Highway Steel Research Articles

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.

A System on 3D-Model Libraries for Maintenance of Steel Highway Bridges

A System on 3D-Model Libraries for Maintenance of Steel Highway Bridges

Intelligent Model for Constructed Facilities Surface Assessment

Computerized intelligent systems can simulate human expertise as well as analyze and process vast amounts of data instantaneously. This paper presents a hybrid intelligent computerized model for constructed facilities surface quality assessment. The model uses computers to analyze digital images of the areas to be assessed to identify and measure defects. Moreover, neural networks are used to train the system to automate the process and replicate the experts' knowledge in identifying the defects. Most techniques, currently used in construction quality assessment, rely mostly on subjective criteria. The model applies digital image processing and neural network techniques for constructed facilities surface quality assessment to make the process objective, quantitative, consistent, and reliable. Highway steel bridge coating assessment was used to exemplify the generic model.

Closure to “Fatigue in Steel Highway Bridges under Random Loading” by Henning Agerskov and Jette Andkjær Nielsen

Closure to “Fatigue in Steel Highway Bridges under Random Loading” by Henning Agerskov and Jette Andkjær Nielsen

Fatigue in Steel Highway Bridges under Random Loading

Fatigue in Steel Highway Bridges under Random Loading

Effect of Cycle-Counting Methods on Effective Stress Range and Number of Stress Cycles for Fatigue-Prone Details

Two important parameters in fatigue life evaluations of existing steel highway bridges are the number of stress cycles experienced and the effective stress range. The inaccuracies in predicting remaining fatigue life can be attributed to either one of these two parameters. However, the AASHTO guide specification has no provisions for the cycle-counting methods to be used to determine these two parameters. A sensitivity analysis that addresses the effects of cycle-counting methods on the effective stress range and the number of cycles for various fatigue-prone details in both main and secondary bridge members is described. A comparison of five cycle-counting methods (level-crossing counting, peak counting, simple-range counting, mean-crossing-peak counting, and rain-flow counting) by using a simple variable-amplitude strain-time history showed that both the stress range and the number of cycles are sensitive to cycle-counting methods. Two of the most commonly used cycle-counting techniques for highway bridge variable-amplitude loading are the mean-crossing-peak and the rainflow cycle-counting methods. A comparison of the two methods by using field data taken under normal traffic showed that the rainflow cycle-counting method is more conservative than the mean-crossing-peak method. The relationship between the mean-crossing-peak and the rainflow cycle-counting methods was determined in the form of a correlation coefficient and a linear regression line. There is a nearly perfect positive correlation between the two methods. Therefore, values obtained for the effective stress range and the number of cycles by the mean-crossing-peak method can be converted to values for the rainflow method.

CALS-ORIENTED EXPERT SYSTEM FOR SUPPORTING DETAIL DESIGN OF STEEL HIGHWAY BRIDGES

CALS-ORIENTED EXPERT SYSTEM FOR SUPPORTING DETAIL DESIGN OF STEEL HIGHWAY BRIDGES

STATISTICAL ANALYSIS OF STEEL WEIGHT INCREASE FOR HIGHWAY STEEL BRIDGES DESIGNED BY NEW LIVE LOAD (B-LOAD)

著者らは前に鋼道路橋の鋼重のデータを集積して分析を行い, また鋼重を偏差値として表わすことを提案した. またその中で, 平成6年に改定された新活荷重 (B荷重) を用いて試設計を行い鋼重増加の予測をした. ここでは新荷重によって設計された橋の実績の鋼重データを集めて分析し, これまでの橋との比較および先の予測の検証を行う. その結果, 単純鈑桁橋では偏差値が53.8となり, 先の合成桁橋の試設計で予測した偏差値53.1に極めて近い値となった. 単純箱桁橋と連続鈑桁橋に対しては, 鋼重増加はこれよりも少ないことがわかった.

