Search

Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. This paper presents an overview of current researches on the typical characteristics and causes of bridge failures based on 10 former investigations. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than 70% of the bridge failures. Causes of bridge failures are closely related to regional economy, structural type, type of use, material type, and service age. The failure rate is very high for steel bridges, which is inseparable from excessive emphasis on structure strength but lack of consideration on structure stability and fatigue in early years. Researchers need to strengthen their research on the stability and fatigue of steel bridges, as well as inspection and maintenance. Extreme loads such as flood, collision, and overload contribute to a large number of bridge failures because of the lack of extreme loads data and design theory defects. It is critical for such bridges to have sufficient redundancy and capacity protection measures to reduce the probability of bridge failure due to extreme loads. Previous statistical methods and classification methods for the characteristics and causes of bridge failures lack unified standards, and a more scientific method needs to be established. A comprehensive electronic database on bridge damage and failures needs to be developed to establish damage models and conduct forensic studies to improve the design theory and specifications. [ABSTRACT FROM AUTHOR]

The disproportionate collapse of an existing cable-stayed bridge was investigated at the numerical level by employing a validated model from the literature and the applied-element method. An earthquake input was used for the numerical simulations and applied at increasing intensity to assess the bridge response. The role of redundancy in the bridge structural scheme was proved to be a strategic measure for avoiding disproportionate collapse and improving robustness. Therefore, an alternative configuration of the structural scheme was assessed as a possible countermeasure to improve the response of the cable-stayed bridge by providing different loading paths against disproportionate collapse. New redundancy indices that account for the system reserve resources are also introduced. [ABSTRACT FROM AUTHOR]

In this paper, the collapse frequencies of bridges are summarised and compared with target values of probabilities of failure and with calculated failure probabilities for real bridges. The determination of the collapse frequencies is based on various publications in the sense of a meta-analysis. First, the various studies are summarised graphically, discussed and examined for a trend. The results show that the collapse frequencies decrease over time and that today they have reached a minimum. In the next step, the observed collapse frequencies, the target failure probabilities and the calculated failure probabilities are compared. There is a good agreement between the collapse frequencies and failure probabilities for real bridges. The collapse frequencies fulfil the current safety targets for time-dependent target probabilities as well as for time-independent target probabilities for dead and traffic loads. Subsequently, the causes of bridge collapses are assessed regarding loads. The main cause for bridge collapses is accidental loads, such as hydraulic events. Such loads can be controlled if they are considered in the correct order of magnitude. The probabilities of failure can be extended regarding further factors and thus the matching between probabilities and frequencies can be further improved. [ABSTRACT FROM AUTHOR]

The international highways within the city limits of Istanbul are used to transit more than 15 million trucks and other heavy good vehicles per year. According to the statistics, the number of single truck run of the road accidents is in the rise. Recent accidents on bridges showed that currently used bridge rails specified by Istanbul Metropolitan Municipality (IMM) lack the required design criteria to safely contain and redirect heavy vehicles. The objective of this study is therefore design, analyze and test a new high containment level (HCL) bridge rail to be used on bridges on high risk locations, within the city limits of Istanbul. After the development and simulation phases, the bridge rail is subjected to full-scale crash testing in accordance with European Standard EN1317 to conclusively prove its adequacy. This study is of importance since the barrier is the first nationally developed high containment level bridge rail in Turkey. The bridge rail, YIM04 is currently in use on several bridge decks in Istanbul. [ABSTRACT FROM AUTHOR]

