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Sign Size and Breakaway Support
Relationships
Chiara Silvestri Dobrovolny, Ph.D. Dusty R. Arrington
Roger P. Bligh, Ph.D., P.E.
2015 Traffic Safety Conference Corpus Christi, Texas
June 10, 2015
Order of Presentation
Objectives
Literature Review
Finite Element Computer Simulations
Full-Scale Crash Testing
Recommendations
Objectives • Establish Minimum Sign Area for Slip Bases
• Conduct FEA Parametric Study of Impact Performance of
Slip Base Support
• Perform MASH Tests (3-61 and 3-62) as Verification of FEA Parametric Study
Literature Review
Texas Slip Base System
10 BWG Wall τ: 0.134”
55,000 psi min yield
Sch 80 Wall τ: 0.276”
46,000 psi min yield
Texas Slip Base System (2.875” O.D. steel support post)
* TxDOT standards (SMD (SLIP-2)-08)
(Sign areas ≤ 16 ft2)*
NOT requirement of min sign area w/ slip base Texas district practices include use of signs as small as 4 ft2 on Sch. 80 Motivation behind this practice reduce inventory and simplify maintenance
(Sign areas ≤ 32 ft2)*
Burn Ban Tests
Test #2 Test #3 Test #4
ALL PASSED Evaluated According to NCHRP Report 350
Evaluate TxDOT practice of appending burn ban sign to an existing slip base sign support system
according to NCHRP Report 350 criteria
BURN BAN Test #2 Videos
BURN BAN Test #2
Test #2
5.1” Occupant Comp. Def.
PASSED (According to NCHRP Report 350)
BURN BAN Test #3
Test #3
5.6” Occupant Comp. Def.
PASSED (According to NCHRP Report 350)
BURN BAN Test #4
Test #4
5.5” Occupant Comp. Def.
PASSED (According to NCHRP Report 350)
New criteria for safety performance evaluation:
MASH
Required test with Pick-up Truck Heavier Pick-up Truck (5,000 lbs) Increased vehicle CG
Occupant compartment deformation ≤ 4” (cfr. 5.9” from NHCRP Report 350)
Lower Center of Mass of Sign Support System
(affected by sign mounting height, sign area and weight)
Lower center of rotation for sign support system
Higher chance to have secondary contact w/ roof and/or windshield
FE Computer Simulations
FE Simulations were run with combination of the following:
10 – 12 – 14 – 16 ft2 Sign Area
BWG-10 (0.134” τ), Sch 80 (0.276” τ), Sch 40 (0.203” τ) Pipe Support
Plain and T-Bracket (2 Configurations) Pipe
1100C (Passenger Car) and 2270P (Pickup-Quad Cab) Vehicles
Simplified FE Matrix
Burn Ban Tests
TEST #2
TEST FE
Vehicle Damage
Impact Location
Schedule 80 Total 8 ft2
62 mph Quarter Point
Burn Ban Tests
TEST #3
TEST FE
Vehicle Damage
Impact Location
Schedule 80 Total 10 ft2
62 mph Quarter Point
Burn Ban Tests
TEST #4
TEST FE
Vehicle Damage
Impact Location
BWG-10 Total 10 ft2
62 mph Quarter Point
FE Impact Predictions w / Different Sign Areas
FE Predictions
Full Scale Crash Tests Recommendations
FE Simulations evaluated w/ respect to:
a) Impact Location b) Occupant Compartment Deformation
Recommendations:
MASH Test Level 3-61 (1100C Vehicle), 62 mph MASH Test Level 3-62 (2270P Vehicle), 62 mph BWG-10 Support T-Bracket Pipe 12 ft2 Sign Area – Square aspect ratio
Full Scale Crash Tests
Test #463631-1 2270P Pickup-Quad Cab BWG-10 (2.875” O.D. - 0.134” τ) T-Bracket 7’ Mounting Height 12 ft2 Sign Area
Test #463631-1 Results
Test #463631-1 Results
Impact Location: Roof Occupant Compartment Deformation: 3.75”
Test PASSED according to MASH
Test #463631-2 1100C Passenger Car BWG-10 (2.875” O.D. - 0.134” τ) T-Bracket 7’ Mounting Height 12 ft2 Sign Area
Test #463631-2 Results
Test #463631-2 Results
Impact Location: Roof Occupant Compartment Deformation: 4.75”
Test FAILED according to MASH
Impact Location
Wind Chart
1100C Passenger Car Full Scale Crash Test (No need for the 2270P Vehicle)
BWG-10
(2.875” O.D. - 0.134” τ)
T-Bracket
7’ Mounting Height
14 ft2 Sign Area
Proposed Test Configuration
Test #463631-3 1100C Passenger Car BWG-10 (2.875” O.D. - 0.134” τ) T-Bracket 7’ Mounting Height 14 ft2 Sign Area
Test #463631-3 Results
Test #463631-3 Results
Impact Location: Back Roof Occupant Compartment Deformation: 2.5”
Test PASSED according to MASH
Recommendations
Acknow ledgements
Research project conducted under cooperative program between TTI, TxDOT, and FHWA
TxDOT project director was Mr. Doug Skowronek TxDOT research engineer was Mr. Wade Odell Authors acknowledge assistance of project monitoring committee
members: • Larry Colclasure (WAC) • Christina Gutierrez (CST) • Carlos Ibarra (ATL) • Karl Janak (CST) • Armen Miskarov (BRG) • Charlie Wicker (TRF)