Fatigue Life Of Bridges Research Articles

Fatigue life prediction for high-speed railway bridges by reconstructing monitoring-based dynamic stress

Abstract Bridge responses that are excited by high-speed trains have the characteristics of high amplitude, high cycle, and large dynamic effects, which greatly affect the fatigue bearing capacity of affected bridges. To achieve reliable analysis of the fatigue performance of high-speed railway bridges, this study developed a bridge fatigue life prediction method based on the reconstruction of the train-induced dynamic stress time history. First, the equations for solving the static stress time history under influence line virtual loading are derived, and then the dynamic stress time history reconstruction method based on two types of dynamic correction factors is proposed. The statistical characteristics of the train loads and dynamic correction factors are fit according to monitoring data, and bridge fatigue life prediction is realized by use of the reliability theory. Finally, the applicability and effectiveness of the proposed method are verified by using a train-bridge interaction model and monitoring data from a long-span high-speed railway bridge. The results show that the proposed method can greatly improve the accuracy of fatigue performance analysis and can effectively predict the fatigue life of high-speed railway bridges under complex loads. These results can provide an important reference for fatigue evaluation of high-speed railway bridges.

Assessment of critical parameters affecting fretting fatigue life of bridge stay cables at saddle supports

Saddle systems are a popular solution for supporting cables in cable-stayed bridges. Fretting fatigue failure of cables at saddle supports is a primary design consideration for these systems. Critical parameters that affect the fretting fatigue life of the cables are the contact forces and the slip displacements at the contact points between the cables and the saddle. Determining these critical parameters is the first step in evaluating the fretting fatigue life of the cables. Wear in the contact points between the cables and the saddle can affect the load distribution in saddle systems and consequently affect these critical parameters. However, the effect of wear has not been studied in the previous works. This paper first discusses the methods proposed in the literature for evaluating contact forces and slip displacements in the contact points between a cable and a saddle. Then, a finite element model of the problem and a framework for modelling the wear are presented. Finally, fretting fatigue life is determined based on the different studied approaches. The main highlights of the current study are considering the effect of wear in the simulation and employing an enhanced FE model for slip displacement calculations. The results of the basic model without wear effects showed that the first contact point between the cable and the saddle is critical for fatigue failure. However, by incorporating wear in the model, the contact force at the first point dropped and the second contact point became critical; this is in line with the observations in large-scale fatigue tests of saddle systems.

Fatigue Life Assessment of a Plate Girder Bridge Using an Uncoupled Iterative Scheme for Bridge–Vehicle Interaction

Most commercial software allows moving-load analysis to be performed on finite-element bridge models. However, the available software does not allow the incorporation of the dynamic load induced by vehicles due to vibration resulting from pavement roughness. The present study, aims to utilize an uncoupled iterative scheme to incorporate road roughness into the numerical model in order to overcome this problem. The vehicle-induced stress history obtained using the uncoupled iterative scheme is then used to determine the fatigue life of a plate girder bridge. A fatigue damage model is proposed, which incorporates the load sequence effects and the segregation of load cycles into crack-initiation and propagation stages. Investigation of various influencing parameters reveals the significance of vehicle speed, vehicle arrival time, pavement category, and the eccentricity of the load and girder design variables on the fatigue life of the bridge.

Fatigue life prediction of a Durga flyover bridge at vijayawada using wireless sensors