Pile supported river bridge failures are still observed in liquefiable soils after most major earthquakes. One of the recurring observations is the mid span collapse of bridges (due to pier failure) with decks falling into the river while the piers close to the abutment and the abutment itself remain stable. This paper proposes a mechanism of the observed collapse. It has been shown previously through experiments and analytically that the natural period of bridge piers increases as soil liquefies. Due to the natural riverbed profile (i.e. increasingly higher water depth towards the centre of the river), the increase in natural period for the central piers is more as compared to the adjacent ones. Correspondingly, the displacement demand on the central pier also increases as soil progressively liquefies further promoting differential pier-cap displacements. If the pier-cap seating lengths for decks are inadequate, it may cause unseating of the decks leading to collapse. The collapse of Showa Bridge (1964 Niigata earthquake) is considered to demonstrate the mechanism. The study suggests that the bridge foundations need to be stiffened at the middle spans to reduce additional displacement demand. [ABSTRACT FROM AUTHOR]

In 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 traffic loads in design specifications, the actual characteristics of EHTs are very difficult to predict because they may be specific to the management, charge policy, or other properties of the route. In a previous publication, the authors researched the characteristics and dynamic impact of EHTs on Chinese expressways. In the current study, long-term traffic monitoring data were statistically analyzed to identify the key characteristics of EHTs on Chinese first-class highways. Based on the EHT scenarios extracted from the weigh-in-motion (WIM) data, which can be used to record the traffic information of moving vehicles, a comprehensive simulation analysis was conducted by an in-house advanced dynamic bridge-traffic interaction model on five typical simply supported T-beam bridges. The bridge response and dynamic impact factors (DIFs) of EHTs were numerically investigated, and reasonable expressions for calculating the DIFs were proposed. Finally, the load effect calibration under EHTs was performed when the road surface condition was average. These findings can be used as additional references for bridge codes and safety assessment by practicing engineers. [ABSTRACT FROM AUTHOR]

Due to the complexity involved and limited study on the topic, the equivalent static method, adopted in the current codes for structural design of bridges under ship collisions, does not take into account the dynamic amplification effect correctly. In this article, impact factor method is proposed to estimate the response of bridge's piers and foundations, as a better alternative of the equivalent static method. Through refined numerical simulations of ship-rigid wall collisions for nine typical ships under various impact velocities, 81 impact force time-histories are obtained. The period-dependent impact factor is defined, and empirical function of it is proposed and parameters in the empirical function are determined by the 81 sample impact force time-histories. Finally, both impact factor method and dynamic time-history method are used to estimate the responses of piers and foundations of two example bridges, and the precision of impact factor method is discussed. [ABSTRACT FROM AUTHOR]

As important load bearing members of cable-stayed bridges, stay cables may experience corrosion, fatigue, and accidental or intentional actions that may lead to possible breakage failure. The current bridge design guidelines require that a cable-stayed bridge be designed against single-cable breakage. A holistic reliability assessment framework is developed for a long-span cable-stayed bridge and traffic system subjected to breakage of stay cables considering service load conditions from both traffic and wind. In addition to the bridge structural ultimate limit state, a new bridge serviceability limit state is also introduced by focusing on the overall traffic safety performance of all vehicles of the traffic flow on the bridge following cable breakage incidents. Random variables are defined by considering uncertainties related to structural material properties, sectional properties, traffic, wind condition, and cable breakage parameters. The Latin hypercube sampling technique is adopted to sample the random variables and establish the simulation models by considering various uncertainties of parameters. Nonlinear dynamic analysis is conducted in each experiment to simulate the breakage of stay cables, during which various sources of nonlinearities and dynamic coupling effects from traffic and wind are incorporated. Fragility analyses of the bridge subjected to cable breakage events in terms of the ultimate limit state and the serviceability limit state are finally conducted. [ABSTRACT FROM AUTHOR]

