NCHRP 350 UPDATED. NCHRP 350 Historical Review Document Source Year Issued Number of Pages Test...

NCHRP 350

UPDATED

NCHRP 350Historical Review

DocumentSource

YearIssued

Number of Pages Test Vehicle& Weight

HRB #482 1962 1 4400 lb. car

NCHRP #115 1971 70 4000 to 5000 lb. cars.

NCHRP #118 1972 96 2000 & 4500 lb. cars

NCHRP #153 1974 19 2250 & 4500 lb. cars

TRC #191 1978 27 *2250 & 4500 lb. cars

NCHRP #230 1981 42 *1800 & 4500 lb. cars

NCHRP #350 1993 132*1800 lb. car & 4400 lb. Pickup

*Large trucks also considered

Current NCHRP Project 22-14(2) to Rewrite NCHRP 350

The current crash testing

and evaluation standards

were published in 1993 as

NCHRP 350

(This was the first time that FHWA

required that all newly installed safety

hardware be capable of meeting the

current evaluation criteria)

“Recommended Procedures for the

Safety Performance Evaluation of Highway Features.”

The Complete System

End Treatment Longitudinal Barrier Transition RigidBridgeRailing

TEST LEVELS VEHICLE MASS IMPACT SPEED IMPACT ANGLE

TL-1 2000kg (4400 lb) 50 km/hr (31mph) 25 deg TL-2 2000kg (4400 lb) 70 km/hr (43mph) 25 deg TL-3 2000kg (4400 lb) 100 km/hr (62mph) 25 deg TL-4 8000kg (17650 lb) 80 km/hr (50mph) 15 deg TL-5 & TL-6 36000kg (79400 lb) 80 km/hr (50mph) 15 deg

NCHRP 350 Terminal TestsTest Level 2 ~ 70 km/hr (43.5 mph)Test Level 3 ~ 100 km/hr (62 mph)

Time For a Change…..

NCHRP 350 Test Vehicles

NCHRP 350Test VehiclesFor Barriers

Test Vehicle Mass Location of Vehicle Center of Mass

Small Car1800 lb.(820 kg)

21.7 in.

Pickup Truck4400 lb. (2000 kg)

27.6 in.

Single-Unit Van Truck(TL-4)

17,650 lb.(8000 kg)

66.9 in.

Tractor Van Trailer(TL-5)

79,400 lb (36000 kg)

72.8 in.

Tractor Tank Trailer(TL-6)

79,400 lb (36000 kg)

80.7 in.

Test Vehicles Have Changed

• Process Started 1997 as NCHRP 22-14 (1)

• 22-14(2) Starting Date – August 2002

• Expected Completion – February 2005

• Identified Areas Where Revisions Could Have a Positive Impact on Safety.

• Identified Areas Where Revisions Could Have Improve Repeatability.

• Identified The Relevance of Each Change Relative to:• Expected Additional Costs• Expected Additional Benefits

• Resolve Inconsistencies.

• Improve International Harmonization.

NCHRP Project 22-14(2) Tasks

--- PHASE 1 – DEVELOP WORK PLAN ------ PHASE 1 – DEVELOP WORK PLAN ---

(1.) Conduct a brief review and reassessment of the 7 issues addressed in NCHRP Project 22-14(1). Topics that were addressed are:

Test vehicles and specifications Impact conditions Critical impact point Efficacy of flair space model Soil type/condition Test documentation Working width measurement


(2.) Review other relevant literature and ongoing research and conduct a survey to identify additional needs that were not addressed in the final report for Project 22-14(1).

(3.) Identify potential revisions to the procedures.


(4.) Develop a test plan for assessing the crash test performance of existing roadside safety devices when subjected to the new procedures proposed in Task 3. The test plan shall consider, but is not limited to, crash testing and finite element analysis.


(5.) Submit an interim report documenting the findings from Tasks 1 through 4. The report, as a minimum, shall include the following:

• Summary and prioritization of information needed to update Report 350 • Test plan developed in Task 4• Estimated costs and time• Future research needs.


(6.) Meet in Washington, D.C., with the NCHRP panel to review the Task 5 interim report, including the test plan, approximately 1 month after its submittal. Submit a revised interim report reflecting the panel's review comments.

STATUS REPORT

---- January 2004 : Above 6 Tasks Complete ----


--- PHASE 2 – IMPLEMENT WORK PLAN ------ PHASE 2 – IMPLEMENT WORK PLAN ---

(7.) Execute the approved test plan.

(8.) Submit for NCHRP review a preliminary draft final report documenting the entire research effort including an appendix, suitable for adoption and publication by AASHTO, containing the recommended procedures. (9.) Revise the preliminary report based on the project panel's recommendations.


