design and testing of a dual support breakaway...
TRANSCRIPT
Design and Testing of a Dual Support Breakaway Sign
Prepared by: Midwest Roadside Safety Facility (MwRSF) Center for Infrastructure Research Civil Engineering Department University of Nebraska 190 1 Y Street, Building C Lincoln, Nebraska 68588-060 I (402) 472-6864
September 6, 1995
TECHNICAL REPORT STANDARD TITLE PAGE
1. Performing Org3nilation Report No 2. R&pOrt Date 3. Type of RepOl1 and Period Covered
TRP-03-48-95 September 6, 1995 Fioal Report: October 1994 to September 1995
4. Title arld Subt itl e
Design and Testing of a Dual Support Breakaway Sign
5. Author( s)
Paulsen , G. W.o Pfeifer, B.O., Hol loway, J.e., and R.eid, J.D.
6. Performing OrganizatiOll Name and Address
Midwest Roadside Safety Facility (MwRSF) Civil Engineering Department Universi ty of Nebraska - Lincoln 1901 Y St., Bldg C Lincoln , Nebraska 68588-0601 (402) 472-6864
7. Sponsoring Ag.mcy Name and Address
Missouri Highway and Transportat ion Department Design Division P.O. Box 270 Jefferson City, MO 65102
8. contract or Grand No
SPR-3(0 17), FY -94 Midwest States Regiona l Poo led Fund Program
9. Abstract
The Missouri Hi ghway Transportation Department (MHTD) has been using a dual leg breakaway roadside sign supports with a perforated tension fuse plate. A very important feature of thi s system is th e abi lity
Or its support to release upon impact and sw ing lip and out of the way when impacted by an errant vehicle. Another critical feature of the sign system is its ability to withstand wind loads without causing structural damage to the system. A modified dual support breakawaysigll system is proposed which im proves both of these criteria.
Recentl y. MHTD added a multi-directional slip base to the breakaway sign design details. MHTD wished to evaluate the perfomlance of the multi-directional slip base and the dual support breakaway system when impacted by a vehicle at some angle other than perpendicularto the face of the sign, to correspond to actual roadside data.
Two full-sca le vehicle crash tests were conducted on the dual support breakaway sign and multi-directiona l sli p base . The safety perrormance orthe system was detennined to be acceptable according to criteria
set rorth by Nat ional Cooperative Highway Research Program (NC HRP) Report No. 350, Recommended Procedures/or {he Safety Pelfol'monce Evaluatioll of Highway Features.
Changing the material orthe fuse plate from ASTM A36 steel to A572 Grade 50 stee l created a stronger connection that significantly improved the wind load capaci ty of the s ign system without hindering its safety
performance.
10, KeywOfds 11. Qistribution Statement
Hi ghway Signs. Breakaway Supports, Slip Base. No restrictions. Th is document is availa ble to Wind Loads, Hi ghway Safety, Crash Tests. the public from the sponsoring agency.
12. Se<:.unty ClasSIficat ion (of thi s repo<t) 13. Se<:u>ity Classmcation (olth is page) 14. No. 01 Pages
Unclassified Unclassified 58
DISCLAIMER
The cOlllents of thi s report reflect the views of the authors who are respons ible for the facts and
accuracy oflile d<1la presen ted herein. The contents do not necessarily refl ecl lhe officia l views or po li cies
of the M isso llri Highway TranSpoltatioll Depm1merlt or the Federal Highway Adm ini stratioll. Th is report
does not constitute a standard , specification, or regulation.
ACKNOWLEDGEMENTS
The authors wish to acknowledge several sources lhat made this project poss ible : ( I) the Midwest
States Regional Pooled Fund Program funded by the Iowa Department of Transportation_ Kansas
Department of Transportati on, Missouri Highway and Transportat ion Department, Nebraska Department
of Roads, and Minnesota Department of Transportation for sponsoring thi s proj ect; (2) Maher Tad ros -
Director o f the Center fo r In frastructure Research Center and Samm y Eli as - Associate Dean for
Engineering Research Centers of the Uni vers ity o f Nebraska-Linco ln for matching support.
A spec ial thanks is a lso g iven to the fo llowing ind ividuals who made a contribution to the
completion of thi s research project.
Midwest Roadside Safety F~,cility (MwRSFl: Dean Sicking. Ph.D., Director Ron Falle r, Research Associate Engineer Kenneth Krenk , Field Operati ons Manager Graduate and Undergraduate Ass istants
Missouri Deuartment of Transportation PaL McDaniel, Des ign Special Ass ignments Engineer Vi nce Imhoff, Specifi cations and Standards Engineer
Iowa Department of Transportation David Little, Des ign Methods Eng ineer
Kansas Department of Transportation Ron Sei tz, Road Design Squad Leader
Nebraska Deuartment of Roads <NDORl Leona Ko lbet, Research Coordinator
Minnesota Dep:u1ment of Transportation Khani Sahebjam, State A id Bridge Engineer
Dunlan Photography James Dunlap. Pres ident and Owner
11
TABLE OF CONTENTS
DISC LA IM ER .
AC KNOWLEDGEMENTS
TAB LE OF CONTENTS
LIST OF FIGUR ES
LI ST OF TA BLES
INTRODUCTION 1.1 Problem Statement. . ... . .... • ....•.... . .. •. ... 1.2 Objective . ... .. . . . . . . . . . . . . . .... . ... .. . . . . . 1.3 Scope . . . . .. ... . . . .. .. . .... .. . . ... . . .. .. . . . . . . .. . . .. .
2 BACKGROUND ..
3 ANALYS IS AN D DESIGN 3.1 W ind Load Anal ys is . . . . . . . . ... ... . . .. . .. . . .. • ....
3. 1.1 Calcul at ion o f W ind Load . .. . . . . . .. . . . .. . . .. . . .. . 3. J.2 Wind Load Charts . . . . . . . . . . . . . . . . . . . ... .. . 3 .1 .3 Missouri Post Des ign Chm1s .... 3. 1.4 Comparison of Post Design Charts
3.2 Fuse Plate Materia ls .. 3.3 Component Testing of Fuse Plate
3.3 .1 Test Setup ..... . 3.3 .2 Data Acqui sition System 3.3.3 Res ults and DisclI ss ion
4 FULL SCALE TEST CON DITIONS
Page
II
'" . . v
v,
3
6 6 6 8 9
10 II 12 12 14 14
16 4. 1 Test Fac ili ty .. . . . . . . . . . . . • . • . . • . . . . . . . . . . . . . . . . . . • . . 16
4. 1. 1 Test S ite . ............... . . • . . .. . . . .. . . . .. . . . • . . . ... . . 16 4.1.2 Vehicl e Tow System 4 . 1.3 Vehic le G uidance System . .
4 .2 Missou ri Dual Support Breakaway S ign Des ign Detai ls .. . . . . . • . 4 .3 Test Vehicle .... . . . . .. . . . . .. .
16 16 17 17
4.4 Data Acq ui s ition System 4.4 .1 Acce lerometers
.... . . . . . .. . . . . . . . . .. ... 21
4.4.2 High Speed Photograph y 4.4 .3 Press ure Tape Switches
5 PERFORMANCE EVA LUATION CRlTERIA
6 FULL SCALE TEST RESULTS 6 . 1 Test M03- 1 (35 .6 kph, 25 deg, o ffset 400 mm passenger s ide)
"'
21 21 21
22
24 24
6.2 Test M03-2 (92.0 kpll , 27.3 deg, offset 475 mm passenger side)
7 CONCLUS IONS . .
8 RECOMMENDA nONS
9 REFERENCES ..... .
10 APPENDICIES APPENDIX A. APP EN DIX B. APP ENDIX C.
WIN D LOAD CHARTS COMPONENT TEST RESULTS ACCELEROMETER PLOTS
IV
29
33
.... . . 34
35
36 37 40 45
I. 2. 3. 4. 5. 6. 7. 8. 9. 10. I I. 12. 13. 14. 15. 16. 17. A-I. A-2. B-1. B-2 . B-3 .
B-4. C-1. C-2. C-3 . C-4 . C-5. C-6. C-7. C-8.
LIST OF FIGURES
Evolution of the f use Plate S ign System . .. . . . . .. .. . .. .... . . . Wind Load Chart ... . .. .. . Misso uri Post Des ign Charts. . ..... . Wind Chart Com parison, 2.44 m. Crane and Pulley System Test Configurati on M03-1.2 Test Insta ll at ion Test Vehicle Dimensions. Impact Location Summary of Test M03-1. Test Ve hi cle Damage, MOJ-J S ign insta llation and Fuse Plate Damage: M03-1. Test Veh icle Damage, M03-2 Summary of Test M03-2. Sign Insta llation Damage: M03-2. Balanced Post Hinge. Wind Load Charts, Elevation: 2.44 III ...