This paper discusses three fundamental questions on the bridge deck-wave interaction: (1) are there countermeasures to mitigate the wave forces on the bridge decks? (2) what is the working mechanism of the countermeasures? and (3) what is the efficacy of such countermeasures? Motivated by these questions, a literature review is conducted and the air venting holes in the bridge deck slab is preliminarily identified to be a countermeasure for the bridge deck-wave interaction. To reach a deeper understanding of such a countermeasure, a solitary wave model is utilized here to carry on the numerical simulations. The shear stress transport (SST) k-ω model is considered as the turbulence closure for the Reynolds-averaged Navier-Stokes (RANS) equations to account for the turbulent bridge deck-wave interaction. Six different venting ratios for cases that the bottom of the bridge deck is at the still water level (SWL) are considered with detailed analysis of the characteristics of the air venting process, such as the pressure change in the chamber, the flow rate of the air and water through the air venting holes, and the force changes. Thereafter, different structure elevations, representing different submerging scenarios, with one target venting ratio are further studied. It is proven that this countermeasure is in favor of reducing the positive vertical (uplift) force substantially, but it results in an increase of the horizontal force correspondingly. This, in turn, requires more designing considerations for the supporting system to the bridge superstructures. This study will improve our understanding of this potential application in future engineering practices. [ABSTRACT FROM AUTHOR]

Falling is the most common one during bridge construction. Current safety management on site mainly relies on checklist assessment. Yet the assessment result is often influenced by the ability and experience of the evaluator, thus is not impossible to achieve consistent and systematic assessment objective. Moreover, most critical factors that can prevent occurrence of accidents cannot be found from existing safety management and assessment method. This paper built a Bayesian network (Bn) model by converting Fault Tree to assess the fall risk of bridge construction projects. We analyse falling factors and their relationships in Bayesian network, and collect prior probability event and calculate the probability for the entire model. Using the model to analyse and validate with the current bridge projects under construction, the results from Bayesian network is consistent with that from conventional labour safety performance assessment. Therefore, the ability to manage site safety of the model is proven to be useful. [ABSTRACT FROM PUBLISHER]

Accidents, breakdowns or incidents threatening both human life and the environment are inherent parts in operating in the offshore sector. Regular monitoring and analysis of all kinds of events are important to isolate the most common and dangerous ones, to be able to prevent them in the future. The article summarizes the sources containing information regarding accidents occurred in the maritime offshore sector. Due to their widespread and easy access, the article is focused on electronically published databases and safety reports concerning the risk and dangers related to the implementation of marine exploration - mining projects. Based on these data, the authors made analyses, presented statistics and proposed ways to minimize threats in the offshore sector of the marine industry. [ABSTRACT FROM AUTHOR]

The most important aspect of the transport of goods by water, including inland waterways, is navigational safety. Formal Safety Assessments (FSAs) are widely-adopted methods of risk analysis used to assess safety. By defining potential risks and describing event scenarios, FSAs allow the estimation and minimization of the level of risk of individual events. The current article presents the characteristics of accidents on inland waterways and the classification of accidents, with a discussion of their effects. After analysis, the research area was narrowly defined to vessels passing under bridges, and the threats arising from barges descending from the axis of the fairway. On the basis of the analysis, the authors have offered a risk assessment model of inland vessel collision with some element of navigational infrastructure during under-bridge passage. Event Tree Analysis (ETA) was used to carry out hazard identification. [ABSTRACT FROM AUTHOR]

Recently suicides have been on the rise and become social issues around the world. Seoul, the capital of South Korea, has been no exception. Hence, to detect and respond early, Seoul Metropolitan Government has installed the suicide corresponding sensor system at two locations of Han-River bridges where suicide occurs frequently. This study analyzed the pilot system's performance of past 1 year and presented the following results. First, rescued people who attempted to suicide have increased in relation of the sensor system and it's determined to be verified based on early discovery, and prompt action of rescue operation. Second, after a pilot test for 1 year, surveillance cameras installed at blind spots have contributed to improve the effectiveness of the security system. Finally, as a result of the analyzing the death leap types, there are three following types of people who attempted to suicide: (1) a form of falling directly from the bridge rail, (2) a form of sitting on the bridge rail and jumping away, (3) a form of standing outside of the bridge rail and jumping away. Based on these results, it was implied that the proactive measures such as utilizing sensors are very effective in suicide prevention and they can be expanded to prevention of death leap in other places such as high-rise buildings. [ABSTRACT FROM AUTHOR]

