EVALUATION OF THE CRASH PERFORMANCE OF TRIPLE STEEL U-CHANNEL SIGN SUPPORT INSTALLATIONS IN STRONG SOIL

Transcription

1 EVALUATON OF THE CRASH PERFORMANCE OF TRPLE STEEL U-CHANNEL SGN SUPPORT NSTALLATONS N STRONG SOL Prepared for The Marion Steel Company 912 Cheney Ave. Marion, OH 4332 Prepared by Dean C. Alberson, P.E. Assistant Research Engineer TTl Project No MAR3 Final Report Texas Transportation nstitute Texas A&M University System College Station, TX June 1995

2 ...,_. ll APPROXMATE CONVERSONS TO Sl UNTS APPROXMATE CONVERSONS FROM Sl UNTS Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol LENGTH LENGTH in inches 25.4 millimeters mm mm millimeters.39 inches in ft feet.35 meters m m meters 3.28 feet ft yd yards.914 meters m m meters 1.9 yards yd mi miles 1.61 kilometers km km kilometers.621 miles mi AREA in 2 square inches square millimeters mm 2 mm2 square millimeters.16 square inches in 2 w square feet.93 square meters mz mt square meters square feet ft2 yd2 square yards.836 square meters mz mz square meters square yards ac ac acres.45 hectares ha ha hectares 2.47 acres mi 2 mi 2 square miles 2.59 square kilometers km 2 km2 square kilometers.386 square miles VOLUME AREA VOLUME floz fluidounces milliliters ml ml milliliters.34 fluidounces floz gal gallons liters liters.264 gallons gal t' cubic feel.28 cubic meters m3 m3 cubic meters cubic feet t' yd3 cubic yards.765 cubic meters m3 m3 cubic meters 1.37 cubic yards yd3 NOTE: Volumes greater than 1 shall be shown in m 3 MASS oz ounces grams g g grams.35 ounces oz lb pounds.454 kilograms kg kg kilograms 2.22 pounds lb T short tons (2 lb).97 megagrams Mg Mg megagrams 1.13 short tons {2 lb) T TEMPERATURE (exact) MASS TEMPERATURE (exact) OF Fahrenheit 5(F-32)/9 Celcius oc oc Celcius 1.8C +32 Fahrenheit OF temperature or (F-32)11.8 temperature temperature temperature LLUMNATON LLUMNATON fc foot-candles 1.76 lux lx lux.929 foot-candles fc foot-l.amberts candela/m 2 cdlm 2 cdlm2 candelalm foot-l.amberts FORCE and PRESSURE or STRESS FORCE and PRESSURE or STRESS lbf poundforce 4.45 newtons N N newtons.225 poundforce lbf psi poundforce per 6.89 kilopascals kpa kpa kilopascals.145 poundforce per psi square inch square inch Sl is the symbol for the nternational System of Units. Appropriate (Revised August 1992) rounding should be made to comply with Section 4 of ASTM E38.

3 DSCLAil\1ER This document is disseminated under the sponsorship of the Marion Steel Company. The contents of this report reflect the views of the author who is solely responsible for the opinions, fmdings, and conclusions presented herein. This report does not necessarily reflect the official views or policies of Texas Transportation nstitute. This report does not constitute a standard, specification, or regulation. Texas Transportation nstitute assumes no liability for its contents or use thereof. Texas Transportation nstitute does not endorse products or manufacturers. iii

4 TABLE OF CONTENTS NTRODUCTON... 1 CONSTRUCTON OF THE TEST ARTCLE... 2 Steel U-channel Supports... 2 FULL-SCALE CRASH TESTS... 4 Description of Crash Test Procedures... 4 Evaluation Criteria Electronic nstrumentation and Data Processing Anthropomorphic Dummy nstrumentation Photographic nstrumentation and Data Processing Test Vehicle Propulsion and Guidance CRASH TEST RESULTS Triple 5.9 kg/m (4. lb/ft) steel U-channel supports anchored in strong soil... 1 Test MAR CONCLUSONS AND RECOMMENDATONS REFERENCES iv

5 LST OF FGURES Page Figure 1. Specifications for Marion Steel U -channel supports Figure 2. Anthromorphic test dummy shown in restrained position prior to test MAR Figure 3. Vehicle/installation geometries before test MAR Figure 4. Vehicle before test MAR Figure 5. Vehicle properties for test MAR Figure 6. nstallation before test MAR Figure 7. After impact trajectory after test MAR Figure 8. Sequential photographs for test MAR3. (perpendicular and oblique views) Figure 9. nstallation after test MAR Figure 1. Vehicle after test MAR Figure 11. Summary of results for test MAR Figure 12. Vehicle angular displacements for test MAR Figure 13. Longitudinal accelerometer trace for impacting vehicle during test MAR Figure 14. Lateral accelerometer trace for impacting vehicle during test MAR Figure 15. Vertical accelerometer trace for impacting vehicle during test MAR v

