Bridge Owners Research Articles

Total reference-free displacements for condition assessment of timber railroad bridges using tilt

The US railroad network carries 40% of the nation\'s total freight. Railroad bridges are the most critical part of the network infrastructure and, therefore, must be properly maintained for the operational safety. Railroad managers inspect bridges by measuring displacements under train crossing events to assess their structural condition and prioritize bridge management and safety decisions accordingly. The displacement of a railroad bridge under train crossings is one parameter of interest to railroad bridge owners, as it quantifies a bridge\'s ability to perform safely and addresses its serviceability. Railroad bridges with poor track conditions will have amplified displacements under heavy loads due to impacts between the wheels and rail joints. Under these circumstances, vehicle-track-bridge interactions could cause excessive bridge displacements, and hence, unsafe train crossings. If displacements during train crossings could be measured objectively, owners could repair or replace less safe bridges first. However, data on bridge displacements is difficult to collect in the field as a fixed point of reference is required for measurement. Accelerations can be used to estimate dynamic displacements, but to date, the pseudo-static displacements cannot be measured using reference-free sensors. This study proposes a method to estimate total transverse displacements of a railroad bridge under live train loads using acceleration and tilt data at the top of the exterior pile bent of a standard timber trestle, where train derailment due to excessive lateral movement is the main concern. Researchers used real bridge transverse displacement data under train traffic from varying bridge serviceability levels. This study explores the design of a new bridge deck-pier experimental model that simulates the vibrations of railroad bridges under traffic using a shake table for the input of train crossing data collected from the field into a laboratory model of a standard timber railroad pile bent. Reference-free sensors measured both the inclination angle and accelerations of the pile cap. Various readings are used to estimate the total displacements of the bridge using data filtering. The estimated displacements are then compared to the true responses of the model measured with displacement sensors. An average peak error of 10% and a root mean square error average of 5% resulted, concluding that this method can cost-effectively measure the total displacement of railroad bridges without a fixed reference.

Performance of highway bridges subjected to blast loads

Since the collapse of the WTC towers in September 2001, concern about the protection of buildings and infrastructures against blast loads has increased significantly. Comprehensive experimental and numerical studies of blast loading effects on buildings have been carried out in recent years, whereas for bridge engineers, blast-resistant design is still a new area which requires separate and systematic investigation. The objective of this paper is to simulate the performance of three modern types of reinforced concrete bridges under various blast loads, including a slab-on-girder bridge, a box-girder bridge and a long-span cable-stayed bridge. To solve the computational constraints in performing numerical analysis on a personal computer, a Multi-Euler domain method based on the fully-coupled Lagrange and Euler models is adopted and further developed for long–span bridge application. This study investigates various detonation scenarios in terms of the explosive weight and location, and their interactions with bridge structures. Both the localized damage mechanism and the global structural response of three bridges are examined. By studying the blast-resistance of each bridge under different explosion threats, the most critical scenarios are identified respectively. Studies of bridge protection against potential attacks by using Carbon Fibre Reinforced Polymer (CFRP) strengthening are also discussed. Numerical results in this study provide bridge owners and engineers with thorough and important information on the structural performance of highway bridges under blast loads, helping them in choosing effective protection strategies for possible potential explosion events.

Low cost bridge load test: Calculating bridge displacement from acceleration for load assessment calculations

Bridge failure to pass load capacity assessment is unfortunately not an uncommon problem in bridge engineering and it is a potentially expensive problem for the bridge owner. Using load test data to justify increase in assessed load capacity is recognised as a viable approach in professional codes of practice. However, load tests are rarely carried out in practice because traditionally they are expensive to conduct and may not always justify an increase in assessed load capacity. Therefore this paper proposes a simple, quick and reliable approach for bridge load testing. In particular a procedure to calculate the bridge displacement to a moving truck by double integration of bridge acceleration is presented. Integrating acceleration to calculate displacement is not a new approach, with authors reporting difficulties due to errors in acceleration signals and unknown initial conditions. Many of the previous approaches have focused on developing signal processing algorithms to correct for the signal errors and while some good results have been reported, typically the derived displacements are very sensitive to parameters used in the correction algorithm, such as passband filter frequencies. Consequently, without comparison with directly measured displacement data, reliability of the procedure cannot be established and errors quantified. Therefore in this study a stripped down procedure is applied placing emphasis instead on minimising the errors in the recorded acceleration by using appropriate hardware and developing a quality control procedure that allows the user to assess the likely accuracy of the calculated displacement signal. The effectiveness of the proposed approach is trialled in the laboratory and in the field, with an accuracy of ±0.5mm observed.