Vessel collisions with bridges occur frequently worldwide and have the potential to cause enormous casualties, substantial property loss, and environmental destruction. Physical protection systems designed for bridge piers against vessel collisions are viable solutions to alleviate/prevent those disruption costs. This paper introduces a floating steel fender system for bridge pier protection and evaluates the performance using an explicit dynamic finite-element analysis code. The analysis method is validated against available drop-weight impact tests of a steel box module, because the steel fender system is constructed by repeatedly stacking and aligning a similar subassembly. The introduced fender system noticeably reduced the peak impact force applied on a bridge pier by approximately 55.3% and on the colliding vessel by approximately 56.2% while extending the impact duration approximately 273.1%as compared to the head-on collision without any protection. It was also shown that the initial kinematic energy of the barge before impact was mainly dissipated by plastic deformation of the steel module (57.5%) and colliding barge (16.5%), as well as the damage of the rubber dampers after impact. The results indicate that the floating steel fender system has excellent energy-absorbing capabilities. [ABSTRACT FROM AUTHOR]

The data of 302 highway bridge catastrophic collapses occurring in China between 2000 and 2014 due to human causes were collected and statistical analyses were conducted from various viewpoints including accident stages (during construction or service), casualties (death or injury), location, time, life span, bridge type, and primary causes behind the accidents. Six representative collapse cases were expounded on to find out their individual peculiarities. These cases encapsulated serious problems in Chinese highway bridge engineering, including design, construction, maintenance, and management, among others. A concise review of highway bridge collapses due to human causes in China was presented. Some typical abnormal phenomena, such as those concerning entities involved in the Chinese highway bridge engineering industry, were analyzed and highlighted. Suggestions were put forward to urge all related parties to obey rules and laws to reduce and avoid bridge collapse accidents. The lessons from these bridge accidents should be fully studied to further ensure the safety, durability, and economy of bridges. This study provides a comprehensive reference of the current situation regarding highway bridge collapses in China, which is also useful for ringing the alarm bell to alert bridge owners, designers, constructors, supervisors, researchers, and maintenance crews of potential dangers. [ABSTRACT FROM AUTHOR]

Understanding of the performance of critical bridges, such as cable-supported bridges, during accidental fire is necessary for developing mitigation strategies against potential fire damage. In this research, the structure-fire interaction of long-span cable-supported bridges, in particular, anchored suspension bridges, self-anchored suspension bridges, and cable-stayed bridges, was investigated through nonlinear finite-element analysis. To investigate the stability of these bridges during fire, a typical steel orthotropic box girder was exposed to different fire scenarios representing fires during ship and truck accidents. The stability of the three bridges during two fire scenarios was investigated in terms of fire intensity and duration and axial compressive force in the deck. Simulation results indicate that the existing axial force in the deck negatively affected the structural performance by causing buckling failure under fire loads. Generally, anchored suspension bridges had the largest safety factor among the three bridges because of nearly zero axial force in the deck. On the other hand, self-anchored suspension bridges had a significantly higher amount of existing axial compressive force in the deck and were the most vulnerable during both the truck and the ship fire scenarios. The axial forces in cable-stayed bridge decks varied longitudinally. Hence, their vulnerability during fires depends on the location of fire, the magnitude of existing axial force, and the design capacity of the deck. [ABSTRACT FROM AUTHOR]

Based on the collapse of Hintze Ribeiro's bridge in Portugal this article highlights the analytic possibilities of a sociology with disasters. This sociology takes into account interaction between the political management of crisis induced by the disaster, the event mediatisation and the interpellative power of suffering and death. The discretionary production of exception amplifies the distance between the state and the citizens, reforming the power of the first and augmenting the dis-power of the left. [ABSTRACT FROM AUTHOR]