Wind Load Charts, Elevation: 6. 10 m ......... . . Componen t Test Results for Material # 1: A J6 Component Test Results for Mate ri al #2: A572 . Component Test Resul ts for Material #3: AS 16.86 Grade 70 Component Test Results for Material #4: A5 14-87 Grade B Longitu di na l Dece lerat ion - Test M03- I Longitu di nal Occupan t Impact Ve locity - T est M03 -1 Latera l Decele rat ion - Test M03-1 Veltical Dece leration - Test M03- I .. Lo ngitud inal Deceleration - Test M03-2 Longitud inal Occupant Impact Ve locity - T est M03-2 Late ral Deceleration - Test M03-2 . . . . . .. . .. . . . . • ..... Vert ical Dece leration - Test M03-2 ..
v
Page
4 7 9
10 II 13 13 18 20 25 27 28 28 30 3 1 32 34 36 37 39 40 41 42 44 45 46 47 48 49 50 5 1
1. 2. 3. 4. 5. 6. 7.
LIST OF TABLES
Drag Coeffic ient Elevat ion Coefficient Post/ Fuse Plate Configurations . . ... . . . . . . •.. . . . . . •. . . . Material Properti es. . . . ... . . . Summary of Test Resul ts ...... . . NCI-IRP Report 350 Safety Evaluation Guidelines. AAS HTO 1994 Safety Evaluation Guidelines
VI
Page
8 8 8
I I 15 23 23
1 1NTRODUCT10N
1.1 Problem Statement
Dual support breakaway s igns have been ll sed across the country for over 25 years now, and have
been cred ited with saving many li ves . A VCIY important feature of this system is the ability of its support
to swing up and out of the way when impacted by an errant vehi cle. Not onl y must the support break
away easi ly at the base, it must swing away witho ut becoming a projectile or impacting the vehicle a
second time. Another critical fealUre of the s ign system is its ability to w ithstand w ind loads w ithout
caus ing any structura l damage to the system.
Multi-directional s li p bases for breakaway supports have existed for many years, as well.
However, their safety perfo rm ance when used in conjunction with dua l support highway signs with ground
mounted wide-nanged posts and attached fuse plates had not been previously eva luated. In add itio n, the
Missouri Highway Transportation Department (MHTD) wished to evaluate the performance of the multi
directiona l s li p-base and the dual support breakaway system when impacted by a vehicle at some angle
other than perpend icular to the face of the s ign. as this occurs frequent ly in actual acc idents.
Further investigation into the fuse plate design was recommended in a 1993 report by thc Midwest
Roads ide Safety Facility (Mw RSF) (D. Concerns were ex pressed that the fuse plate currently em ployed
in the breaka way systems used by MHTD would fa il under design w ind loads.
1.2 Objective
There were two mtU or objectives of thi s research: to increase the wi nd load capac ity of the dual
support breakaway sign without reducing the qua lity of the hinge mechani sm, and to determ ine the safety
performance of a multi-directional s lip base 0 11 the improved s ign.
1.3 Scope
Prior to Full scale crash testing, laboratory testing as we ll as stTuctural analysis was performed
ill order to determine opt imum design recommendations for specify ing the materia l and design details of
the fuse plate. This included an analysis of the Willd loads on the sign, and component tests on various
cand idate fuse plates.
The perfo rmance of the highway sign was eva luated by im pacting one post of the sign with a
vehicle from a direction of 25 degrees perpendicular to the face of the highway sign with a 400-mm
vehic le offset toward the passenger's side . Two fu ll-scale vehicle crash tests were conducted with the
des igned fu se plate and multi-d irecti onal slip base us ing an 823-kg (1790- lb) mini-compact sedan at target
speeds of 35 kph (21 .7 mph) and 100 kph (62 mph) . The safety performance was evaluated from cri teria
set forth by National Cooperati ve Highway Research Program (NCHRP) Report No. 350 (£).
2
2 BACKGROUND
I.n the ear ly 19605 it became apparent that rig id s ign supports were unsafe roads ide appu rtenance,
as impacts with sLich signs by errant vehi cles resulted in numero us fataliti es. In ord er to reso lve thi s
pro blem, the Texas Transportation Institute (TTl ) began to investigate the use of breakaway structures in
roads ide signs .Q)
A very important feature of the breakaway system is the abili ty of its su pport to swing li p and OLit
o f the way when impacted by an errant vehic le. The supp0l1 must not only break away eas il y at the base,
but it must swing away w ithout becoming a projecti le or impacting the vehic le a second time . Today, the
most common s ign supports are made of stee l W-shapes w ith a 4-bo lt s lip base and a plastic hinge located
just undcr the sign.
During the first iteration of the hinge mecha ni sm, the W-shape was cut entire ly in ha lf j ust be low
the sign. The front and back fl anges were then recollnected with cast iron plates . When th is system was
impacted duri ng a full sca le vehicle crash test, both cast iron p lates fractured , and the post support
completely di sengaged from the sign. As a resu lt, the support fe ll on the test vehi cle as it passed under
the sign, breaki ng the w indshield and deforming the roof of the vehic le. The nced for a y ie ldi ng hinge
versus a fractu ri ng hinge became evident du ri ng th is test.
The y ie ld ing hinge was created by cutt ing th rough the fro nt flange and web of the W -shape beam,
and then reconnecting the front fl ange with a fuse plate. The concept is to des ign th is fuse plate so that
the post w ill be strong enough to withstand wi nd loads, but weak enough to fa il when the support is
impacted by a ve hi cle . Upon fai lure o f the fu se plate, the support rotates abollt the back fl ange, and the
SUp p0l1 swings up and out of the way of the veh icle.
In the y ie ld ing hinge des ign, the first fuse plate was a cast-i ron p late, shown in Figure I . The fuse
plate was bo lted to the front face to prov ide SUppOlt against wind loads, but wo uld fracture when the post
was impacted by a vehicle. Crash tests on thi s syste m were sllccessful 0), however diffi culti es in casting,
3
handl ing, bo lting and maintaining cast-iron fuse plates led researchers to consider other alternatives.
STEEL POST
~t "'", r ON. stUB
Figure 1. Evolution of the Fuse Plate CD.
A fi'i ction fuse plate was then deve loped to replace the cast-iron plate. A standard 9 .S-mm ( 2 - in.) 8
thick ASTM 441 steel plate, also shown in Figure I, was cut with the bottom two holes notched so that
the plate would sl ip under impact. The operation of this fuse plate is based on the frictiona l resistance
between the bolts, the plate, and the support. Several stati c tensile load tests were performed on the steel
slip plate to verify that it would withstand des ign w ind loads (1). This SUppOlt performed well in itially,
but after a number of years the bo lts became loose, and wi nd forces caused the hinge to fai l, resu lti ng in
signs fo lding over duri ng moderate wind storms. T his problem was recognized and an alternate des ign
to the stee l s lip plate was deve loped.
4
In 1984, 'IT I developed a breakaway sign that cons isted of a steel, perforated tension fuse plate
(2.). The development of this system consisted of nine static tens ile tests to deteml ine the proper materia l
and cross-sect ional area of the plate. One fu ll-sca le vehicle crash test was conducted with an 828-kg
( ISOO-Ib) vehicle at 32.2 kph (20 mph) on the new des ign. The fuse plate did not acti vate during thi s test,
but all of the safety criteria were met, so the system was approved for lise.
The slate of Missouri used this design on its highway systems from 1985 to 1989 and had
numerous report s of the hinge fa iling to acti vate wilen thc support was impacted by an erran t vehicle. In
1990 Ihis perforMed tension fu se plate was modified by reduci ng the effective cross-sectional area,
allowing it to fa il when subjected to a smaller load. In 1993. by request of MI-ITD, MwRSF subjected thi s
modified design to a series of full-sca le vehicle crash t.ests to confirm its successful perfonnance (D.
Researchers ve rified the successful crash performance of thi s new design; the design eas ily passed all of
the safety crit eria. However, concems were ra ised about the wind load capacity of the new fuse plate.
rurtiler analys is was recommended to create a design that would sati sfY the wind load as well as mcet the
safety criteria .
Rccentl y, M HTD began to use mult i-di rectional slip bases on thei r dual SLiPPOIt signs, as opposed
(0 a rectangul ar slip base. The l11ulti-directional s lip base is tri angular in shape and ut ili zes three s li p
bo lts, as opposed to the four sl ip bolts used in the rectangular slip base. This system had not yet been
tested accordi ng to NC I-I RP 350 spec ificat ions.
5
3 ANALYSIS AND DESIGN
3.1 Wind Load Analysis
Highway s igns must be des igned to withstand hi gh wind loads. On breakaway s igns which
incorporate a fu se plate a contradiction occurs in the design of the fuse plate. It is desired that the fuse
plate be strong to withstand the wind loads, but weak enough that it fa il s under impact of an errant
vehicle. The fo llowing discuss ion w ill ou tline the minimum requi rements Ihe fuse plate must meet in
order to support the wind loads.
3.1.1 Calculati on of Wind Load
Figure 2 shows a schematic drawing of the sign system. The maximu m force in the fu se plate,
Fp. can not exceed the product of the materi a l yield strength, Sy. and the cross-sect ional area, A, of the
fuse plate.
