Eugene C Buth.

NCHRP report 350 testing of Montana portable concrete safety shape barriers (Volume 2003) online

. (page 1 of 4)
Online LibraryEugene C ButhNCHRP report 350 testing of Montana portable concrete safety shape barriers (Volume 2003) → online text (page 1 of 4)
Font size
QR-code for this ebook


m Texas
Transportation
Institute



NCHRP REPORT 350 TESTING OF
MONTANA PORTABLE CONCRETE
SAFETY SHAPE BARRIERS



by



C. Eugene Buth, P.E.
Senior Research Engineer

Nauman Sheikh

Assistant Transportation Researcher

Roger P. Bligh, P.E.
Associate Research Engineer

Wanda L. Menges
Associate Research Specialist

and

Rebecca R. Haug

Assistant Research Specialist

Contract No.

Project No. RF 474550-1

Sponsored by

Montana Department of Transportation and

Federal Highway Administration

U.S. Department of Transportation

April 2003



TEXAS TRANSPORTATION INSTITUTE
THE TEXAS A&M UNIVERSITY SYSTEM
COLLEGE STATION, TEXAS 77843



TECHNICAL REPORT DOCUMENTATION PAGE



1. Report No.

FHWA/MT-03-002/8162



2. Government Accession No.



3. Recipient's Catalog No.



4. Title and Subtitle

NCHRP Report 350 Testing of the Montana Portable
Concrete Safety Shaped Barriers



5. Report Date

April 2003



6. Performing Organization Code



7. Author(s)

C. Eugene Buth, Nauman Sheikh, Roger P. Bligh,
Wanda L. Menges and Rebecca R. Haug



8. Perform Ing Organization Report No.



9. Performing Organization Name and Address

Safety and Structural Systems Division
Texas Transportation Institute
The Texas A&M University System
College Station, Tx 77843-3135



10.Worl<UnitNo.



1 1 . Contract or G rant No.

8162



12. Sponsoring Agency Name and Address

Research Section

Montana Department of Transportation

2701 Prospect Avenue

PO Box 201001

Helena MT 59620-1001



13. Type of Report and Period Covered

Final Report:

April 2002 - February 2003



14. Sponsoring Agency Code

5401



15. Supplementary Notes

Research performed in cooperation with the Montana Department of Transportation and the US Department of
Transportation, Federal Highway Administration.



16. Abstract



The existing IVIontana DOT concrete median barrier sections are 3.048 m (10 ft) long New
Jersey shaped barriers with a pin-and-loop connection. Two pairs of 25 mm (1 inch) diameter wire
rope loops are connected using a 660 mm (26 inch) long, 25 mm (1 inch) diameter pin that is not
restrained at the bottom. Since the system has a low probability of complying with the NCHRP Report
350 guidelines, and the expected dynamic barrier deflection under design impact conditions are
greater than desired by Montana DOT, two alternate barrier connection concepts were proposed and
evaluated using computer simulations. These included a modified pin-and-loop connection and a
newly conceived lapped splice connection.

After these two designs appeared to perform acceptably during simulation, the proposed
designs were constructed for full-scale crash testing to determine whether the designs would actually
meet NCHRP Report 350 crash test criteria. This report presents the details of the simulation
analysis, the details of the proposed barrier designs, the details of the full-scale crash tests, and the
NCHRP Report 350 evaluation of each of the tests. Both the modified pin-and-loop barrier and the
lapped splice connection barrier performed acceptably for NCHRP Report 350 test 3-1 1 .



17. Key Words

Portable Concrete Barriers, PCB, Concrete Median
Barriers, CMB, Crash Testing, Roadside Safety,
Computer Simulation



18. Distribution Statem ent

Unrestricted. This document is available through
the National Technical Information Service,
Springfield, VA 21161.



19. Security Classif. (of this report)

Unclassified



20. Security Classif. (of this pa

Unclassified



21. No. of Pages

93



22. Price



11



DISCLAIMER STATEMENT

This document is disseminated under the sponsorship of the IVIontana Department of
Transportation and the United States Department of Transportation in the interest of information
exchange. The State of IVIontana, the United States Government, Texas Transportation
Institute, and The Texas A&M University System assume no liability of its contents or use
thereof.

