WIM Data Research Articles

Research on the longitudinal movement and influence of restraint parameters of the long-span suspension bridge’s main girder

The long-span suspension bridge has suffered from multiple failures of restraints such as supports, dampers, and expansion joints due to excessive accumulated displacement at the girder end. To investigate the main girders’ characteristics in the longitudinal motion of these bridges and the influence of the restraint device on the longitudinal displacement, the motion characteristics were first analyzed based on the measured displacement data of a certain bridge’s main girder; a dynamic finite element model of the bridge’s random traffic flow was then established based on the measured WIM data; combined with the girder end displacement monitoring data, the Euclidean distance was used to verify the correctness and rationality of the proposed model; finally, the model is used to discuss the influence of restraint devices (i.e., viscous dampers and supports) on the main girder in the longitudinal direction. The results show that dynamic loads (such as vehicles and wind) are the principal reasons for huge accumulated travel at the girder end; The viscous damper can effectively control the longitudinal movement; in a certain range, the larger the damping index, the better the control effect of the damper; meanwhile, the friction coefficient of the support also affects the longitudinal motion, but the effect is limited. When the friction coefficient is ≤ 0.03, the girder end’s cumulative displacement gradually decreases with the increasing friction coefficient, and compared to the damping index, the friction coefficient plays a major controlling role in the girder end displacement; when the friction coefficient is >0.03, the damping index plays a major controlling role in the girder end displacement.

Establishment and effect analysis of traffic load for long-span bridge via fusion of parameter correlation

Traffic flow is the main driver behind the dynamic response in operation of long-span bridges. To further improve the effectiveness of safety analysis for long span bridges, the bridge dynamic response should be analyzed under traffic flow. This paper investigated the simulation method of traffic flow and the bridge dynamic response under it. Firstly, the potential parameter correlation in the traffic flow was analyzed based on WIM data. Secondly, a refined simulation method of stochastic traffic flow that considers the correlation in vehicle arriving sequence and axle weight (AW) was proposed and validated. The Markov Chain Monte Carlo (MCMC) method and the correlation random sampling Monte Carlo simulation (CMCS) method were used to simulate the correlation of vehicle arriving sequence and axle weight, respectively. Finally, the constructed stochastic traffic flow is used to evaluate the influence of parameter correlation of traffic flow on dynamic response for long span suspension bridges. Results highlight the correlation of traffic flow. For the vehicle arriving sequence, those vehicles with a small quality rarely follow those with a large quality. The vehicles of different types follow certain transfer relationship. The correlation of vehicle arriving sequence can be effectively simulated that the vehicle type distribution and transition probability of the samples are both close to the WIM data. Meanwhile, the correlation of vehicle AW is mainly observed among multi-axle vehicles, and that in two- and three-axle vehicles is not significant. In the bridge application, the proposed method outperforms the MC method in the simulation of multi-axle vehicles. The parameter correlation of traffic flow has obvious influence on the response of the girder of long-span suspension bridge. The distribution of vertical displacement and bending moment of SC is closer to WIM data, and due to the small ratio of live load to dead load, some indexes such as the suspender force are less affected. The consideration of parameter correlation brings the load effect closer to the WIM data, the parameter correlation should be considered in the evaluation of the fatigue life of components, which can positively contribute to the long-term evaluation of bridge response under traffic flow.

Algorithm for Freight Transportation Performance Estimation on Expressway Using TCS and WIM Data

Algorithm for Freight Transportation Performance Estimation on Expressway Using TCS and WIM Data

Large field monitoring system of vehicle load on long-span bridge based on the fusion of multiple vision and WIM data

Vehicle Load Monitoring (VLM) on entire long-span bridge decks presents significant challenges due to the spatial and temporal randomness of vehicles. Existing VLM systems often suffer from limited viewing coverage and poor continuity of multi-vehicle tracking methods. This paper proposes a VLM system consisting of multi-vision image pre-processing, modified YOLO-v4 model, kinematics-enhanced vehicle tracking algorithm, and data fusion method between vision and Weigh-In-Motion sub-systems. The system was tested on a long-span bridge using six cameras, achieving vehicle monitoring of entire deck. The precision of multi-vehicle tracking achieved 99.28% built upon YOLO-v4 model with 96.2% mean Average Precision (mAP). Comparative results demonstrate that the modified YOLO-v4 model outperforms state-of-the-art approaches, and our proposed tracking method surpasses other methods. Our proposed system offers a comprehensive solution for VLM on entire bridge deck, overcoming the limitations of existing methods. Future work could extend the system's capability to include complex traffic patterns.

