Orthotropic Steel Plates Research Articles

A novel acoustic emission source location method for crack monitoring of orthotropic steel plates

As the fatigue problem of orthotropic steel plates becomes increasingly severe in medium- and long-span bridges, structural health monitoring of the plates that could identify cracks timely is in great demand. Considering that orthotropic steel plates are of multiple structural elements and complex geometries, it is challenging to locate the cracks accurately. To this end, a novel acoustic emission (AE) source location method based on empirical wavelet transform and long short-term memory neural network was developed for crack monitoring of orthotropic steel plates. Empirical wavelet transform adaptively decomposed prominent components contained in the raw AE signal, of which the one with distinct dispersive modes was selected as the characteristic component to more precisely determine the arrival time through Akiake information criteria. The long short-term memory model established a more exact relationship between the arrival time differences of AE signals at multiple sensors and the source coordinates. With the help of empirical wavelet transform and long short-term memory model, it significantly eliminated the influence of dispersion, reflection, scattering, multiple propagation paths and noise, and thus guaranteed higher crack location accuracy. Through field experiment on a long-span suspension bridge, where cracks were simulated by artificial AE sources, a comprehensive comparison was carried out among traditional time-of-arrival method, delta-T mapping method, improved delta-T mapping method based on Akiake information criteria and Gaussian process, a counterpart of the proposed method based on empirical wavelet transform and Gaussian process, as well as the proposed method based on empirical wavelet transform and long short-term memory neural network. The location errors and their variations of the proposed method were found far less than those of the other existing methods. The location accuracy could be further improved by increasing the grid resolution of pencil lead break pre-tests. The results demonstrated the feasibility and superiority of the proposed crack location method for field applications on large-scale complex structures like orthotropic steel plates.

Stability of full-scale orthotropic steel plates under axial and biased loading: Experimental and numerical studies

In this study, three full-scale orthotropic steel plates set with single U rib, double U ribs and three U ribs were fabricated based on the mechanical characteristics of Changhong bridge in Ningbo. Several displacement and strain measuring points were selected as the analysis indexes, and two loading modes of axial and biased loading were designed. The buckling shape, out of plane displacement and strain variation law of the components under different loading conditions were analyzed. The DIC method was used to analyze the buckling and force transfer mechanism of the component in the loading process. Moreover, the finite element simulation and parameter analysis were carried out under eight component parameters by using ANSYS software. Through the experimental and parameter analysis in this paper, the instability mode, change of out of plane displacement, strain distribution and force transfer mechanism of orthotropic steel plates under different loading modes were obtained, which can provide reference value for the stability study of orthotropic steel plate and orthotropic steel box girder.

Full-Scale Experimental Study on the Negative Flexural Behavior of Orthotropic Steel–Concrete Composite Bridge Deck

The orthotropic steel–concrete composite deck, which consists of a concrete slab, an orthotropic steel plate, and shear connectors, has been applied for ameliorating the vehicle-induced fatigue damage on steel bridge decks. However, its static performance, especially its negative bending performance, has rarely been considered, despite its critical role in bridge durability and safety. Accordingly, negative bending tests on four full-scale composite deck specimens were carried out, in which the effects of steel-fiber-reinforced concrete (SFRC), the reinforcement ratio, and the shear connector type were investigated. The full-scale orthotropic steel plates of the test specimens were stiffened by large U-ribs, which were designed for construction convenience and cost reduction in applied engineering practice. The test results show that the bending stiffness of the composite deck was influenced by the reinforcement ratio and the shear connector type, and the load-carrying capacity was sensitive to the reinforcement ratio. The ultimate status was found to be dominated by buckling of the steel ribs. The use of SFRC had an obvious restraining effect on the crack-width development. Finally, the applicability of the current codes for the composite girder to the composite deck was verified by comparing the corresponding evaluations of reinforcement stress, bending stiffness, and crack feature with the test results.