(I)
Us ing stntics, a summati on armaments aballtthe hinge point yie lds a relation for the force in the
fuse plate. It was assumed in thi s calculati on that the hin ge point is fixed at 152 mm (6 in.).
The effective static force on each support can be calcu lated from the pressure.
F " l(Phw) , 2
(2)
(3)
The method used to determine the wind load on the s ign is described in Slandard Specifications
.Ii)r Structural Supportsjor Highway Signs, Lumil/ares, alld Traffic Signals, 1994 (0. According to this
specification, the pressu re exerted on a sign by the wind can be computed us ing the following formula:
6
P =O.0474(lJ V)'C dC" (4)
where:
P = Wind Pressure CPa)
v = Wi nd Speed (k pb), n-year mean recurrence interval (the factor 1.3 is a safety factor that
accommodates for w ind gusts of 30%)
Ch = Coeffic ient relating to the e levat ion of the s ign
CJ = Drag Coefficient
Accord ing to AAS HTO (2.), the maximum wind speed in Missouri and across most of the United
States is 112 .6 kph (70 mph ), so th is value was used in the calcu lations. The coeffi c ient of drag, Cd' and
the e levation coeffi c ient, Ch, depend on the geometry of the s ign as shown in Tables I and 2, respectively.
e =
F = .'
p
_-+S_ I § j" .. ::::" 0'
F,
_ 152 ...... (Eo ;n)
rs ~.·"~9'" POln"t
Figure 2 . S ign System
Elevation of sign (in meters) " = Height of Sign (ill meters)
Width of S ign (in meters) !I = Hinge Length (in millimeters)
Effective Wind Force on the Sign Fp = Force in th e Fuse Plate
7
Table I. Drag Coefficien t
w C, h
1.0 1. 13
2.0 1.1 9
5.0 1.20
10.0 1.23
15.0 1.30
Table 2. Elevation Coefficient II e+- C II 2
0-4 .6 rn 0 .8
4.6-9. 1 III 1.0
9. 1- 15.2 rn 1.10
15 .2-30.5 J11 1.25
30. 5-9 1.4 m 1.50
The state of Missouri implements s ix d iffere nt post s izes on breakaway systems. For each of these
post sizes, the hinge length, s, and the cross-sectiOl1al area, A, varies for each post configuration . The
detail s o f each configuration are illustrated in Table 3 .
Table 3. Post/Fuse Plate Configurations
Post Post Size Fuse Plate Area Web Thickness Configuration mm2 (in.2
) (Hinge Length) mm (in.)
1 W6x9 121 (0. 1875) 149 (5.875)
2 W6x 15 161 (0.25) 152 (6.000)
3 W8x18 161 (0.25) 206 (8. 125)
4 W10x22 252 (0.39) 257 ( 10. 125)
5 W1 0x26 252 (0 .39) 263 ( 10.375)
6 W1 2x26 252.0 (0.39) 211.2 ( 12.250)
3 . 1.2 Wind Load Charts
The Wind Load Chal1 s show the maxim um sign size each post configuration can withstand based
on the fuse plate material and the elevation height (also kn own as clearance height). Equat ions 1-4 and
Tables 1-3 can be used to construct wind load charts for an y variety of fuse plate materia l and c learance
he ight. One sllch example, for an A36 steel fu se plate with a s ign elevation of 2.44 m (8 ft) is shown in
Figure 3. The d ifferent lines on the figure represent the different post s ize configurations li sted in Table
3 . Note that the s ign systems in this study arc all dual post configurations.
8
Elevation: 2.44 m 60 ======~' .~ ... ~ . . ~ .. ~ .. ~ .. -===== 5.5 .
c CI' 4.0
U) '- 3.5 o
::c 3.0 . ~
'iii 2.5 I
2.0
1.5 .
......• ~~ . "'';1 1
.......
. ... . .... .. ... .
1.0 ';-"-=--='-:~~O-:7cCo-"-=--:':c-c;':-:-=':-;;'::-:;';-;! 2.5 3.0 3.5 4.0 4.5 5.0 5.5 5.0 5.5 7.0 7.5 8.0 8.5 9 .0 Wid th of Sign em)
Figure 3. Wind Load Chart.
The Wind Load Charts are used by finding the point on the chart corresponding to the height and
width of the s ign which is of interest. The curve di rectly above thi s point represents a post configuration
w ith an accompanying fuse plate that will support the wind loads incurred with a s ign o f such a size. For
example, if you plan to instal l a s ign that has a c lear height of 2.44 m (8 ft) and is 4 .88 m (16 ft)wide
and 2 .44 m (8 ft ) high, then the Wind Load Chart spec ifies the use of 2-N a. 3 posts.
3 .1 .3 Missouri Post Des ign C harts
The Misso uri Post Des ign Charts (1) are currentl y llsed by MHTD to determine the proper post
configuration for a certa in sign s ize. There are severa l charts to use depending on th e e levation, or clear
heighl of th e sign. Figure 4 shows one such chart for a c learance height o f 2 .44 111 (8 ft). Once again ,
the chart shown depicts only dual leg sign systems . This chart is used in the same manner as the Wind
Load Charts .
9
Elevation : 2 .44 m
60 ~-===C=========== 5.5 .,-..,5.0 -
S 45 c 0'4 .0 -Vi _ .3 .5 o :c .3.0 ~
'iii 2 .5 I
2.0
'5H-~1ifttt~ 1.0~ 2.5 .3.0 .3.5 4-.0 4 .5 5.0 5.5 6.0 6.5 7.0 7.5 B.O B.5 9.0
Width of Sig n (m)
Figure 4. Mis..">Ouri Post Design Charts.
3. 1.4 Comparison of Post Design Chalts
The Wi nd Load Charts and the Missouri Post Des ign Charts were each constructed in a d ifferent
manner. Idea ll y. the post configuration specified by the Missouri Des ign Charts should be ab le to
withstand the loads due to wind. Figure 5 shows that thi s is not the case. The demarcati on lines for the
Missouri Charts often li e well above the Wind Load li nes. Thi s indicates that, under the ex isting des ign
criteria, the Missouri Design C harts do not al ways meet the wind load condi tions. In order to a ll eviate
this problem, alternati ve stee ls were examined as poss ible replacements for the A36 stee l current ly being
used.
10
Material # 1 :A36
6.0,r============== 5.5
____ 5.0
.§.4-.5 C 0'4.0
"' '0 3.5
~ 3.0 ~ i 2.5
~:P~ .. .. /t ... ; ... ; ..
2°Ul±£t:t:t~ ' 5
' 0 2.5 3.0 35 4.0 455.0 5.56.06.57.07.5 E.O 8.5 g.o
Width of Sign (m)
F igu re 5. Wind Chan Comparison, 2 .44 m. Missouri chart Ii nes have markers.
3.2 Fuse Plate Mate ria ls
Preliminary iterati ons. llsing equations 1-4, showed that if the fuse p late materia l had a y ield
strength of 410-450 MPa (60-65 ks i) it would support the wind loads adeq uate ly for smaller post
configurat ions. Th ree d ifferent stee l materials that met thi s criteria were examined, as we ll as the origina l
material A36 stee l. These materials and the ir manufacturer specified properties are li sted in Tab le 4 .
Table 4 Material Properties
No. M~l te rial Yield Stren gth Ultimate Strength 'Yo elongation ASTM DcsignMion MPa (ksi) MPa (ksi)
I A36 284 (41.2) 410 (59.6) 25%
2 A572 Grade 50 462 (67.0) 537 (78.0) 27%
3 A516.86 Grade 70 424 (61.5) 562 (8 1.5) 18%
4 A5 14-87 Grade B 800( 116) 833 ( 12 1) 20%
A fter choosing these materi als, w ind load charts were constructed for each materi al, at an elevation
of 2.44 and 6. 10 III (8 and 20 fl), fo r post configura t ions I, 3. and 6. These chm1s are shown in Appendi x
A, the Missouri Post Design Charts are superimposed on the charts for comparison purposes.
II
When calculating the wind load charts, the thickness of the plate for Materia l No.4 was red uced
from 4.76 mm (0. 1875 in.) to 2.54 mm (0. 1 in.) so that thi s material would have a yield fo rce comparab le
to the materials with lower yield strength. This modification provides an effective Yield Strength of 426
MPa (61.9 ksi) in Material No.4.
With the cand idate materia ls, the Missou ri Post Des ign Charts sati sfied the wind load cr iteria to
a greater degree Ihan the current material (A36 steel). At an e levation of 6.10 m (20 ft) , there are no
wind load problems. However, at an elevation of 2.44 m (8 ft), the new materials do not a lways meet
the wi nd load criteria for larger signs. The three candidate materials all sati sfied the criteria to nearly the
same degree. Materia l No.2 (A572 steel) sati sfies the criteria slightly better than the other materia ls.