The adequate seismic performance of transportation infrastructures is important for the functioning of the economy and society. This paper focuses on the seismic assessment and analysis of one of the most important components of these infrastructures, the bridges. In this field, nonlinear static procedures (NSPs) have gained significant attention, resulting in different proposals to improve the accuracy of the procedures while keeping their simplicity. The main goal of this study is focused on the evaluation of the applicability of NSPs for irregular reinforced concrete viaducts. A comparative approach is pursued by resorting to (1) the analyses of the performance of three well-known NSPs (N2 method, modal pushover analysis and adaptive capacity spectrum method) and (2) the extension of the scope of previous studies in this field to a more recent method, the extended N2. As such, a set of bridges with different levels of irregularity, configurations and lengths is investigated. The accuracy of different NSPs is evaluated by comparing the results of NSPs with the ones obtained by means of nonlinear dynamic analyses. The comparison of results confirms the acceptable performance of the multi-modal NSPs and highlights the effectiveness of extended N2 method with respect to its simplicity. [ABSTRACT FROM PUBLISHER]

Tay Road Bridge is a 42-span, 2ṡ25 km-long twin box viaduct carrying the A92 over the Tay Estuary between Dundee and Fife. Two navigation spans are located on either side of pier 32. Cargo vessels of up to 3500 DWT regularly transit the bridge inbound or outbound from Perth 33 km to the west passing under the bridge 2 h before or after high tide to complete the trips in one uninterrupted movement. The 4 kn tidal flow and the vessels' need to maintain a 'through the water' speed of 8 kn for steering combine to necessitate an unusually high 'over ground' speed of over 12 kn. Consequently, while relatively small, transitting vessels possess high kinetic energy, and in the event of collision it is this energy that has to be absorbed by the pier protection system. Assessment revealed that the consequence of ship collision would be severe, affecting structural equilibrium. The structures provided are reinforced concrete fender beams. For the most severe collision events, the tubular steel supporting piles are designed to deflect beyond the point at which the end moments cause section yielding, and it is the work done in the rotation of these plastic hinges that absorbs the majority of the collision energy. This paper describes the development and design of the protection structures, early contractor involvement, contract form and construction. [ABSTRACT FROM AUTHOR]

This paper investigates the ship–bridge collision process and its influences on the running safety of the moving light rail train. Taking a long span cable-stayed bridge across the Huangpu River as example, the 3-D dynamic model of train-bridge coupled system subjected to ship impact was studied with the aid of the finite element analysis (FEA) code LS-DYNA 971. The bridge model and the coupled rigid–flexible multi-body train model were coupled through non-linear wheel–rail interface, and the coupled dynamic model was solved using mixed time explicit integration approach. By studying the effects of train speed and the momentum of impacting ship on the running safety of the rail train, the relationship between the maximum safety speed of the train and the momentum of the impacting ship is predicted, that is, the maximum allowable train speed decreases with the increase of the momentum of the impacting ship. The mixed time integration method could speed up the calculation process for crashworthiness analysis with great differences in element sizes at different parts of model. [ABSTRACT FROM PUBLISHER]

The Interstate-35 West Bridge collapse offers a unique case of state crime. First, it illuminates a new topical area in the state crime literature, public infrastructure. Second, it illustrates how the bridge collapse was not a discrete act (Tombs in State Crime 1(2):170-195, ), but rather the outcome of relationships between different social institutions. Specifically, it demonstrates how processes within a state, in confluence with the broader political economy, produced decisions (omissions) not to invest in infrastructure repair, take expert advice, and improve coordination between agencies. Simultaneously, these same processes resulted in deliberate actions (commissions) to invest in new infrastructure rather than in maintenance and repair of existing infrastructure, and to reduce both regulatory oversight and safety procedures. We provide a detailed overview of the bridge collapse, then utilizing Kauzlarich and Kramer's (Crimes of the American nuclear state, Northeastern University Press, Boston, ) integrated theoretical framework, contextualize the causes of the collapse and highlight how state processes and political-economic conditions resulted in the simultaneous occurrence of crimes of omission and commission on the part of the state. [ABSTRACT FROM AUTHOR]