POD-based spanwise correlation analysis of aerodynamic and aeroelastic pressures on twin-box bridge decks

The conventional spanwise correlation analysis based on buffeting-induced forces is not quite suitable for stress and fatigue analysis of a long-span cable-supported bridge, especially with a twin-box deck made of orthotropic steel plates. This study thus investigates the spanwise correlation of wind-induced pressures over the surface of a twin-box bridge deck in terms of the pressure modes calculated by using the proper orthogonal decomposition (POD) method. Each POD pressure mode obtained is likely to be associated with a particular excitation mechanism, aeroelastic (self-excited) pressure component due to motion or aerodynamic (buffeting) pressure component due to both incident and signature turbulence. Since the spanwise correlation of each pressure component can be quite different from others, the indicial functions are introduced to separate the aeroelastic component from the aerodynamic component. The empirical mode decomposition (EMD) method is applied to the aerodynamic component to further separate the incident turbulence-induced component from the signature turbulence-induced counterpart. The spanwise correlation coefficient and root coherence of each pressure component are investigated by using the pressure data measured from wind tunnel tests on a spring-suspended sectional twin-box deck model. The results show that the spanwise correlation coefficients of the aeroelastic pressures are close to 1. The root coherences of the signature turbulence-induced pressures show completely different characteristics from the incident turbulence-induced pressures. Therefore, a new coherence fitting scheme for signature turbulence-induced pressures is proposed based on the empirical functions for incident turbulence component. With this framework for the POD-based spanwise correlation analysis, the root coherence of each component pressures can be obtained, and the root coherence of the pressures at any two points on the surface of the twin-box deck can be reconstructed.

Performance characteristics of epoxy asphalt paving material for thin orthotropic steel plate decks

ABSTRACTEarly pavement distress caused by heavy traffic is frequently observed on bridges with relatively thin decks of orthotropic design, particularly in hot climates. This study investigates the possible use of epoxy asphalt to stiffen the thin deck/pavement composite, minimise deflection and ultimately fatigue failure. Three different epoxy asphalt binders were used and two pavement mix designs were employed. The binder and pavement mixture properties were evaluated by direct tensile and pull-off strength test on the binder, Marshall test of the paving mixture and flexural fatigue tests of paving mixture on steel plates. Test results show that a relatively high modulus binder and a relatively stiff pavement can effectively reduce the composite’s deflection and improve fatigue resistance on a relatively thin steel plate. Binder adhesion to the aggregate in the composite seems to play a pivotal role and the strength of this bond may have a close relationship with the stiffness of the pavement.

Multiscale Numerical Modeling of Steel Bridge Deck Pavements Considering Vehicle–Pavement Interaction

AbstractCracking is a major distress in steel bridge deck pavements. To determine the critical cracking zone, a numerical multiscale structural analysis was proposed and performed on the basis of a case study. First, a whole bridge model was analyzed, which revealed that the critical segment under critical load combination was one-fourth of the bridge span. Second, the critical segment was modeled using the finite mixed element method, and the critical local plate was determined. Third, using a submodel technique, the critical orthotropic steel plate with pavement was analyzed. The constructed model was then updated through an equivalent impact factor obtained from a numerical model analysis that considered vehicle–pavement interaction. From such multiscale model analysis, the crack distribution law of steel deck pavements was determined. Comparison of the analysis results from a traditional model with the multiscale model revealed the non-negligible effects of bridge structure and pavement evenness. Find...

Application of Composite Structures in Bridge Engineering. Problems of Construction Process and Strength Analysis

Steel-concrete composite structures have been used in bridge engineering from decades. This is due to rational utilisation of the strength properties of the two materials. At the same time, the reinforced concrete (or prestressed) deck slab is more favourable than the orthotropic steel plate used in steel bridges (higher mass, better vibration damping, longer life). The most commonly found in practice are composite girder bridges, particularly in highway bridges of small and medium spans, but the spans may reach over 200 m. In larger spans steel truss girders are applied. Bridge composite structures are also employed in cable-stayed bridge decks of the main girder spans of the order of 600, 800 m. The aim of the article is to present the cionstruction process and strength analysis problems concerning of this type of structures. Much attention is paid to the design and calculation of the shear connectors characteristic for the discussed objects. The authors focused mainly on the issues of single composite structures. The effect of assembly states on the stresses and strains in composite members are highlighted. A separate part of problems is devoted to the influence of rheological factors, i.e. concrete shrinkage and creep, as well as thermal factors on the stresses and strains and redistribution of internal forces.