3.3 Component Testing of Fuse Plate
After it was shown that the three candidate material s sign ificantl y improved the wind load
capacity, component tests were performed. Th is was done to study how the candidate material s wou ld
behave under the dynamic loading that they wou ld be subjected to on a sign impacted by an errant
aUlomobi le.
3.3 . 1 Test Setup
To test the dynamic properties of the fu se plate, a W6x9 wide fl ange beam was cut and fit
with a fuse plate accord ing to Missouri des ign plans. Fuse plates were fabricated from each of the
fall I' test materia ls discussed in Table 4. The th ickness of the plate for Material No.4 was reduced
from 4.76 mm (0. 1875 in.) to 2.54 mm (0.1 in.) by scor ing the plate across the face to reduce the
cross-sectional area at the middle of the plate where the fai lure occurs. Thi s was done so the phys ical
test sample co rresponded with the wind load ana lysis on the materia l, as d iscussed in Section 3.2.
To attain a high activation speed, a IS-ton crane olltfitted with an 8: I cab le/pulley system was
used to pull the end of the post leg. The test configuration is shown in Figu re 6.
12
H
Figure 6 . Crane and Pulley System
The cable was connected to the beam 71 1 mm (28 in.) from the hinge point (Figure 7). The
crane alone had a travel speed of approximately 74 mm/sec (2.9 in ./sec) and with the pulley system
intact it woul d pull the end of the beam 589 mm/sec (23.3 in .lsec). This would produce a speed
equivalent to a 5. 1 kph (3.2 mph) impact by an automobile 1753 mm (69 in.) below the hinge point.
1753 mOl (69 in.) is the d istance between the bumper o f an average mini-compact car to the hinge
point of a sign mounted 2.44 m (8 ft) off of the ground.
'" ___ 1oI6.i b ~~.., .-V r....:p Plot.
r r----
I (,1 < ~ (l . In.)
71.1 c ~ (za ,",)
Str;no Po1rnt ;OIW t !?r
---G[] Cel( ~
Figure 7. Test ConfiguratIOn.
13
3.3.2 Data Acquisition System
To acqu ire the necessary force and deOection data, a string potentiometer and load ce ll were
used . A 44.5 kN (10 kip) load cell was placed in series with the cable/pull ey system . A 3810-lllm
(! 50- in .) string potent iometer was auached to the beam 610 mill (24 in) from the hinge point. The
signa ls from each instrument were sampled at 1250 J-Iz.
3.3.3 Resu lts and Discuss ion
Three tests, termed dynamic tests, were run on each material with the setup described above.
Three additiona l lests, termed stat ic tests, were run by removing the intermed iate pu lleys, which
yie lded a simple 2: I cable/pulley system. The resu lts from the tests are di splayed in Append ix B.
The peak fo rce and energy absorption for each material is givcn in Tab le 5.
By anal yzing the string potentiomcter data~ it was discovered that the actual act ivat ion speed
of the end of the beam was 51 mm /s (2 in/s) whicb was much slower than expected. This speed
corre lates to an automobile im pacting at 0.5 kph (0.33 mph). The static test yie lded a speed of one
half of the dynamic test.
Recall tlHlt one of the purposes of the fuse plate is to fa il when impacted by an errant vehicl e.
The exact force leve l the plate undergoes under impact is unknown, therefore, the best material is that
which fail s at the lowest force leve l during the physical tests.
From the charts in Appendix B, Materia l No. 4 fail s at the lowest force leve l and lowest
energy level of the three alternative materials. However, additional manufacturing concerns eliminated
thi s mater ial from consideration. A514-87 steel is a high strength stee l that wo uld have to be
galvani zed in a different process than the wide fl ange posts and other parts of the breakaway sign
system . This factor, in addition to the relative unavailab ility of the material, would result in add itional
costs that d id not appear to outweigh the benefits of the lower force level.
14
The elimination of Material No.4 from cons iderat ion left two material s remaining. Because
Material NO.2. A572 Grade 50, failed at a lower force and energy level tban Material No.3; and
because it provides superior wind load capacity, it was the material of cboice for full sca le testing.
Table 5 Summary of Test Results
Peak 110l"ce (kN) Energy Absorption (kN-mm) M~\tcrial ASTM Designation
No. St:ltic Dynamic StMic Dynamic
I A36 10.36 10.85 297.8 347.4
2 A572 Grade 50 13 .1 5 12.93 423. 1 388.1
3 A5 16.86 Grade 70 14.24 14.00 476.5 480.6
4 A514-87 Grade B 10.69 1l.35 284.6 276.9
15
4 FULL SCALE TEST CONDITIONS
Two vehicle crash tests were performed on the dual support breakaway sign system that
incorporated the candidate fuse plate material (A572 Grade 50 sleel). Additiona lly, the vehicle crash tests
were performed ill an im pact angle of25 degrees to test the safety perfOnllanCe of the multidirectional s li p
basco
4.1 Test Facility
4.1.1 Test Site
The testing fac ility is located at the Linco ln Air-Park on the NW end of the Linco ln Municipa l
Airport. The lest faci lity is approximately 8. [ kill (5 mil NW orille University of Nebraska-Linco ln. The
si te is surrounded and protected by an 2.5-m (8-ft) high chain-link security fence.
4.1.2 Vehi cle Tow System
A reverse cable lOW with a 1:2 mechanical advantage was ll sed to prope l the test vehicle during
the full scal e vehicle crash tests. The d istance traveled and the speed of the lOw vehicle are onc-half of
that of the test vehicle. The lest vehicle is released from the tow cable before impact with the sign
support. The tow vchicle used in the test is equipped with a fifth-wheel speedometer apparatus. The fifth
wheel , built by the Nucleus Corporation, was used in conjunction with a di g ital speedometer to increase
the accuracy o f the test vehicle impact speed.
4. 1.3 Vehicle Guidance System
A vehicle guidance system developed by Hinch no was lI sed to steer the test vehicle during the
fu ll-scale crash test. A guide flag attached to the right front wheel and Ihe guide cable was sheared off
before impact. The O.95-clll (0.375- in .) d iameter g uide cable was tens ioned to 13.4 kN (3,000 Ibs), and
supported laterally and vert ically every 30.5 111 ( 100 ft) by hinged stanchions. The hinged stanchions
stood upright while ho lding lip the guide cab le, but as the vehicle was towed down the line, the guide-nag
struck and kn ocked each stanchion 10 the groun d. The vehicle guidance system was 215m (700 ft. ) long
16
for each test.
4.2 Missouri Dual Support Breakaway Sign Design Details
The install at ion of the Missouri Dual Support Breakaway Sign was constructed in accordance to
1994 Missouri Standard Plans for Highway Construction. Figure 8 shows a plan drawing of the system
which consisted of four major components: (I) \vide-flanged posts; (2) s ign panel; (3) multi -directional
s lip base; and (4) fu se plate. The W6x9 wide flanged posts were 4. 78 m (15 ft-8 in .) ta ll and extended
from the anchored slip base to the top of the extruded aluminum sign pane l. The 3.05-m (I O-ft) wide by
2.44-m (8-h) ta ll s ign panel consists of 305-mm (12- in.) by 3.0S-m (IO-ft) long extruded sections. The
sign panel is secured to each s ide of both posts every 305 111111 (1 2 in .) with cast aluminum clips. The
bottom of the sign was mounted 2.44 m (8 ft) above the ground surface. The hinge mechanism was
located 76 mm (3 in.) be low the s ign . The hinge plate was constructed of 5 mm (0.1875 in.) thi ck A572
stee l.
At the base of the sign post, a multid irectional , tri angular s lip base secured the s ign to the ground.
The slip base was secured to the anchor using three 16 111m (0 .625 in.) diameter bo lts torq ued to 4030 kg
mill (345 ill-Ib). The s li p bo lts were held in place by a bo lt retainer made from 30 gauge galvanized sheet
metal. The heigh t of the permanent sl ip base asse mbly was 102 mm (4 in .) . The permanen t sli p base
assemble was anchored in 1381 111m ( 15 in .) diameter by 0.9 1 m (3 ft) deep concrete footing.
4.3 Test Vehicle
The test vehicle used for Test M03- 1 and M03-2 was a 1989 Ford Festiva. The test vehicle had
a test inertial we ight of 823 kg (1790 Ibs). The vehicle dimensions are shown in Figure 9. The front
whee ls of the test vehicle were aligned for camber, caster, and toe-in values of zero so that the vehicle
would track properl y along the guide cable. A surrogate occupant with a weight of 73 .6 kg (160 Ibs) was
belted to the dri ver's seat for both of the tests. A remote contro ll ed brake system was installed in the
vehicle so it could be brought safely to a stop after the test.