Assessment of an existing fully prestressed box-girder bridge

The N.S. da Guia Bridge is a 250 m-long post-tensioned box-girder bridge built in the late 1970s using the balanced cantilever method. During a routine inspection, a systematic cracking pattern that exhibited both longitudinal and transversal symmetry was detected in the webs and bottom slab, which raised concerns about the condition of the embedded post-tensioned cables. The working programme that was devised to perform the condition examination of the bridge is described. Besides a detailed visual inspection campaign and a short-term monitoring programme, non-destructive testing was also employed, most notably gamma-ray imaging of the internal tendons. Special attention is devoted to the numerical studies developed to explain the origin of the observed crack patterns. This information was crucial in order to decide on the best rehabilitation strategies. The crack pattern could be satisfactorily reproduced by taking into account the local stress conditions around the tendon anchorages, and the concerns related to the condition of the prestressed steel could be ruled out. The applied methodology constitutes an example of how detailed analysis techniques can be used in practice to help bridge owners evaluate the condition of special bridges and plan the rehabilitation intervention in a cost-effective way.

Waterloo Bridge – structural behaviour and strength

Waterloo Bridge, carrying the A301 road across the River Thames in London, was completed in 1942. It comprises twin multi-cell reinforced-concrete box girders of variable depth with connecting transverse slab, supported on caisson foundations. The paper describes the analysis and load assessment using modern techniques of a structure originally designed without the use of computers. The original articulation system incorporated stops to restrict longitudinal movement, and dynamic damping devices. The assessment has taken account of the actual behaviour of the structure determined from movement measurements. The centre suspended span is supported by hinge joints, which comprise steel roller bearings attached to concrete with pre-stressed vertical and diagonal bars. These bearings and their associated supports were subject to detailed analysis to determine their ultimate strength. The assessment has led to a much better understanding of bridge performance and residual life, which will enable the bridge owner to plan future maintenance interventions.

Enhancing Resilience of Bridges to Extreme Events by Rapid Damage Assessment and Response Strategies

The U.S. highway transportation network consists of more than 650,000 bridges that are essential to maintaining the performance of the network. The existing bridges are, however, vulnerable to a variety of natural and manufactured (human-caused) hazards and may act as bottlenecks in the case of any failures. The most common extreme events include natural hazards, such as ground excitation during earthquakes, high wind and storm surges in hurricanes, and scouring and debris impacts during floods. Despite several advances in the technologies available for the design of new bridges and the retrofitting of existing ones, incidents in which bridges fail partially or completely after an extreme event still occur. In such cases, it is important for the federal, state, and local authorities to identify the damaged bridges, quantify the extent of the damage, plan for rapid recovery, and provide alternative routes for emergency response and evacuation activities. For this purpose, NCHRP Synthesis Topic 46-11 gathered the relevant information on the technologies available for the rapid assessment of damage to highway bridges after an extreme event, the availability of data from these techniques to transportation agencies and bridge owners, decision-making tools or processes that would use the data, and the emergency planning protocols in place to address the failures in bridges. This paper provides a summary of the findings of that project.

Parametric study of the finite element modeling of shot peening on welded joints

Nowadays, welding in steel structure design is the most widely used assembly technology. In the case of bridge structures, it has replaced riveting and bolting for the past thirty years. It is well known that this type of structure may deteriorate not just because of corrosion but also because of fatigue issues. In the case of corrosion, specific maintenance actions are currently being undertaken by bridge owners to increase the life span of their structures, such as painting operations. In the case of fatigue issues, it is well known that the high level of residual stresses due to the welding process may increase fatigue hazards. Several techniques may be used to reduce the high level of tensile stresses in the top layer of the weld near the welding toe. In this paper, the influence of welding and shot-peening parameters is investigated. A 3D finite element model is proposed and improved. The model results are compared to the residual stresses measured on several samples using X-ray diffraction method. Effects of the shot diameter, speed and angle impact are investigated. The transverse and longitudinal residual stresses near the welded joint, with a peak tensile stress value of 250MPa and 280MPa respectively, drop to a compressive stress value of more than 50MPa and fit with the experimental results.

Case Study on Rapid Scanning Techniques for Concrete Bridge Decks with Asphalt Overlay: Ground-Penetrating Radar and Infrared Thermography

AbstractAs of 2013, the Federal Highway Administration (FHWA) estimated that one-third of the total bridge deck area in the United States was structurally deficient. Providing for the effective management and repair of these decks requires transportation agencies to have access to the best available information about structural conditions. Bridge deck inspection has long relied on sounding techniques, such as tapping and chain drag, which can be time intensive and may not provide enough information for accurate repair estimating. Nondestructive evaluation (NDE) techniques may provide faster and more accurate data collection, but their value needs to be proven to transportation agencies and bridge owners. This paper describes a case study considering the two NDE techniques available for inspecting bridge decks with asphalt overlay: ground-penetrating radar (GPR) and infrared (IR) thermography. NDE scanning results and as-built repair data for four bridge decks were made available to the research team. Comp...