It is essential to inspect and assess any fatigue damage to the components of a structure in order to determine how long it will last. This is necessary for constructions such as concrete bridges, which are subjected to fluctuating loads with high intensity and frequency. This study presents a computer application method for calculating the fatigue life of the Durga flyover (reinforced concrete) bridge. The damage to bridge components can be evaluated based on the dynamics of the interaction between the bridge and vehicles caused by actual traffic. The computer code initially calculates the fluctuation of stresses caused by the passage of various types of vehicles in a given segment of a bridge. The other module has a continuous set of loads to measure the strains and calculate the stress variations across the section components. The rainflow method is used to count stress cycles owing to the fact that the peak intensities of the stress cycles are not steady, and the appropriate S-N curves are utilized to determine the damage caused by each cycle. In this analysis, the stress range amplitude waveform and fatigue toughness characteristics of bridge elements were employed to systematically detect continuous bridge girder fatigue damage. The most severe flexural stresses induced by vehicles were detected, and a stress-range frequency waveform was created while accounting for the total traffic volume. Linear damage accumulation theory was used to calculate the cumulative damage index and bridge fatigue life. The Miner's rule was used to calculate the overall damage caused by the passage of the vehicles. The major factors affecting the fatigue life are the effects of the span, pavement quality, increase in the speed of operation, weight, and suspension characteristics of the bridge.

Fatigue Life Assessment of Intercity Track Viaduct Based on Vehicle–Bridge Coupled System

During the long-term operation of an urban railway viaduct, it is subjected to multiple cyclic loads caused by the movement of a vehicle. As a result, the fatigue life of the bridge should be fully considered during the design process. Furthermore, the bridge structure will be subject to environmental corrosion for an extended period of time, resulting in concrete carbonization and reinforcement corrosion, which aggravates the bridge structure’s fatigue damage. To compensate for the disadvantage of the traditional static analysis method’s inability to consider vehicle speed, a vehicle–bridge system coupled model is established, material corrosion is considered, railway bridge damage under vehicle load is analyzed, and the service life of common 30 m and 25 m span bridges is calculated. The results show that ignoring corrosion will understate the bridge damage, and vehicle speed has a significant impact on bridge fatigue life. Finally, the recommended operating speeds for 30 m span and 25 m span bridges are provided.

Static and dynamic vehicle load identification with lane detection from measured bridge acceleration and inclination responses

The effects from passing vehicle's load on bridge are divided into two categories: static effect and dynamic effect. The static effect usually indicates the pseudo-static responses of the bridge caused by the vehicle gross weight while the dynamic effect means dynamic responses due to vehicle and bridge dynamic properties and bridge pavement roughness. Both effects need to be properly evaluated because the vehicle static weight is a governing factor in determining bridge's fatigue life while the dynamic part of the vehicle load tends to amplify the bridge responses. In this paper, a method based on an extended Kalman filter is proposed to identify vehicle static and dynamic load only from responses recorded by portable accelerometers, together with their transverse position, which affects the identification of the loads. Even though only accelerometers are employed as sensors, the bridge vertical acceleration can capture the dynamic load components and the inclination obtained from the projection of the gravitational acceleration in the longitudinal direction can capture the low-frequency component. The feasibility of the proposed method is proved through numerical simulation and an experimental test on a bridge. This paper makes full use of three-axis accelerometers to estimate vehicle's static and dynamic load considering the vehicle's passing route, thus solving the nonlinear problem caused by vehicle's transverse position. Moreover, the proposed method eliminates the need of using other devices like displacement sensor or strain gauges to obtain low-frequency components.

Pre-damage effect on the residual behavior of externally post-tensioned fatigued steel-concrete composite beams

Steel-concrete composite beams in highway bridges are susceptible to various types of damage during their service life. These damages can greatly affect the structural performance and shorten the fatigue life of bridges. The efficacy of adding external post-tensioning, as a strengthening technique, to steel–concrete composite beams that are subjected to fatigue loading is not well investigated. Therefore, this study includes fatigue testing of post-tensioned steel–concrete composite beams with various types of pre-damage. Three of the tested samples were subjected to outdoor environmental changes, cyclic preloading, and static overloading as pre-damages before applying the external post-tensioning. The strengthened samples were exposed to fatigue tests to a million cycles under four-point bending. Samples without pre-damage were tested as references to those with pre-damages. The crack patterns in the concrete decks were evaluated during these tests. Static tests to failure were performed to explore the residual capacities, deformations, and strains of all fatigued samples. The crack patterns in concrete decks were significantly affected by the type of pre-damage that was applied before the post-tensioning. The static overloading pre-damage reduced the number of cracks and their rate of propagation while the exposure to outdoor environment pre-damage induced more cracks, which negatively affected the crack patterns during fatigue loading. Subjecting the sample to plastic deformation pre-damage slightly improved its performance in terms of residual stiffness and ultimate load. The residual ultimate load was increased by 7% relative to the fatigued sample without pre-damage. However, the ductility was reduced by 40% due to the initial plastic deformation. This reduction in ductility was combined with a decrease in the interface slippage between the concrete deck and steel flange.