Ultimate limit state of orthotropic steel plates of composite bridges

In traditional orthotropic plates the trapezoidal longitudinal stiffener is welded to the transverse girder web and to the bottom flange of the main girder. In a recently developed orthotropic plate the stiffeners and the transverse girder web are not connected. This approach provides for a significant reduction in the amount of flame cutting and welding, but more importantly there is no longer a need to assess the fatigue condition of the weld between the stiffener and the web. On the other hand, the potential for local buckling of the free edge of the web near the trapezoidal stiffener must be considered.

Ductility of orthotropic plated steel structures

The design practice of structural engineering is currently undergoing a considerable amount of fundamental change. For example, in recent years, limit state design has been introduced in Europe for the design of steel structures, and load and resistance factor design has become mandatory in the United States. However, other more dramatic changes in the practice of structural steel design attributable to a shift in the design philosophy as evidenced by the introduction of numerous new codes and standards that now require design for stability and ductility response. This paper discusses the yield mechanism forms of different solutions of the connections of trapezoidal stiffeners and cross beams for orthotropic steel plates.

Experimental Evaluation of Compressive Behavior of Orthotropic Steel Plates for the New San Francisco–Oakland Bay Bridge

Compression tests were conducted on two reduced-scale orthotropic plates to verify the design strength of steel box girders for the new San Francisco-Oakland Bay Bridge. The first specimen was composed of three longitudinal closed ribs and a top deck plate. It failed in global buckling, followed by local buckling in the deck plate and ribs. The second specimen, which was composed of four longitudinal T-shaped ribs and a bottom deck plate, experienced global buckling as well as local buckling in the ribs and the deck plate. The ultimate strength and failure mode of both specimens were evaluated by two bridge design specifications: the 1998 AASHTO load and resistance factor design specification and the 2002 Japanese JRA specification. Findings from code comparisons showed that: 1 Sufficient flexural rigidity of ribs were provided for both specimens; 2 the JRA specification slightly overestimated the ultimate strength of both specimens; and 3 neither specifications predicted the observed buckling sequence in Specimen 2. A general-purpose nonlinear finite element analysis program ABAQUS was used to perform correlation study. The analysis showed that the ultimate strength and postbuckling behavior of the specimens could be reliably predicted when both the effects of residual stresses and initial geometric imperfections were considered in the model.

Influence of Wearing Surfacing on Performance of Orthotropic Steel Plate Decks

The AASHTO Bridge Design Specifications first incorporated provisions for the design of orthotropic steel plate deck bridges in 1973. This and subsequent editions as well as the technical literature provided few requirements or guidelines for the design of the wearing surface. Little information is available in the United States today to help bridge designers find suitable materials and design methods for orthotropic deck wearing surfacings. An orthotropic steel deck plate requires a wearing surfacing for skid resistance, for smooth riding, and for corrosion protection. The wearing surfacing is subjected to the heavy impact of loaded truck wheels imposed by the passage of millions of trucks during the several decades of its service life. The performance of the wearing surfacings on orthotropic decks in the United States varies from excellent to poor, depending largely on deck plate flexibility, volume of heavy-truck traffic using the bridge, and, in particular, the type and thickness of the surfacing. Influences of the thickness and modulus of wearing surfacings on the performance of orthotropic steel plate decks are presented. Graphs using AASHTO truck wheel loading are presented; they show the wheel loading demand on the wearing surfacing as a function of thickness and the n value, which is the ratio of the wearing surface modulus to the steel modulus. A successful surfacing material must have properties that meet these demands initially, as well as many millions of wheel load applications during many years of service. Laboratory testing may be required to determine the durability properties of the surfacing.

