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Session 2. Standard Guardrail Systems: Testing, Performance, and Characteristics. Session 2 Outcomes. Define the Tests Required for Guardrail Acceptance Explain How Guardrail Systems Function. Barrier System Elements. (AASHTO RDG). Functional Requirements of Guardrails. Contain Vehicle
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Session 2 Standard Guardrail Systems: Testing, Performance, and Characteristics
Session 2 Outcomes • Define the Tests Required for Guardrail Acceptance • Explain How Guardrail Systems Function
Barrier System Elements (AASHTO RDG)
Functional Requirements of Guardrails • Contain Vehicle • No Penetration • No Vaulting • Redirect Vehicle • No Snagging 3. Tolerable Impact Forces
Weak Post W-Beam TL-3 2-11
Blockouts for Strong Post W-beam Steel posts: Non-collapsing blockout must be routed (or as tested) Wood posts: Wood blockout should be toe-nailed to post on each side* *Proprietary end treatments using wood blockouts and posts must have the blockouts toe-nailed to the post
Lapping of Guardrail “In the Direction of Traffic” - Upstream rail is in front of downstream rail
Lapping of Guardrail TRAFFIC Improper Lap
WASHERS on Standard Strong-Post W-beam NO WASHERS
I I I I I I I I What happens when a vehicle hits a metal guardrail?
Schematic I I I I I I I I
Schematic I I I I I I I I
I I I I I I I I What happened?
Critical Feature for Guardrail Performance MUSTMaintain TENSION
Session 2 Review What is the current criteria used to determine if barrier is acceptable for use on the National Highway? • Indianapolis 500 crashes • Anything existing on the highways today • NCHRP Report 230 • NCHRP Report 350
Session 2 Review What modification was made to enable strong-post W-beam guardrails with steel posts to pass NCHRP 350 testing? • Bigger post size was used • Non-collapsible blockouts (wood) • Nested W-beam rail element added • Longer post length in the ground
Session 2 Review What two features of metal guardrails are essential for optimum barrier performance? • Tension continuity and Color of rail element • Tension continuity and Minimum height • Minimum height and Direction of lap • Minimum height and Deflection distance for a fill slope
SESSION 2 OUTCOMES • Define the Tests Required for Guardrail Acceptance • Explain How Guardrail Systems Function