17
(2') (6 ' ) (2') r O.61 m,--j ______ 1.83 "-_____ --j-'0.61 m
l 3.05 m ~ 2.~ 4 m
V-(10' - 0· • 8' - 0") E.truded Alum inum P<onei S;q,.,
2.44m (8')
I I
II II II II II
M03- 1,2
II
II II II II II
4.88 m (16 ' ) ~ [ 76 mm (Y) ••
1.34 m (7 ' - 8"')
ob.l.,.,.-_1 9 mm (J/4·) Base Plotes
L-:=-===,~,-"~ l >0, mm 1'"' 0
• . , Hinge PlCla ("'-:572 G r<Jd~ :50) • ""-(102 mm ~ l OB mm , 4.B mm)
(,," ~ <I 1/"" • 3/11;") !-fonge Plote 6<>11 . ("'-325) (4 _ 1) mm 1\ ~ 32 mm) (4 _ 1/'£ ~ ~ 1 1/4")
~ W6~9 Po.t Des ign No.1
80se Prote Bolls (A- J 25)
Vr! - 16 m...-.ll , 89 mm /4030 kq_ mm) J - 5/8" ... J 1/7 (]45 on-Ibs)
t SWb Lfng1l1 " 0.610 m (2')
1
;']'rl;;.1 ~ rool ing Size \ / )jBl mm (IS") ... 0.91 m en deep!
~".\ (lireclion of Kit
Figure 8. M03- 1,2 Test 1 nstallatioll .
18
Make: Ford Test No .. M03-1.2 Vehicle Geometry centimeters (in.)
Model: Festivo Tir e Size: P145/80R12 0-158.8 (62.5) b - 62.2 (24.5)
Year: 1989 VlN: KNJ8T06K1K61 4 3626 c - 229.9 (905) d - 142.2 (56.0)
Dote: 06/21/1995 e - S8A (23.0) 1 - 350,5 ( 138.0)
.[£:]:t:eF g - 55.9 (22.0) h - 83.8 (330)
[0 J - 48.3 (19 .0) m- 15.2 (6.0)
, - 11.4 (4.5) 0- 40.6 ( 16.0)
P -139, 1 (54.75) q- 139 .1 (5475)
c - 53.3 (210) <- 33.0 ( 13.0)
73.7 (29.0)
Engine Size: 4 cyl.
Transm ission: Manual
Moss Curb 1 Test 2 Gross 3 kg (Ibs ) Inert ia l Stat ic
WI 529 ( 1150) 522 ( 1135) 559 ( 1215)
W2 299 (650) 301 (655 ) 338 (735)
wtot a l 828 (1800) 823 ( 179 D) 897 ( 1950)
Damage prior to test: NONE
1 Curb _ moss of test vehicl e in its stondord manufacture condi t ion 2Test Inert ial - moss of test vehic le and a ll items including ballast and test equipment 3Gross - Slot ic - total of test inertial and dummy mosses.
Figure 9. Test Vehicle Dimensions.
19
4.4 Data Acquisition System
4.4.1 Accelerometers
A triaxia l piezoresisti ve accelerometer system with a range of ±200 G's was used to measure the
acceleration in the longitud inal , lateral , and verti cal directions at a sample rate of 3,200 Hz. The
environmental shock and vibration sensor/recorder system, Model EDR-3, was configured with 256 Kb
of RAM memory and a 1,120 Hz filter. Computer software, "DynaMax I (DM-I)" and "DADiSP" were
lI sed to dig iti ze, filter, analyze, and plot the accelerometer data. The data was filtered using a 180 Hz low
pass filter and processed with a 10 ms moving average.
4.4.2 High Speed Photography
Four high-speed 16-111111 cameras, with operating speeds of approximately 500 frames/sec, were
used to film the crash test. A DC powered Locam, with a 76-mm lens, was placed approximately 75 m
(250 f!) downstream of the im pact point. A Locam, with a 12.5-mm lens was placed approximately 19
m (62 ft) perpendicular to the s ign system. Two other Locams were placed to obtain closeup views of
the crit ical components of the system. One Locam, with a 135-111m lens, was placed 20 m (65 ft)
perpendicular to the system and focllsed on both slip base. A fOllrth camera was placed 10m (33 ft)
upstream from the sign system and focllsed on the fuse plate on the impacted post. The film was analyzed
using a Vanguard Motion Analyzer.
4.4.3 Pressllre Tape Switches
Five pressure tape switches, spaced at 1.52-m (5-f!) intervals, were used to detennine the speed
of the vehicle before impact. Each tape switch fired a strobe light and sent an electronic timing mark to
the data acquisition system as the left front tire of the test vehicle passed over it. Test veh icle speeds were
determined from recorded electronic tim ing m<lrk data. Strobe lights and high speed film analysis were
Llsed only as a backup in the event that vehicle speeds could not be determined from the electronic data.
20
5 PERFORMANCE EVALUATION CRITERI A
The safety performance eva luat ion was conducted accord ing to the gu idelines presented in NCHRP
Report 350 (£) and the 1994 AAS HTO Slolldard Specifications for Struclural Supporlsjor Hig/lljl(~y Signs,
Luminaires, and Traffic Si&Tnals (§). These guidelines, shown in Tables 6 and 7, requ ire two compliance
tests in order to evaluate the perfo rmance of a breakaway support. These two compliance tests are level
3 tests (Tests 60 and 61). Descripti ons of these tests are as follows:
]) Test 3-60: An 820-kg (1808- lb) vehicle impacting the support struclUrc head-on at a nomi nal
impact speed o f 35 km/h (21.7 mph) w ith the center of the front bumper aligned with the center of the
insta ll at ion . The object ive of this test is to investigate the breakaway or fracture mechanism oflhe support.
2) Test 3-61: An S20-kg (ISOS-Ib) vehicle im pact ing the support structure head-on at a nominal
impact speed of 100 km/h (62.1 mph) with the quarter point of the front bumper al igned with the center
of the insta ll at ion. The object ive of thi s test is \0 illVestigate the trajectories of both the test insta ll at ion
and the test veh icle .
The impact angle for the full scale crash tests was changed to 2S degrees as th is was determ ined
to be the SOth percentil e encroachment ang le from accident data. In addition , the change in im pact angle
would also increase the severity of the impact and prov ide more ins ight in to the safety of the dev ice.
The veh ic le damage was assessed by the traffic accident sca le (TAD) (2) and the vehicle damage
index (VOl) (lQ).
21
Table 6 NCHRP RepOlt 350 Safety Eva luation Guidel ines
Evaluation Evaluation Criteria Factors
Structura l B. The test article shou l<i read ily act ivate in a pred ictab le manner Adequacy by breaking away, fracturi ng, or yielding.
Occupant Risk D. Detached elements, fragments or other debris from thc test artic le should not penetrate or show potentia l for penetrat ing the occupant compartment, or present an unduc hazard to other traffic, pedestrians, or personnel in a work zone. Deformat ions of, or intrusions i n to~ the occupant compartment that could cause serious inju ries should not be permitted .
F. The vehicle should remain upri ght during and after co lli sion a lthough moderate ro ll , pitching and yawing are acceptab le.
H. Longitudina l occupant impact ve locity shou ld satisfy the following limits:
Preferred: 3 mls (9.8 Fps) Maximum: 5 m/s (16.4 fps)
I. Occupant ridedown acce lerations should satisfy the fo llowing longitudina l and latera l li mits :
Preferred: 15 G's Maximum: 20 G's
Veh icle K. After coll ision it is pTeferable that the veh ic le' s trajectory not intrude Trajectory in to adjacent traffic lanes.
N. Vehicle trajectory bell ind the lest article is acceptab le.
Table 7. AASHTO 1994 Safety Evaluatio n Guide lines .
Evaluation Evaluat ion Criteria Factors
Vehicle Satisfactory dy nam ic performance is indicated when the Change in maxim um change in velocity of the vehicle, str iki ng a Speed (Ll V) breakaway support at speeds from 32 kph to 97 kph (20 mph
to 60 mph) does not exceed 4.87 mls ( 16 fps), bu t preferably does not exceed 3.05 mls (10 fps)
22
6 FULL SCALE TEST RESULTS
6.1 Test M03-.1 (35.6 kph, 25 dcg, offset 400 111m p~tssenger side)
Test MOJ- J was conducted with a 1989 Ford Festi va under the impact conditions of 35.6 kph
(22. 1 mph) and 25 deg with respect to a line perpendicular to the face of the sign. The impact location,
shown in Figure 10, was the offset 400 111111 (15.75 in.) from the centerl ine of the vehicle toward the
passenger's side of the vehicle. The vehicle impacted the s ign system on the corn er o f the s ign post. A
SlI1ll11Hlry of the lest results and sequential photographs are shown in Figure II.
The bumper of the car defonned for approx imately 6 ms aftcr impact at which po in t the s lip base
began to move. 14 illS after im pact, the slip base was completely actuated, eliminating its dIcel a ll the
vehicle. The s lip base became complete ly clear from the stub at 34 ms. As the vehicle continued in a
forward moti on, the post remained straight as a large bend deve loped in the s ign. At approximatc ly 240
ms, the fuse plate failed and the sign post sta rted to bend abou t the hinge. At 270 ill S, the post lost
contact with the vehicle and started to swing away. At 520 ms, the end of the post reached its highest
peak and began to fa ll back down: however. the s ign panel continlled to rotate abo ut the un impacted post.