(10.) Submit the revised report to an AASHTO task group for review. Summarize the comments from the task group review and make recommendations to the panel for revision of the report. Incorporate the approved recommendations into the procedures. (11.) Prepare and submit a final report documenting the entire research effort including an appendix containing the recommended procedures.

Specific Issues Being Addressed

Test Conditions


Test Conditions

Test Vehicles


Test Conditions

Test Vehicles

Critical Impact Point Selection


Test Conditions

Test Vehicles


Soil Type / Conditions


Test Conditions

Test Vehicles



Efficacy of Flail Space Model


Test Conditions

Test Vehicles




Occupant Compartment Deform / Intrusion


Test Conditions

Test Vehicles





Windshield Damage


Test Conditions

Test Vehicles





Windshield Damage

In-Service Performance Evaluation


Test Conditions: Impact Speed:

• Now use 100km/hr (62.2 mph) TL-3.

• Recommend maintaining same impact speed and not changing to 110km/hr (68.4 mph).

• Consider “optional” impact speed of 110km/hr (68.4 mph).


Test Conditions: Impact Angles:(Barriers)

• Keep 25-deg for pickup truck.

• Currently use 20-deg for small car. Evaluate 20 vs. 25-deg for small car.


Test Conditions: Impact Angles:(Terminals & CC)

• Currently use 20-deg for pickup. Evaluate 20 vs. 25-deg for pickup.


Test Conditions: Side Impacts:

• Side impact testing may be added as an optional test.


Test Vehicles: Small Car

• Now use 1800# (820 kg) Small Car.

• An 1800# Small Car is no longer produced.

• Recommend using 2420# (1100 kg) Small Car.


Test Vehicles: Light Truck

• Now 4400# Pickup. Will use ¾ ton 5000# Pickup (std cab / 2-wheel drive)

• A 4400# (¾ ton Pickup Truck) is no longer produced.

• Over 21% of light trucks and 10% of all vehicles sold in 2001 weigh more than 4400#.


Test Vehicles: Intermediate Car

• Normally not used in testing.

• For barriers, it is believed if passes with small car and pickup truck, it will pass with this vehicle.

• May not always be true for staged attenuation systems.


Test Vehicles: Heavy Truck

• Now use 80,000# (36,000 kg) Truck.

• Issues are density of ballast and method to secure the load.



• The impact point varies depending on the device.

• The intent is to identify a potential failure impact point to create vehicle instability (i.e. wheel snag) or product failure.



• For terminals, currently use small car at a point between end of device and LON. Evaluate new CIP where device separates from redirective to gating.



• Some devices perform better in weak soils (sign supports, W-Beam).

• Some devices perform better in strong soils (frangible sign supports).

• Soil types vary by test and by testing agency.



For every crash, there are 3 impacts:

1. The vehicle with the hazard.2. The body with the vehicle interior.3. The internal organs with bones,

chest and scull.



• Designed to estimate the speed at which an unbelted occupant would impact with the interior of a vehicle.

• Occupant Impact Velocity (OIV) and Ridedown Acceleration (RA) are measured.

• Unrestrained Passenger Decelerations: – Under 9 m/sec preferred– 12 m/sec max

• Occupant deceleration over a 10 millisecond period:– Should not exceed 15 G’s– 20 G’s is allowable




Occupant Compartment Deformation and/or Intrusion

• At what point does deformation into the passenger compartment become unacceptable?

• The location of the passenger compartment deformation is more critical in some areas.


Windshield Damage

• Windshield damage that currently defines test failure includes:

1. Any hole through the glass.2. Any part of windshield becomes

separate from the frame.3. An area of cracking sufficient to

obstruct the drivers view > 12” dia.

In-Service Evaluation


In-Service Evaluation

Differences between field performance and crash test results can arise due to:

• Impact conditions different than test conditions such as non-tracking and side impacts.

• Site conditions different than test conditions such as a slope, curb, ditch. (before/during/after impact)

• Sensitivity to installation details as soil conditions or barrier flare.

In-Service Evaluation Purpose:

Determine and document the manner in which the safety feature performs during a broad range of collision, environmental, operational and maintenance situations for typical site and traffic conditions.

NCHRP 350

In-Service Evaluation Objectives:

• Are design goals achieved?• Were installation problems incurred?• Acquire wide range of collision data.• Identify unforeseen problems or road modifications.• Examine influence of severe climate or environmental conditions.• Examine disruption of normal traffic patterns.• Obtain information on maintenance.

In-Service Evaluation Proposed Approach:

3-Tiered System:

• Level I – Computerized data base.• Level II – Supplemental field data collected.• Level III – More detailed research such as accident reconstruction.

In-Service Evaluation CharacteristicsExample:

• 2-year minimum trial period.• Sufficient length of barrier or number of devices to obtain data.• Installations frequently examined.• Evaluated on a before/after basis.• Accident reporting technique established.• Maintenance forces perform field evaluations.• In-service report to be prepared.

