Composite Highway Bridges Research Articles

Advances in Methodology for Fatigue Assessment of Composite Steel–Concrete Highway Bridges Based on the Vehicle–Bridge Dynamic Interaction and Pavement Deterioration Model

Fatigue cracking is one of the most prominent causes of mechanical failure limiting the service life of existing steel and composite steel–concrete bridges and is among the central concerns of structural and bridge engineers. In this context, the current work presents some recent advancements in an existing methodology for fatigue analysis developed by the authors throughout the years. The methodology is specifically devoted to the fatigue assessment of composite steel–concrete bridges employing the local hot-spot S-N approach and a coupled vehicle–pavement–bridge system considering progressive pavement deterioration with stochastically generated roughness profiles. Two different methodologies were used to solve the dynamic equilibrium equations: the modal superposition method to solve the bridge dynamic equations and a direct integration method to solve the vehicle dynamic equations. From a computational point of view, the present approach is more efficient and detailed than previous versions, as it allows a significant reduction in the analysis time and the use of complex bridge and vehicle finite element models. In this regard, a case study of a highway composite steel–concrete bridge spanning 40 m was selected in order to demonstrate the usefulness of the presented improved methodology by carrying out a fatigue analysis. The results of this investigation (displacements and stresses) are presented, aiming to verify the factors that directly influence the structural response and, consequently, the service life of steel–concrete composite highway bridges.

Avaliação do comportamento estrutural dinâmico de pontes rodoviárias mistas (aço-concreto) considerando o efeito da deterioração progressiva do pavimento

abstract: Highway bridges are usually subjected to random dynamic actions of variable magnitude due to vehicles convoys crossing on the bridge pavement deck along their service life. In this context, the asphalt pavement deteriorated road surface condition represents a key issue to assess the bridge displacement and stress values. This way, this research work aims to develop an analysis methodology in order to assess the dynamic structural behaviour of steel-concrete composite highway bridges including the vehicles convoys dynamic actions and the pavement progressive deterioration effect. The conclusions of this investigation have indicated that the displacements and stresses values are considerably higher, with relevant amplifications up to four times, when the road pavement deterioration effect is considered in the bridge dynamic analysis.

Comparison of International Brittle Fracture Design Code Provisions for Steel Bridges

Brittle fracture is a major concern to structural engineers as it has significant consequences for safety and cost. Although modern day occurrences of brittle fracture are rare, it is well known that they can occur without warning and may lead to the sudden closure of a bridge, loss of service, expensive repairs, and/or loss of property or life. In Canada, steel bridge fracture is a particularly significant concern because of the harsh climate. If the toughness properties are improperly specified, many steels could be on the lower shelf of the toughness-temperature curve. A comparison of brittle fracture design provisions around the world reveals that more sophisticated approaches have been developed for modeling and understanding brittle fracture in existing and new bridges than those currently in use in North America, including Canada and the U.S.A. This paper describes the European brittle fracture provisions and presents a comparison of the North American and European design provisions using the example of a typical steel-concrete composite highway bridge. On the basis of this comparison, situations where one set of design rules may be more or less conservative are identified, and opportunities for improvement and areas warranting further study are highlighted.

Assessing steel and composite highway structures: background to new UK design standards

The UK's design documents for assessment of steel and composite highway bridges and structures have been updated in line with Highways England's overall plan for modernising the Design Manual for Roads and Bridges. This paper describes the key changes that have been made to the document and their impact on users, providing reassurance that, despite the new format, the methods and requirements are largely unchanged, or changed to facilitate future assessments by allowing more general approaches to be adopted. For steel bridges the key changes are described that affect robustness assessment, notch toughness, bearing stiffeners, cross-girders, stiffened panel buckling and inspection criteria for existing welds. For composite bridges, the changes relate mainly to the serviceability limit state verifications, to fatigue and to the shear connection, as well as the general improvements to remove outdated content and simplify the document. The changes for both documents include greater references to the Eurocodes in general, which will facilitate an easier transition to Eurocode assessment standards when these are published in the future.