Fatigue Assessment for Deck-Rib Welded Joints of Orthotropic Steel Deck Using a Simplified Nodal Force Structural Stress Approach

Abstract The fatigue cracking of orthotropic steel deck (OSD) has long been a problem of bridge structures. It is meaningful to assess bridge fatigue life using an appropriate method. In this paper...

Fatigue life estimation of continuous girder bridges based on the sequence of loading

A need exists to determine the fatigue life of multi-span continuous bridges in the design stage. It is difficult to conduct a full-scale fatigue test of a bridge, hence the simulation of bridge-vehicle interaction dynamics is important to estimate the fatigue life of bridges. The vehicles entering the bridge are random in nature. In the present study, the arrival time of the vehicles is considered a random variable following Poisson process to simulate the actual traffic. The bridge-vehicle coupled system equations have been derived wherein the vehicle arrival rate appears as random variable casting difficulty in obtaining a direct solution. The solution approach has been devised using Orthogonal Polynomial Expansion method. Response statistics so obtained for a multi-span continuous bridge has been used in fatigue life estimation involving crack initiation phase and crack propagation phase modifying conventional linear damage rule. The sequence of loading is also considered in the modified fatigue formulation. The effect of the vehicle speed, road surface irregularity and the arrival rate of the vehicle on fatigue life estimation of the bridge have been studied.

Influence of Weld Parameters on the Fatigue Life of Deck-Rib Welding Details in Orthotropic Steel Decks Based on the Improved Stress Integration Approach

Fatigue cracks in orthotropic steel decks (OSDs) have been a serious problem of steel bridges for a long time. The structural stress approach is an important approach for fatigue life evaluation of welded structures. Firstly, two parameters and the mesh sensitivity of the stress-based integration equivalent structural stress approach (stress integration approach for short) are analyzed in this paper. Then, the applicability of the master S-N curve is verified based on experimental data of the deck-rib welding details in OSDs. Finally, the multi-scale finite element model (FEM) of Jiangyin Bridge is established, and the bridge fatigue life calculation steps based on the stress integration approach are given. The influence of the slope of the master S-N curve at high cycles on the bridge fatigue life is discussed. Further, the weld parameter influences on the bridge fatigue life are analyzed, as including the following: (1) The determination of the influence of the weld size changes caused by weld manufacturing errors on the bridge fatigue life; (2) the proposal of a new grinding treatment type, and the analysis of influence of the grinding radius on fatigue life; and (3) a comparison of the fatigue life of the deck-rib welding details under 80% partial penetration and 100% full penetration. The results show that the structural stress calculated by the stress integration approach does not change significantly with the parameters of the isolation body width w and the distance δ between the crack propagation surface and the reference surface. To simplify the calculation, δ is set as 0, and w can be set as the mesh size along the weld length direction. The mesh size of the stress integration approach is recommended as 0.25 times the deck thickness. The slope of the master S-N curve at high cycles significantly affects the bridge fatigue life, and a slope of 5 is reasonable. The weld parameter studies for the deck-rib welding details in the OSD of Jiangyin Bridge show that the change of weld size caused by manufacturing errors can obviously affect the bridge fatigue life, and the fatigue life of five different weld types varies from 51 years to 113 years. The new grinding treatment type, without weakening the deck, is beneficial to improving the bridge fatigue life. The fatigue life increases by approximately 5% with an increase of the grinding radius of 2 mm. The fatigue life of 80% partial penetration is slightly higher than that of 100% full penetration.