The contents of this report reflect the views of the authors, who are responsible for the facts and
accuracy of the data presented herein. The contents do not necessarily reflect the official
policies of the Montana Department of Transportation, the United States Department of
Transportation, Texas Transportation Institute, or The Texas A&M University System.

The State of Montana, the United States Government, Texas Transportation Institute, and The
Texas A&M University System do not endorse products of manufacturers. Trademarks or
manufacturers' names appear herein only because they are considered essential to the object
of this document

This report does not constitute a standard, specification, or regulation.



ALTERNATIVE FORMAT STATEMENT

The Montana Department of Transportation attempts to provide reasonable accommodations for
any known disability that may interfere with a person participating in any service, program, or
activity of the Department. Alternative accessible formats of this document will be provided upon
request. For further information, call (406) 444-7693 or TTY (406) 444-7696.



Ill



TABLE OF CONTENTS



Section Page

1.0 INTRODUCTION 1

1.1 PROBLEM 1

1.2 BACKGROUND 1

1.3 OBJECTIVES/SCOPE OF RESEARCH 2

2.0 COMPUTER SIMULATION 3

2.1 INTRODUCTION 3

2.2 FINITE ELEMENT MODELING 3

2.2.1 Pin-and-Loop Model 5

2.2.2 Pin-and-Loop Simulation Results 7

2.2.3 Lapped Plate Model 11

2.2.4 Lapped Plate Simulation Results 12

2.3 SUMMARY 12

3.0 CRASH TEST PARAMETERS 17

3.1 TEST FACILITY 17

3.2 TEST ARTICLES - DESIGN AND CONSTRUCTION 17

3.2.1 Modified Pin-and-Loop Barrier Used in Test 474550-1 1 7

3.2.2 Lapped Splice Connection Barrier Used in Test 474550-2 18

3.3 TEST CONDITIONS 18

3.4 EVALUATION CRITERIA 28

4.0 MODIFIED PIN-AND-LOOP BARRIER (TEST NO. 474550-1) 29

4.1 TEST VEHICLE 29

4.2 SOIL AND WEATHER CONDITIONS 29

4.3 IMPACT DESCRIPTION 29

4.4 DAMAGE TO TEST ARTICLE 32

4.5 VEHICLE DAMAGE 32

4.6 OCCUPANT RISK FACTORS 32

4.7 ASSESSMENT OF TEST RESULTS 37

5.0 LAPPED SPLICE CONNECTION BARRIER (TEST NO. 474550-2) 41

5.1 TEST VEHICLE 41

5.2 SOIL AND WEATHER CONDITIONS 41

5.3 IMPACT DESCRIPTION 41

5.4 DAMAGE TO TEST ARTICLE 44

5.5 VEHICLE DAMAGE 44

5.6 OCCUPANT RISK FACTORS 44

5.7 ASSESSMENT OF TEST RESULTS 49



IV



TABLE OF CONTENTS (continued)

