Design and Construction of Modern Curved Bridges

 

 

 

 

 

 

 

 

 

by

 

James S. Davidson, Ramy S. Abdalla

and Mahendra Madhavan

Department of Civil and Environmental Engineering

The University of Alabama at Birmingham

Birmingham, Alabama

 

 

 

 

 

 

 

 

 

Prepared by

 

UTCA

University Transportation Center for Alabama

The University of Alabama, The University of Alabama at Birmingham,

and the University of Alabama at Huntsville

 

UTCA Report Number 01223

December 31, 2002
Technical Report Documentation Page

1.  Report No

     FHWA/CA/OR-

 

2.  Government Accession No.

3.  Recipient Catalog No.

 

4.  Title and Subtitle

Design and Construction of Modern Curved Bridges

5.  Report Date

 

December 31, 2002

 

6.  Performing Organization Code

 

7.  Authors

James S. Davidson, Ramy S. Abdalla, and Mahendra Madhavan

8.  Performing Organization Report No.

 

UTCA Report 01223

9.  Performing Organization Name and Address

Department of Civil & Environmental Engineering

The University of Alabama at Birmingham

1075 13th Street South

Birmingham, AL 35294-4440

10. Work Unit No.

 

 

 

11. Contract or Grant No.    DTR598-G-0028

12. Sponsoring Agency Name and Address

University Transportation Center for Alabama

The University of Alabama

P.O. Box 870205

Tuscaloosa, AL 35487-0205

13. Type of Report and Period Covered

 

Final Report;  September 1, 2001 - December 31, 2002

 

14. Sponsoring Agency Code

15. Supplementary Notes

 

16. Abstract

 

The overall objectives of this project were to investigate and synthesize state-of-the-art practice for the efficient design and construction of curved bridges, and to identify research needs regarding strength and stability of curved bridges.  The project resulted in progress towards establishing a curved steel bridge stability research program within The University of Alabama system.  The work was conducted by graduate students whose efforts have resulted in several papers and presentations. The project enabled the investigators to participate in national level conferences and meetings.  Research literature was collected that will facilitate continued research efforts.  The planning, design, fabrication, and construction of a local curved I-girder bridge flyover was studied to gain a better understanding of practical challenges associated with curved bridge design and construction.  Curved I-girder and box girder stability topics that can be tackled within a university research environment were identified through the background research and interaction with industry leaders.  A meeting with Alabama Department of Transportation bridge engineers provided insight into the research and education needs and interests of Alabama.  The project facilitated interaction with prominent curved bridge researchers, industry leaders, and state and federal government division and program managers.  This report concisely summarizes the activities and accomplishments of the research team.  Technical results of the effort will be disseminated through conference presentations and proceedings, journal publications, student theses and dissertations, and the final report of a follow-on project, UTCA Project 03228, “Stability of Curved Bridges during Construction.”

 

The generation of so much information on this topic and contacts with so many experts in the field made the Principal Investigator uniquely prepared to advance the state of practice of curved bridge design in Alabama.  Future civil engineering students and bridge owners (ALDOT, counties, and cities) will certainly benefit from this knowledge.

 

17.  Key Words

Bridges, curved bridge, I-girder, box girder, stability, specifications

18.  Distribution Statement

19.   Security Classif (of this     report)

                Unclassified

 

20.  Security Classif. (of this page)

      Unclassified

21.  No of Pages

22.  Price

Form DOT F 1700.7 (8-72)


 

 

 

Contents

 

Contents............................................................................................................................... iii

Figures.................................................................................................................................. iv

Executive Summary................................................................................................................ v

 

1.0       Introduction    ......................................................................................................... 1

1.1       General                                                                                                          1

1.2       Objectives..................................................................................................... 2

1.3       Scope and Project Description....................................................................... 3

1.3.1    Tasks................................................................................................ 3

1.3.2    Project Team..................................................................................... 4

1.4       Report Content and Organization................................................................... 5

 

2.0       Accomplishments ................................................................................................... 6

2.1       Overview...................................................................................................... 6

2.2       Stability Research Accomplishments............................................................... 6

2.2.1        Design and Construction of Curved Box Girder Bridges .................... 6

2.2.2        Stability of Curved I-Girders during Construction .............................. 8

2.2.3    Analysis of Single I-girders during Erection......................................... 8

2.2.4    Case Study of the I-459 Flyover...................................................... 10

2.2.5    Papers, Presentations, and Reports.................................................. 11

2.3       Outreach and Interaction.............................................................................. 12

2.3.1    Conferences and Meetings............................................................... 12

2.3.2        Curved Bridge Research Interests of the Alabama Department

of Transportation............................................................................. 13