Railroad bridge fatigue life estimation using the probabilistic method and new fatigue resistance for riveted details

Existing fatigue life evaluation procedures are often over-simplified and do not account accurately for the uncertainty in applied load and fatigue resistance of steel railway bridges. Simplified calculations and conservative assumptions often lead to significant reductions in estimated life that indicate older structures ceased to be functional decades ago. Fitness for service assessments that utilise probabilistic methods and that are informed by and consistent with detailed physical inspections of the structures provide a more accurate assessment of the expected life of bridges and can be used to establish improved bridge inspection programmes. This paper focuses on development of probabilistic, risk-based methods and models for assessing steel bridge Fitness for Service (FFS) and remaining life. The fatigue resistance models developed in this project are calibrated, validated, and verified against all available and relevant fatigue test results. For some bridge types, these models provide remaining fatigue life estimates that are double and sometimes even triple those obtained by using existing simplified methods. In this paper, a probabilistic method is demonstrated on two, riveted deck plate girder spans that exceed 100 years of service and are currently located at the Facility for Accelerated Service Testing (FAST) near Pueblo, CO.

Extending the Fatigue Life of Steel Truss Bridges with Tuned Mass Damper Systems

The increasing traffic demand is continuously growing worldwide. Therefore, the life of a large stock of bridges that still exist throughout the world must be extended, ensuring at the same time that safety is not compromised for economic reason. This paper introduces the possibility to control the fatigue life of existing bridges by using a vibration control system. Based on a dynamic optimization analysis, the stresses from traffic on the bridge are obtained. Subsequently, a plate finite element (FE) model of the whole bridge is developed. The equation of motion is presented for a case study bridge, equipped with different tuned mass damper system, and the combination of external loads and train/track interaction with or without the TMD system is developed through own‐developed routines and FEM software. The procedure is showcased for a case study bridge. After gaining the stress states at the critical hotspot, the fatigue crack life is evaluated by using the linear cumulative damage theory. The different TMD solution presented is demonstrated to be able to diminish the stress level in critical hotspots, improving the overall fatigue life of the bridge over an established lifetime.

Fatigue Life Evaluation for Deck-Rib Welding Details of Orthotropic Steel Deck Integrating Mean Stress Effects

The early fatigue cracking of orthotropic steel decks has been a long-standing problem for heavy traffic regions of China’s long-span bridges. However, the actual fatigue life is much lower than the fatigue life calculated by fatigue design codes. In this study, a modified full range S-N curve, the M-S-N method, is proposed to evaluate welded joint fatigue life, considering mean stress, which is based on metal fatigue theory. As an example, a combined shell-solid finite-element model of a segmental bridge is first built for the Jiangyin Bridge to obtain the real stress, integrating welding residual stress and vehicle load stress. The fatigue life is then calculated and compared in order to consider the influence of different vehicle loads and deck-plate thicknesses. The calculation results show that the fatigue life of the deck-rib welded joint in the Jiangyin Yangtze River Bridge decreases nonlinear at a staggering rate with the increase in vehicle load. Under the condition of severe overload heavy vehicles, the Jiangyin Bridge fatigue life is only 2.17 years according to the M-S-N method, which matches practical situations. Deck-rib fatigue life obviously increases with the increase in deck thickness. The current steel bridge deck design with a 16-mm-thick plate is not safe under heavy traffic conditions.