6 LST OF TABLES Table 1. Assessment of compliance with NCHRP Report 35 evaluation criteria for test MAR vi

7 NTRODUCTON The Marion Steel Company initiated a crash-test program at the Texas Transportation nstitute (TTl) Proving Ground to evaluate the safety performance of a 5.9 kg/m (4lb/ft) triple steel U-channel support sign installation according to the new National Cooperative Highway Research Program (NCHRP) Report 35. A sign installation constructed from steel U-channel supports was erected and tested by means of a full-scale low-speed vehicular crash test. The installation was tested in "strong" soil. This report details the construction and performance of the low-speed crash test conducted on the small sign support installation when erected in NCHRP Report 35 "strong" soil. The crash test was performed and evaluated in accordance with the 1994 American Association of State Highway Transportation Officials (AASHTO) "Standards Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals"< 1 > and National Cooperative Highway Research Program (NCHRP) Report 35 "Recommended Procedures for the Safety Performance Evaluation of Highway Features" < 2 >. 1

8 CONSTRUCTON OF THE TEST ARTCLE Steel U-channel Sup_ports A triple support sign installation was constructed from Marion Steel SP-8 RB-BAK, 5.9 kg/m (4. lb/ft) steel U-channel sign supports. The sign installation was erected at a minimum height of 2.1 m (7. ft) above the elevation of the near edge of the traveled way to the bottom of the sign panel. A normal lap splice was used to connect the ground support stub and the sign support. The lap splice system securely nests the sign support behind the ground support stub. The two pieces are fastened together using HS Grade 9 steel bolts, self locking flange nuts, Grade 9 cut washers, and unique threaded spacers. The threaded spacers used are dimensionally 19 rnm (.75 in) square and drilled and tapped for a 8 rnm (5/16-18 UNC) bolt. All steel U-channel ground supports were driven with 12 rnm (4. in) remaining above grade. Following the installation of the ground support stubs, the soil surrounding the support was regraded and recompacted, as needed. The length of the U-channel supports were 3.4 m (11. ft) overall. A plywood sign panell.8 m (6. ft) wide x 1.2 m (4. ft) high was attached to the supports using three 7.9 rnm (.3 in) x 64 rnm (2.5 in) hex bolts with fender washers and hex nuts per support. Detailed specifications of the Marion Steel U-channel Lap Splice sign support type installation are shown in Figure 1. 2

9 w.. ] w (/) <( CD.. A-..' rmnm ~jbj~ B ORLL & TAP FOR 5/16"-18 UNC <ll1llld.ll. - <lllllld.ll. - t _l 3/4" -T-L ~~~.:/<~ bfd~ LAP SPLCE SPACER NOTE: ZNC PLATED SPECFCATONS DESGN A ground mounted breakaway post that incorporates Rib Bok U-Channel posts spliced at ground level by means of special bolt-splice hardware MATERAL AND FNSH Rib-Bak U-Chonnel posts shall be fabricated from hot rolled carbon steel bars conforming to the requirements of Marion Steel Company Grade SP-8. Yield point of the steel shall be 8, PS (minimum). The cost heat analysis of the steel shall conform to the following requirements: Element Carbon Manganese Phosphorous Max Sulphur Max Silicon Composition (Percent) Posts shall be a uniform, modified, flanged channel section, of the Rib-Bok design. ~~~~~~n~! i~: ~~:t~ :~~~~ ~ee p ~nc 5 tfe 6 dcif~j~ %nw;u~~:r 3/~udi~~eT~~uhol;s P~~c;~t c~~ft~~~ for the entire length of the post. The first hole shall be 1" from the top. The post shall consist of two ports, a sign post and o bose post. The sign post lengths shall be supplied in 12" increments up to 2 ft. as required for \he installation location. The base posts shall be 42" in length and pointed at one end and have at least 18 holes in the bose post, starting r from the top and continuing at,.. increments. The posts shall be machine straightened to hove a smooth uniform finish, free from defects affecting their strength, durability, or appearance. All holes and rough edges shalt be free from burrs. The permissoble tolerance for straightness shall be within 1/4" in 5 feel. Posts shall be galvanized after fabrication in accordance with the requirements of ASTM A 123. Bolts, nuts, washers and spacers shall be cadmium plated in accordance with the requirements of ASTM A 165 or zinc plated in accordance with the requirements of ASTM Splice hardware shall consist of two fully threaded, 5/16'' X 1-1 /2", Grode 9 plated, hex head bolts, with flat washers, lock washers and hex nuts per post. n addition, two 3/4" X 3/4" X 3/8" ploted spacers shall be used, per post, to stiffen the splice connection. Each spacer shall be drilled and topped with 5/16" X 18 UNC threads. The spacer shall be fabricated from hot rolled carbon steel bars conforming to ASTM A 36 or M 12. A Grode G flanged lock nut (5/16" -18) may be substituted for the lock washer and hex nul SECTON PROPERTES WEGHT DMENSONS AREA X-X AXS Y-Y AXS ibs/11. "Pi' "8" "C" "D" N!(N') S(N')!(N') S(N') , Q_ * + or - 5% ** Governing section NTENDED USE Breakaway Small Sign Supports SUPPLER: MARON STEEL co. LAP SPLCE BREAKAWAY SYSTEM OF 3 Figure 1. Specifications for Marion Steel U-channel supports.

