Upcoming Standard Changes Mash Training/Updates to Standard ssn.pdf · • Since MASH requires a...
Transcript of Upcoming Standard Changes Mash Training/Updates to Standard ssn.pdf · • Since MASH requires a...
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MashDevelopment length / Splices
Upcoming Standard Changes
Stuart Nielsen
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BarrierRails
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NCHRP 350 – “Recommended Procedures for the Safety Performance Evaluation of Highway Features”• Publication in 1993• Implementation in 1998 - calculations
Manual for Assessing Safety Hardware (MASH)• Originally published in 2009 - Second edition published in 2016• All new hardware (barrier rails) must be tested to MASH (not NCHRP 350) starting January 1, 2011
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• Specifically the TL-4 rails have to have a minimum height of 36 inches instead of the current 32 inches.
• Since MASH requires a tested TL-4 rail, Road Design decided to go to a safer rail profile.
• Current bridge barrier rails designs are changing because our existing rails do not meet new the MASH requirements.
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• On National Highway System (NHS)• Bridge barriers let after December 31, 2019• New installation or full replacement• Existing systems do not need to be replaced• Full testing is required; finite element analysis alone is insufficient to validate NCHRP 350 devices meets MASH
FHWA/AASHTO Bridge Implementation Plan to meet MASH
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MASH
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Significant differences at TL‐4
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Base 1’-1
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Base 1’-3 1/2
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General Barrier Shape• Testing currently underway
• 39” Tall• 36” satisfy TL-4
• 3” future overlay
• Single Slope Front Face• Near vertical 1:19.5
• Vehicle stability
• Vertical Back• Sloped back acceptable
• Vertical more critical
Midwest Roadside Safety Facility
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Development length and lap lengths
AASHTO 7th AASHTO 8th
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Splice Lengths
AASHTO 7th three classes A,B and C AASHTO 8th two classes A and B
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Example – tension splice#6 epoxy coated bar 60 ksi2” concrete cover6” spacing
OldNew
Class C
Class B
Lap 3’-7Lap 3’-1
ld = 22”1.7*22”=
ld = 54”Ldf =33”1.3*33”=
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5d1 - Spacing > 6”, 2.5” cover, is it a top bar?
New 2’-5 Top Bar 3’-1
TB 2’-11?
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Transverse Steel Splice in a bridge deck. Length of splice? Tension?
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Future• Projects started after October 1, 2018 shall
use the AASHTO 8th edition• Standards will be updated as fast as possible
for MASH and splices / development lengths• Use standards “AS IS” until new standards
are updated• Non standard designs use new AASHTO 8th
development lengths (projects started after October 1, 2018).
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Questions?