle–bridge–bridge deck pavement (BDP) coupling vibration model was built to investigate the coupled effect of bridge surface roughness and vehicle velocity on the dynamic response of BDPs under random vehicle loads. The results obtained show that, compared with the stress response of a fixed node at the midspan, the response of stress extremes of the BDP not only reflect the stochastic characters of vehicle loads but also directly reflect the most disadvantageous response of the structure. In addition, it was found that the amplification coefficients of different control stresses were very close for a certain international roughness index, the stress response of the BDP considering roughness was significantly greater than that of smooth surfacing and when vehicles are travelling on a bridge with a rough surface, speed should be controlled to be neither too fast nor too slow.

Equivalent constant-amplitude fatigue load method based on the energy equivalence principle

An equivalent constant-amplitude cyclic loading method for random vehicle load is proposed based on the concept of energy equivalence. The filtered compound Poisson process is adopted to describe random vehicle load, through which the vehicle load spectrum is gained. The total dissipated energy due to fatigue loads subjected to concrete structures is deduced by introducing a multi-scale model, in which the energy dissipation induced by the nano-cracks level is presented, and the energy transition from nano to macro scales is derived. By assuming that the total energy dissipation under random loading equals that under equivalent constant-amplitude loading, the equivalent load ratio and amplitude as well as the number of equivalent cycles for random vehicle load are obtained. To validate the effectiveness of the proposed method, a set of numerical simulations is presented. The fatigue damage accumulations for concrete structures under both the random load and the equivalent loads converted by the proposed method and the classic root mean square method are calculated. By comparing with the root mean square method, the accuracy and advantage of the proposed equivalent load model are verified.

A stochastic dynamic model of train-track-bridge coupled system based on probability density evolution method

• A new stochastic dynamic model of train-track-bridge coupled system (TTBS) based on PDEM is developed. • The multi-coupling effect of excitations can be simultaneously input into the new model. • The new developed approach NTM- mp succeeded in getting the discrete point design of TTBS. • Based on PDEM, the stochastic probability evolutionary mechanism of TTBS are reproduced accurately. An innovative stochastic dynamic model of a 3D train-track-bridge coupled system (TTBS) with refined wheel/rail interaction is established for a high-speed railway based on the random theory of probability density evolution method (PDEM). The multi-coupling effect of excitations can be simultaneously input into the new model, e.g. random track irregularity, random vehicle loads, stochastic system parameters, et al. Moreover, a new approach, named “Number theoretic method of multi-target probability functions” (NTM- mp ), is developed to obtain the discrete point sets of multidimensional random parameters in hypercube space, aims to solve the point design of system uncertainty. The stochastic harmonic function (SHF) is applied to generate representative random track irregularity samples. The results of TTBS got by PDEM are verified with several typical case studies for its efficiency and reliability, which are the deterministic results in the representative publication, the Monte Carlo method (MCM) results, and the field testing results on the high-speed railway. At last, a typical case study of TTBS on a high-speed railway is presented for numerical analysis. Discussions and significant conclusions on the random dynamic responses are presented.

PROBABILITY MODEL AND RELIABILITY ANALYSIS OF CABLE STRESS FOR CABLE-STAYED BRIDGE

The aim of this paper is to investigate the time-varying effect of stay cable of long-span cable-stayed bridges subject to vehicle load. The analysis has been carried out on the Su-Tong cable-stayed bridge in Jiangsu, China that has the second-longest span among the completed composite-deck cable-stayed bridges in the world currently. Probability models of vehicle load in each lane (fast lane, middle lane and slow lane) and cable stress under random vehicle load were developed based on the stochastic process theory. The results show the gross vehicle weight follows lognormal distribution or multi-peak distribution, and the time-interval of the vehicle follows a lognormal distribution. Then, the probability function of maximum cable stress was determined using up-crossing theory. Finally, the reliability of stay cable under random vehicle load was analysed. The reliability index ranges from 9.59 to 10.82 that satisfies the target reliability index of highway bridge structure of finished dead state.