More than 20% of the bridges in the United States were built more than 50 years ago, at a time in which intense precipitation events were much less common. However, very little work has been done on the use of scour risk-assessment models to assess how climate change increases bridge failure probabilities. This paper develops a risk-assessment framework based on HYRISK, a model developed to assess the probability of a bridge failure due to scour, and illustrates one way in which current engineering risk-assessment models can be used to quantify the additional risks and expected economic losses associated with a changing climate. Application of this framework to all bridges in the United States that carry vehicular traffic over water finds that economic losses due to climate change factors will increase by at least 15% over current losses and that the expected number of annual bridge failures in the United States will increase by at least 10% over current failures. Climate-based risk measures, such as those developed as part of this study, could be included in asset management systems to help state DOTs prioritize maintenance, operation, and replacement schedules. [ABSTRACT FROM AUTHOR]

Thedynamic behavior of cable-stayed bridges subjected tomoving loads and affected by an accidental failure in the cable suspension system is investigated. The main aim of the paper is to quantify, numerically, the dynamic amplification factors of typical kinematic and stress design variables, by means of a parametric study developed in terms of the structural characteristics of the bridge components. The bridge formulation is developed by using a geometric nonlinear formulation, in which the effects of local vibrations of the stays and of large displacements in the girder and the pylons are taken into account. Explicit time dependent damage laws, reproducing the failure mechanism in the cable system, are considered to investigate the influence of the failuremode characteristics on the dynamic bridge behavior. The analysis focuses attention on the influence of the inertial characteristics of the moving loads, by accounting coupling effects arising from the interaction between girder and moving system. Sensitivity analyses of typical design bridge variables are proposed. In particular, the effects produced by the moving system characteristics, the tower typologies, and the failure mode characteristics involved in the cable system are investigated by means of comparisons between damaged and undamaged bridge configurations. [ABSTRACT FROM AUTHOR]

This paper establishes relations--historical, material and evidential connections--between two responses to a 'crisis'. The first features in the history of industrialised iron construction, specifically period reporting on the spectacular collapse of the River Dee bridge in Cheshire, England, in 1847. The second response highlights a blind spot in the historiography of modern architecture. Robert Stephenson became suspect when his cast- and wrought-iron railway bridge across the River Dee failed, resulting in death and injury and continuing uncertainty as to its cause. At the time the incident sparked national furore, setting off a coroner's inquest followed by a Royal Commission into the perilous state of Britain's bridges. The inquest jury concluded no one was to blame; rather, it was an accident brought about by use of iron, an uncertain and "treacherous" metal. This explanation has failed to satisfy contemporary materials specialists who have reopened the case, albeit under different terms of reference. The paper examines the initial verdict, firstly, in view of aspects of the social context of evidence and proof prevailing at the inquest and, secondly, given historical writing on iron construction whereby the inquest's seemingly imprecise and arbitrary judgment is taken as sign of the subsequent progress of engineering as a practical and moral science. This paper adopts the leitmotif of 'crisis' to highlight a parallel history that challenges progressivist narratives of industrialised iron construction and modernist architecture. It invites reflection on the provenance and unstable forms of agency associated with engineering as a propositional and socially contingent enterprise. [ABSTRACT FROM AUTHOR]

Abstract: Vessel collisions with bridge piers are one of the most frequent accidents that may lead to bridge failure. To reliably assess bridge response and damage due to barge impact, and design the bridge piers to resist such impact, the impact force should be accurately defined. In most of the previous works of numerical simulation of barge collision with bridge piers for defining the barge impact force, the pier was assumed to be rigid or elastic and the interaction between the barge and the pier was neglected. As pier plastic deformation and damage will absorb impact energy and also prolong the interaction time, the impact force acting on the bridge pier might not be accurately predicted with rigid and elastic pier assumption. In this paper, a detailed numerical model of barge–pier impact is developed in LS-DYNA. The bridge pier is modelled with nonlinear materials to more realistically generate the bridge pier characteristics. Barge–pier impact force time history, barge crush depth and pier displacements are calculated in this paper. The reliability of the numerical model is calibrated with some results available in the literature. Based on numerical results simplified formulae are derived to predict the impact force time history with respect to the collision conditions. Numerical results are compared with the previous works. The adequacy of current code specifications is also discussed. [Copyright &y& Elsevier]

