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BrDR 7.0 IMPLEMENTATION PREVIEW OF AASHTO BRIDGE SPECIFICATION
UPDATESKRISHA KENNELLY, [email protected]
AASHTOWare RADBUG MeetingAugust 3-5, 2020New Orleans, LA -
Virtual Meeting 1
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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Interims Unpublished as of this meeting date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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6
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7
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8
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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
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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
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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.
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LRFD 9th Edition Updates
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LONGITUDINAL STIFFENERSImproved flexural capacity for
longitudinally
stiffened steel beamsArticle 6.10.1.10.2
Web load-shedding factor, Rb
..
15LRFD 9th Edition Updates
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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
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LONGITUDINAL STIFFENERS
Implementation in BrDR:Vertical legs in angle stiffeners are
ignored in the flexural capacity
17LRFD 9th Edition Updates
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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
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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
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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
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STEEL BEAM SHEAR CAPACITY
New MBE Article: 6A.6.10.1
22MBE 3rd Edition, 2020 Interims
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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
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STEEL BEAM SHEAR CAPACITY
Implementation in BrRLRFR, LFR, ASR
Curved steel beam LFR
24MBE 3rd Edition, 2020 Interims
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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