Section Page

6.0 SUMMARY AND CONCLUSIONS 53

6.1 SUMMARY OF TEST RESULTS 53

6.1 .1 Modified Pin-and-Loop Barrier (Test No. 474550-1 ) 53

6.1 .2 Lapped Splice Connection Barrier (Test No. 474550-2) 53

6.2 CONCLUSIONS 53

7.0 REFERENCES 56

APPENDIX A. CRASH TEST PROCEDURES AND DATA ANALYSIS 57

A.I ELECTRONIC INSTRUMENTATION AND DATA PROCESSING 57

A.2 ANTHROPOMORPHIC DUMMY INSTRUMENTATION 58

A.3 PHOTOGRAPHIC INSTRUMENTATION AND DATA PROCESSING 58

A.4 TEST VEHICLE PROPULSION AND GUIDANCE 58

APPENDIX B. TEST VEHICLE PROPERTIES AND INFORMATION 60

APPENDIX C. SEOUENTIAL PHOTOGRAPHS 66

APPENDIX D. VEHICLE ANGULAR DISPLACEMENTS 72

APPENDIX E. VEHICLE ACCELERATIONS 74



LIST OF FIGURES



Figure Page

2.2.1 FE model of the CMB segment with solid elements 4

2.2.2 CMB segment covering with shell elements and a refined mesh 5

2.2.3 Steel loop model using shell elements 6

2.2.4 Steel pin, loops and washer model 6

2.2.5 Simulation setup for the modified pin-and-loop model 7

2.2.6 Overhead view of simulation of modified pin-and-loop barrier connection 8

2.2.7 Rear view of simulation of modified pin-and-loop barrier connection 9

2.2.8 Rear view of barrier joint with maximum deflection 10

2.2.9 Simulation setup for the lapped plate model 12

2.2.1 Overhead view of simulation of lapped plate barrier connection 1 3

2.2.11 Rear view of simulation of lapped plate barrier connection 14

2.2.12 Field side view of barrier joint with maximum deflection 15

3.2.1 Details of modified pin-and-loop safety shape barriers

used in test 474550-1 19

3.2.2 Modified pin-and-loop barriers prior to test 474550-1 22

3.2.3 Details of lapped splice connection safety shape barriers

used in test 474550-2 24

3.2.4 Lapped splice connection barriers prior to test 474550-2 27

4.2.1 Wind direction diagram 29

4.1.1 Vehicle/installation geometries for test 474550-1 30

4.1.2 Vehicle before test 474550-1 31

4.4.1 Vehicle trajectory after test 474550-1 33

4.4.2 Modified pin-and-loop barrier installation after test 474550-1 34

4.5.1 Vehicle after test 474550-1 35

4.5.2 Interior of vehicle for test 474550-1 36

4.6.1 Summary of results for modified pin-and-loop barrier (test 474550-1) 38

5.2.1 Wind direction diagram 41

5.1 .1 Vehicle/installation geometries for test 474550-2 42

5.1.2 Vehicle before test 474550-2 43

5.4.1 Vehicle trajectory after test 474550-2 45

5.4.2 Lapped splice barrier installation after test 474550-2 46

5.5.1 Vehicle after test 474550-2 47

5.5.2 Interior of vehicle for test 474550-2 48

5.6.1 Summary of results for lapped splice connection barrier (test 474550-2) 50

B.1.1 Vehicle properties for test 474550-1 60

B.2.1 Vehicle properties for test 474550-2 63

C.I .1 Sequential photographs for test 474550-1

(overhead and frontal views) 66

C.I .2 Sequential photographs for test 474550-1

(rear view) 68



VI



LIST OF FIGURES (continued)



