PREFACE AASHTO first published Guide Specifications for Horizontally Curved Highway Bridges in 1980. These Guide Specifications included Allowable Stress Design (ASD) provisions developed by the Consortium of University Research Teams (CURT) and approved by ballot of the AASHTO Highway Subcommittee on Bridges and Structures in November 1976. CURT consisted of Carnegie-Mellon University@ the University of Pennsylvania@ the University of Rhode Island and Syracuse University. The 1980 Guide Specifications also included Load Factor Design (LFD) provisions developed in American Iron and Steel Institute (AISI) Project 190 and approved by ballot of the AASHTO Highway Subcommittee on Bridges and Structures (HSCOBS) in October 1979. The Guide Specifications covered both I and box girders. Changes to the 1980 Guide Specifications were included in the AASHTO Interim Specifications - Bridges for the years 1981@ 1982@ 1984@ 1985@ 1986@ and 1990. A new version of the Guide Specifications for Horizontally Curved Highway Bridges was published in 1993. It included these interim changes@ and additional changes@ but did not reflect the extensive research on curvedgirder bridges that has been conducted since 1980 or many important changes in related provisions of the straight-girder specifications. As a result of the research work on curved bridges conducted by the FHWA and several research institutes@ design provisions for both straight and curved bridges were developed. As part of the NCHRP 12-52 project@ these design provisions were incorporated into the AASHTO-LRFD Bridge Design Specifications in two stages. The design provisions for straight bridges were approved by ballot of the HSCOBS in 2003 and were incorporated into the third edition of the AASHTO-LRFD Bridge Design Specifications@ published in 2004. The design provisions for curved bridges were approved by ballot of the HSCOBS in 2004 and are to be published as part of the 2005 Interim Specifications to the AASHTO-LRFD Bridge Design Specifications. This Horizontally Curved Steel Box Girder Bridge Design Example was originally developed in the NCHRP 12-38 project using the 1993 AASHTO Guide Specifications for Horizontally Curved Steel Girder Bridges. It was updated to illustrate the applicability of the revisions to the AASHTOLRFD Bridge Design Specifications included in the 2005 Interim Specifications which were meant to incorporate curved bridges. As in the NCHRP 12-38 example@ a composite bottom flange option is provided for the bottom flange in the negative moment regions. This Design Example was compiled as a part of the deliverables in National Cooperative Highway Research Program Project 12-52. The following terms are used to identify particular specifications: ? ANSI/AASHTO/AWS refers to the 2002 edition of D1.5:2002 Bridge Welding Code@ American Welding Society and 2003 Interim Specifications@ ? LFD/ASD refers to the current year AASHTO Standard Specifications for Highway Bridges@ 17th edition and Interim Specifications and ? LRFD refers to the 2003 AASHTO-LRFD Bridge Design Specifications@ Third Edition@ with the 2005 Interims. Article and equation numbers in this example refer to those of the AASHTO-LRFD Specifications.