At 710 ms. the end o f the post passed "round the outside of the car on the driver' s s ide. At 950
ms, the car was completely c lear of the system. The s ign panel continued to pivot arou nd the un impacted
post unti l it became perpend icular to its original configuration at abou t 1.28 seconds. At 1.65 seconds
the s ign panel began to swing back towards irs orig ina l position until it came to rest at 3.18 seconds.
Figure J 2 shows the damage to the vehicle, which consisted o f a maximum crush depth o f 13 mill
(0 .5 in .) in the bumpcr. No other damage occurred to the vehic le and the bum per was rep laced fo r test
M03-2. Damage to the s ign is shoWI1 in Figure 13. The impacted support and co rresponding fuse plate
were destroyed when the hinge mechanism act ivated . The other support deformed during impact as the
rest of the s ign system rotated about it durin g impact. Both sign supports and fu se plates had 10 be
replaced for the second test. The s ign panel was replaced as well , even though it was undamaged.
23
The ridedown acceleration and occupant impact velocity were not applicab le to thi s test since it
was determined that the hypothetical occupant did not contact the dashboard within the time that sign was
in contact with the vehicle. The results of the occupant ri sk, detennined from accelerometer data, are
summarized in Figure II. The results are shown graphically in Appendix C. The appurtenance met the
criteria set forth by NCHRP 350 Test Designation 3-60.
24
Test Numbe r ..... . .. ...... M03· 1 Test Date .. ..... . .. ...... 6/2 1/1995 Appurtenance. . .......... Dual Steel Support Breakaway Sign Sign Size ... .... . . . 3.05 m x 2.44 m (10 ft x 8 ft) Sign Mounting Height . . . ... 2.44 m (8 ft) Support Size .............. W6x9 Post Spacing .............. 1.83 m (6 ft) Perforated Tension Fuse Plate
Locat ion ........... 76 mm (3 in.) be low sign Material ........... ASTM A572 Stee l Plate Thickness ...... 4.8 mm (0. J 875 in.) Cross·Sectional Area. 121 mm! (0.1875 in.2
)
Triangular Slip Base Assembly Slip Bolt Size .. .. . 15.9 mm (0.625 in.) dia. Bolt Torque ......... 39.0 N-m (345 in-lbs) Stub He ight ......... 102 mm (4 in.)
Sign Panel ..... ........... Extruded Aluminum NCHRP 350 Veh icle Class .... 820C
Mode l . Mass (Weight)
Curb .... Test Inertial Gross Static
1989 Ford Festiva
.828 kg (1800 Ib)
. 823 kg (1790 Ib) ... 897 kg (1950 Ib)
Veh icle Speed Impact Exit ..... .
Vehicle Angle
· . . 35.6 kph (22 .1 mph) · . . 32.6 kph (20.25 mph)
Impact ... .. ....... 24.3 degrees Exit ...... . . . 24.3 degrees
Vehicle Impact Location ...... 400 mm (15 .75 in.) right of center Vehicle Snagging ........... None Vehicle Stability ............ Satisfactory Occupant Ridedown Deceleration
Longitudinal ........ N/A (no occupant impact) Occupant Impact Velocity
Longitudinal .. Vehic le Change in Speed .. . Ve hicle Damage
TAD (2) VO l UQl.
Vehicle Front-end Crush Sign Damage ...... .
. N/A (no occupant impact)
. 0.83 mI, (2 .7 fp,)
I-Fe- I .0 I FRLN I
· .. 13 mm (0.5 in.) · .. Impacted Fuse Plate Destroyed
Both Posts Bent
Figure 11. Summary of Test M03- 1.
Plate Damage: MOJ-!.
26
6.2 Test M03-2 (92.0 kph, 27.3 deg, offset 475 mm passenger side)
Test M03 -2 was conducted with a 1989 Ford Festi va under the impact conditions of 92.0 kpb
(57.2 mph) and 27. 1 deg with respect to a line perpendicular to tbe face of the sign. The impact location
was the offset 475 mm (1 8.75 in .) from the cente rline of the vehicle toward the passenger side. The
vehicle impacted the sign system at the corner of the sign post. The sign installation was constructed in
the manner described in Section 4.2 A summary of the test results and sequential photographs are shown
In Figure 15.
The car defonlled for approx imate ly 2 111 S after impact at which point the slip base began to move.
6 ill S after impact, the slip base slipped from all three bolts, eliminating its effect on the vehicle. The slip
base became complete ly clear from the foot ing at 14 ill S . Review of the fuse plate closeup fil m showed
a gap developi ng in the web of the post at the fu se plate connection 4 ms after impact. The sign remained
straight as the post began to bend and the fuse plate started to deform . At approximate ly 9.6 ms, the fuse
plate fail ed.
At approx imately 50 ms after impact, the po st lost contact with the vehic le. At thi s point, the post
had moved th rough an angle of 35 degrees. 82 ms after impact, the sign panel began to move, the sign
developed a sligh t bend in iI, and then started 10 rotate about the unimpacted post. At 219 ill S, the car
was complete ly c lear of the system. The post continued to rotate about the hinge point al a high rate until
it im pacted the back side of the sign at 360 ms.
The sign panel rotated about the non-impacted post until it reached a point perpendicular to its
original pos ition at 700 ms. At 720 ms, the fuse plate on the non-impacted post fail ed due to the excess
we ight and swinging of the sign panel, at this po int the sign began to fall to the ground. The sign system
came to rest 1.9 seconds after initial impact.
Figure 14 shows damage to the vehicle consisting of a max imum crush depth of 76 nun (3.0 in .)
in the bumper, and 38 mm ( 1. 5 in) ill the hood. No other damage occurred to the vehicle . The sign
27
damage, shown in Figure 16, was extensive. Both fuse plates fa iled. and both sign supports were bent
at the hinge point. The sign panel became damaged when it was impacted by the base of the post support.
The longitudinal occupant impact veloc ity and ridedown acce leration were not app licable to this
test since it was detenn ined that the hypothetica l occupant did not contact the dashboard with in the time
that the sign was in contact with the vehicle. The results of the occupant risk. detennined from
accelerometer data, are summarized in Figure 15. The results are shown graphically in Appendix C. The
appurtenance met the criteria set forth by NCHRP 350 Test Designation 3-6\.
28
Oms 24 ms
Test Number .... .... .. .... M03-2 Test Date ..... .. . ..... . . 6/2 111995 Appurtenance ......... ... .. Dual Steel Support Breakaway Sign Sign Size . .. . . 3.05 m x 2.44 m ( 10 ft x 8 ft) Sign Mounting Height ...... .. 2.44 m (8 ft) Support Size ..... .. . . . W6x9 Post Spacing ... ......... 1.83 m (6 ft) Perforated Tension Fuse Plate
Location ........... 76 mm (3 in .) below sign Material .... ..... .. ASTM A572 Steel Plate Thickness .. .. 4 .8 mm (0.1875 in .) Cross-Sectional Area .. 121 mm2 (0.1875 in. ~ )
Triangular Slip Base Assembly Sli p Bolt Size 15.9 mm (0.625 in. ) dia. Bo lt Torque. . . 39.0 N-m (345 in-Ibs) Stub Height ......... 102 mm (4 in .)
Sign Panel. . . . . . . . ... Extruded Aluminum NCHRP 350 Vehicle Class .... S20e
Model ..... .. ... .. . 1989 Ford Festiva Mass (Weight)
Curb ........ 828 kg (1800 Ib) Test Ineni.1 ... 823 kg (1790 Ib) Gross Static ... 897 kg ( 1950 lb)
50 ms 127 ms
Vehicle Speed impact .... . .... . . 92.0 kph (57.2 mph) Exit .... . .••. • . . . 83.3 kph (52.1 mph)
Vehicle Angle Impact ... . ..... .. 27 .3 degrees Exit . ..... . . .. . 27.3 degrees
237 ms
Vehicle impact Location ..... . 475 mm ( 18.75 in.) right of center Vehicle Snagging ...... ..... None Vehicle Stab ility ............ Sat isfactory Occupant Ridedown Deceleration
Longitudinal ...... . . N/A (no occupant impact) Occupant Impact Velocity
Longitudinal .... . . N /A (no occupant impact) Veh icle Change in Speed ...... 2.35 mls (7.7 fps) Vehicle Damage
TAD (2) .......... . I·FC·I VDI UQ) .. .... ..... OIFRENI
Vehicle Front-end Crush . . .. .. 76 mm (3.0 in.) Sign Damage. . . . . . . . . . . Both Fuse Plates Destroyed
Both Posts Bent Sign Panel Bent
Figure IS. Summary of Test M03-2.
Figure 16. Sign Installat ion Damage: M03·2.