Figure Page

C.2.1 Sequential photographs for test 474550-2

(overhead and frontal views) 69

C.2.2 Sequential photographs for test 474550-2

(rear view) 71

D.1 .1 Vehicle angular displacements for test 474550-1 72

D.2.1 Vehicle angular displacements for test 474550-2 73

E.I .1 Vehicle longitudinal accelerometer trace for test 474550-1

(accelerometer located at center of gravity) 74

E.I .2 Vehicle lateral accelerometer trace for test 474550-1

(accelerometer located at center of gravity) 75

E.I .3 Vehicle vertical accelerometer trace for test 474550-1

(accelerometer located at center of gravity) 76

E.I .4 Vehicle longitudinal accelerometer trace for test 474550-1

(accelerometer located over rear axle) 77

E.I .5 Vehicle lateral accelerometer trace for test 474550-1

(accelerometer located over rear axle) 78

E.I .6 Vehicle vertical accelerometer trace for test 474550-1

(accelerometer located over rear axle) 79

E.2.1 Vehicle longitudinal accelerometer trace for test 474550-2

(accelerometer located at center of gravity) 80

E.2.2 Vehicle lateral accelerometer trace for test 474550-2

(accelerometer located at center of gravity) 81

E.2.3 Vehicle vertical accelerometer trace for test 474550-2

(accelerometer located at center of gravity) 82

E.2.4 Vehicle longitudinal accelerometer trace for test 474550-2

(accelerometer located over rear axle) 83

E.2.5 Vehicle lateral accelerometer trace for test 474550-2

(accelerometer located over rear axle) 84

E.2.6 Vehicle vertical accelerometer trace for test 474550-2

(accelerometer located over rear axle) 85



Vll



LIST OF TABLES



Table No. Page

6.2.1 Performance evaluation summary for MDT

modified pin-and-loop barrier (test no. 474550-1) 54

6.2.2 Performance evaluation summary for MDT

lapped splice connection barrier (test no. 474550-2) 55

B.I .1 Exterior crush measurements for test 474550-1 61

B.I .2 Occupant compartment measurements for test 474550-1 62

B.2.1 Exterior crush measurements for test 474550-2 64

B.2.2 Occupant compartment measurements for test 474550-2 65



Vlll



1.0 INTRODUCTION



1.1 PROBLEM

Previous testing experience and finite element modeling has shown marginal
performance on a number of portable concrete safety shapes with unrestrained pin and
loop connections. Problems have been encountered with joint failures and vehicle
instabilities. Joint failures have included pin failures, loop failures, under-reinforcement
and/or inadequate development lengths in the concrete adjacent to the joint. Vehicle
instabilities are usually introduced through rotation of the barrier and subsequent
climbing by the vehicle. Increased rigidity of the joint and increased size of the barrier
segments can improve vehicle stability in the crash sequence. The crash performance
of the barriers is typically degraded as the segment lengths and masses are reduced.



1.2 BACKGROUND

The Federal Highway Administration (FHWA) formally adopted the performance
evaluation guidelines for highway safety features set forth in National Cooperative
Highway Research Program {NCHRP) Report 350 as a "Guide or Reference document
in Federal Register, Volume 58, Number 135, dated July 16, 1993, which added
paragraph (a) (13) to 23 CFR, Part 625.5. (Ross, 1993) FHWA further mandated that,
starting in October 1998, only Category III Work Zone Devices, such as portable
concrete barriers that have successfully met the performance evaluation guidelines set
forth in NCHRP Report 350 may be used on the National Highway System (NHS) for
new installations. On August 28, 1998, deadlines were revised for the use of NCHRP
Report 350 dey\ces. (FHWA, 1998) The deadline for Category III devices was extended
to October 2002 with the following statement: "Barriers with joints that fail to transfer
tension and moment from one segment to another must be updated by October 1 , 2000.
New units purchased after October 1, 2002 shall comply with 350. (Agencies can
phase out existing devices after they complete their normal service life, except that
barriers with joints that fail to transfer tension and moment from one segment to another
will not be acceptable after October 1, 2000, unless demonstrated to be crashworthy.)"
FHWA went on to state, "A barrier will be considered crashworthy if (a) it has been
crash tested and met the acceptance requirements proposed in either NCHRP Reports
230 or 350 or (b) it is a barrier with one of the five joints listed as "Tested and
Operational Connections" starting on page 9-3 of the 1996 American Association of
State Highway and Transportation Officials (AASHTO) Roadside Design Guide or (c) if
an Engineering Study of in-service performance demonstrates the barrier will provide
the performance requirements of the site where it is to be used." (Michie, 1981;
AASHTO, 1996)



1 .3 OBJECTIVES/SCOPE OF RESEARCH

The existing IVIontana Department of Transportation (DOT) concrete median
barrier sections are 3.048 m (10 ft) long New Jersey shaped barriers with a pin-and-loop
connection. Two pairs of 25 mm (1 inch) diameter wire rope loops are connected using
a 660 mm (26 inch) long, 25 mm (1 inch) diameter pin that is not restrained at the
bottom. Since the system has a low probability of complying with the NCHRP Report
350 guidelines, and the expected dynamic barrier deflection under design impact
conditions are greater than desired by Montana DOT, two alternate barrier connection
concepts were proposed and evaluated using computer simulations. These included a
modified pin-and-loop connection and a newly conceived lapped splice connection.

After these two designs appeared to perform acceptably during simulation, the
proposed designs were constructed for full-scale crash testing to determine whether the
designs would actually meet NCHRP Report 350 crash test criteria. This report
presents the details of the simulation analysis, the details of the proposed barrier
designs, the details of the full-scale crash tests, and the NCHRP Report 350 evaluation
of each of the tests.