Research on Differences and Effects of Lateral Distribution Characteristics of Multi-lane Traffic Flow on Freeway

In order to obtain the probability distribution characteristics and change rules of the vehicle flow in different lanes of the expressway, based on the WIM data, the probability statistics analysis of the distribution characteristics of the vehicle type, the distance between the heads, the vehicle weight, and the speed on the different lanes of the expressway was carried out, and based on the extreme value theory. The extreme vehicle weights of different lanes were extrapolated, and the load effect was further analyzed. The results show that the probability distribution of vehicle types in each lane is different. Vehicles on one-way two-lane expressways have obvious two-tier distribution probabilities. For slow lanes, the selection probability of vehicles with 3 axles and above exceeds 0.85;The selection probability of cars with 3 axles and above on the slow lane of a one-way 3-lane expressway is higher than 0.4, while the selection probability of cars with 2 axles is about 0.15; The lateral distribution of vehicle weight meets the law of increasing from the inner lane to the outer side. The average vehicle weight of the same model on the slow lane is about 1.3-2.0 times that of the fast lane, and the average total weight of the middle lane of the three lane high-speed is the largest; The probability density distribution of vehicle weight in slow lane shows the characteristics of thick tail and long tail, while that in fast lane shows single peak distribution, and the vehicle weight is mainly concentrated in 3000kg; Each vehicle has a specific speed range, and the vehicle mixing ratio has a certain impact on the vehicle speed. The average speed of 2-axle vehicles in the same lane is 20km · h-1 higher than that of 3-axle and above vehicles. The extrapolation results of the extreme value of the load effect show that the bending moment effect of the slow lane is about 1.3-1.4 times that of the fast lane and 1.1-1.2 times that of the middle lane. The middle-span bending moment effect value increases from the inner lane to the outer lane. The transverse reduction coefficients of vehicle load on multi-lane expressways are all higher than the normative values.

Development of heavy truck models and their effects on girder bridges

The traffic on highway bridges has been increasing in both volume and magnitude, which even has become one of the main reasons leading to damages and collapse of bridges. Most of the existing regulations for overloading checking are carried out based on various limits of gross vehicle weights and axle loads. However, the results of relevant researches show that weight is only a potential factor but not the dominating factor in threatening the safety of bridges. In this study, the concept of load-effect-based heavy truck is proposed for overloading checking, and then three years of WIM data were collected and used to develop heavy truck models for each truck type, based on the understanding of the characteristics and configurations of heavy trucks as well as the distribution of their main parameters. Furthermore, the typical heavy truck models selected and their possible combinations are applied to a simply supported pre-stressed concrete T-beam bridge model with three loading levels, considering one-lane, two-lane and three-lane loaded respectively, then the induced load effect, deflection and stress are discussed for 20 loading cases. The results show the bending moment caused by heavy trucks moving on multiple lanes is 1.6 times the value of the standard truck model in Chinese specification, and the eccentric loading due to a very heavy vehicle moving on single lane usually lead to more severe effect.

Time-dependent reliability analysis for a set of RC T-beam bridges under realistic traffic considering creep and shrinkage

Reinforced concrete bridges constitute the major part of existing bridges. The purpose of this paper is to present a serviceability evaluation methodology for RC bridges under probabilistic conditions. It will be based on analytical calculations with no need to complex modeling or advanced software. For this purpose, a realistic traffic model is simulated based on existing weigh-in-motion WIM data from some European sites. The probabilistic distributions of the time-dependent load effects, moment and deflection, are then deduced after hundreds of simulations. The degradation effects are introduced in the analysis by considering the concrete creep and shrinkage. A simplified model to introduce creep effect under variable traffic load is also proposed. The time dependent reliability indices are then calculated for a set of 21 simply supported RC T-beam bridges with varying parameters such as span lengths, number of girders, girder spacing and number of design lanes. The first order reliability method FORM, is used in the reliability calculation in order to evaluate the structural performance under the considered failure scenario.

Influence of overloaded vehicles on pavement life based on WIM data

In this paper, the weight distribution characteristics of overloaded vehicles and the influence of overloaded vehicles on pavement service life are studied based on WIM data. Based on the vehicle weight data collected from weight in motion station, the vehicle weight distribution function of different axle type trucks and the weight overload ratio distribution function of different axle types are obtained by fitting. Equivalent single axle loads of the pavement under different weight limits are calculated based on the vehicle weight distribution function, and finally the pavement life growth factors under different weight limits are determined. The calculation results show that: the maximum overload ratio of two-axle vehicle can reach 340%; the number of six-axle overloaded vehicle accounts for more than 50% of the total number of overloaded vehicles, which is the largest proportion. Pavement life can be improved effectively by limiting load, and the road life growth factor shows a quadratic parabolic trend to increase with the decrease of load limit value. For two axle trucks with serious overload, the pavement life can be increased by more than 15 times with a strict load limit value.

