ASPIRE Spring 11 - Aspire - The Concrete Bridge Magazine

AASHTO LRFD2011 Interim RevisionsRelated to ConcreteStructuresby Dr. Dennis R. MertzThe Fifth Edition of the AASHTO LRFDBridge Design Specifications waspublished in 2010. It was subsequently revisedwhen the American Association of StateHighway and Transportation Officials (AASHTO)Subcommittee on Bridges and Structures(SCOBS) considered and adopted changes attheir annual meeting in Sacramento, Calif., inMay of 2010. Technical Committee T-10, ConcreteDesign, developed Agenda Items 22, 23, and 31over the past several years and moved them tothe full subcommittee ballot during this meeting.These revisions are described in this article.Agenda Item 22 adds provisions to Article5.11.5.2.1 for lap splices of reinforcement.Based on research published in the WashingtonState Department of Transportation (WSDOT)Transportation Center (TRAC) ReportWA-RD 417.1, titled “Noncontact Lap Splicesin Bridge Column-Shaft Connections,” anequation was added to limit the spacing oftransverse reinforcement in the splice zone ofsuch shafts. The provisions are for columnswith longitudinal reinforcement that anchorsinto oversized drilled shafts, where the barsare spliced by noncontact lap splices, and thelongitudinal column and shaft reinforcementare spaced farther apart transversely than onefifththe required lap splice length or 6 in.Agenda Item 23 deleted provisions andcommentary from Article 5.12.2 relative toaggregates that are known to be excessivelyalkali-silica reactive (ASR). These provisionsand the commentary related to the testingof aggregates for ASR were deemed moreappropriate for the AASHTO LRFD BridgeConstruction Specifications. Appropriatereference was made to the ConstructionSpecifications.As a companion to Agenda Item 23, AgendaItem 31 was approved in conjunction withSCOBS Technical Committee T-4, Construction.Through this agenda item, the provisions deletedfrom the LRFD Bridge Design Specificationsin Agenda Item 23 were revised, updated, andinserted into the LRFD Bridge ConstructionSpecifications.These and the complete set of 2011 InterimRevisions to the AASHTO LRFD Bridge DesignSpecifications will be published in 2011 byAASHTO.Editor’s NoteIf you would like to have a specificprovision of the AASHTO LRFD BridgeDesign Specifications explained in thisseries of articles, please contact us at www.aspirebridge.org.52 | ASPIRE, Spring 2011