This study evaluates the effects of the I-35W bridge collapse on road-users in the Minneapolis-St Paul, Minnesota Twin Cities metropolitan area. We adopted the Twin Cities Seven-County travel demand model developed in previous research, re-calibrated it against July 2007 loop detector traffic data, and used this model to carry out an evaluation of economic loss incurred by increased travel delay in alternative scenarios before and after the bridge collapse. We conclude that the failure of the I-35W bridge resulted in an economic loss of US$71,000 to US$220,000 a day, depending on how flexible road-users in the system adjusted their trip destinations in response to the bridge closing. We also estimate that the major traffic restoration projects Minnesota Department of Transportation has implemented in quick response to the bridge collapse can save road-users US$9500-17,500 a day. This translates into a benefit-cost ratio of 2.0-9.0, suggesting these projects are highly beneficial in an economic sense. In this analysis, the use of a simplified, scaled-down travel demand model enabled us to carry out the analysis quickly and accurately, which could see its contributions in transportation planning under situations such as emergency relief and comprehensive design. [ABSTRACT FROM AUTHOR]

Abstract: Many references and design codes propose the use of a dynamic amplification factor applied to the static response of a structure for estimating its dynamic response. This is the case of the present recommendations on cable stayed bridges or other references for evaluating the dynamic effects produced by the accidental loss of a segment during the cantilever construction of a precast concrete bridge. This paper deals with the dynamic amplification factor of multiple degree of freedom systems under the action of a rectangular pulse load of infinite duration. A theoretical study of the possible maximum values that the dynamic amplification factor can reach has been carried out, establishing the relation between this factor and the strain energy of the system under the load statically applied. This relation allows us to determine if the dynamic amplification factor can exceed the value of 2.0 and to derive a simple method for comparing the dynamic effects of different pulse loads. Finally, a numerical example illustrates this method applied to determine which rectangular pulse load, produced by the accidental loss of a segment of a bridge, can produce a larger and a smaller dynamic amplification factor on a cantilever precast segmental bridge under construction. In this example, the possible maximum dynamic amplification factor obtained has been 3.24. [Copyright &y& Elsevier]

Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This article investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The article presents the results of small-scale impact experiments using the proposed bridge bumper with several options of energy-absorbing materials to protect a reinforced concrete beam. Finite element analyses are carried out to simulate the small-scale impact experiments. Optimization of the finite element model is conducted for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries. A possible full-scale implementation of the proposed bridge bumper is also described. [ABSTRACT FROM AUTHOR]

Scour at bridge piers has long been recognized as an issue of considerable importance as it pertains to pier hydraulic design, according to a large number of scour studies conducted over the past few decades. Despite this long record of study, pier scour remains the most significant cause of bridge failure. The current study, which was based on field evaluations of pier scour failures in rivers with cohesionless beds, focused on a general view of the scouring process. The study was based on the results obtained from the investigation of 6 bridges on 3 rivers in Fars Province, Iran. The hydraulic effects of flow depth and velocity, sediment characteristics such as specific gravity, internal friction angle, particle size, and particle size distribution, and bridge pier geometry were considered. A certainty analysis based on field data was performed to provide a very rough estimate of risk. Statistical and physico-mathematical methods were used in analyzing the data. When possible, a simple comparison was made between the depth of scour and some existing empirical formulae. Among these formulae, the Hanco, CSU, Veiga, and Neill equations exhibited rather good agreement with the field data; however, the Laursen and Inglis equations overestimated scour depth. [ABSTRACT FROM AUTHOR]