Comprehensive benefit analysis of reinforced concrete bridge under different axle load limits

Limiting the vehicle load crossing the bridge can improve the safety of the bridge, but the transportation efficiency might be reduced. In order to reasonably evaluate the comprehensive impact of vehicle load limit on bridges, a comprehensive benefit evaluation factor K was defined to analyze the comprehensive benefits of highway bridge transportation under different axle load limits. Firstly, based on WIM data, the random distribution function of total vehicle weight and axle load was fitted, and the loss ratio of transportation benefit before and after limiting the axle load was defined and calculated based on the principle of invariable total vehicle weight. Combined with the random distribution function of the total weight and axle load, Monte-Carlo method was used to simulate the random traffic flow under different load limit levels and calculate the time-varying reliability of typical bridges under different load limit levels. Finally, the evaluation factor K was introduced to evaluate the influence of axle load limit on the comprehensive benefit of highway reinforced cocrete bridges, and reasonable axle load limit suggestions were put forward.

Probabilistic study on the macro-crack initiation of the rib-to-deck welded joint on orthotropic steel deck

The inherent randomness of the fatigue issues on the orthotropic steel deck (OSD) requires a probabilistic investigation. With respect to the unfavorable crack on the rib-to-deck welded joint of OSD, the macro-crack initiation, namely the process of the crack growth until it is detected, is studied using the probabilistic fracture mechanics (PFM). The PFM model is established based on the two-stage crack growth model and validated by test results. It is applied in the Monte-Carlo simulation (MCS) to reproduce the crack growth under the realistic traffic load obtained by the WIM data on an OSD for one year, suggesting that a lognormal function can be used in fitting the distribution of the life till the crack grows to half of the deck plate thickness. Based on the MCS results, further analysis is carried out on the macro-crack initiation by considering the probability of detection (PoD) of two different ways of non-destructive evaluation (NDE) method. Due to the lack of ability in detecting tiny cracks, it is stated that the endeavors in finding cracks in the early years could be inefficient, especially for the first 10 years. Fortunately, it is highly possible to detect the crack when it grows to a larger size by applying multiple times of inspections. With consideration of the repairs works for detected cracks, the probability that the crack grows to the critical size, e.g. half of the deck plate thickness, can be calculated. Accordingly, the inspections for the fatigue-prone sites can be optimized in a probabilistic way for the maintenance and management of the bridge.

Retracted] Calibration of the Live Load Factor for Highway Bridges with Different Requirements of Loading

Highway bridge load rating has been moving toward structural reliability since the issuance of AASHTO LRFR specifications; however, the recommended load factors were carried out by a few reliable truck data. The objective of this study is to calibrate the live load factor in AASHTO LRFR Rating Specification by using huge amount of WIM data collected in California for more than ten years between 2001 and 2013. Since traffic volumes, vehicular overloads, and traffic components are highly related to the load effect induced, a set of calibration equations is proposed here, in which the nominal standard load effect models are used and different requirements of loading are taken into account. By the analytical model of platoons of trucks and the extrapolation of the gathered WIM data over a short period of time to remote future over a longer time period, the expected maximum live load effects over the rating period of 5 years are also obtained. Then, the live load factor is calibrated as the product of the codified value multiplied by the ratio between the nominal standard load effect and the expected mean value. The results show that the products of the two ratios present rather constant, implying the proposed method and load configurations selected are effective. In the end, the live load factors of 1.0 and 0.7 along with load configurations are recommended for a simple span length less than 300 ft. The recommended calibration method and live load factors will eliminate the unnecessary overconservatism in rating specifications.

Research on vehicle distribution model based on POT theory

The vehicle overload phenomenon in expressway has become increasingly serious in China. Research on the extreme value of the vehicle load with its development trend is an urgent problem in the toll-by-weight mode. On the basis of statistical analysis of WIM data in Beijing-Zhuhai Expressway, by the extreme value theory and POT theory, a POT model had been developed. Vehicle weight distribution in the tail of the distribution function was obtained, which can predict the extreme value of vehicle load in any return period. Results showed that more heavy vehicles will appear in the future. It provided a useful reference for effective forecast of overweight vehicles.

Study on POT model of vehicle load under toll-by-weight mode

The overload and overweight operations of vehicles in expressway are particularly serious in China recently. Research on the extreme maximum value of the vehicle loads is an urgent problem in the bridge design. On the basis of statistical analysis of the WIM data from Yu-Zhan Expressway under toll-by-weight mode in Guangdong Province, the POT probability model of gross weight of the vehicle was established by the extreme value theory. It can predict the probability distribution of operating vehicle loads in any recurrence period. Results showed that the overweight vehicles were not accidental, and there may be heavier vehicles in the future. It is necessary to improve and modify the current toll-by-weight charging policy.