CASE ReportedNot

ReportedRepaired

Not

Repaired

1 X X

Types of Accidents:

CASE ReportedNot

ReportedRepaired

Not

Repaired

1 X X2 X X

Types of Accidents:

CASE ReportedNot

ReportedRepaired

Not

Repaired

1 X X2 X X3 X X

Types of Accidents:

CASE ReportedNot

ReportedRepaired

Not

Repaired

1 X X2 X X3 X X4 X X

Types of Accidents:


Full Scale Crash Test Program

• Total of 12 tests proposed.

• Two tests with 4-wheel drive vehicle.

• Results used to estimate expected cost associated with implementing proposed test vehicles and test conditions.


Full Scale Crash Test Program(Early Priorities ASAP all at 25-deg. The results will determine the direction of future decisions.)

Standard W-Beam (steel post with wood block) with new pickup truck. If above fails, Midwest Guardrail System with new pickup truck. Permanent concrete SS small car. Temporary concrete SS pickup.

MGSMidwest Guardrail System

W-Beam Barrier

What does the barrier need to do?• Contain and redirect the barrier

• Perform to anticipated deflections

Sometimes You Just Get Lucky…

AASHTO Roadside

Design Guide (updated 2002)

Where does the barrier need to be

placed?

Test Levels for Barriers

NCHRP 350Test Level For Barriers

Largest Vehicle Mass

Large VehicleImpact Speed

Impact Anglefor Barriers

TL-1 4400 lb.(2000 kg)

31 mph (50 km/h)

25 deg.

TL-2 4400 lb (2000 kg)

43 mph (70 km/h)

25 deg.

TL-3 4400 lb.(2000 kg)

62 mph(100 km/h)

25 deg.

TL-4 17,650 lb(8000 kg)

50 mph (80 km/h)

15 deg

TL-5 & TL-6 79,400 lb(36000 kg)

50 mph (80 km/h)

15 deg.

MGS Midwest Guardrail System Introduction

• MGS research began in 2000 (non-proprietary)- 31” top rail height- reduced post embedment- 12” blockout depth- midspan rail splice

• Use of strong-post W-beam guardrails.

• Early W-beam systems designed for full-size sedans / small cars.

• Differing levels of safety performance for 27” high W-beam rails.

• Metrication led to 27-3/4” guardrail height – most systems had acceptable performance.

• Potential exists to improve barrier’s performance.

MGSMidwest Guardrail System

Background and Design Considerations

• Weaknesses of current W-beam design

Light truck rollover rates and high CG vehicles

Installation height sensitivity

Rail ruptures

Vehicle Override

1,963 kg / 95.3 km/hr / 24.0 deg686 mm (27 in.) HeightVehicle Rollover (Failure)Dynamic Deflection = 28.1 in.

1,979 kg / 103.2 km/hr / 24.5 deg706 mm (27.8 in.) HeightRail Rupture & Vehicle Penetration (Failure)Dynamic Deflection = NA

2,034 kg / 99.8 km/hr / 27.7 deg706 mm (27.8 in.) HeightVehicle Override & Redirection (Failure)Dynamic Deflection = 42.7 in.

Rail Element

Rail Height

Block Size

Rail Splice

Current Design

12” W-Beam

27”+

8”

At the Post

MGS Design

12” W-Beam

31”

12”

Mid-span of Posts

Current and MGS W-Beam Comparison

Blockout Change From 8” to 12”

Rail Post

Blockout

Rail height will be changed to 31”

Rail Splices Mid-span Between Posts

Rail Splices

12’-6”

Rail Section

MGS Midwest Guardrail System

(6’-3”)

(40.12”)

(31.89”)

(12”)

(31”)

(24.89”)

887 kg / 102.9 km/hr / 20.0 deg813 mm (32 in.) HeightVehicle Redirected (Pass)Dynamic Deflection = 17.4 in.

1,986 kg / 98.1 km/hr / 25.6 deg787 mm (31 in.) HeightVehicle Redirected (Pass)Dynamic Deflection = 43.1 in.

Applications

• Along roadside with 6’-3” post spacing

• Positioning near hazards with limited space1/4 (18 ¾”) or 1/2 (37 ½”) post spacing

• Placement over or near curbs6” curb placed 6” in front of barrier

MGS Midwest Guardrail System

The Terminal is Almost Completed

The “TF-13”

Hardware Guide

Published 1995

What About Inventories?Will They Change?

Some WillSome Will Not

Midwest States Pooled Fund Program

NCHRP 350 UPDATED. NCHRP 350 Historical Review Document Source Year Issued Number of Pages Test...

Documents

Transcript of NCHRP 350 UPDATED. NCHRP 350 Historical Review Document Source Year Issued Number of Pages Test...