Highway Steel Composite Bridge Design using Limit State Design Method

Bridges are the pathways constructed over the obstacles without changing the alignment of the way beneath. While considering the design of steel composite bridges, Indian code is in the revision process; from Working Stress Method, it is updated to Limit State Design under IRC 24:2010. This paper illustrates a design example of a steel composite highway bridge with both longitudinal girders and cross girders under Limit State Design using IRC 24:2010 and IRC 22:2015. The concrete deck slab and steel girders together act as a composite structure which is connected using shear connectors. The effective span of the bridge is taken as 35m. There are four longitudinal girders having a spacing of 2750 mm c/c and cross girders are considered with spacing 5500mm c/c.

The Influence of Slab Concreting Sequence on a Continuous Composite Girder Bridge

This paper deals with the slab concreting sequence and its influence on a composite steel and concrete continuous highway girder bridge. The bridge has a symmetrical composite two-girder structure with three spans of 60 m, 80 m, 60 m (i.e. a total length between abutments of 200.0 m). The horizontal alignment is straight. The top face of the deck is flat. The bridge is straight. The transverse cross-section of the slab is symmetrical with respect to the axis of the bridge. The total slab width is 12 m. The slab thickness varies from 0.4 m on main girders to 0.25 m at its free edges and 0.3075 m at its axis of symmetry. The center-to-center spacing between main girders is 7 m and the slab cantilever on either side is 2.5 m long. Every main girder has a constant depth of 2800 mm and the thicknesses of the upper and lower flanges are variable. The lower flange is 1200 mm wide whereas the upper flange is 1000 mm wide. The two main girders have transverse bracing at abutments and at internal supports and at regular intervals in every span. The material of concrete slab is C35/45 and of steel members S355. The on-site pouring of the concrete slab segments is performed by casting them in a selected order and is done after the launching of the steel two girder bridge. The paper presents several concreting sequences and their influence on the normal stresses and deflections of the composite bridge girder.

Influence of Maintenance Strategies on the Life Cycle Performance of Composite Highway Bridges

In the context of sustainability, life cycle approaches are becoming increasingly popular for the assessment of potential impacts of a product or a system, from raw materials production to decommissioning and end-of-life processes. In relation to highway bridges, lifetime analysis implies consideration of the way the bridge is maintained over the lifespan of the analysis. Different maintenance strategies can be defined depending on the policy followed by highway administrations, which are usually subject to budget restraints. An overview of different European practices in the maintenance of highway bridges is provided in this paper; then, a methodology for life cycle analysis of bridges is presented, which enables assessment of the influence of different strategies of maintenance of highway bridges, in terms of environmental burdens, and direct and indirect costs over the lifespan of the bridge. The discussion is based on a case study of a composite bridge crossing a dual carriageway. The methodology presented in this paper is part of a research work carried out in the framework of the European research project SBRI: Sustainable Steel-Composite Bridges in Built Environment.

Numerical study on post-fracture redundancy of the two-girder steel-concrete composite highway bridges

As the Japan bridge inventory ages and traffic volumes increase, the government is spending more on maintaining their existing structures to extend the service life of the current bridge inventory. This includes two-girder bridges that are classified as fracture critical and non-redundant. Owing to the increased inspection costs associated with these fracture-critical bridges, there is a need to evaluate alternate load paths and to implement retrofit methods on existing bridge structures to avoid bridge replacement. In this paper, fracture redundancy of the two-girder bridge is investigated through a case study for a three-span continuous twin I-girder bridge. The finite element analysis is carried out to evaluate the load-carrying capacity after fracture of a girder of the two-girder bridge. Damage of studs near the moment contra-flexure regions are also considered in this study. Spacing between the transverse beams is discussed as possible techniques to improve redundancy and reduce the fracture potential of two-girder bridge structures. The concrete slab is indicated to be a significant member for guarantying the redundancy of the two-girder steel-concrete composite bridges.