A simple corrosion fatigue design method for bridges considering the coupled corrosion-overloading effect

Corrosion fatigue is more detrimental than either corrosion or overloading applied separately. Nevertheless, corrosion was not explicitly covered in the AASHTO LRFD fatigue design specifications, which may lead to underestimation of the fatigue damage of bridges. Moreover, simple approaches to evaluating the fatigue life of corroded steel components are still lacking. In this study, a steel girder bridge was adopted to study the coupled corrosion-overloading effect on the fatigue life of bridges. The variation of stress range, equivalent number of stress cycle, and the resulted cumulative fatigue damage under different corrosion and overloading conditions were investigated. Then, a simple corrosion fatigue design method was proposed by considering the coupled corrosion-overloading effect which covers the individual effects due to pure overloading, pure corrosion, and the corrosion-overloading interaction. The results showed that the relationship between the corrosion-overloading interaction and the corrosion depth can be well described by an exponential function which is applicable for different overloading and corrosion conditions. Moreover, the coupled corrosion-overloading effect can greatly reduce the fatigue life of bridges and should be carefully considered in bridge fatigue design wherever necessary.

Fatigue Analysis of a Railway Steel Bridge

One of the significant means of transportation in India are railways and has many steel bridges which are very old having historical importance and their design period is terminating. To appraisal, the levels of damage for workable repairs, stands a tedious job for government authorities. The prediction of fatigue life of bridges are important because at present these are subjected to elephantine loads than the design loads and the environmental conditions boost these aspects to turn up fatigue life. This paper studies the analytical analysis of a steel railway bridge subjected to EURO and INDIAN fatigue loading to evaluate the fatigue life of a bridge and stresses are calculated from S-N curves by nominal stress method. The fatigue verification has been done by λ-coefficient method. Fatigue life of critical section was found out by sub-modelling the welded joint where the stress are maximum. The crack initiation starts at powerless members and propagates it along the section leads to fracture the entire structure under elastic behaviour. Hence, if the results of the critical section are satisfactory, it can be concluded that entire bridge is safe in fatigue point of view. INDIAN HM loadings generate more damage than EURO LM-71 loading.

Nonlinear cumulative damage model and application to bridge fatigue life evaluation

Fatigue is a damage accumulation process in which material property deteriorates continuously. Fatigue life prediction issues are important for safety. This article aims to develop a nonlinear cumulative damage model. A fatigue damage model based on the continuum damage mechanics is addressed and applied to bridge fatigue life evaluation. First, the bridge nonlinear cumulative damage model based on damage mechanics is propounded and equivalent effective stress range is given. Then, the effects of the main parameter in the model are analyzed. Finally, Xinghai Bay Bridge is taken as a case study. The results indicate that the damage is increased with the material parameter [Formula: see text] reduced. [Formula: see text] is a material parameter depending on stress amplitude and without physical meaning. If [Formula: see text], the effect of [Formula: see text] is negligible. If [Formula: see text], nonlinear cumulative damage model degrades into Miner’s rule and effect of [Formula: see text] to structural damage is maximum. The cumulative damage curve calculated by the nonlinear cumulative damage model is nonlinear, with a low cumulative rate initially but a very high cumulative rate at the end of the design life, whereas the Miner’s rule is linear. The nonlinear cumulative damage model can reflect actual damage process, while Miner’s rule is pessimistic.

Strain Energy-Based Fatigue Life Evaluation of Deck-to-Rib Welded Joints in OSD Considering Combined Effects of Stochastic Traffic Load and Welded Residual Stress

Welded residual stress and stochastic traffic at the deck-to-rib welded joints in the orthotropic steel deck (OSD) of bridges highly affects the fatigue life of bridges. This study presents a strain energy-based method to evaluate the service life of welded joints in the OSD considering the combined effects of traffic load and welded residual stress. Thermomechanical analysis is performed for the welding process of the welded joints using a finite-element model to analyze the distribution of welded residual stress at critical locations of the welded joints. An analysis model is developed to simplify the nonlinear superposition of vehicle-induced stress and welded residual stress. A modified strain energy-based fatigue evaluation approach is presented based on the superposition of stresses. Based on the presented model, a new Wa–Nf curve is proposed to take the effects of welded residual stress into consideration. The presented method is validated against experimental results, and then it is applied to investigate the fatigue life of welded joints in an in-service cable-stayed bridge. The theoretical and inspection results are compared and analyzed. The results show that there is a better coincidence between the predicted fatigue life using the presented approach and the inspected fatigue life in contrast with the conventional approach of neglecting the effects of welded residual stress.

