Curved Steel Bridges Research Articles

Experimental and Analytical Studies of a Horizontally Curved Steel I-Girder Bridge during Erection

A series of studies on an experimental, full-scale curved steel bridge structure during erection are discussed. The work was part of the Federal Highway Administration’s curved steel bridge research project (CSBRP). The CSBRP is intended to improve the understanding of curved bridge behavior and to develop more rational design guidelines. The main purpose of the studies reported herein was to assess the capability of analytical tools for predicting response during erection. Nine erection studies, examining six different framing plans, are presented. The framing plans are not necessarily representative of curved bridge subassemblies as they would be erected in the field; however, they represent a variety of conditions that would test the robustness of analysis tools and assess the importance of erection sequence on initial stresses in a curved girder bridge. The simply supported, three I-girder system used for the tests is described and methods for reducing and examining the data are discussed. Comparisons...

Historical Perspective on Horizontally Curved I Girder Bridge Design in the United States

This paper provides a historical overview of the development of horizontally curved steel I girder bridge design specifications in the United States. The background to the development of curved I girder design and analysis provisions in the 1993 and 2003 AASHTO Guide Specifications for Horizontally Curved Highway Bridges is discussed, and the status of recently completed and ongoing curved steel bridge research projects is summarized. In addition, the manuscript focuses on how the 2003 Guide Specifications can be used to analyze and design horizontally curved I girder bridges. Comparisons are made to prior provisions in the 1993 Guide Specifications.

Cross-frame and lateral bracing influence on curved steel bridge free vibration response

Accurately quantifying the free vibration response of curved steel bridges has been a topic of interest for researchers and practitioners. This study examines the response of an experimental, single-span, noncomposite, curved I-girder bridge superstructure during free vibration. Finite element models of the experimental bridge system, which was tested for the FHWA Curved Steel Bridge Research Project (CSBRP), were constructed and calibrated against experimental data from dynamic investigations of the bridge by the Virginia Transportation Research Center (VTRC). Parametric studies of the experimental curved bridge system were conducted using these finite element models to investigate the effects of cross-frame and lateral bracing parameters on the structure’s free vibration response.

Comparison of measured and predicted response of manufactured circular steel tubular members under concentric and eccentric compressive and tensile loads

Tubular steel members are seeing increased usage both in building and bridge structures due to their efficient geometry and to aesthetic benefits that they offer over more traditional open, thin-walled cross sections. While the utilization of small (152 mm or less), stocky (wall thickness greater than 1.6 mm) diameter circular tubes has been increasing, experimental studies of these types of structural members have been rather limited, with most research focusing on large diameter, thin-walled tubes prevalent in offshore structures. Therefore, this manuscript discusses a series of tests of manufactured steel circular tubes under concentric and eccentric axial loads. These tests were performed to (1) examine their behavior, (2) develop instrumentation schemes and (3) ascertain the capacity of round tubular members used in cross-frames of a prototype curved steel bridge tested by the Federal Highway Administration as part of their Curved Steel Bridge Research Project. Testing procedures are described and results are presented and discussed. In addition, data produced from the tests was utilized to perform comparisons between experimental results and predicted capacities from AASHTO and AISC design specifications, which utilize approximations coupled with interaction concepts to quantify behavior. Results from the comparisons indicated that measured ultimate loads were an average of 1.3 times higher than values from factored AASHTO and AISC ultimate load predictions. However, when reduction factors were removed from the AASHTO or AISC prediction equations, actual ultimate loads were an average of 5% higher than predicted values, with certain predictions being slightly nonconservative. While the nonconservative predictions were attributed to member imperfections and slight specimen misalignment, they do demonstrate the sensitivity that can exist when attempting to predict stockier circular tube ultimate loads using approximate, design-based criteria.

Effects of Distortion on Strength of Curved I-Shaped Bridge Girders

The curved I-shaped plate girders used in bridges with curved alignment are subjected to forces that cause significant distortion of the cross section during construction and during application of live loads after the deck has hardened. Furthermore, the addition of curvature reduces the vertical bending stiffness, increases deflection nonlinearities, and changes stability characteristics of behavior. Although the design equations of the AASHTO Guide Specifications for Horizontally Curved Highway Bridges are formulated to address these behavioral issues, design and construction engineers often are not familiar with the difficulties curvature introduces and do not understand the relationship between distortion and deflection amplification with the design equations. Analytical research conducted as part of the FHWA Curved Steel Bridge Research Project was used to highlight and describe the effects of curvature on the strength and stability of curved I-girder bridge superstructures. Issues described include the following: ( a) effects of cross-frame and diaphragm spacing on system behavior, ( b) effects of curvature on the lateral-torsional stability of curved I-shaped beams, ( c) effects of warping stresses on flange buckling, ( d) effects of curvature on web behavior, and ( e) effects of curvature on initiation and propagation of yield stresses in the girders of curved I-girder frames.

