Curved Steel I-girder Bridges Research Articles

Load Distribution Factors For Horizontally Curved Composite Concrete-Steel Girder Bridges

This paper focuses on Load distribution factors for horizontally curved composite concrete-steel girder bridges. The finite-element analysis software“SAP2000” is used to examine the key parameters that can influence the distribution factors for horizontally curved composite steelgirders. A parametric study is conducted to study the load distribution characteristics of such bridge system due to dead loading and AASHTO truck loading using finite elements method. The key parameters considered in this study are: span-to-radius of curvature ratio, span length, number of girders, girders spacing, number of lanes, and truck loading conditions. The results have shown that the curvature is the most critical factor which plays an important role in the design of curved girders in horizontally curved composite bridges. Span length, number of girders and girder spacing generally affect the values of the moment distribution factors. Moreover, present study reveals that AASHTO Guide criterion to treat curved bridges with limited curvature as straight one is conservative. Based on the data generated from the parametric study, sets of empirical equations are developed for the moment distribution factors for straight and curved steel I-girder bridges when subjected to the AASHTO truck loading and due to dead loading.

Analisis I-Girder Baja Pada Jembatan Lengkung Horizontal Menggunakan Standar AASHTO LRFD 2012

Horizontal curved bridge is a bridge with a cross section of a curved steel I-girder that requires complex geometry and has certain requirements. which different between a straight bridge with a horizontal curved bridge that is in addition to the vertical bending effect and the shear effect is also influenced by torsional effects, lack of stability, and special constructive attention, and consideration of system behavior in the analysis. The purpose of writing this final project is to be able to do the bridge structure modeling using Midas Civil software, to design the structure of the horizontally curved steel I-girder bridge, and Obtaining the dimensions of I-Girder steel horizontally curved bridge that is able to resistance the effects of curvature and loads that work in accordance with predetermined conditions, and know the behavior of elements from horizontally curved steel I-Girder bridge. This design refers to AASHTO LRFD 2012 and design carried out namely three continuous span (42 m + 55 m + 42 m) by using two pieres. the dimensions of steel I-girder with 2000 mm girder height of 20 mm body thickness, top flange width 500 mm thickness 25 mm, and bottom flange width 600 mm thickness 40 mm. From the results of the girder design there are some of conditions which can be said to be extreme because comparison between the compressive stress with capacity almost the same, that is 99.8% at the inertia-x on maximum positive moment fatigue condition, 95% at the inertia-y on maximum positive moment strength lime state condition, and 98% the maximum positive moment Constructibility on torsion. This proves that every agreed has extreme. However, this value is still within safe limits in accordance with the standards used.

ACCURATE MODELING OF CURVED STEEL I-GIRDER BRIDGE

A curved and/or skewed steel I-girder bridge, in addition to the basic vertical shear and bending effects, will be subjected to torsional and warping effects. Thus, simplified hand calculation and line girder methods, might not be enough when bridges are to be analyzed. Refined methods, termed by AASHTO, have to be adopted. This paper has investigated the closeness and difference between curved bridge finite element models using 2-D gird and 3-D shell elements of I-girders, both are part of AASHTO refined method. Moreover, the results are calibrated by comparing analysis result with various two-dimensional and three-dimensional computations with varied curvature effects. It is concluded that when introducing torsional effects to finite element models, the modified torsional constant J with consideration of warping effect should be taken into the 2-D grid model as a refined model. When using 3-D shell elements as the refined model, stiffeners and connection plates play an important role of global model stiffness and should not be ignored, especially for sharp curved steel I-girder bridges.

Probabilistic seismic restoration cost estimation for transportation infrastructure portfolios with an emphasis on curved steel I-girder bridges

This paper develops a rapid probabilistic seismic restoration cost estimate framework for transportation infrastructures (i.e., bridge portfolios) by integrating Response Surface Metamodels (RSMs) coupled with Monte Carlo Simulation (MCS) into seismic restoration cost curve generation. A portfolio of curved steel I-girder bridges located in the Eastern United States is used for this study. As part of the restoration curve generation, joint RSM-MCS models are created and utilized to assess seismic vulnerabilities of the target bridge portfolio and estimate their damage ratios. Probabilistic damage factor models in conjunction with MCS to treat uncertainties in damage ratios, curved bridge characteristics, and volatile construction conditions are simulated with the joint RSM-MCS-based vulnerability functions. Relevant restoration cost curves are then generated based upon average construction cost data of the United States. Findings reveal that characteristics for the restoration curves vary relying on variability in damage ratios and vulnerabilities, emphasizing that an increase in the difference between lower and upper cost bounds occurs as the seismic intensity increases. This evidence highlights the significance of considering variability in both damage ratios and vulnerabilities for more reliable decision-making for seismic restoration on such bridge portfolios.