Crossing motorways under traffic without intermediate piers

AbstractThe European research programme SBRI attempted to reveal the costs caused during the service life of a bridge – direct costs for the bridge owner as well as indirect costs for users. The principal results of SBRI should make it possible to take better account of the true costs of a central pier by considering the risks in the construction phase and those that may threaten the highway overpass during its service life.CEREMA has developed two economic solutions to reach the objective of avoiding the central pier: The solution implemented at Ko Wé Kara in New Caledonia is a steel‐concrete composite tied arch bridge with innovative and economic details: innovative radial hangers made of welded plates, and innovative reinforcement against accidental impact of over‐height vehicles. One other possible solution is the composite steel‐concrete gantry bridge. The European research programme PRECOBEAM allowed the use of tests and experimental projects to finalize a new system of connection to lower the cost of this type of structure: a strip along which the cutting line of the steel dowels is made in a clothoid shape (CL), which improves the fatigue resistance. CEREMA introduced this innovation in its research programme. A composite structure can take various forms. It can associate, for instance, the steel web of a beam directly with a concrete flange. It can also constitute a composite deck with a bottom plate stiffened by connecting CL‐shape indented strips. An outstanding project of this type in New Caledonia is described in detail. Of course, this type of bridge is an integral bridge and the article includes some recommendations for the design and construction of integral bridges.

Steel Bridge Service Life Prediction Using Bootstrap Method

Steel bridges play an important role in the transportation system of many countries. To ensure that bridges are structurally sound, engineers monitor their performance, which is known as structural health monitoring. Historical evidence indicates that bridge damage is pervasive and that the service life of bridges is decreasing. To manage safety and costs, engineers must be able to accurately predict the service life of bridges. A statistical method to predict service life for steel bridges is presented, which can assist bridge engineers, bridge owners, and state officials in the objective assessment of deteriorated bridges for retrofit or replacement. Timely repair and retrofit of bridges increase their safety levels and decrease costs. A nonparametric statistical approach based on the bootstrap method for stress analysis for fatigue life prediction of steel bridge components is proposed. The bootstrap provides a simple approach for the reproduction of the extremely complex probability distribution of measured strain data. It is completely automated numerical method which requires no theoretical calculations and it is not based on the asymptotic results. The service life index is introduced which quantifies the fatigue life of steel bridges under daily traffic loads. A regression model is developed for the prediction of remaining service life of steel bridges using a service life function. The predicted remaining service life derived from the function can contribute to effective management of steel bridges.

Failure Mechanism of Expansion Joints in a Suspension Bridge

Premature failure of expansion joints is a concern for bridge owners. After opening to traffic, the Jiangyin suspension bridge experienced frequent damage in expansion joints, and the problem remained unsolved even after replacement with new expansion joints and installation of viscous dampers at the girder end. This paper aims to clarify the failure mechanism of the expansion joints based on field test results. The field tests consist of three scenarios: static test, influence line test, and truck pass-by test. The tests aimed to investigate the behavior of expansion joints on both global and local scales. In the static and the influence line tests, it was found that strain response of the expansion joint is affected by the girder deformation, which reflects effect of global behavior of the bridge on the expansion joints. The truck pass-by test result shows that direct impact of heavy truck axles could induce high strain in expansion joints, which indicates that the expansion joints are affected by vehicle axle loading on a local scale. These results are in accordance with the premature failures observed in the expansion joints of the Jiangyin Bridge.

Nonlinear dynamic analysis and seismic fragility assessment of a corrosion damaged integral bridge