2.0 COMPUTER SIMULATION

2.1 INTRODUCTION

Numerous research studies have successfully utilized simulation codes to
simulate vehicle handling, vehicle impacts with roadside objects, and encroachments
over roadside geometric features such as slopes, ditches, and driveways. In these
studies, researchers have utilized varying levels of vehicle model sophistication ranging
from simple lumped masses, springs and dampers, to detailed finite element
representations using many thousands of elements. All simulation codes have their
limitations and they all incorporate a different level of assumptions. Having said that, it
was considered crucial that the simulation code(s) selected for use in this study be
capable of accurately modeling relevant characteristics of the vehicle, the concrete
median barrier, and the interactions between them. The decision to choose the explicit
finite element code (LS-DYNA) for this study was based on several reasons including:

1 . The availability of vehicle models that correspond to NCHRP Report 350 design
test vehicles. The 2000P pickup truck model has been used for roadside safety
applications for the last five years and its fidelity and limitations are reasonably
understood.

2. The ability to model the roadside device with a high degree of fidelity. The
geometry of the device (which affects the mechanics of the vehicle-barrier
interaction), its mass and inertial distribution (which affects the kinetic behavior of
the barrier) and the stress-strain relationship of the materials (which affects the
deformation of the device) can all be reasonably represented.

3. The ability to model contact-impact problems. LS-DYNA has a very extensive set
of contact definitions that fit several impact-contact scenarios. These contact
definitions that have the option of including frictional sliding are well suited to
model the dynamic interaction between the vehicle and the roadside barrier.

The existing Montana DOT concrete median barrier sections are 3.048 m (10 ft)
long New Jersey shaped barriers with a pin-and-loop connection. Two pairs of 25 mm
(1 inch) diameter wire rope loops are connected using a 660 mm (25 inch) long, 25 mm
(1 inch) diameter pin that is not restrained at the bottom. Since the system has a low
probability of complying with the NCHRP Report 350 guidelines, and the expected
dynamic barrier deflection under design impact conditions are greater than desired by
Montana DOT, two alternate barrier connection concepts were proposed and evaluated
using computer simulations. These included a modified pin-and-loop connection and a
newly conceived lapped plate connection. The details of the modeling and simulation of
these connections follows.



2.2 FINITE ELEMENT MODELING

In order to evaluate the alternate design concepts, full-scale finite element
computer models were developed for both the modified pin-and-loop connection and the



lapped plate connection. Some of the essential components of these models were the
concrete barriers, pin and loops for the pin-and-loop connection, and slotted plates and
bolts for the lapped plate connection.

The concrete segments were modeled using the same New Jersey profile and
overall dimensions (height, width, and length) as the original Montana DOT concrete
median barriers. In order to help limit dynamic deflection, it was desirable to minimize
the gap between the adjacent barrier segments. To accomplish this and still provide
sufficient clearance to accommodate the connection hardware, recesses or channels
were cast into the ends of the barrier. The concrete median barrier (CMB) model was
assigned the mass density of concrete, which makes the total mass of the CMB model
equivalent to that of the actual CMB unit.

The finite element (FE) model for the CMB was meshed with solid elements that
belong to two parts as shown in Figure 2.2.1. The lowest layer of solid elements which
are in contact with the ground surface were assigned elastic material properties and the
rest of the elements comprising the barrier segment were assigned rigid material
properties. Rigid material representation helps speed up numerical calculations
significantly.




Figure 2.2.1. FE model of the CMB segment with solid elements.

A limitation to this type of rigid CMB model is that concrete failure is not captured.
Modeling concrete failure requires a much higher mesh density and a reliable, validated
concrete material model that considers fracture. Although the Federal Highway
Administration is currently funding the development of such a material model, the
research effort is still in the early stages and the results were not available for use in this
project. Without the ability to incorporate concrete failure into the analysis, it should be
noted that the results of the simulation will represent a lower bound estimate of the
overall CMB system deflection. If significant concrete fracture and spalling occurs on the
ends of one or more barrier segments during an actual impact, additional joint rotation
can occur and deflections can increase.