The cause of the collapse of the Tacoma Narrows Bridge has been a topic of much debate and confusion over the years. Many mischaracterizations of the observed phenomena have limited the understanding of the collapse even though there has always been an abundance of evidence in favor of a negative damping model. Negative damping, or positive feedback, is responsible for large amplitude oscillations in many systems, from musical instruments to the Tacoma Narrows Bridge failure. We discuss some of the more well known examples of positive feedback, and then show how the interaction of the wind with the oscillating bridge, especially the development of large scale vortices above and below the deck of the bridge, led to such a positive feedback instability. We support our model by computational, experimental, and historical data. [ABSTRACT FROM AUTHOR]

In the late 19th century, the transportation needs of Quebec led to proposals for bridging the St. Lawrence River. The Quebec Bridge was the longest cantilever structure attempted until that time. In its final design, the clear span was 548.6 m (1,800 ft) long. The bridge project was financially troubled from the beginning. This caused many setbacks in the design and construction. Construction finally began in October 1900. In August 1907, the bridge collapsed suddenly. Seventy five workers were killed in the accident, and there were only 11 survivors from the workers on the span. A distinguished panel was assembled to investigate the disaster. The panel’s report found that the main cause of the bridge’s failure was improper design of the latticing on the compression chords. The collapse was initiated by the buckling failure of Chord A9L, on the anchor arm near the pier, immediately followed by Chord A9R. Theodore Cooper had been the consulting engineer for the Quebec Bridge project, and most of the blame for the disaster fell on his shoulders. He mandated unusually high allowable stresses, and failed to require recalculation of the bridge dead load when the span was lengthened. [ABSTRACT FROM AUTHOR]

Over 500 failures of bridge structures in the United States between 1989 and 2000 were studied. The age of the failed bridges ranged from 1 year (during construction) to 157 years, with an average of 52.5 years. The most frequent causes of bridge failures were attributed to floods and collisions. Flood and scour, with the major flood disaster in 1993, contributed to the frequency peak of bridge failures (almost 53% of all failures). Bridge overload and lateral impact forces from trucks, barges/ships, and trains constitute 20% of the total bridge failures. Other frequent principal causes are design, detailing, construction, material, and maintenance. Comparison made among three periods of similar studies (1977–1981, 1982–1988, and 1989–2000) revealed almost similar trends, with most failures occurring during the bridge’s service life. Also, human-induced external events occurred frequently in all three periods, but were most dominant in the first and third periods. Technological advances in information systems have a great impact on data collection and analysis. [ABSTRACT FROM AUTHOR]

Identifies the causes of motor-vehicle crash patterns and contributing factors to bridge crashes and related counter measure opportunities in the New York metropolitan area. Physical properties and operational characteristics of the Mill Basin Bridge, Willis Avenue Bridge, Berry Creek Bridge and Tappan Zee Bridge; Rear-end crash; Sideswipe/overtaking crashes; Fixed object crashes.

Abstract: The injury experience related to motor vehicle crashes on four bridges and one tunnel in Montreal, Quebec, Canada, from 1978 to 1982, are described. Particular attention is given to the Jacques Cartier Bridge, publicly perceived as being excessively dangerous. Data from the Quebec Automobile Insurance Board and police reports confirm an excess of deaths (19/34: rate ratio = 4.5) and severe injuries (69/109: rate ratio = 6.2) on the Jacques Cartier Bridge, and the association of 74 per ¢ of the fatalities and 64 per ¢ of the severe injury cases on this bridge with a single curve. Crashes follow a consistent pattern: vehicles tail to negotiate the curve and strike vehicles moving in the opposite direction. The demonstrated association between crashes and design factors provides a basis for identifying effective remedial and preventive measures. (Am J Public Health 1985:75:871-874.) [ABSTRACT FROM AUTHOR]

Analyzes the collapse of the Tacoma Narrows Bridge while focusing on the importance of documentation. Reason bridge collapsed; Collapse of bridge used to educate persons that if one does not know the history of a problem one is doomed repeat it.