Purpose In this paper the impact of corrosion of reinforcing steel in RC columns on the seismic performance of a multi-span concrete integral bridge is explored. A new constitutive model for corroded reinforcing steel is used. This model simulates the buckling of longitudinal reinforcement under cyclic loading and the impact of corrosion on buckling strength. Cover concrete strength is adjusted to account for corrosion induced damage and core concrete strength and ductility is adjusted to account for corrosion induced damage to transverse reinforcement. This study evaluates the impact which chloride induced corrosion of the reinforced concrete columns on the seismic fragility of the bridge. Fragility curves are developed at a various time intervals over the lifetime. The results of this study show that the bridge fragility increases significantly with corrosion. Design/methodology/approach This paper firstly evaluates the impact which chloride induced corrosion of the columns has on bridge fragility. Finally, fragility curves are developed at various time intervals over the lifetime of the bridge. The results of this study show that the bridge fragility increases significantly with corrosion. Findings 1) It was found that columns dominate the system fragility at all levels of deterioration. Therefore, it highlights the importance of good column design in terms of both seismic detailing and durability for this integral bridge type. 2) In terms of foundation settlement coupled with corrosion, it was found that settlements on the order of the discrete levels adopted for this study increased the system fragility at the slight, moderate and extensive damage states but their impact at the complete damage states is negligible. 3) Ageing considerations are currently neglected in widespread regional risk assessment and loss estimation packages for transport infrastructure. The result of this study provides a methodology that enables bridge managers and owners to employ in seismic risk assessment of existing aging bridges. Originality/value The modelling technician developed in this paper considers the impact of detailed corrosion damaged of RC column on nonlinear dynamic response and fragility of a corroded integral bridge under earthquake loading. The current modelling technique is the most comprehensive 3D fibre element model for seismic analysis and risk assessment of corroded bridges.

An approach to the development of connections between fibre reinforced polymer bridge decks

The use of fibre reinforced polymer (FRP) bridge decks has attracted increasing interest as a competitive alternative to traditional decking solutions. Even though the use of FRP decks started in the early 1990s, the uptake of these decks has been slow in bridge construction and there remains a need for research in diverse technical areas to promote the widespread use of these decks. One such area is the detailing and design of deck panel level connections which enable rapid on-site assembly. The development of connections in FRP decks is a somewhat complex process, which should take account of not only the structural performance and durability of the joint but also the ease of application and the tolerances this necessitates. It should therefore be regarded as a process in which the bridge owner, the designer, the manufacturer and the contractor are all involved. This process has been applied in the development of a novel joint configuration for panel level connections presented in this paper. The collaboration between the bridge owner, designer, manufacturer and contractor led to the development of a connection concept, in which expectations originating from the views of all parties were included. In this way, a concept focusing on meeting the requirements of all bodies was designed.

Full-Scale Testing of Shear Key Details for Precast Concrete Box-Beam Bridges

AbstractBox-beam bridge shear key connection designs are investigated by conducting full-scale structural tests. The authors’ evaluation included connection details, which are considered current good practice using high-strength nonshrink grout in combination with transverse posttensioning and novel details using ultra-high-performance concrete (UHPC). The factors that affect shear key performance, including simulated traffic loading, thermal loads, level of transverse posttensioning, and different connection designs, are presented in this paper. A simplified model for calculating the transverse shear is proposed, and the possible transverse tensile force caused by eccentrically placed loads is discussed. The performances of different connection details are presented and compared. The findings of the research can be used to assist bridge owners in the use of this economical bridge type and can provide innovative solutions that advance state-of-the-practice in bridge construction.

Fatigue Response of a Fracture-Critical Bridge at the End of Service Life

AbstractA fracture-critical bridge along Interstate Highway 35 with a relatively high volume of traffic had exceeded its original design life and was monitored before and after a repair was implemented to strengthen the bridge. Strain gauges and crack propagation gauges were installed at critical locations near existing fatigue cracks identified from annual manual inspections. The initial data were evaluated and indicated that the fatigue life of the bridge had been exceeded, such that the bridge needed to be repaired or replaced. The bridge owner placed the bridge on a fast-track schedule for replacement; however, because it would take 2 to 3 years to complete the bridge, the bridge owner also elected to strengthen the bridge in the interim. The girders were strengthened by installing bolted cover plates between the top flanges of the longitudinal girder and transverse floor beams. The response of the bridge was monitored before, during, and after the bridge was strengthened. In the strengthened conditio...

A review of experimental investigations and assessment methods for masonry arch bridges

Masonry arch bridges constitute a significant proportion of European road and rail infrastructures. Most of them are well over 100 years old and are supporting traffic loads many times above those originally envisaged. The inherent variation in their constituent materials, the traditional design criteria and methods used for their construction, their deterioration over time caused by weathering processes and the development of other defects, significantly influence the mechanical response of these historic structures. A deep understanding on the numerous factors that affect the structural behaviour of masonry arch bridges and on the analysis methods to assess the life expectancy of such bridges and inform maintenance and strengthening strategies is essential. This paper provides a critical review of the experimental studies that have been carried out and of the assessment approaches that have been developed in the last three decades to these aims. The current knowledge is established and areas of possible future research work are identified, with the aim of providing students and researchers, asset managers and bridge owners, and practitioners with a guidance for research activities and maintenace strategies.