The Role of Computer Models in Full‐Scale Bridge Laboratory Tests

The role of computer modeling in an extensive series of curved steel bridge laboratory tests recently completed at the Federal Highway Administration's (FHWA) Turner‐Fairbank Highway Research Center (TFHRC) is discussed. Computer models were involved extensively throughout the process, from design of the testing frame to analysis of data that were produced. Predicted results from a series of finite‐element models are compared with data recorded from nine tests that occurred during construction. Results from the tests and from finite‐element analyses are also compared against those produced using the V‐load method, a simplified curved bridge analysis tool. The use of computer‐generated Monte Carlo simulations to help reduce and analyze data generated during the construction tests is also discussed.

Evaluation of Strength Formulations for Horizontally Curved Flexural Members

In 1992, the U.S. Federal Highway Administration, along with 13 states, began a project to study the behavior of horizontally curved steel bridges. The project is referred to as the Curved Steel Bridge Research Project and involves studying the behavior of curved members through theoretical, analytical, and experimental research. In this paper, detailed finite-element models representing a curved 3-girder test frame, are used to evaluate the effects of curvature on the bending strength of curved I-girders, linear-elastic static, and buckling. Combined material and geometric nonlinear analysis are conducted using models that represent the test frame and component test specimens that will be inserted into it. Results are compared to various predictor equations developed from analytical work by the authors and to work by other researchers. It is demonstrated that the predictor equations of the authors are accurate in representing the behavior of the system. Limitations and needed improvements are described as well.

Federal Highway Administration’s Horizontally Curved Steel Bridge Research Project: An Update

Since 1992, FHWA has had a major concentrated research project in the area of horizontally curved steel bridges, the objective of which is to conduct research to better define the fundamental behavior of such bridges. The project involves theoretical work leading to the development of refined predictor equations and verification of those equations through linear and nonlinear analysis and experimental testing of I-girder components. The overall experimental program involves testing of a series of full-scale bending and shear curved steel I-girder components and subsequently a full-size bridge. The development and refinement of predictor equations are summarized, and the work leading to the first series of experimental tests, which involve testing of full-scale bending components, is described.

Curved steel I-girder bridges: experimental and analytical studies

This paper describes the large-scale experimental and analytical program, initiated by the Federal Highway Administration (FHWA), aimed at developing new rational design guidelines for horizontally curved steel bridges. Analytical and experimental efforts dedicated to establish the size of the full-scale components that will be tested as part of an entire three-girder bridge system are also presented.

Construction Issues in Steel Curved-Girder Bridges

The construction of horizontally curved steel bridges is generally more complex than the construction of comparable straight-girder bridges of similar span. Curved-girder bridges, once completed, have generally performed as intended. Most problems that have occurred with curved-girder bridges have been related to fabrication and assembly procedures or unanticipated and unaccounted for deformations that occur during construction. As a result, these construction issues take on primary importance in the successful completion of the structure. Successful completion requires that each phase of construction proceeds as anticipated to ensure that the final structure is at the correct elevation to provide proper deck drainage and good riding quality. In some cases, construction issues for curved bridges have been given little or no special consideration by designers, or, at the very least, no more consideration than has been given to these issues for straight bridges. Thus, there is a need to better identify these issues, assemble and provide more in depth information on each of these issues to the design community, and emphasize their importance to designers. The significance of construction issues to complex horizontally curved steel bridges is in many ways analogous to their prominence in the design of segmental concrete bridges; construction issues often drive the design decisions. The objective is to promote awareness in the design of horizontally curved steel bridges to some of these construction issues.

Construction Issues in Steel Curved-Girder Bridges

The construction of horizontally curved steel bridges is generally more complex than the construction of comparable straight-girder bridges of similar span. Curved-girder bridges, once completed, have generally performed as intended. Most problems that have occurred with curved-girder bridges have been related to fabrication and assembly procedures or unanticipated and unaccounted for deformations that occur during construction. As a result, these construction issues take on primary importance in the successful completion of the structure. Successful completion requires that each phase of construction proceeds as anticipated to ensure that the final structure is at the correct elevation to provide proper deck drainage and good riding quality. In some cases, construction issues for curved bridges have been given little or no special consideration by designers, or, at the very least, no more consideration than has been given to these issues for straight bridges. Thus, there is a need to better identify these issues, assemble and provide more in depth information on each of these issues to the design community, and emphasize their importance to designers. The significance of construction issues to complex horizontally curved steel bridges is in many ways analogous to their prominence in the design of segmental concrete bridges; construction issues often drive the design decisions. The objective is to promote awareness in the design of horizontally curved steel bridges to some of these construction issues.