Evaluation of multi-lane transverse reduction factor under random vehicle load

This paper presents the two-, three-, and four-lane transverse reduction factor based on FEA method, probability theory, and the recently actual traffic flow data. A total of 72 composite girder bridges with various spans, number of lanes, loading mode, and bridge type are analyzed with time-varying static load FEA method by ANSYS, and the probability models of vehicle load effects at arbitrary-time point are developed. Based on these probability models, in accordance to the principle of the same exceeding probability, the multi-lane transverse reduction factor of these composite girder bridges and the relationship between the multi-lane transverse reduction factor and the span of bridge are determined. Finally, the multi-lane transverse reduction factor obtained is compared with those from AASHTO LRFD, BS5400, JTG D60 or Eurocode. The results show that the vehicle load effect at arbitrary-time point follows lognormal distribution. The two-, three-, and four-lane transverse reduction factors calculated by using FEA method and probability respectively range between 0.781 and 1.027, 0.616 and 0.795, 0.468 and 0.645. Furthermore, a correlation between the FEA and AASHTO LRFD, BS5400, JTG D60 or Eurocode transverse reduction factors is made for composite girder bridges. For the two-, three-, and four-lane bridge cases, the Eurocode code underestimated the FEA transverse reduction factors by 27%, 25% and 13%, respectively. This underestimation is more pronounced in short-span bridges. The AASHTO LRFD, BS5400 and JTG D60 codes overestimated the FEA transverse reduction factors. The FEA results highlight the importance of considering span length in determining the multi-lane transverse reduction factors when designing two-lane or more composite girder bridges. This paper will assist bridge engineers in quantifying the adjustment factors used in analyzing and designing multi-lane composite girder bridges.

Fatigue Behavior of Hangers on a Three Tower Suspension Bridge

Oujiang Beikou Bridge under design is a three tower suspension bridge with a main span of 217.405+2×800+275=2092.405m. Fatigue analysis of the hangers on the bridge is a necessity in the design to ensure safety and functionality. In this paper, fatigue life assessment of the hangers is proposed considering both the load effect and the hanger resistance. The load effect is calculated through the random traffic model based on the Monte Carlo simulation and the finite element model established by ANSYS. Random vehicle load and spacing are both simulated in the model and the traffic volume is predicted. The resistance is calculated according to the Eurocode and the corrosion effect is also taken into consideration using the S-N curves for the corroded steel wires. It is noted in the paper that the influence lines of hangers have a wide range and the load effect can be shared by 80 hangers. The fatigue life of hangers on three tower suspension bridge is much longer than the lifetime when the corrosion effect is not considered and the corrosion has a big impact on the fatigue life. The length of hangers is associated with the fatigue damage and the hangers at the two ends of the three tower suspension bridge on the side span suffer the largest fatigue damage.

Distribution Characteristics of Random Loads in Aizhai Bridge

AbstractParametric expressions of the normal and lognormal-distribution functions are derived by the maximum-likelihood method, whereas parametric expressions of the Weibull distribution function are derived by the least-square method. Based on a 48 h real-time survey of random vehicle loads on the Aizhai bridge, some parameters are analyzed and optimally fitted. These parameters are tested using the Kolmogorov-Smirnov (K-S) method to satisfy the requirements so that the optimum distribution parameters and types can be identified out according to the measured distributions. Results show that vehicles on the Aizhai bridge can be divided into seven types, with the dominant ones being the second (car) and seventh (large truck) types, accounting for 49.5% and 21.56%, respectively. Based on analytical results, the distribution characteristics of vehicle speed are as follows: (1) The speeds of the third, fourth, and fifth types of vehicles satisfy normal distribution using the K-S method; (2) Although the speed...

Examining the Stationarity and Ergodicity of Traffic Flow on Highway Bridges

According to the information of vehicles collected by weigh-in-motion (WIM) systems on 28 lanes of 6 highway bridges, stochastic processes of the type of traffic flow on each lane are generated respectively. Time means and time-correlation functions were calculated accordingly based on stochastic process theory. The stationarity and ergodicity of the composed stochastic processes of the vehicle type of traffic flow were then examined. The statistical characterization of samples collected by WIM systems on actual highways will approach the total value if the samples are sufficiently plenitudinous. Moreover, the statistical characterization of the collected vehicle information will exhibit the characters of the entire specimen. Such results can be used as guides to model random vehicle load further.