Dynamic characteristic analysis and fatigue life estimation of bridges with considering the shear residual stress

Firstly, this paper established a finite element model of the steel bridge and applied movable vehicle loads measured by experiments into the finite element model so that stress and strain distribution characteristics in detail structures of bridges were computed. The change process in the direction of detailed element of diaphragm plate after the shear residual stress was taken into account. Results showed that the direction of its principal tension stress was vertical to the actual crack direction of cracks. To analyze the inner relationship between the internal force of diaphragm plate and local stress amplitude, vehicle loads moved horizontally to record the change trend of principal stress at the arc hole and shear force and bending moment in the cross section. Through making a comparison, this paper found that stress amplitude at the arc hole was mainly affected by shear force and local wheel pressure. Stress amplitude at the arc hole close to diaphragm plate was larger than that at the arc hole close to the middle line, which was easier to crack and consistent with actual damage. Finally, the fatigue life of bridges which took into account the shear residual stress was estimated according to stress and strain to compare with the result which did not take into account the shear stress. Comparison results showed that the shear residual stress had an obvious effect on fatigue life of the steel bridge, so it cannot be neglected during numerical computation.

SHM-Based Probabilistic Fatigue Life Prediction for Bridges Based on FE Model Updating.

Fatigue life prediction for a bridge should be based on the current condition of the bridge, and various sources of uncertainty, such as material properties, anticipated vehicle loads and environmental conditions, make the prediction very challenging. This paper presents a new approach for probabilistic fatigue life prediction for bridges using finite element (FE) model updating based on structural health monitoring (SHM) data. Recently, various types of SHM systems have been used to monitor and evaluate the long-term structural performance of bridges. For example, SHM data can be used to estimate the degradation of an in-service bridge, which makes it possible to update the initial FE model. The proposed method consists of three steps: (1) identifying the modal properties of a bridge, such as mode shapes and natural frequencies, based on the ambient vibration under passing vehicles; (2) updating the structural parameters of an initial FE model using the identified modal properties; and (3) predicting the probabilistic fatigue life using the updated FE model. The proposed method is demonstrated by application to a numerical model of a bridge, and the impact of FE model updating on the bridge fatigue life is discussed.

REMAINING FATIGUE LIFE AND BEHAVIOUR OF DAMAGED RCBEAMS-REVIEW

Reinforced concrete bridges are often adopted in Railway construction of shorter spans to achieve simplicity in casting for required shape and size, easy to strengthen, riding comfort and speed of construction. These bridges consist of girders and deck slabs. When the speed and type of loading vary to transport ores, commodities and passengers, the bridges are subjected to higher stress range of fatigue than that designed. Assessment of remaining fatigue life of bridges either for retaining or strengthening or discarding purposes. Discarding the bridge can result in obstruction of traffic, reduction of revenue and loss of time, strategic needs and monumental structures. Experimental studies have been carried out for assessing the remaining fatigue cycles and flexural behavior of Damaged (cracked) Beams by fracture of tension reinforcement. The parameters of the study are; strength of concrete, percentage steel reinforcement and extent of damage in rebars. Load-deformation response and variation of strains across the depth at the level of center of beam, tension and compression reinforcements, extreme compressive strain in concrete, and crack propagation under fatigue load were analyzed. Review of Previous research on the fatigue life of bridges is presented. The test results are compared with the current ACI SP 75 design practice.