Fatigue in Steel Highway Bridges under Random Loading

Fatigue damage accumulation in steel highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test specimens have been carried through. The materials that have been used are either conventional structural steel with a yield stress of fy ∼ 400–410 MPa or high-strength steel with a yield stress of fy ∼ 810–840 MPa. The fatigue tests have been carried out using load histories, which correspond to one week's traffic loading, determined by means of strain gauge measurements on the orthotropic steel deck structure of the Farø Bridges in Denmark. The test series carried through show a significant difference between constant amplitude and variable amplitude fatigue test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel bridges, may give results that are unconservative. The validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression.

Vibration of highway steel bridges with longitudinal grades

The purpose of this paper is to analyze the effect of longitudinal grade on the vibration of highway bridges. The bridges are modeled as grillage beam systems. The vehicle is simulated as a nonlinear vehicle model with 11 independent degrees of freedom according to the HS20-44 truck design loading specified in the American Associate of State Highway and Transportation Officials (AASHTO) specifications. A good road surface roughness generated from the power spectral density function for the approach roadways and bridge decks is used in the analysis. Two types of longitudinal grade shape with six different grades ranging from 1% to 6% are analyzed. The dynamic responses of three steel multigirder bridges with different span lengths due to multiple vehicles moving across rough bridge decks with different vehicle speeds are evaluated. The analytic results are useful for practical bridge design.

DESIGN ASSESSMENT OF HIGHWAY STEEL BRIDGES USING STEEL WEIGHT DATA-BASE

DESIGN ASSESSMENT OF HIGHWAY STEEL BRIDGES USING STEEL WEIGHT DATA-BASE

Influence of Bridge Approach, Surface Condition, and Velocity on Impact Factors for Fatigue-Prone Details

An impact study on a long-span continuous highway steel girder bridge is described. Crawl and full-speed test data were analyzed to examine the influence of bridge approach, surface condition, and truck velocity on impact factors for fatigue-prone details in both main and secondary bridge members. The measured impact factors for fatigue stress categories A, B, E, and E’ details were compared with values obtained using the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications formula. For fatigue-prone details, the test results showed that surface roughness, truck velocity, and bridge approach affect the impact factor. Measured impact factors varied with the location of the detail. Also, the study showed that the AASHTO design impact factors were unconservative for details located in the bridge approach or end span.

Quantitative Approach to Rapid Seismic Evaluation of Slab-on-Girder Steel Highway Bridges

A quantitative approach follows for developing a methodology for the rapid seismic evaluation and ranking of slab-on-girder steel highway bridges. In the development of this methodology, analytical expressions are introduced to calculate the seismically induced forces and displacements in bridge components, first assuming that damage to bearings is not acceptable and then removing this constraint. In the latter case, the superstructure is assumed to become unrestrained and slide on its supports. The seismic screening of the bridges is based on the calculation of a ranking index defined as the product of an importance index and overall damage index. Unlike other existing methodologies, the overall damage index of the structure is determined considering the impact of damage to each component on the successive failure of other components and structure as a whole. A cut-off mechanism is introduced to prevent the potentially undue impact some dominating societal aspects could have on the ranking of existing bridges with otherwise excellent seismic-resistance adequacy. The proposed methodology also quantitatively addresses the risk inherent to all seismic hazard zones.

Seismic Analysis and Design of Modern Steel Highway Connectors

This paper discusses the seismic analysis and design of modern steel plate girder connectors. Full 3-D finite element analyses were conducted on a two-span two-girder bridge to determine its seismic load path and to establish the seismic performance of the bridge with several cross frame configurations. The results of the study showed that the cross frames play a significant role in the seismic behavior since they transfer the inertia forces to the substructure, a phenomenon not accounted for in the current design bridge codes.