Seismic Performance and Response of Seismically Isolated Curved Steel I-Girder Bridge

AbstractA 0.4-scale model of a three-span, seismically isolated, curved steel I-girder bridge was tested on multiple shake tables. The isolation system consisted of 12 lead-rubber isolators. The bridge is highly curved with total subtended angle equal to 104° (1.8 radians). The objectives of this study were: (1) investigate the effect of curvature on the seismic response of an isolated bridge, (2) evaluate the performance of reinforced concrete (R/C) columns during the design-level earthquake using seismic isolation, and (3) determine the failure limit states of an isolated bridge under extreme shaking. It was found that the horizontal curvature had little effect on the response of the isolators but it did cause asymmetry in the seismic response resulting in higher lateral displacements in the abutment isolators. Elastic performance was achieved in the R/C columns at the design earthquake level, with no concrete spalling in potential plastic hinge zones and only minor surface cracking. Essentially elastic...

The flexural behavior of horizontally curved steel I-girder bridge systems and single-girders

The structural system of a horizontally curved steel I-girder bridge consists of a number of curved girders that are laterally braced by interconnected cross-frames. The modeling and nonlinear analysis procedures of large and complex systems of curved bridges are time consuming and demand a high computational cost. In order to facilitate the preliminary design procedures, it is suggested that the complicated bridge system might be replaced by simple single curved I-girders. In this paper, the applicability of single-girder models in determining the flexural response, elastic stiffness and the ultimate strength of curved bridge girders is examined. In addition, a series of finite element parametric studies is conducted to consider the effect of curvature on the accuracy of single-girder models. It is observed that the spread of plasticity, flexural strength and failure mechanism of bridge girders can be well predicted by the use of equivalent single-girder models. Yet, single-girder models cannot accurately predict the elastic stiffness and vertical and lateral and deflections of horizontally curved steel bridge girders.

Instrumentation of a Horizontally Curved Steel I-Girder Bridge during Construction

Horizontally curved, steel I-girder bridges can present unique challenges for engineers and contractors because the curved geometry can result in a complicated torsional response. The most complicated stages for predicting behavior of the girders usually occur during erection and construction when the loads and support conditions are the most unpredictable. Although laboratory experiments can provide valuable insight into the behavior, the high cost of the specimens often precludes meaningful experiments, whereas field monitoring of bridges during construction provides invaluable opportunities to understand the behavior and gather data for validating computational models. A horizontally curved, steel I-girder bridge was instrumented to monitor the bridge during erection and concrete deck placement. Stresses were monitored as girders were lifted into position, followed by measurements of vertical deflections, rotations, and stresses during the concrete deck placement. The stresses during the erection process were relatively low owing to the proper use of lifting and placing methods; however, high stresses can be induced after girders are placed when the cross frames are ratcheted into position. As expected, higher stresses, compared with the steel erection process, were recorded during the concrete deck placement. Nonetheless, the monitored bridge did not have stability problems because the bridge utilized a relatively stocky flange width-to-depth ratio. For bridges more susceptible to stability challenges, such as tightly curved bridges, highly skewed bridges, narrow bridges, bridges with odd span arrangement, or some combination of these attributes, it is recommended that the designer consider the implication of slender girders and explicitly design for the possibility of construction-related stability challenges. In addition, resulting from the limited availability of field measurements of horizontally curved girders throughout the construction process, the data represent a valuable resource researchers can use to validate computational models for conducting parametric investigations. This paper outlines the methods used during the field monitoring and summarizes the results from the field measurements.