Load Spectrum and Fatigue Life Computer Analysis of Prestressed Concrete Bridges

With respect to fatigue damage of heavy traffic on the bridge structure, this paper studied on load spectrum and fatigue simulation. The author used manual recording, live cameras, vehicle dynamic weighing system (WIM) to conduct traffic investigation in a continuous 24-hour period. Basing on these data in Hebei province, we established typical vehicle load spectrum using probabilistic and statistical methods, and deduced a standard fatigue vehicle model on this basis. Then we prepared random load spectrum by MATLAB and realized loading it on a finite element model (FEM). Next, the paper assessed the fatigue life of in-service highway bridges that in Hebei by comparing typical vehicle load and random vehicle load. Results showed that vehicle speed has significant influence on fatigue damage under typical vehicle load. Equivalent stress amplitude is small in two operational states under random vehicle load, the general operation state and intensive operation state. Fatigue damage to bridge under general operation is obvious. After verified the applicability of the standard fatigue vehicle model, we can believe that this model developed in this article can be further used as a reference to check highway fatigue damage in the entire Hebei province. Moreover, all the results showed that the bridges wouldn’t get fatigue failure under a normal operation state when there is no impact of environmental factors.

Vehicle Load Spectrum Simulation of Long-Span Bridges

Based on the requirement for fatigue damage evaluation of long-span bridges, and existing research literatures, the vehicle type, vehicle weight and time duration are taken as characteristic parameters of random vehicle load. Taking the Second Nanjing Yangtze River Bridge as an example, the characteristics of traffic load are obtained by traffic investigation and the data from existing research results. In the paper the method and process for vehicle load spectrum simulation which includes data acquisition of random traffic load, statistical analysis and Monte Carlo simulation is proposed. The simulation program of random traffic flow is verified using the measured data. The proposed method can provide a reference for random traffic load simulation.

Corrosion fatigue effects on life estimation of deteriorated bridges under vehicle impacts

Corrosion fatigue is more detrimental that of either one acting separately. The safety and reliability are greatly endangered by the combined effects from environmental corrosions and vehicle-induced fatigue damages, which could possibly lead to a catastrophic failure. In this paper, the corrosion fatigue effects on life estimation of deteriorated bridges subjected to dynamic vehicle loads are evaluated based on a reliability-based approach. Both the road surface deterioration and the structural member corrosion are considered in the vehicle-bridge dynamic system for stress range estimations. Varied material corrosion rates, vehicle types, vehicle speeds, and time-varied road surface conditions are considered. At the end of each stress block, the fatigue life is estimated by evaluating the cumulative probability of failure. The effects of the corrosion induced area loss and moment of inertia reduction are limited and are much less than the random effects from road surface condition. Corrosion induced fatigue strength reduction have a large effect on fatigue life. More than 60% reduction of fatigue life is predicted for different corrosion levels. The fatigue strength reduction is found more sensitive for the fatigue life estimation. With the refined vehicle-bridge dynamic analysis model and a refined material corrosion model, it is possible to assess the time-variant damages from random vehicle loads, environmental corrosion and their combined effects.

Mechanical Performance of Bridge Structures under the Random Dense Vehicle Loads

Based on the investigation of vehicle loads, the model of the random dense vehicle load was simulated, and three different degree dense vehicle loads were obtained with the simulated model. The calculated results show that the random dense vehicle loads moving on the bridge structures is very dangerous for the security of the structures.

Safety Assessment of Bridge Structures under the Random Dense Vehicle Loads

Based on the investigation of vehicle loads, the model of the random dense vehicle load was simulated, and three different degree dense vehicle loads were obtained with the simulated model. The calculated results show that the random dense vehicle loads moving on the bridge structures is very dangerous for the security of the structures; the combination factor 1.4 designed in the code is not precise for the situation of random dense vehicle loads, and it is suitable for the common vehicle loads.