Experimental and numerical evaluation of a folded plate girder system for short-span bridges – A case study

Bridge owners and engineers focusing on bridge design, management and maintenance continue to search for more efficient ways to design, construct, and maintain their bridge inventory. Recently, a folded plate girder system has been promoted as a cost-effective alternative for the design and construction of bridge superstructures due to merits such as low cost and facilitation of accelerated bridge construction. The folded plate girder system has a structural shape strategically press-brake formed from a single sheet of plate steel and achieves composite action with a concrete deck utilizing shear studs in between. To further facilitate the development and adaptation of the system for bridge application, this paper presents a systematic performance evaluation of the folded plate girder system through experimental and numerical programs. To this end, a folded plated girder specimen was designed, fabricated, and tested to evaluate the constructability and capacity of the girder specimen. Finite Element (FE) Analysis was performed to understand the behavior of the girder specimen under different loading conditions. The predictions using traditional design calculations and FE analysis were compared with the test results. After the FE models were validated against the test data, a full bridge model was established to further investigate the behavior of the bridge under loading condition up to the ultimate load. It was found that the ultimate capacity of the bridge girders were much higher than the bridge demand and the bridge had good ductility until failure. The predictions using the design calculations based on the AASHTO LRFD Bridge Design Specifications were in reasonable agreement with the test results. The FE models showed better predictions since more sophisticated modeling techniques and material constitutive models were used. Results obtained from the sophisticated non-linear bridge model indicated that the girder distribution factors varied along with an increase of the truck loading and especially their change trend was gradually reversed after the yield of the girder steel. And according to the FE results, the distribution factor based on the AASHTO LRFD Bridge Design Specifications was sufficient for the design of the folded plate girder bridge investigated in this study.

New Framework for Risk-Based Inspection of Highway Bridges

This paper presents a new methodology for determining bridge inspection intervals and procedures. The methodology was developed using established risk-based methodologies with the goals of improving bridge safety and serviceability and optimizing the use of resources for bridge inspection. Current inspection intervals are calendar based and generally require routine inspections at a maximum interval of 24 months. This uniform, calendar-based approach results in the same inspection interval for new bridges and aging and deteriorated bridges. The uniform inspection interval does not consider the inspection needs for a given bridge based on age, condition, materials, environment, etc., and as a result, inspection resources may not be utilized most effectively. Using the methodology described in this paper, a bridge owner performs a simple risk-based assessment of bridges in his or her inventory to identify those for which shorter inspection intervals are needed and those for which longer intervals are more appropriate. This assessment identifies likely damage modes and associated consequences in terms of safety and serviceability of a bridge. A simple risk matrix is used to identify the appropriate inspection interval for bridges. The new, risk-based approach represents a new paradigm for bridge inspection that could transform traditional, uniform, and calendar-based inspection approaches and improve the allocation of resources for bridge inspection to improve the reliability and safety of bridges.

Resiliency Planning: Prioritizing the Vulnerability of Coastal Bridges to Flooding and Scour

Bridge owners are faced with the daunting task of maintaining or replacing aging infrastructure over the next century. Added to this challenge are climate change projections such as rising sea levels. A major concern to bridge owners is the need to strengthen the resiliency of their bridges while utilizing a limited amount of financial resources. This paper will offer a methodology for prioritizing the vulnerability to flooding and scour for a state department of transportation's bridge inventory. Through the use of geographic information system (GIS) software, data is mined from the National Bridge Inventory (NBI) - making this methodology applicable to any state agency in the country. The New York City metropolitan region will be presented as a case study.

Implementing a Successful Risk-Based, Data-Driven Scour Program

The adoption of risk-based and data-driven (risk–data) approaches is leading to a successful FHWA Scour Program for highway bridges. FHWA, which has oversight for 463,000 bridges spanning waterways, estimates that 60% of bridge failures have hydraulic-related components. Prominent scour failures led to the FHWA Scour Program’s use of legal authority under the National Bridge Inspection Standards. The fundamentals of the FHWA Scour Program include scour evaluations and development of action plans. Quandaries for bridge owners include prioritization and the appropriate level of effort for these fundamentals. In 2011, FHWA implemented a risk–data approach for oversight of the National Bridge Inspection Program. Specific to scour, bridge owners compare the consequence of failure (risk) against facility operational characteristics (data). The risk–data approach prioritizes and applies resources toward bridges posing the greatest threat to public safety or disruption of vital services. The keys to the program’s success are outreach to facilitate progress; comprehensive enhancements to publications and training; and promotion of risk–data within policy, programmatic, stewardship, deployment, and research initiatives.