Use of response surface metamodels to generate system level fragilities for existing curved steel bridges

Fragility curves that have been developed for curved steel bridges have not extensively addressed horizontal curvature and do not sufficiently account for major contributing curved bridge components that influence their seismic response (e.g., radius of curvature, cross-frame spacing, etc.). This study considers a group of horizontally curved steel I-girder bridges located in Pennsylvania, New York and Maryland to examine the influence of important parameters on their seismic response and develop system level fragility curves for the bridge group. The developed methodology is then applied to specific bridges. This paper provides description of the procedure used to generate representative curved bridge fragility curves using input from select component fragilities. The curves were generated for representative bridge systems, and utilized fragilities from important bridge seismic components created using Response Surface Metamodels (RSMs). The critical components included items at the bearings and the supporting pier columns. A statistical screening approach, using design of experiments and incorporating seismic response information obtained from nonlinear time history analyses, was used to determine critical curved bridge component seismic response ranges. Monte Carlo simulation was then implemented to assist with fragility generation for both the group of bridges and sample bridges. Using the generated fragility, case studies were performed to investigate the effects of the certain bridge parameters on seismic vulnerability. Findings indicated that parameters that significantly influenced seismic fragilities were the number of spans, radius of curvature, and maximum span length.

Stability of Curved Steel I-Girder Bridges during Construction

Structural stability is one of the essential aspects of the construction of curved steel I-girder bridges. The AASHTO load and resistance factor design (LRFD) bridge design specifications require the consideration of stability-critical conditions during the construction of curved I-girder bridges through checking (a) nominal initial yielding due to combined major-axis bending and flange lateral bending, (b) strength under combined major-axis and flange lateral bending, and (c) web-bend buckling. These specifications limit the flange lateral bending stress to 0.6Fy. In some cases, these rules may not be sufficient unless global second-order amplification of the lateral-torsional response is considered. In particular, structures with narrow widths and long spans may be susceptible to large second-order amplification that could compromise the overall system constructability. This paper presents analytical studies of a slender curved and skewed I-girder bridge unit that exhibited difficulties during the placement of the concrete deck. The results of approximate one-and two-dimensional analyses of the construction phase are compared with refined three-dimensional finite element solutions to highlight their differences. Guidelines are provided for handling cases in which the slender geometry of the structure may be an important constructability consideration.

Effect of Temporary Shoring Location on Horizontally Curved Steel I-Girder Bridges during Construction

Temporary shoring supports are used in construction of horizontally curved bridges to help ensure that the final constructed geometry is maintained by mitigating excessive girder deformations. Limited guidance currently exists in available design specifications and guidelines with respect to optimal placement of shoring towers because the number and locations of these supports are often site specific. However, if preliminary information could be provided to bridge designers and constructors with respect to shoring tower placement as a function of global curved bridge parameters, such as number of spans and radius of curvature, the amount of time required to specifically locate and proportion the towers could be reduced. This research aimed to examine the effects of shoring tower positioning on curved bridge behavior at different stages of construction. Sequential analyses of multiple idealized double-span curved bridges with varying radii were conducted using nonlinear finite-element models and vertical deformations and rotations of the girders, and shoring tower reactions were compared for different shoring support locations and different erection sequences. On the basis of the results, optimal shoring locations were obtained for the curved girders at different construction stages.

Curved Girder Deformation Prediction Effectiveness Using First-Order, Linear Geometric Finite-Element Models

This study examines whether a first-order, linear geometric finite-element static model analysis is capable of accurately predicting the deflection and rotation response of a curved steel I-girder bridge and curved steel I-girders. Girder deflections obtained during the erection of a horizontally-curved steel I-girder bridge and deflection and rotation data from curved-beam laboratory tests were used to determine if a linear geometric finite-element analysis could accurately predict their static behavior. Results indicate that the first-order, linear geometric finite-element model accurately predicts the deflection behavior of a horizontally-curved steel I-girder bridge and a curved steel I-girder beam tested under point loads. The results also indicate that the first-order, linear geometric finite-element model predicted the general rotation trends of the experimental beam accurately. However, the model overpredicted peak flange-tip displacements when compared with the experimental results.

End Forces on Crossframes in Horizontally Curved Steel I-Girder Bridges

Crossframes in horizontally curved steel I-girder bridges are primary members. They must be designed for strength and fatigue. Curved girder analysis computer programs typically compute crossframe ...