Fatigue analysis and life prediction of composite highway bridge decks under traffic loading

STEEL AND COMPOSITE (STEEL-CONCRETE) HIGHWAY BRIDGES ARE CURRENTLY SUBJECTED TO DYNAMIC ACTIONS OF VARIABLE MAGNITUDE DUE TO CONVOY OF VEHICLES CROSSING ON THE DECK PAVEMENT. THESE DYNAMIC ACTIONS CAN GENERATE THE NUCLEATION OF FRACTURES OR EVEN THEIR PROPAGATION ON THE BRIDGE DECK STRUCTURE. PROPER CONSIDERATION OF ALL OF THE ASPECTS MENTIONED POINTED OUR TEAM TO DEVELOP AN ANALYSIS METHODOLOGY WITH EMPHASIS TO EVALUATE THE STRESSES THROUGH A DYNAMIC ANALYSIS OF HIGHWAY BRIDGE DECKS INCLUDING THE ACTION OF VEHICLES. THE DESIGN CODES RECOMMEND THE APPLICATION OF THE CURVES S-N ASSOCIATED TO THE MINERRS DAMAGE RULE TO EVALUATE THE FATIGUE AND SERVICE LIFE OF STEEL AND COMPOSITE (STEEL-CONCRETE) BRIDGES. IN THIS WORK, THE DEVELOPED COMPUTATIONAL MODEL ADOPTED THE USUAL MESH REFINEMENT TECHNIQUES PRESENT IN FINITE ELEMENT METHOD SIMULATIONS IMPLEMENTED IN THE ANSYS PROGRAM. THE INVESTIGATED HIGHWAY BRIDGE IS CONSTITUTED BY FOUR LONGITUDINAL COMPOSITE GIRDERS AND A CONCRETE DECK, SPANNING 40.0M BY 13.5M. THE ANALYSIS METHODOLOGY AND PROCEDURES PRESENTED IN THE DESIGN CODES WERE APPLIED TO EVALUATE THE FATIGUE OF THE BRIDGE DETERMINING THE SERVICE LIFE OF THE STRUCTURE. THE MAIN CONCLUSIONS OF THIS INVESTIGATION FOCUSED ON ALERTING STRUCTURAL ENGINEERS TO THE POSSIBLE DISTORTIONS, ASSOCIATED TO THE STEEL AND COMPOSITE BRIDGERS SERVICE LIFE WHEN SUBJECTED TO VEHICLERS DYNAMIC ACTIONS.

Steel–concrete composite bridge design charts for Eurocodes

The switch to Eurocodes from April 2010 requires the development and updating of many existing design tools. For many years Corus, and British Steel before them, have published preliminary design charts for steel–concrete composite highway bridges as part of their suite of design guidance for bridge engineers. These charts were originally developed using BS 5400 and the Highways Agency's design manual for roads and bridges. This paper describes the development of a new set of charts based on the structural Eurocodes. The new charts take advantage of benefits in efficiency permitted by the Eurocodes and also extend the scope of the original charts. The process adopted to generate the data for the charts is described and the key differences between the BS 5400 design approach and the Eurocode approach are discussed.

Discussion on “Composite (steel–concrete) highway bridge fatigue assessment” by F.N. Leitão, J.G.S. da Silva, P.C.G. da S. Vellasco, S.A.L. de Andrade, and L.R.O. de Lima [J Constr Steel Res 2011; 67(1): 14–24

A discussion was proposed on the paper “Composite (steel–concrete) highway bridge fatigue assessment” by F.N. Leitão, J.G.S. da Silva, P.C.G. da S. Vellasco, S.A.L. de Andrade, and L.R.O. de Lima. The main point of the discussion is the finite element model, in which the shear connectors of the steel–concrete composite girders were not considered. Besides, several issues such as the influence of other variable loads, the dynamic effects of vehicle loads due to irregular pavement surface, and critical locations of fatigue assessment of steel–concrete composite girders require further explanation to the readers.