30
I \ \ \ ' \
\ ~t :t
7 CONCLUSIONS
The perfomum ce of the Missouri Dual Support Breakaway Sign was acceptab le based o n the
requiremen ts scI rorth by NCHRP Report 350 (f.). The research study described herein c lear ly ind icates
that the system does not pose any significant haz.:1rd for vehicles impacti ng one of Ihe supports at an ang le.
The muhi-d irect iona l sli p base perfonned as designed during the veh icle impact at 25 degrees.
C hangi ng the material of the fuse plate creates a stronger connection that wi ll sati sfy the wi nd load
cri teria for smaller s igns, and s ignificantly im prove performance for larger s igns. The increased strength
in the fuse plate did not hinder the safety perfonllance of the fu se plate . During vehicle crash tests,
M03-J and M03-2, the fuse plate performed as des igned under the impact conditions.
31
8 RECOMMENDATIONS
To flUt her im prove the wi nd load capac ity o f dual support s igns add itional research is requ ired.
Implementing higher strength materials, or increas ing the cross-sectional area o f the fuse plate, wi ll c reate
a more rigid collnecti on, which may not activate upon impact of an errant vehicle. Therefore, a lternat ive
designs must be sought to improve the wind load -capacity of larger signs. One sLlch alternati ve is the
balanced hinge po int, shown in Figure 17 (ll). whe re the hinge po int is located in line with the effecti ve
wind load , eliminating all moment from this force.
Figure 17. Balanced Post Hinge.
Vehicle crash tests were perfonned on a s imilar system by TTl in 1988 em. However, in these
crash tests a fr ic tion fuse plate was used, the cuI in the post did not angle down below the sign (it
remained horizonwl ), and the s ign was not connected to the post below the hinge po int. Crash t'ests were
sl1ccessfu l a ll thi s des ign; however, it wi ll behave differentl y from the proposed design in Fig ure 17.
32
9 REFERENCES
I. Pfeifer. Brian G. , Safety Evaluatioll of a Modified Perforated Tellsioll Fuse Plate/or Dual Support Breakaway Signs. Midwest Roadside Safety Fac ility, University of Nebraska, Lincoln . NE. February 1993.
2. Ross, I-I. E., Sicking, D.L. . Z immer, R.A., a nd Michie, J.D., Recommended Procedures/or 'he Sa/elY PCI/orm{lnce Evaluation of Highway Feafures, National Cooperative Highway Research Program Report 350, Transportation Research Board , Washington, D. c., 1993.
3. Olson, R.M. , Rowan, N.J. , and Edwards, T .C., Breakaway COli/poI/ellIs Produce Safer Roadside Signs, Highway Research Record No. 174, Washington D. C., 1967.
4. Rowan. N.J ., O lson, R.M., and White, M.e., DeveloplIJelll of Break-Away Sign Supparls and Siol/ed Steel Plate Mechanical Fuses, Texas Transp0l1ation Institute. Texas A&M Univers ity, Co ll ege Station, TX, 1968.
5. Hirsch, T.J ., Fairbanks, W. L. , and Arnold, A. , Pelf orated Tension Fuse Plate for Breakaway Rood\'ide Signs, Texas Transportation Institute, Texas A&M Univers ity. Co llege Station. Texas. [984.
6. Sllllldanl\' Specifications for Structural SUjJjJorts for Highway Siglls, Luminaires. Gnd Traffic Signals. American Assoc iation of State Highway and Transportation Officials (AASHTO), 1994.
7. Policy. Procedllre. and Design Mallual. Di'vis ion of Design, Missouri Highway Transportation Depart men t.
8. I-linch. J .. Yang, T-L, and Owings, R .. Guidanc.-e Systems for Vehicle Testing, ENSCO, Inc ., Spring liclcl , VA, 1986.
9. Vehicle Damage Scale jor Traffic Invesligalors, Traffic Acc ident Data Project Technical Bu lletin No. I , Nationa l Safety Council , Cilicago, IL, 1971.
10. Collisioll Deformarioll Classijicalioll , Recommended Pract ice J224 March 1980, SAE Handbook Vo l. 4, Soc iety of Automotive Engineers, Warrendale, Penn. , 1985.
II . Bloom. J.A. , and I-linch, J.A., Laborat01Y Evaluatioll of Exisling Breakaway StructuresVolullle /I - Technical Results. ENSCO. Inc., June 1980.
12. Ross, I-I.E ., Jr., Sicking, D.L. , Campise. W_L. , and Zi mmer. R.A., Small Sign Support Al1alysis: Phase I - Crash Test Program. Texas Transportation Institute, Texas A&M Univers ity , Co llege Station Texas, August 1988.
33
10 APPENDICIES
34
APPENDIX A. WIND LOAD CHARTS
Figure A-I. Wind Load Charts. Elevation: 2.44 Ill .
Figure A-2. Wind Load Charts. Elevation: 6.10 III
35
w
'"
5.5
__ 5 .0
E 4 -~ 0
c 0> 4.0
en '0.3.5
:c .3.0
'" ' iii 2 .5 I
Materia l # 1 :A.36 Material #2: AS72
6.0 ,-~:--~~-.:c-'--'--=--'---'~--'
55
__ 5.0
--S 1'..5 c I'-~", 0'4.0
en _ 3 .5 o L 3.0
'" 'iii 2.5 :r:
\.".
2 .0L~~ 1.5
1.0 2 .5 3.0 3.5 4 .0 4.5 5 .0 S.S 0 .0 O.S 7.0 7.S 5.0 8 .5 9.0
2.0
I..
1.0~~~~~~~~:;====~ 2 .5 3.0 3.5 4.0 4.5 5.0 S.5 0 .0 6.5 7.0 7.S 8 .0 8 .S 9. 0
55
____ 5.0
£4.5 c 0'4.0
en __ 3.5 o L 3.0
'" 'Iii 2.5 I
2.0
Width of Sig n em)
Material #3:A516 Grode 70
.5 ..-.. 5.0
£4.5 c 0'4.0
en __ 3.5 o L 3.0
'" 'iii 2.5 :r:
20
lvid th af Sign (m )
Moteria l #4:A514-87 Grode B
1.51 • ~~~~ 1.51 .,-;-;-;~~~ 1 .0~ 1.0~ 2.5'~ ' .54~4.55055M657~ 7.5M&590 DJ~ '.54~ 4 . 55 .05'~6 . ' 7~7.'M65 9 . 0
Widlr o f Siqn (m \tl idth of Si n m
Figure A-I. Wind Load Charts, Elevation Height 2.44 m Missouri chart lines have markers.
Material if 1 :A36 6.0 ,-.,.--,:-~-,--~~--,----,-~----,---,~---,
55
......... 5.0
£4.5 5, 4.0
Vi 0 03 .5
:c 3.0
'" '.1) 2.5 I
2.0
,.5 f----!'"~::::f~~ 1.0~
2.503.0 03.5 4.0 4,5 5.0 5.5 6.0 6 ,5 7.0 7.5 8.0 8.5 9.0 :,idth of Sign (m)
Material #3:A516 Grade 70
6.0r=,.....-----~-~~------,
5.5
5.5
......... 5.0
--S4.5 §,4.0
Vi '0 03 .5
:L: 03.0
'" ' 4:) 2.5 I
2.0
1.5
Material #2:A572
1.0 ,:-=-=-=".,:-:--:-:c::-~-ccccc~c:-==-=-~ 2.5 03.0 03.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 Width of Sign (m)
Material #4:AS14-87 Grode 8
6.0
55
5.0 ~
E .......... 4.5 c 0> 4 .0
Vi "' _ J.5 0
:E' 3.0
'" ' iV 2.5 I
2.0
1.5
Figure A-2. Wind Load C harts, Elevation Height 6.10 m Missouri chart lines have markers.