Construction Engineering for Horizontally Curved Steel I-Girder Bridges

The erection of horizontally curved steel I-girder bridges is inherently more complex than the erection of straight I-girder bridges of similar span lengths. Complexities associated with curved steel I-girder bridge erection are a direct result of the natural behavior of curved steel I-girders. The bridge erector and contractor is often directed to provide a construction plan, stamped and signed by a professional engineer, that details the steel erection procedure and provides calculations that demonstrate the girders and bridge components meet stability and structural capacity requirements. Bridge engineers must be aware of the complexities associated with the behavior of curved steel I-girders when they are developing erection plans. When these complexities are not considered by the contractor's engineer, significant problems or even a girder collapse can result. Currently, little guidance is given in design specifications and archival literature that illustrates what is required in the construction plans for curved steel I-girder erection and the calculations and design checks that should be carried out. This paper highlights aspects of curved steel I-girder bridge erection that should be considered by the contractor's engineer in the development of the steel erection plans for horizontally curved I-girder bridges in order to provide for a successful bridge construction project.

Probabilistic Vulnerability Scenarios for Horizontally Curved Steel I-Girder Bridges under Earthquake Loads

Horizontally curved steel I-girder bridges are located in all seismic zones in the United States. Research has shown that damage can occur to steel bridge components under earthquake loads. Probabilistic-based techniques are one tool that can be used to assess more accurately the seismic vulnerability of curved bridges for various damage states and at various seismic hazard levels. To examine probabilistic-based vulnerability criteria efficiently, the study used response surface metamodels (RSMs) in conjunction with Monte Carlo simulations to generate horizontally curved steel I-girder bridge fragility curves. The generated curves were then used to evaluate bridge damage in terms of previously published structure damage states. The use of RSMs reduces the required number of computer simulations needed to generate the fragility curves. The paper summarizes the fragility curve generation procedure for a group of horizontally curved steel I-girder bridges using RSMs in association with Monte Carlo simulation. Probabilistic vulnerability scenarios are presented via application to existing horizontally curved steel bridges located in Pennsylvania, New York, and Maryland to estimate seismic demands for those bridges and to generate fragility curves.

User-Friendly Finite Element Analysis Software for Analysis of Curved-Steel I-Girder Bridges

The design of curved I-girders is complicated because of the many performance stages that must be evaluated, including erection, construction, and in service. Evaluation of girder stability during early stages of construction is particularly complicated because of the limited presence of bracing. In addition to stability issues during girder lifting, guidelines for the necessity of shore towers during erection are not available. The Texas Department of Transportation funded a research project to investigate girder stability during early stages of construction. Results from this project will be used to develop guidelines for evaluating girder stability during early construction stages as well as to proportion the girder cross sections for safe and economic construction. The research includes field monitoring, a parametric study using finite element analysis (FEA), and development of user-friendly finite element analytic software that will serve as a tool for designers. This paper summarizes the development of an analysis tool as part of the UT Bridge research project, which provides engineers with a three-dimensional FEA of plate girder bridges during erection and concrete deck placement. The software provides a user-friendly preprocessor to guide input and a three-dimensional visual postprocessor output. UT Bridge performs a linear elastic or eigenvalue buckling analysis for a curved or straight bridge's defined construction procedure and is available free from the website of the University of Texas at Austin Ferguson Structural Engineering Laboratory.

Evaluation of Live-Load Lateral Flange Bending Distribution for a Horizontally Curved I-Girder Bridge

This paper focuses on levels of live-load lateral bending moment (bimoment) distribution in a horizontally curved steel I-girder bridge. Work centered primarily on the examination of (1) data from field testing of an in-service horizontally curved steel I-girder bridge and (2) results from a three-dimensional numerical model. Experimental data sets were used for calibration of the numerical model and the calibrated model was then used to examine the accuracy of lateral bending distribution factor equations presented in the 1993 Edition of the (AASHTO) Guide Specifications for Horizontally Curved Bridges. It is of interest to examine these equations for potential use in preliminary design even though they have been eliminated during recent AASHTO specification modifications that addressed curved bridge analysis, the 2005 Interims to the AASHTO LRFD Bridge Design Specifications. In addition, they were developed using idealized computer models and small-scale laboratory testing with very few field tests of i...

