AASHTO WSDOT Questionnaire: Prestressed Girder Design Criteria

Paul SantoBridge Design Engineer 808-692-7611paul.santo@hawaii.govIdaho Transportation DepartmentLuis Zarate Technical Engineer2208-334-8545luis.zarate@itd.idaho.govIllinois DOTJohn CicconeSenior Standards Engineer217-782-9111John.Ciccone@Illinois.govIndiana DOTRandy StrainINDOT Bridge StandardsEngineer317-232-3339Gross Section Properties,have allowed the use ofTransformed SectionPropertiesGross Section propertiesGross section properties ascalculated in LEAPConspanstatePer AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Table5.9.4.2.2-1 In accordance withthe code5.14.1.4 - Bridges Composed ofSimple Span Precast GirdersMade ContinuousWe design continuous prestressedgirder bridges as simple spans forall loads, but then addreinforcement over the piers tocontrol cracking. We do use5.14.1.4 to design the positivemoment connection at the pier.We also allow the girder to bedesigned fully continuous for liveload and superimposed dead withapproval.Generally IDOT follows 5.14.1.4however some of the particularswere modified based on ourexperience. These are noted inour in house manuals and designguides. For example IDOT choseto adopt a 45 day rule instead ofthe 90 day rule specified in5.14.1.4. Our 45 day rulerequires the fabricator to hold abeam at the yard for 45 daysbefore shipping. When youconsider deck forming afterdelivery we estimate 60 daysbefore a beam is locked into thestructure. The reinforcement usedto handle the positive restraintmoments is designed for aminimum capacity of 1.2 Mcr.This reinforcement has beenstandardized for the sections weuse and is either 2 or 3 - #8hooked bars. Detailed calculationfor creep and shrinkage are notrequired.Girders Made Continuous Per5.14.1.4 and detailed perStandardsestimate!1/23/2013Approximate Estimate for I girderbridges designed with compositedeck. b) for everything else.Approximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.3Approximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.3 Unless thereare unique design requirements thisrequirement is per code.