APPENDIX B. COMPONENT TEST RESULTS
Figure 8 -\. Component Test Results for Materi al #1: A36
Figure 8-2. Component Test Results for Material #2: A572
Figure 8-3. Component Test Results for Materia l #3: AS16.86 Grade 70
Figure 8-4. Component Test Results for Material #4: A514-87 Grade B
38
Test Results for Material #1 . A36
[ DYNAMIC - - - STATiC] E DYNAMIC - - - STATIC I 600 16
14 500
12 -
400
E • z
'" 300 '" e>
w • '"
c w
200
, ,
, I
, ,
, I ,
, [7 , ,
, ,
- I--
V ,
,Y
10
Z
'" • 8 ~ 0 ~
6
100
o
, , /' , ,
II , ,
, J
,
1/ , ,
, ,
,
, ,
, ,
,
- ' - -4
2
o o 20 40 60 80 100 o 20 40 60 80 100
Displacement (mm) Displacement (mm)
Figure B-1. Component Test Results for Materia l # 1: A36
Test Results for Material #2. A572 Grade 50
c:= DYNAMIC - - - STATIC I DYNAMIC - - - STATIC
600 ~-----~-------~ 16
14 500 ~ - , ,
12 /' , , , ,
400
10 E I; z z
t "" 300
I "" 6 ~ • E' ~ ... • c ~ 0 w
- I :'} ,
, ,
, - -,
, ,
,
r 6 200
, ,
4 , 100 ,
,
,
1/ ,+: ,
--
, , 2
0 0 20 40 60 60 100 0
o 20 40 60 80 100 Displacement (mm)
Displacement (mm)
Figure B-2 . Component Tes t Results for Material #2: A572
Test Results for Material #3. A516.86 Grade 70
DYNAMIC - - - STATIC] C DYNAMIC - - - STATIC I
600 16 I ,
400
E ~ z "'- 300 '" ~ • ... c - w
200
II • •
/ • • • •
7 • •
• • •
II • •
/ • •
/ ,
, ,
, ,
10
Z "'-• 8 ~ a ~
6
500
100
I •
I ~ /k II -+
, ,
, ,
, ,
[7 ,
-
'---,
-, , , ,
-, ,
,
14
12
4
, ,
/ ,
, , , o
, , . • 2
o o 20 40 60 80 100 o 20 40 60 80 100
Displacement (mm ) Displacement (mm )
Figure B-3. Component Test Results for Material #3: A5 16.86 Grade 70
Test Results for Material #4. A514-87 Grade B
DYNAMIC - - - STATIC DYNAMIC - - - STATIC I
600 i 16 I
I 14 -
500
12 - ,
400
-if- • 10
E • ~ z "- 300 '" E" • .. c
'" w
•
":f J •
•
7- -- • 6
• • ---- -6
200 • •
• 4 --
• 100 •
•
/ r: o
f----2
o o 20 40 60 60 100 o 20 40 60 60 100
Displacement (mm) Displacement (mm)
Figure 8-4. Component Test Results for Materi al #4: A514-87 Grade B
APPENDIX C. ACCELEROMETER PLOTS
Figure C- I. Longitudina l Deceleration - Test M03- 1
Figure C-2. Longitud ina l Occupant Impact Velocity - Test M03- 1
Figure C-3. Lateral Deceleration - Test M03-'
Figure C-4. Vertica l Deceleration - Test MOJ-l
Figure C-5. Longitudinal Deceleration - Test M03-2
Figure C-6. Longitudi na l Occupant Impact Velocity - Test M03-2
Figure C-7. Lateral Decelerat ion - Test M03-2
Figure C-8. Vertical Decelerat ion - Test M03-2
43
W4 M03- 1 LONGITUDINAL OCCUPANT RIDEDOWN DECELERATION
6 . 0
4. 0
2 . 0
o. 0
-2. 0
O. 0
... ! ...................... J. ..•..••
.. L ..
..••...•• j ..•. . . . t····
O. 1 O. 2
............................................ l ............... ......... ~ .. ......................... ............. , ...................... 1 .. .
. ....................................... , ................... ... + ......................•. .................... , ... ............... .;. .............. .
• .•. •...•.•..•....•. ... j .
O. 3 O. 4
! ..... +.... . . ···r ................. t···· . ·········f······ ............... + .
~ ...................... L .......................... .
O. 5 Sec
O. 6 O. 7 O. 8 O. 9
Figure C-l. Longitudinal Deceleration - Test M03-1
Wii: M03-i LON GITUDINRL OCCUP RNT IMPRCT VE LOCIT Y
, 1 . 0 ................• ·····f--··· ........ ························t····
(\v , : ....................... ; ................. --- ', --0 ••••••••• •••• ••••••••• 1 ............ .;.. O. 5
... ~ ... - ........ -··f-·· .. ····· i , O. 0 ....... ............ ... i. .... ___ _ __ ............ .
l
O. 0 O. 1 O. 2 O. 3 O. 4
........ + .....
... . ........ .,. ........ ..
+ ...
O. 5 Sec
j . ......... + .. _-- ............ ! ............................................. .
. ....... ; ............................ . --_ ........ ..1. ..................... ...[ .................... .
._-- -+--
O. 6 O. 7 O. 8 o. 9
Figure C-2 . Longitudinal Occupant Impact Ve locity - Test M03-1
W4. M03 -1 UHERRL DECELERRTION
3. 0+················+····················+·············· ....... + ...................... + ................... + ................................................... , ...... ·············i,······················,····· ·········· · .. ..... .
2 . 0 tI········· .··················'1··················+····· ·· ... L ....................... l ............... .. ...... ! .................... ! .................... L .......................• .. ................
1 . 0 ............. ·1'····1'···· ....... . .......... .j ................ , .. .... ............ , .... .,..................., .................... , .................... .
o. 0
-1. 0 ...... .
-2 . 0
O. 0
·····v ···~·~ .. vv\r·····tr-I~~~· ; , . ..
i : j : ······i··· ..................... . ... ~.
! ................ + .............................................. ~ ·······················l·························!···· ..... .
O. 1
..
i . ; i !
.................. ...................... L ........................................... _ .................... _. _._ .................... ! ....................... ~ ........................... .
O. 2 O. 3 O. 4 O. 5 Sec
O. 6
Figure C-3. Lateral Deceleration - Test M03-J
O. 7 O. 8 O. 9
W4: M03-1 VERTICAL DEC ELERATION
4. 0 .... _ .... , ...................... ! ...................... 1. ................................. ______ ._ .......................... .,. ........ _.,_ .... .
,
2. 0
! i"" I i ................... i. .................... + ...................... , ................................................................. ····f· ............... -i -- -- ...... .. .. ............................. 1. .. . : ; i
o. 0
-2.0 ..... .
O. 0
, .................... !:' ! .............. j... . ..................... .c .•....•••...•...•.. •.• : • ...•.••..•..•..•..•••• l ............ ..
O. 1 O. 2 o. 3
,
o. 4 O. 5 Sec
, ..-....................................................•..•...••.•• l- ....• _ ................ .
O. 6 O. 7 O. 8 O. 9
Figure C-4. Vertical Deceleration ~ Test M03-\
W~ : M03-2 LONGITUDINRL OCCUP RNT RIDED OWN DEC ELE RRTION
, o. 0 1
"- -j ······················4·······················+·_··· ... _-_ ........................ .
i i ! i
j
···············_··t················ ...... ~ ..... . ·----········· ·l························~-··· .. ··.
5. 0 ..... . ... .... { .................. . . ................... __ ....... , ............ -... _ ... -
! !
j~~," O. 0
I
....... . i\, .... ... xrAJ1j'''''r/\v''''- .~
-5. 0 t=.:=:::=· =;J;:==,=· ;.==;::::::::=~::::::=;:;;::::::=;J;::::::=::;:=:::;t:::=.J O. 0 O. 1 O. 2 o. 3 O. 4 O. 5 O. 6 O. 7 O. 8 o. 9
Sec
Figure C-S. Longitudinal Deceleration - Test M03-2
Wll M03-2 LONGITUDINAL OCCUPANT I MPACT VE LOCITY
: :
........................ . ......... L. ................. f ...... ;=""'. .;...' ~
~f. !. v--
! : . -../~
, .... ---- .......... , ....................... , ....... -............... . 2. 0
,
\ .......... " ... ,~ ...... " ............ + i ..... -1 ........... . ·····f ....... --- - ..... J ...................... ..!. .... . 1 . 0 . _j- ..•..•..•.•..•.••.•..•
i
! ! 0.0 !-d .... i ...................... ,. . ...... L ....................... ; ..
, ·,to. ·· .. · ........... _ ... i. ................. .. . .•.•.• •••• ••.. .. •.. .. _ ···············t-
O. 0 O. 1 O. 2 O. 3 O. 4 O. 5 Sec
O. 6 O. 7
Figure C-6. Longitud inal Occupant Impact Velocity - Test M03-2
O. 8 O. 9
WS : M03 -2 L ATERAL DECELERA T I ON
! . . ---i ...................... ..; ...................... L ........................ j ..•.•................... 4. 0
; ! ·················f························ ..... ----...... -.. ..-............. - .... ~
; i
,
2. 0 .. ............. , ................... .
O. 0
!
i ! i ................. + ..
- 2 . 0 ........ .. ............ , ...................... ; ................. ·····r .....................•. , ......... .
! ;
- 4. 0 .............. i .............. .
O. 0 O. 1 O. 2 O. 3 O. 4
1
... .......... 1. ................. -,-............ ................................... 1 ................... .
I,,'
.. ! ....................... .1 ...................... r. -- . -, ........ +
O. 5 Sec
i
........ + ........ .
O. 6
"'T" ........................................ ··r
O. 7 O. 8 O. 9
Figure C~7 . Lateral Deceleration - Test M03-2
WS M03-2 VERTICf'lL DECELER f'l TIO N
4. 0
2 0 ............. .
····¥A 1\ r1~ ~ ~ ~~ b( \(1AJ o. 0 ....... \.r"JVv
~
'"'
-2 . 0
-4. 0
O. 0 O. 1 O. 2 O. 3 O. 4- O. 5 O. 6 O. 7 O. 8 O. 9 Sec
Figure C-S. Vertical Deceleration - Test M03-2