Fatigue-Based Methodology for Managing Impact of Heavy-Permit Trucks on Steel Highway Bridges

Currently, in many areas of North America, special permits are issued to extra heavy vehicles without a detailed evaluation of individual components, considering only the ultimate capacity of the bridge inventory as a whole. Based on this, a large number of special permits have been issued to extra heavy vehicles. In this perspective, the ultimate and cumulative effect of such overloads on steel bridge components is studied. It is found that steel bridge members have adequate ultimate capacity to accommodate such overloads; however, they may suffer fatigue damage due to the cumulative effect of these overloads. Accordingly, a fatigue-based methodology is developed to assess the reduction in service life of bridges due to heavy-permit trucks. It is found that a reasonably large number of special permits can be issued at small reductions in fatigue life, but because stress ranges in excess of the constant-amplitude fatigue limit significantly alter the shape of the \IS-N\N curve, it is essential to appreciate that the concept of infinite fatigue life cannot be relied upon anymore.

Seismic Performance of Single-Span Simply Supported and Continuous Slab-on-Girder Steel Highway Bridges

Seismic response of single-span simply supported and continuous slab-on-girder steel bridges is studied. Linear elastic and nonlinear inelastic analyses are conducted for various ground-acceleration inputs. Bearings with higher stiffnesses that are closer to the edge of the deck are found to attract larger forces than other bearings, whereas bearings with small stiffness attract almost equal forces regardless of the width of the bridge. Assuming that the anchors of otherwise stable bearings are severed, sliding of the bridges is also investigated. It is found that narrower bridges with longer spans may have considerable sliding displacements and may fall off their supports if adequate seat width is not provided. Wider bridges with shorter spans can survive rather severe earthquakes, even more so in eastern North America. It is found that if bearings are not damaged, 2- and 3-lane continuous bridges with two spans of up to 40 and 50 m each, respectively, are capable to resist earthquakes with 0.4 g peak acceleration without any damage to columns. However, bridges with only about 80% of these spans can survive similarly intense earthquakes if the bearings are damaged.

Probabilistic fatigue life analysis of highway steel bridges

The purpose of this paper was to calculate the fatigue lives of highway steel bridges using a reliability-based methodology. An HS20-44 truck model with 12 degrees of freedom was developed and used in the analysis. Both noncomposite and composite steel beam, 60 ft (18.3 m) long, highway bridges were adopted in this study. Two percent of critical damping was assumed for the bridges. The road surface roughness of the approach roadways and bridge decks was generated from a power spectral density (PSD) function for very good, good, average, and poor roads in accordance with International Organization for Standardization (ISO) specifications. The fatigue life of both noncomposite and composite steel beam bridges for different vehicle speeds and classes of road surface roughness is calculated from the generated stress time-histories.

Closure to “ Fatigue Strength of Deteriorated Steel Highway Bridges ” by Patrick D. Zuraski and John E. Johnson (October, 1990, Vol. 116, No. 10)

Closure to “ <i>Fatigue Strength of Deteriorated Steel Highway Bridges</i> ” by Patrick D. Zuraski and John E. Johnson (October, 1990, Vol. 116, No. 10)

Discussion of “ Fatigue Strength of Deteriorated Steel Highway Bridges ” by Patrick D. Zuraski and John E. Johnson (October, 1990, Vol. 116, No. 10)

Discussion of “ <i>Fatigue Strength of Deteriorated Steel Highway Bridges</i> ” by Patrick D. Zuraski and John E. Johnson (October, 1990, Vol. 116, No. 10)

Fatigue Strength of Deteriorated Steel Highway Bridges

The effect of long-term environmental exposure and an extended history of highway loading was quantitatively determined for steel bridge beams that had been in service more than 50 years. Fatigue tests were conducted on specimens removed from the tension flange of truss stringers salvaged from four bridge replacement projects. Based on the fatigue strength reduction factor \IK\df\N determined on a basis of mean fatigue life for all specimens in one bridge, the fatigue sensitivities encountered were less than that associated with an AASHTO Category C welded connection detail. For individual specimens, the maximum \IK\df\N value determined was 3.0. At 36-ksi (248-MPa) stress range, average specimen lives exceeded 300,000 cycles for all bridges, for both center-span (maximum prior stress history) and near-support (insignificant prior stress history) specimens. The corrosion deterioration experienced by the plain (nonwelded) simple-span steel bridge beams in this study caused the average fatigue strength to be reduced by approximately one AASHTO fatigue category.