2.4       Stability Research Topics............................................................................. 14

 

3.0       Conclusions and Recommendations ................................................................... 16

 

4.0       References     ....................................................................................................... 18

 


 

 

 

 

List of Figures

 

Number                                                                                                                              Page

2-1       Cross sections commonly used in curved bridge superstructures.................................. 7

2-2       Support conditions considered in lifting studies............................................................ 9

2-3       Construction site of the Galleria Flyover................................................................... 10

2-4       Erection of girders at the Galleria Flyover construction site........................................ 11

 


 

 

Executive Summary

 

As the population of Alabama’s major metropolitan areas grows, there will be a need for smooth traffic flow transitions into and out of interstate highways and other major roadways.    Optimum traffic flow designs are essential for increased safety as well as increased efficiency of the roadway system.  In urban areas, this inevitably requires curved roadway alignment, and very often requires bridges to be constructed on curved alignment.  In fact, nationwide, over one-third of all steel superstructure bridges constructed today are curved.  But, design and construction of curved bridges is far more complicated and problematic than that of the typical straight bridge.

 

The overall objectives of this project were to investigate and synthesize state-of-the-art practice for the efficient design and construction of curved bridges, and to identify research needs regarding strength and stability of curved bridges.  The project resulted in progress towards establishing a curved steel bridge stability research program within The University of Alabama system.  The work was conducted by graduate students whose efforts have resulted in several papers and presentations. The project enabled the investigators to participate in national level conferences and meetings.  Research literature was collected that will facilitate continued research efforts.  The planning, design, fabrication, and construction of a local curved I-girder bridge flyover was studied to gain a better understanding of practical challenges associated with curved bridge design and construction.  Curved I-girder and box girder stability topics that can be tackled within a university research environment were identified through the background research and interaction with industry leaders.  A meeting with Alabama Department of Transportation bridge engineers provided insight into the research and education needs and interests of Alabama.  The project facilitated interaction with prominent curved bridge researchers, industry leaders, and state and federal government division and program managers.  This report concisely summarizes the activities and accomplishments of the research team.  Technical results of the effort will be disseminated through conference presentations and proceedings, journal publications, student theses and dissertations, and the final report of a follow-on project, UTCA Project 03228, “Stability of Curved Bridges during Construction.”

 

 

 


 

 

1.0 Introduction

 

 

1.1    General

 

As the population of Alabama’s major metropolitan areas grows, there will be a need for smooth traffic flow off of interstate highways and other major roadways.  This will inevitably require curved roadway alignment, and will often require curved bridges.  In fact, nationwide, over one-third of all steel superstructure bridges constructed today are curved.  Efficient design of curved bridges results in a superstructure that uses horizontally curved beams.

 

In the early days of curved bridge design and construction, bridge superstructures supporting curved roadway alignment were comprised of short straight girders linked together at the supports.  This resulted in inefficient use of very short spans between support piers.  As the technology for designing and fabricating curved girders became available, it became possible to design curved bridges with much greater distances between supports.

 

Today, curved girders are widely used in bridge superstructures.  The designer has many choices including material (concrete vs. steel), cross-section shape (tub girder vs. I-beam), etc.  Furthermore, the past three decades have resulted in advances in optimizing curved bridge design, resulting in innovative, aesthetically pleasing structures.  However, due to the simple addition of curvature, the design and construction of bridges becomes immensely more complicated than that of straight bridges.  While the girders, stringers, and floor beams of straight bridges can be designed by systematically isolating each member and applying standard loads, curved bridges must be designed with careful consideration to system-wide behavior.  In essence, the addition of curvature adds torsion to the system that results in significant warping and distortional stresses within the member cross-sections.  Furthermore, “secondary members” such as cross frames and diaphragms that provide stability in straight bridges become primary load carrying members in curved bridges.