Plastic load bearing capacity of multispan composite highway bridges with longitudinally stiffened webs

The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.

Composite (steel–concrete) highway bridge fatigue assessment

Steel and composite highway bridges are currently subjected to dynamic actions with variable magnitudes due to the action of vehicles crossing on the deck pavement. These dynamic actions can generate the nucleation of fractures or even their propagation in the structures. Depending on the magnitude and intensity, these adverse effects can compromise the structural system response and the reliability which may also lead to a reduction of the expected bridge service life. A composite (steel–concrete) bridge with a 12.50 m roadway width and 0.23 m concrete deck thickness, spanning 40.0 m by 13.5 m was investigated in this work. The computational model, developed for the composite bridge dynamic analysis, adopted the usual mesh refinement techniques present in finite element method simulations, and was implemented in the ANSYS program. The proposed analysis methodology and the procedures presented in the design codes were initially assessed to evaluate the bridge fatigue response in terms of its structural service life. The stress cycle counting techniques and the cumulative damage rule application had been analyzed through S–N curves, based on an extensive revision of steel and composite bridges’ service life and theoretical fatigue aspects in steel structures. The investigation also considered the recommended procedures used for the steel and composite structures’ main codes. The main conclusions of this paper focused on alerting structural engineers to the possible distortions, associated with the steel and composite bridges’ service life when subjected to vehicles’ dynamic actions.

Long-term Structural Health Monitoring System for a FRP Composite Highway Bridge Structure

This article discusses the implementation of a long-term structural health monitoring system for a FRP highway bridge using vibration-based monitoring techniques. The design and installation of such a system is prompted by the need to present a quantitative assessment of structural response to owners and operators in order to provide early warnings for major changes in response in the case of impending catastrophic failures. The bridge under discussion is instrumented with accelerometers as well as corresponding data acquisition and transmission equipment for automatic data collection. Ambient vibration based techniques are used to extract modal parameters from measured bridge response. Information regarding the change of internal structural characteristics is then obtained through a mode shape curvature based approach. Structural stiffness change is based on the analysis of collected data. A finite element model updating technique is used to provide an improved baseline model. The updated model is then used for simulation of damage effects.

Approximate Series Solution for Analysis of FRP Composite Highway Bridges

The design of a deck-and-stringer bridge system is usually reduced to the analysis of a T-beam section, loaded by concentrated loads corresponding to an equivalent fraction of the applied truck load. This equivalent load is defined by wheel load–distribution factors, which approximate the overall behavior of the bridge superstructure. In this paper, a one-term approximation of a macroflexibility series solution including deformations for fiber-reinforced polymer (FRP) deck-and-stringer orthotropic bridge systems, is used to develop explicit expressions for symmetric and asymmetric load distribution factors. It is significant that the equations presented herein include important parameters that represent, as accurately as possible, the response characteristics of the super structure, such as the geometry and material properties of the FRP deck and stringers, bridge aspect ratio, and number and spacing of stringers. As an illustration in actual design applications, the formulation presented in this paper is...

FEA of Complex Bridge System with FRP Composite Deck

Innovative fiber-reinforced polymer (FRP) composite highway bridge deck systems are gradually gaining acceptance in replacing damaged/deteriorated concrete and timber decks. FRP bridge decks can be designed to meet the American Association of State Highway and Transportation Officials (AASHTO) HS-25 load requirements. Because a rather complex sub- and superstructure system is used to support the FRP deck, it is important to include the entire system in analyzing the deck behavior and performance. In this paper, we will present a finite-element analysis (FEA) that is able to consider the structural complexity of the entire bridge system and the material complexity of an FRP sandwich deck. The FEA is constructed using a two-step analysis approach. The first step is to analyze the global behavior of the entire bridge under the AASHTO HS-25 loading. The next step is to analyze the local behavior of the FRP deck with appropriate load and boundary conditions determined from the first step. For the latter, a layered FEA module is proposed to compute the internal stresses and deformations of the FRP sandwich deck. This approach produces predictions that are in good agreement with experimental measurements.

