1、american association of state highway and transportation officialsGSDPB2-I1ISBN: 978156051619-4www.transportation.orgLRFD Guide Specifications for the Design ofPedestrian BridgesDECEMBER 20092015 Interim RevisionsLRFD GUIDE SPECIFICATIONS FOR THE DESIGN OF PEDESTRIAN BRIDGES DECEMBER 2009 AMERICAN A
2、SSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS 2015 Interim Revisions 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.ISBN: 978-1-56051-619-4 Pub Code: GSDPB-2-I1 444 North Capitol Street, NW S
3、uite 249 Washington, DC 20001 202-624-5800 phone/202-624-5806 fax www.transportation.org 2014 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. 2014 by the American Association of State Highway and Transporta
4、tion Officials.All rights reserved. Duplication is a violation of applicable law.2015 INTERIM TO LRFD GUIDE SPECIFICATIONS FOR THE INSTRUCTIONS AND INFORMATION DESIGN OF PEDESTRIAN BRIDGES, SECOND EDITION iiiINSTRUCTIONS AND INFORMATION General AASHTO has issued interim revisions to AASHTO LRFD Guid
5、e Specification for the Design of Pedestrian Bridges (2009). This packet contains the revised pages. Affected Articles Underlined text indicates revisions that were approved in 2014 by the AASHTO Highways Subcommittee on Bridges and Structures. Strikethrough text indicates any deletions that were li
6、kewise approved by the Subcommittee. A list of affected articles is included below. All interim pages are printed on pink paper to make the changes stand out when inserted in the second edition binder. They also have a page header displaying the section number affected and the interim publication ye
7、ar. Please note that these pages may also contain non-technical (e.g., editorial) changes made by AASHTO publications staff; any changes of this type will not be marked in any way so as not to distract the reader from the technical changes. 2014 Changed Articles SECTION 7: STEEL TWIN I-GIRDER AND SI
8、NGLE TUB GIRDER SYSTEMS 7.2.2 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.SECTION 7: STEEL TWIN I-GIRDER 2015 INTERIM TO LRFD GUIDE SPECIFICATIONS FOR AND SINGLE TUB GIRDER SYSTEMS DESIGN OF PEDESTRI
9、AN BRIDGES, SECOND EDITION 7.2STEEL TWIN I-GIRDER AND SINGLE TUB GIRDER SYSTEMS 7.2.1General For potentially torsionally flexible systems such astwin I-girder and single tub girder structural systems,the designer shall consider: The out-of-plane stiffness of twin I-girders, prior to becoming composi
10、te with a concrete deck, can be significantly smaller than the in-plane, or vertical, stiffness. This can lead to a lateral-torsional buckling instability during construction. Single tub girders, prior to becoming composite with a concrete deck, behave as singly symmetric sections with a shear cente
11、r below the bottom flange. AASHTO LRFD Article 6.7.5.3 requires top lateral bracing in tub section members to prevent lateral torsional buckling of these sections. Prior to becoming composite with a concrete deck, twin I-girders with bottom flange bracing will behave as a tub girder and will exhibit
12、 the same tendencies toward lateral-torsional buckling. Top lateral bracing shall be provided as for tub sections, or the stability shall be checked as a singly symmetric member. C7.2.1 Several incidents have highlighted the need for a careful evaluation of the stability of pedestrian bridges, espec
13、ially during the construction stages. Structural systems consisting of two parallel girders can exhibit very different behavior during construction, depending on the bracing systems used. Lateral bracing contributes significantly to the lateral-torsional buckling capacity of the beam. For girders wi
14、thout lateral bracing during construction, lateral-torsional buckling capacity should be carefully evaluated. After the deck is cast, the section is effectively a “C” shape, which is singly symmetrical. Use of the appropriate lateral-torsional buckling equation is critical, and reference should be m
15、ade to Galambos (1998). Further information is contained in Yura and Widianto (2005), as well as Kozy and Tunstall (2007). 7.2.2Lateral-Torsional Buckling Resistance Twin I-Girder For evaluating the stability of twin I-girder systemswithout a composite deck or lateral bracing, theequation given by Y
16、ura and Widianto (2005) may beused: 22ncr yoxo pxsEM MIIML= (7.2.2-1) where: Mn= nominal in-plane flexural resistance of onegirder (kip-in.) Mcr= critical elastic lateral-torsional bucklingmoment of one girder (kip-in.) s = spacing between girders (in.) E = modulus of elasticity of steel (ksi) L = e
17、ffective buckling length for lateral-torsional buckling (ft) (in.) Iyo= out-of-plane moment of inertia of one girder(in.4) 1 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.SECTION 7: STEEL TWIN I-GIRDER
18、 2015 INTERIM TO LRFD GUIDE SPECIFICATIONS FOR AND SINGLE TUB GIRDER SYSTEMS DESIGN OF PEDESTRIAN BRIDGES, SECOND EDITION Ixo= in-plane moment of inertia of one girder (in.4) Mpx= in-plane plastic moment of one girder (kip-in.)Where a concrete deck is used, continuous twin I-girder systems shall be
19、made composite with the deck for theentire length of the bridge. 7.2.3Lateral-Torsional Buckling ResistanceSingly Symmetric Sections The lateral-torsional stability of singly symmetricsections not covered in Article 7.2.2 shall beinvestigated using information available in theliterature. C7.2.3 Equa
20、tions for the determination of the lateral-torsional buckling moment in singly symmetric sections are given in the Guide to Stability Design Criteria for Metal Structures by Galambos (1998), specifically in Chapter 5. Equation 5.10 of that chapter presents the general formula for singly symmetric me
21、mbers where bending is in the plane of symmetry. Methods for accounting for location of loading with respect to the shear center are provided, as well as for determining the appropriate buckling lengths considering rotational restraints. 8TYPE SPECIFIC PROVISIONS 8.1Arches Arches shall be designed i
22、n accordance with theprovisions of AASHTO LRFD with guidance fromNettleton (1977). 8.2Steel HSS Members 8.2.1General The capacities or resistances of connections for steelHSS members shall be in accordance with Chapter K ofthe specifications and commentary of AISC (2005) orAASHTO Signs. Resistances
23、for fatigue design shall bein accordance with Section 2.20.6 of Structural WeldingCodeSteel ANSI/AWS D1.1 or Section 11 ofAASHTO Signs. All loads, load factors, and resistancefactors shall be as specified by AASHTO LRFD and these Guide Specifications. For member design otherthan connections: Flexure
24、 resistance of steel HSS members shall be according to AASHTO LRFD Article 6.12 as box sections. Shear resistance of steel HSS members shall be according to AASHTO LRFD Article 6.11.9 as box sections. C8.2.1 AISC has partnered with CIDECT to publish a set of HSS Design Guides. These guides are publi
25、shed internationally and have not been reviewed by AISC and are not necessarily in accordance with the AISC Specifications. However, the documents are a good resource on HSS connections and systems. 2 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