 

Although the design of curved bridges is much more complex than that of straight bridges, there are no requirements specific to the design of curved bridges integrated into the American Association of State Highway Transportation Officials (AASHTO) Standard Specifications for Highway Bridges (AASHTO 1992).  There is, however, the “Guide Specifications for Horizontally Curved Highway Bridges,” which was first adopted in 1981 (AASHTO 1993).   This “guide” is widely recognized to be outdated, disjointed, and difficult to use.  Several significant research projects have been conducted over the past few years including the Federal Highway Administration (FHWA) “Curved Steel Bridge Research Project (CSBRP)” and the National Cooperative Highway Research Program (NCHRP) Project 12-38, “Improved Design Specifications for Horizontally Curved Steel Girder Highway Bridges.”  Currently, NCHRP Project 12-52, “LRFD Specifications for Horizontally Curved Steel Girder Highway Bridges,” is being conducted by Modjeski & Masters to prepare specifications for the design and construction of horizontally curved steel girder bridges (for both I- and box girders) in a calibrated load and resistance factor design (LRFD) format that can be recommended to AASHTO for adoption (www.modjeski.com).  Furthermore, many states have recently conducted or supported research on curved bridge design and construction.  The only other bridge design document in the world that specifically addresses curved bridge design is the Japanese “Guidelines for the Design of Horizontally Curved Girder Bridges” by the Hanshin Expressway Public Corporation (Hanshin 1988).   Several researchers, including the primary author of this report (Davidson), have demonstrated disparity in the strength formulations between the Japanese and American curved bridge design guides, which further emphasizes the need for additional research.

 

In addition to improving design equations for curved bridges, another area that has been widely recognized for further research is that of lifting and transporting curved girders during construction.  By far, the most frequent problems are encountered during construction.  The problems are typically more severe and more common than those encountered during the construction of straight bridges.  During the construction of straight bridges, girders and stringers are easily erected by one crane using one or two pick-up points, or by two cranes using one pick-up point each.  The individual straight girders can simply be set in place with little concern for instability.  Lifting and setting presents little difficulty for straight beams where the center of gravity is coincident with the centroidal axis of the beam cross-section.  But for horizontally curved girders, the center of gravity is non-coincident with the cross-section centroid. Depending on the lifting/support mechanism used, significant torsional stresses and minor-axis bending stresses may be induced.  The handling and erection of horizontally curved girders requires engineering expertise beyond that needed for the construction of straight bridges.  Engineers not experienced in the design of curved bridge systems often make the mistake of assuming that behavior and design is the same as that for straight bridges.   Instability during construction can easily translate into unsafe conditions for construction workers, not to mention unforeseen additional costs.

 

Because of the increasing demand for curved bridges combined with challenges of design and construction, there is need to investigate and synthesize state-of-the-art practice for the efficient design and construction of curved bridges.  This report summarizes the activities and accomplishments of a first phase project aimed at establishing a curved steel bridge research program within The University of Alabama system.  A follow-on project, UTCA Project 03228, “Stability of Curved Bridges during Construction,” is currently underway using the contacts, literature survey, and research needs synthesis of this project.  Technical results of the effort will be disseminated through conference presentations and proceedings, journal publications, student theses and dissertations, and the final report of UTCA Project 03228.

 

 

1.2    Objectives

 

The overall objectives of this project were to investigate and synthesize state-of-the-art practice for the efficient design and construction of curved bridges and to identify research needs regarding strength and stability of curved bridges.  Additional goals of the project included:

 

·        Develop relationships with Alabama Department of Transportation (ALDOT) bridge engineers, FHWA program managers, prominent curved bridge researchers, and industry leaders;

 

·        Identify research needs and topics suitable for graduate research;

 

·        Identify technology transfer and continuing education needs of ALDOT and the bridge design industry of the region;

 

·        Contribute to bridge stability research needs through graduate student research;

 

·        Identify potential sources of future support;

 

·        Transfer project results to stakeholders.

 

 

1.3    Scope and Project Description

 

1.3.1  Tasks

 

The four tasks of the project work plan and a synopsis of the accomplishments associated with each are described below.  The work was accomplished over a 16-month period beginning September 1, 2001.

 

TASK 1. Synthesis of current practice

 

The data-gathering effort involved investigating the current state-of-the-art curved bridge design and construction practice around the country.  The usual avenues of collecting information such as publication database searches and Web-based searches were used.  However, the synthesis largely depended upon direct contacts by the investigators.  Many states have conducted investigations to improve the design and construction of curved bridges and the resulting reports of such projects often do not show up in the typical library or journal database search.  Investigators at the University of Texas, the University of Houston, the University of Pittsburgh, and the University of Pennsylvania, for example, were contacted,