BrDR 7.0 IMPLEMENTATION PREVIEW OF AASHTO BRIDGE SPECIFICATION UPDATESKRISHA KENNELLY, [email protected]
AASHTOWare RADBUG MeetingAugust 3-5, 2020New Orleans, LA - Virtual Meeting 1
RECENT SPEC UPDATE HISTORY IN BrDRAASHTO LRFD Bridge Design Specifications
LRFD Specification 8th Edition, 2017 BrDR 6.8.2 LRFD 8th Edition Errata, May 2018 BrDR 6.8.3 LRFD Specification 9th Edition, 2020 BrDR 7.0
AASHTO Manual for Bridge Evaluation MBE 3rd Edition, 2018 BrDR 6.8.2 MBE 3rd Edition Errata, October 2018 BrDR 6.8.4 MBE, 3rd Edition, 2019 interims BrDR 6.8.4 MBE, 3rd Edition, 2020 interims BrDR 7.0
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2020 SPECIFICATION UPDATESIN BrDR 7.0AASHTO LRFD Bridge Design Specifications,
9th Edition 2020 store.transportation.org
AASHTO Manual for Bridge Evaluation, 3rdEdition with 2020 Interims Unpublished as of this meeting date
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LRFD BRIDGE DESIGN SPECIFICATIONS, 9TH EDITION
IN BrDR 7.0
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HTTP://DOWNLOADS.TRANSPORTATION.ORG/PUBLICATIONS/FLYERS/LRFDBDS-9_CHANGES.PDF
http://downloads.transportation.org/publications/flyers/LRFDBDS-9_Changes.pdf
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LRFD 9TH EDITION UPDATES IN BrDR
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LRFD 9TH EDITION UPDATES IN BrDR
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LRFD 9TH EDITION UPDATES IN BrDR
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SHEAR CAPACITY OF POST-TENSION BRIDGES
TXDOT Research Articles 5.7.2.8, 5.7.3.3
Grouted PT duct 𝝀𝝀duct shear strength reduction factor due to presence of PT duct
Ungrouted PT duct 𝝀𝝀duct = 1.0, reduce bv by duct diameter
12LRFD 9th Edition Updates
LONGITUDINAL STIFFENERSLongitudinally stiffened steel beamsResearch at Georgia Institute of
TechnologyImproved flexural capacity of girders
with longitudinally stiffened websReduced capacity (up to 10%) of non-
longitudinally stiffened girders with small compression flanges compared to web area 13
LRFD 9th Edition Updates
LONGITUDINAL STIFFENERS
Improved flexural capacity for longitudinally stiffened steel beamsArticles 6.10.11.3.1, D6.2.1All longitudinal stiffeners should be included in
the calculation of Dc, yield moment as well as other section properties pertaining to the major-axis of bending, such as Sxc and Sct utilized in the calculation of the girder flexural stress. 14
LRFD 9th Edition Updates
LONGITUDINAL STIFFENERSImproved flexural capacity for longitudinally
stiffened steel beamsArticle 6.10.1.10.2
Web load-shedding factor, Rb
..
15LRFD 9th Edition Updates
LONGITUDINAL STIFFENERS Potential reduced capacity of non-longitudinally
stiffened steel beams from 𝝀𝝀rw changes Articles 6.10.6.2.3, Appendix A6.1, A6.2 From 2017 AASHTO Bridge Committee Agenda Item 18:
“The proposed change to the noncompact web limit, 𝝀𝝀rw, for non-longitudinally stiffened girders gives a reduction in the flexural resistance at the strength limit state of up to approximately 10% in the most extreme cases for these types of girders with awc larger than 3.33 and Fyc up to 100 ksi. This change reflects the finding by Subramanian and White (2016c) that girders with relatively small compression flanges compared to the web area tend to exhibit reduced flexural resistances due to slender web effects. The flexural resistances for non-longitudinally stiffened girders with awc
LONGITUDINAL STIFFENERS
Implementation in BrDR:Vertical legs in angle stiffeners are
ignored in the flexural capacity
17LRFD 9th Edition Updates
FHWA & AASHTO sponsored researchArticles 6.8.2.3, 6.9.2.2, 6.9.4.1, 6.9.4.2, 6.9.4.5,
6.12.2Truss members in BrDR
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NONCOMPOSITE STEEL BOX-SECTIONS
LRFD 9th Edition Updates
Article 6.12.2.2.4Truss members, diaphragms, lateral bracing
in BrDRSeparate provisions for tees and anglesMore accurate predictions of LTB resistance
of tees and double angles 19
FLEXURAL RESISTANCE OF TEES AND DOUBLE ANGLES
LRFD 9th Edition Updates
MANUAL FOR BRIDGE EVALUATION, 3RD EDITION, 2020 INTERIMS
IN BrDR 7.0
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STEEL BEAM SHEAR CAPACITYLRFD Spec limits end panels to shear-yielding or shear-
buckling resistanceUCSD research shows tension-field action exists based
on top flange and bearing stiffener contributions in stiffened end panels
New MBE Article: 6A.6.10.1Consider tension-field action in stiffened web end
panelsLRFR, LFR, ASR 21
MBE 3rd Edition, 2020 Interims
STEEL BEAM SHEAR CAPACITY
New MBE Article: 6A.6.10.1
22MBE 3rd Edition, 2020 Interims
STEEL BEAM SHEAR CAPACITY
Curved steel beam LFR shear capacityStiffened web interior panels
– use LRFD 6.10.9Stiffened web end panels
– consider tension-field action
23MBE 3rd Edition, 2020 Interims
STEEL BEAM SHEAR CAPACITY
Implementation in BrRLRFR, LFR, ASR
Curved steel beam LFR
24MBE 3rd Edition, 2020 Interims
Thank You
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Brdr 7.0 Implementation preview of AASHTo Bridge specification updates��Krisha Kennelly, PE�[email protected]��Recent Spec update history in brdr2020 Specification updates�in brDR 7.0Slide Number 4http://downloads.transportation.org/publications/flyers/LRFDBDS-9_Changes.pdf�Slide Number 6Slide Number 7Slide Number 8LRFD 9th Edition updates in brDRLRFD 9th Edition updates in brDRLRFD 9th Edition updates in brDRShear capacity of post-tension bridges�Longitudinal stiffenersLongitudinal stiffenersLongitudinal stiffenersLongitudinal stiffenersLongitudinal stiffenersNoncomposite steel box-sectionsFlexural Resistance of tees and double anglesSlide Number 20Steel beam shear capacitySteel beam shear capacitySteel beam shear capacitySteel Beam Shear CapacitySlide Number 25