AASHTO WSDOT Questionnaire: Prestressed Girder Design Criteria

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MoDOTGregory Sanders StructuralDevelopment and SupportEngineer573.526.0245gregory.sanders@modot. Mo.govMontana DOTJeff Olsen, P.E Bridge AreaEngineer – Billings District406-444-7610 jolsen@mt.govNCDOTTodd M Garrison, PEAdvanced Engineer(919) 707-6538tgarrison@ncdot.govNebraska Department OfroadsFouad JaberAssistant State Bridge Engineer402-479-3967fouad.jaber@nebraska.govNHDOTDavid L. ScottIn-House Design Chief(603) 271-2731dscott@dot.state.nh.usNJDOTEric KraehenbuehlManager609-530-2552eric.kraehenbuehl@dot.state.nj.usNMDOTZann Jones Civil EngineerAdvanced(505) 827-5583zann.jones@state.nm.usNV DOTTodd StefonowiczAss’t Chief Structures Engr775.888.7550tstefonowicz@dot.state.nv.usTransformed SectionPropertiesWe use gross properties as astandard, but may usetransformed on a case-bycasebasisGross Section properties(routinely used)Transformed SectionProperties (used whenbeneficial)Gross Section propertiesTransformed SectionPropertiesGross Section propertiesGross Section propertiesNet section propertiesPer AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Table5.9.4.2.2-1 (for AASHTOgirders and modified bulb tees)b) Zero tension at service limitstate (for cored slab and boxbeam units, and for all girdersin corrosive environments)Our present policy is to use0.095sq.rtf’c and rate for0.19sq.rtf”cZero tension at service limitstateZero tension at service limitstatePer AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Section5.14.1.4 - Bridges Composed ofSimple Span Precast GirdersMade ContinuousPer AASHTO LRFD Section5.14.1.4 - Bridges Composed ofSimple Span Precast GirdersMade ContinuousSimple span moments forsuperimposed dead loads and liveloadPer AASHTO LRFD 5.14.1.4NH has not done a continuousprecast prestressed girder bridgesince prior to LRFDimplementation. When we designour next one, our first attempt willbe option A.Per AASHTO LRFD Section5.14.1.4 - Bridges Composed ofSimple Span Precast GirdersMade ContinuousPer AASHTO LRFD Section5.14.1.4 - Bridges Composed ofSimple Span Precast GirdersMade ContinuousPer AASHTO LRFD Section5.14.1.4 - Bridges Composed ofSimple Span Precast GirdersMade Continuous1/23/2013Refined Estimates of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.4We use the approximate method withgross section properties and therefined method if we are using thetransformed section properties.a) Approximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.3b) Refined Estimates of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.4We don’t have a policy but in generalwe use the approximate methodApproximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.3Refined Estimates of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.4Approximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.Approximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.3
NYS DOTRajesh TanejaAssistant Director, Bridge DesignBureau518-457-2595rtaneja@dot.state.ny.usOhio DOTSean MeddlesBridge Standards Engineer614-466-2464Sean.Meddles@dot.state.oh.usOklahoma DOTRoland SisonDesigner(405) 325-4140rsison@odot.orgOregon DOTCraig ShikeInterim Bridge StandardsManaging Engineer503-986-3323Craig.L.SHIKE@odot.state.or.usGross Section PropertiesComposite with slab.Gross Section propertiesGross Section propertiesGross Section propertiesOregon does not permit theprestress gain due to liveload to be included in theprestress loss calculation.Therefore, use oftransformed sectionproperties is not permittedsince it would automaticallyinclude the prestress gaindue to live load.Per AASHTO LRFD Table5.9.4.2.2-1 (for HL-93 LiveLoad)1. For NYSDOT DesignPermit Vehicle stress limitis 0.14√f’c (for other thansegmentally constructedbridges)2. All bridges in NYS aresubjected to severecorrosion conditions.Per AASHTO LRFD Table5.9.4.2.2-1Per AASHTO LRFD Table5.9.4.2.2-1Simple spans –0.0948*sqrt(f’c). This is 50%the tension allowed in LRFD.This level of allowable tensionwas selected after a study ofdesigns prepared using thestandard specifications with0.0948*sqrt(f’c) for HS25loading and no tension forHS20 loading. Precastprestressed concrete slabs,boxes and girders form themajority of Oregon’s bridgeinventory. When LRFD wasintroduced, Oregon did notwant to begin building newSimple span moments forsuperimposed dead loads and liveloadWe also design the slab joint overthe pier for superimposed deadloads & live load.ODOT requires designers toconsider two loading conditions:1. Simple span for noncompositeloadings andcontinuous for live load andcomposite dead loadincluding an allowance forfuture wearing courses.2. Simple span for all noncompositeand compositeloadings excluding anallowance for future wearingcourses.Simple span moments forsuperimposed dead loads and liveloadOregon follows Section 5.14.1.4,but also requires bridges to beevaluated as if they were simplysupported with the tension nearmidspan limited to 0.19*sqrt(f’c).1/23/2013Refined Estimates of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.4We use Commercial Software, LEAPsoftware from Conspan andVirtis/OpisApproximate Estimate of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.3Refined Estimates of Time-Dependent Losses Per AASHTOLRFD Article 5.9.5.4Oregon believes the refined estimateof losses per 5.9.5.4 provides the bestaccuracy. Before this method wasavailable, Oregon used a methodwhich provided similar estimates.Oregon has never seen a prestressedmember with noticeable momentcracks. For this reason, we believethe refined method provides asatisfactory level of conservatism.
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AASHTO WSDOT Questionnaire: Prestressed Girder Design Criteria

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