Load Distribution for a Highly Skewed Bridge: Testing and Analysis

The American Association of State Highway and Transportation Officials (AASHTO) specifications provide formulas for determining live load distribution factors for bridges. For load distribution factors to be accurate, the behavior of the bridge must be understood. While the behavior of right-angle bridges and bridges with limited skews is relatively well understood, that of highly skewed bridges is not. This paper presents a study aimed at developing a better understanding of the transverse load distribution for highly skewed slab-on-steel girder bridges. The study involved both a diagnostic field test of a recently constructed bridge and an extensive numerical analysis. The bridge tested and analyzed is a two-span, continuous, slab-on-steel composite highway bridge with a skew angle of 60°. The bridge behavior is defined based on the field test data. Finite-element analyses of the bridge were conducted to investigate the influence of model mesh, transverse stiffness, diaphragms, and modeling of the supports. The resulting test and analytical results are compared with AASHTO’s Load and Resistance Factor Design formulas for live load distribution to assess the accuracy of the current empirical formulas.

Thermal Effects on Skewed Steel Highway Bridges and Bearing Orientation

An investigation is conducted to characterize and quantify external effects in composite steel highway bridges under thermal loading. Based on the results of a literature review, including thermal and thermoelastic analyses as well as current design code provisions, a simple but realistic thermal loading is developed for winter and summer conditions for AASHTO load and resistance factor design (LRFD) Zone 3. Three cases of bearing orientation, representative of current design practice, are examined. Parametric studies are then conducted. Hypothetical bridges are designed for a range of different span lengths, section depths, widths, and skews. Each bridge model is tested under all three constraint cases and both winter and summer thermal loading. Variations in structural response with each parameter are plotted, and the relative influence of each parameter is discussed. Design equations to predict the observed displacements and restraint forces at the bearings are then developed by a systematic regression procedure. The applicability of these proposed design equations is demonstrated by examples.

Life-Cycle Cost of All-Composite Suspension Bridge

This paper reports on the design of two highway suspension bridges made of conventional steel and advanced all-composite carbon fiber reinforced polymer (CFRP), and analyzed their life-cycle costs. The writers assumed that the pultrusion molding method would mainly be used for all composite highway bridges, because of its relatively high quality control performance and mass-production capability. First, the writers obtained the steel and composite highway bridge design in the same dimensional specification. Second, they acquired the future cost of the CFRP pultrusion product through hearing research from a fiber reinforced polymer manufacturer. Third, they calculated the initial costs of the steel bridge and CFRP bridge based on the design specification and the future cost of CFRP. Fourth, they compared the life-cycle cost of the steel and CFRP bridges under several conditions of discount rate, repair cost, and cycle. Finally, they found the critical condition where the CFRP bridge becomes more life-cycle cost-effective than the conventional steel bridge, if they could have expected the drastic cost reduction of the CFRP product.

Design Recommendations for Externally Restrained Highway Bridge Decks

A severe maintenance penalty exists for composite multibeam highway bridges in areas where the use of deicing chemicals is prevalent. This maintenance concern is largely due to the corrosion of embedded steel reinforcing bars and the attendant concrete degradation in the deck slab. Transverse steel straps, placed below the concrete slab, eliminate the deleterious effects of corrosion on the concrete. Further, the straps can be designed to provide the restraint necessary to promote the development of internal arching in the concrete slab in response to a concentrated load. A design procedure is presented for an externally restrained highway bridge deck. The method has been developed, based on the Canadian Limit States design philosophy, considering both the strength and serviceability requirements. It is demonstrated that the ultimate strength requirements dictate the external restraint requirements, and a numerical example of the design procedure is given.