A robust nonlinear mathematical programming model for design of laterally loaded orthotropic steel plates

The main objective of the present paper is to address a formal procedure for orthotropic steel plates design. The theme of the proposed approach is to recast the design procedure into a mathematical programming model. The objective function to be optimized is the total weight of the structure. The total weight is function of its layout parameters and structural element design variables. Mean while the proposed approach takes into consideration the strength and rigidity criteria in addition to other dimensional constraints. A nonlinear programming model is developed which consists of a nonlinear objective function and a set of implicit/explicit nonlinear constraints. A transformation method is adopted for minimization strategy, where the primal model constrained problem is transformed into a sequence of unconstrained minimization models. The search strategy is based on the well-known Fletcher/Powell algorithm. The finite element technique is adopted for discretization and analysis strategies. Mindlin theory is selected to simulate the finite element model and a selective reduced integration scheme is exploited to avoid a shear lock problem.

Mission Bridge—Design and Construction of the Steel Box Girder

The main span of the four-lane highway Mission Bridge is 440 ft (134.1 m) long with 290 ft (88.4 m) flanking spans, and consists of a steel box girder with an orthotropic steel plate deck. A box girder was adopted due to the structural efficiency of the box section and advantages in using thin plate material. The design is based on CSA Standard S6-1966 and the AISC Design Manual for Orthotropic Steel Plate Deck Bridges as far as applicable and with some deviations. The design was reviewed subsequent to the failure of steel box girder bridges abroad. The strength of the bottom plate in compression and the transverse bolted joints in compression received special attention. The joints of the deck plate made in the field are welded.In the fabrication and erection of the bridge, advantage was taken of the marine location of the fabrication yard. Special erection equipment was developed for the job. A key element in the scheme was ease with which the erection crane scow could be positioned.The application of the hot asphaltic concrete paving caused considerable thermal expansion of the steel structure.The cost of the steel superstructure was about the same as was estimated for a concrete superstructure. However, site conditions were such that the weight of the concrete structure would have increased the foundation costs.

Wearing Surfaces for Orthotropic Decks

Chapter 8, "Wearing Surfaces", of the AISC Design Manual for Orthotropic Steel Plate Deck Bridges1 contains the most complete descriptions of current steel deck surfacing systems and specific information on surfacing materials to be found in English language references. This paper presents new information on steel deck surfacing systems in use in the United States, systems proposed for three large orthotropic steel plate deck bridges being constructed or to be constructed in North America, and suggestions on novel components for surfacing systems that possibly justify consideration and further research. Despite the number of unprotected steel plate deck bridges giving satisfactory service in this country, there is agreement that a steel plate bridge deck requires some type of surfacing. Most existing steel plate bridge decks employ "pattern" or "checkered" steel plates. Such plates have different regular patterns of metal projections on the plate surface. The principal objection to unprotected pattern plate for highway bridge decks has not been corrosion of the steel plate, but the low friction developed between the steel plate and rubber tires in most conditions of service. It is generally agreed that steel plate decks require surfacing to improve resistance to skidding. It then follows that the surfacing system must be impervious to moisture. Trapped moisture on a steel plate under a surfacing system, admitted through cracks or holes in the surfacing system, will create a corrosion condition considerably worse than if the surfacing system were not present. The importance of the steel plate deck in orthotropic plate construction, as a member to distribute loads to stringers and as the top flange of stringers and floor beams, requires that the steel deck not be subject to corrosion. Thus, the two foremost requirements for a steel deck surfacing system are that the system must not admit moisture to the steel plate and the surface of the system must provide good resistance to skidding.

The Poplar Street Bridge

The Poplar Street Bridge will cross the Mississippi, between East St. Louis and the central business district of St. Louis. In addition to carrying Interstate Routes 55 and 70, it will be the terminal for Interstate 44 from the west and Interstate 64 from the east. This will be the first long span orthotropic steel plate deck girder bridge to be constructed in the United States. A contract for the substructure has already been awarded, and the superstructure will be advertised for bids in mid-1964. At the Missouri end of the bridge is the Jefferson National Expansion Memorial, a National Park commemorating the Louisiana Purchase, which will be completed, with its 630-ft stainless steel arch, in 1965. The view of the river from the Memorial will be framed on the north by the fine old Eads Bridge, a deck type arch truss design built in 1874, and on the south by the new bridge. Immediately west of the Memorial and adjacent to the central business district is an 80-acre area being redeveloped around a 50,000-seat sports stadium, which will be completed about the same time as the bridge.