An assessment of modeling strategies for composite curved steel I-girder bridges

This paper investigates the qualities and limitations of a number of modeling strategies for design analysis of composite curved steel I-girder bridges. The strategies range from modified line-girder analysis to 3D finite element approaches. Several key modeling considerations, including girder web distortion, the idealization of the cross-frames, support and load height, and displacement compatibility between the girders and slab, are addressed. Approximate approaches are investigated for the capture of composite I-girder web-distortion effects when modeling the girders using open-section thin-walled beam theory. A representative full-scale composite curved I-girder bridge, tested at the Federal Highway Administration (FHWA) Turner-Fairbank Highway Research Center (TFHRC), is utilized for assessment of the different approaches. The predictions of key lateral and vertical displacements, reactions, cross-frame forces, major-axis bending stresses and flange lateral bending stresses are evaluated using the test bridge. The paper highlights a number of subtle but critical blunders that can occur in the context of the different methods. Engineers need to be aware of these pitfalls in order to avoid potential problems due to inaccurate analysis predictions. The paper closes with a discussion of the efficacy of the various approaches.

Curved Steel I-Girder Bridge Response during Construction Loading: Effects of Web Plumbness

Horizontally curved steel I-girder bridge systems tend to deflect and rotate out of plane under the action of gravity. Oftentimes, this response will lead to a condition wherein the subsequent girder cross-sectional orientation is one where the web is out of plumb. Currently, there exists little guidance concerning what effect this web out of plumbness has on structural performance. As a result of this lack of guidance from design specifications, there is tendency within current practice to work to alleviate the out of plumb condition through various detailing and erection strategies, since the performance implications of its presence within the structure are poorly understood. The present research employs nonlinear finite-element modeling strategies to study the various effects that web out of plumbness has on flange tip stresses, vertical and lateral deflections, cross-sectional distortion, and cross-frame demands. The focus of the present work is the construction stage, and thus steel dead load is the governing loading condition treated. Web out of plumbness magnitudes of up to 5° are considered.

Live-Load Analysis of a Curved I-Girder Bridge

Horizontally curved, steel girder bridges are often used in our modern infrastructural system. The curve in the bridge allows for a smother transition for traffic, which creates better road travel. However, some of the disadvantages of horizontally curved bridges are that they are more difficult to analyze, design, and sometimes construct in comparison to conventional straight bridges. This study focuses on a three-span, curved steel I-girder bridge which was tested under three boundary condition states to determine it's response to live load. The measured live-load strains were used to calibrate a finite-element model. The finite-element design moments and distribution factors for the three condition states were then compared with the results based on the V-load method. These different boundary conditions provided the researchers a unique opportunity to evaluate the impact that these changes had on the bridges behavior. It was found that while the V-load method produced positive bending moments that were close to the finite-element moments for some of the girders, this was a result of the V-load moment being unconservative and the distribution factor being conservative.

Erection Procedure Effects on Deformations and Stresses in a Large-Radius, Horizontally Curved, I-Girder Bridge

Special attention is required in the construction of horizontally curved steel I-girder bridges due to coupled effects of primary bending and torsional forces. Misguided steel erection procedures can lead to undesired stresses, deflections, and rotations in these types of bridges, resulting in a structure with misaligned geometry and in an unknown state of stress. Further complicating the issue, little guidance related to curved bridge behavior during construction is provided by current design codes, leaving contractors and designers uncertain as to the most appropriate steps to take to achieve an efficient, safe structure. A horizontally curved, six-span steel I-girder bridge located in central Pennsylvania that experienced severe geometric misalignments and fit-up complications during steel erection was studied to investigate curved girder behavior during construction. The structure was monitored during corrective procedures intended to realign it with the design geometry, and field data used to calibrate a three-dimensional computer model generated via SAP2000. The techniques and assumptions proven in the calibration process were used to create a numerical model of a three-span continuous portion of the bridge, which was the subject of several analyses exploring the effects erection sequencing, implementation of upper lateral bracing, and use of temporary supports had on the final deformed shape of the curved superstructure. Findings indicated that using paired girder erection produced smaller radial and vertical deformations than single girder techniques for this structure, and that the use of lateral bracing between the fascia and adjacent interior girders and the placement of temporary shoring towers at span quarter points are both effective means of further reducing levels of deflection.