An improved cellular automaton with axis information for microscopic traffic simulation

Cellular Automaton (CA), an efficient dynamic modeling method that is widely used in traffic engineering, is newly introduced for traffic load modeling. This modeling method significantly addresses the modest traffic loads for long-span bridges. It does, however, require improvement to calculate precise load effects. This paper proposed an improved cellular automaton with axis information, defined as the Multi-axle Single-cell Cellular Automaton (MSCA), for the precise micro-simulation of random traffic loads on bridges. Four main ingredients of lattice, cells’ states, neighborhoods and transition rules are redefined in MSCA to generate microscopic vehicle sequences with detailed vehicle axle positions, user-defined cell sizes and time steps. The simulation methodology of MSCA is then proposed. Finally, MSCA is carefully calibrated and validated using site-specific WIM data. The results indicate: (1) the relative errors (REs) for the traffic parameters, such as volumes, speeds, weights, and headways, from MSCA are basically no more than ±10% of those of WIM data; (2) the load effects of three typical influence lines (ILs) with varied lengths of 50, 200 and 1000m are also confidently comparable, both of which validate the rationality and precision of MSCA. Furthermore, the accurate vehicle parameters and gaps generated from MSCA can be applied not only for precise traffic loading on infrastructures but also for the accurate estimation of vehicle dynamics and safety. Hence, wide application of MSCA can potentially be expected.

POT Model of Operation Vehicle Load under Toll-by-weight Mode

The phenomenon of overload operation of Expressway vehicles is particularly serious in China recently. Research on the extreme value of the vehicle load and its development trend is an urgent problem in the design of toll-by-weight mode. On the basis of statistical analysis of a highway WIM data under toll-by-weight mode in Guangdong Province, the vehicle load according to the models of the gross vehicle weight of the statistical analysis by the extreme value analysis theory to establish the pot model, gross vehicle weight distribution in the tail of the distribution function is obtained, and scientifically predict future arbitrary reproduce that may arise during the period of vehicle load value. Results show that the high speed sections of large tonnage vehicles is not accidental, in the future may also appear more large tonnage vehicle load and to pose a serious threat to the safe operation of the bridges and roads. Finally, based on the research results, the toll-by-weight standards proposed improvement suggestions and comments. It provided a useful reference for effectively control ling overloading vehicle loads.

Dynamic Impact of Heavy Traffic Load on Typical T-Beam Bridges Based on WIM Data

AbstractIn recent years, many bridge collapse accidents have been attributed to the passage of extra heavy trucks (EHTs, gross weight ≥80 t) in numerous countries. Compared with the standard traff...

Analysis of Design Live Load of Railway Bridge Through Statistical Analysis of WIM Data for High-speed Rail

In this paper, the live load model for the design of high-speed railway bridge is analyzed by statistic and probabilistic methods and the safety level that is given by the load factors of the load combination is analyzed. This study is a part of the development of the limit state design method for the railway bridge, and the train data collected from the Gyeongbu high-speed railway for about one month are utilized. The four different statistical methods are applied to estimate the design load to match the bridge design life and the results are compared. In order to examine the safety level that the design load combination of the railway bridge gives, the reliability indexes are determined and the results are analyzed. The load effect from the current design live load for the high-speed rail bridge which is 0.75 times of the standard train load is came out greater than at least 30-22% that from the estimated load from the measured data. If it is judged based on the ultimate limit state, there is a possibility of additional reduction of the safety factors through the reliability analysis.

고속축중계 자료를 이용한 차량하중 다차로재하계수 결정

The purpose of this study is to calculate and propose rational multi-lane loading factors for bridge design considering the probability of simultaneous truck passing in adjacent lanes and real truck weights. The probability of simultaneous truck passing is calculated by analyzing video image taken at various locations in highways and national roads. Weigh-In-Motion system data at two locations are used, which is combined with the probability of multiple presence to calculate the multi-lane loading factors for typical 2 lane and 5 lane bridges. Statistical properties of multi-lane loading factors are also calculated assuming that locations for video images and WIM data represent the overall traffic condition in the country. Results are compared with various design codes in the world and they show that the values are between the current Korea Bridge Design Code and AASHTO LRFD specification or Eurocode and are similar to Canadian Code.

Determination of Truck Factor from WIM Data in Thailand

Determination of Truck Factor from WIM Data in Thailand

Study of Load Spectra of the Jaozhou Bay Expressway Based on MEPDG

To study the traffic characteristic and axles load spectra of Jaozhou bay expressway, WIM data was collected, axle configuration and vehicles classification was determined. The characteristic of truck traffic monthly distribution and the truck hourly distribution was studied and axle load spectra for major tuck class groups were developed. The results show that there were more than 22 truck types running on the expressway, the peaks of truck traffic monthly distribution was in December and the rush hour of the hourly distribution was at noon. All major axles had a bimodal pattern of load spectra.