The lower elastic layer of solid elements was incorporated into the barrier model
to provide a reliable account of friction in the contact between the CMB segments and
the ground. A friction coefficient of 0.4 was used between the CMB and the ground.

Solids elements tend to behave less reliably compared to shell elements for
contact purposes. During earlier simulations with a vehicle impact, small but significant
penetrations were observed between the solid elements of adjacent barriers. Similarly,
penetrations were observed between the vehicle shell elements and the CMB solid
elements. In order to have a more robust contact, the CMB segment models were
covered with a layer of finely meshed rigid shell elements as shown in Figure 2.2.2. All
contacts involving the barriers were defined with this shell cover.




Figure 2.2.2. CMB segment covering with shell elements and a refined mesh.



Deformable loops or plates were attached to the end of the CMB segments by
making the end nodes of the loops or plates a part of the CMB segment rigid body
definition. This provides an efficient means of tying them to the CMB segments.
However, it is noted that the stresses at the edges of the loops or plates will be
overestimated in the simulation since the actual connection will generally have some
relative movement due to minor cracking and/or spalling of the surrounding concrete
that helps redistribute stresses.



2.2.1 Pin-and-Loop Model

The modified pin-and-loop connection is made up of an unrestrained 32-mm
(1.25 inch) diameter steel pin inserted into three sets of 19-mm (0.75 inch) diameter
steel bar loops. The additional intermediate set of loops changes the deformation mode
of the pin and helps reduce deflections of the joint. It also adds some redundancy to the
connection so that integrity of the connection is not lost if the pin pulls out of the lowest
set of loops.



The pin and loops were assigned non-linear elastic-plastic properties of steel.
Ideally the pin and loops would be meshed using solid elements. However due to the
circular geometry and small diameter of the loop cross section, using solid elements
becomes less feasible. In order to accurately model the pins and loops using solid
elements, a very fine mesh would be required. This decreases the time-step for numeric
calculations significantly, hence increasing the CPU time required for each simulation.

Shell elements were used as an alternative modeling option for the solid pin and
loop parts. The diameter and thickness of shell elements were selected such that the
resulting models of the steel loops and pins had 96% of the area and 99% of the second
moment of area (i.e., moment of inertia) of the solid section. A steel loop model
comprised of shell elements is depicted in Figure 2.2.3. Similarly, the pin and washer
were modeled using shell elements as shown in Figure 2.2.4.




Figure 2.2.3. Steel loop model using shell elements.



Figure 2.2.4. Steel pin, loops and washer model.



The full-scale simulation replicated Test Designation 3-1 1 of NCHRP Report 350,
which involves a 2000-kg (4405 lb) pickup truck impacting the barrier at a speed of
100 km/h (62 mi/h) and an angle of 25 degrees. The initial simulation setup prior to
impact is shown in Figure 2.2.5. A total of 14 CMB segments were used in the
simulation with the truck impacting the 7*^ segment 1200 mm (48 inches) upstream from
the joint.




Figure 2.2.5. Simulation setup for the modified pin-and-loop model.



AUTOMATIC_SINGLE_SURFACE contact type with EDGE = 1 and SOFT = 2
was used to define contact between the pins, loops and washer.
NODES_TO_SURFACE contact was defined between the shell covers of adjacent
barrier segments. Contacts were individually defined for each joint in the CMB system.



2.2.2 Pin-and-Loop Simulation Results

The vehicle was successfully contained and redirected by the modified barrier
system. The results from the simulation showed an overall dynamic deflection of 1.2 m
(4 ft). As previously discussed, this was considered to be a lower bound estimate. The
amount that the actual dynamic barrier deflection might exceed this value is a function
of the degree of concrete damage encountered in the test.



Figure 2.2.6 shows the overhead view of the full-scale simulation of the modified


1 3 4

Online LibraryEugene C ButhNCHRP report 350 testing of Montana portable concrete safety shape barriers (Volume 2003) → online text (page 1 of 4)