10 FULL-SCALE CRASH TESTS Description of Crash Test Procedures According to NCHRP Report 35 guidelines, two crash tests are recommended for test level- 3 (TL3) evaluation of support structures: NCHRP Test Designation 3-6: 82C (1,88 lb) vehicle impacting the support structure at a speed of 35 km/h (21.8 mi/h) with the vehicle bumper at an impact angle between and 2 degrees. NCHRP Test Designation 3-61: 82C (1,88lb) vehicle impacting the support at a speed of 1 km/h (62.2 mi/h) with the vehicle bumper at an impact angle between and 2 degrees. The low-speed test is primarily performed for evaluating the breakaway or yielding characteristics of a test installation. The high-speed test is performed for. the purpose of evaluating the post-test article and vehicle trajectory. Occupant risks are of foremost concern in the evaluation of both the low-speed and high-speed tests. Only a low-speed crash test was performed. The sponsor elected to extrapolate the high-speed crash performance from data collected in the low-speed crash test. Evaluation Criteria The crash test was evaluated in accordance with the criteria presented in NCHRP Report 35 and the 1994 AASHTO Standards. As stated in NCHRP Report 23 and reiterated in NCHRP Report 35, "Safety performance of a highway appurtenance cannot be measured directly but can be judged on the basis of three factors: structural adequacy, occupant risk, and vehicle trajectory after collision." Accordingly, the following safety evaluation criteria from Table 5.1 of NCHRP Report 35 were used in this study: 4

11 e Structural adequacy (B) The test article should readily activate in a predictable manner by breaking away, fracturing, or yielding. (D) Detached elements, fragments or other debris from the test article should not penetrate or show potential for penetrating the occupant compartment or present undue hazard to other traffic, pedestrians, or personnel in a work zone. Deformations of, or intrusions into, the occupant compartment that could cause serious injuries should not be permitted. e Occupant Risk (F) The vehicle shall remain upright during and after collision although moderate roll, pitching and yawing are acceptable. (H) Occupant impact velocity of hypothetical front seat passenger against vehicle interior, calculated from the vehicle accelerations and.6 m (23.6 in) forward and.3 m (11.8 in) lateral displacement, shall be less than: Lon~itudinal Occupant mpact Velocity - mps Preferred 3 Maximum 5 () Highest 1 ms average occupant ridedown accelerations subsequent to instant of hypothetical passenger impact should be less than: Lon~itudinal and Lateral Occupant Ridedown Accelerations - ~' s Preferred Maximum

12 e Vehicle Trajectory (K) After collision, it is preferable that the vehicle, s trajectory not intrude into adjacent traffic lanes. (N) Vehicle trajectory behind the test article is acceptable. n addition, the 1994 AASHTO standards states: Satisfactory dynamic performance is indicated when the maximum change in velocity for a standard 1,8 pound (816.5 kg) vehicle, or its equivalent, striking a breakaway support at speeds from 2 rni!h to 6 rnilh (32 kmlh to 97 km/h) does not exceed 16 fps (4.87 mps), but preferably does not exceed 1 fps (3. 5 mps) or less. Electronic nstrumentation and Data Processin~ The test vehicle was instrumented with three solid-state angular rate transducers to measure roll, pitch and yaw rates; a triaxial accelerometer near the vehicle center-of-gravity to measure longitudinal, lateral, and vertical acceleration levels; and a back-up biaxial accelerometer in the rear of the vehicle to measure longitudinal and lateral acceleration levels. The accelerometers were strain gauge type with a linear millivolt output proportional to acceleration. Electronic signals from the accelerometers and transducers were transmitted to a base station by means of a constant bandwidth FM/FM telemetry link. Calibration signals were recorded before and after the tests, and accurate, time reference signals were recorded simultaneously with the data. A pressure sensitive switch on the bumper of the impacting vehicle was actuated just prior to impact by wooden dowels to indicate the elapsed time over known distances to provide measurement of impact velocity. The initial contact also produced an, event, mark on the data record to establish the exact instant of contact with the test installation. The multiplex of data channels, transmitted on one radio frequency, was received at the 6

13 data acquisition station, and demultiplexed into separate tracks of nter-range nstrumentation Group (RG} tape recorders. After the test, the data were played back from the tape machines, filtered with ansae J211 filter, and digitized using a microcomputer. The digitized data were then processed using two computer programs: DGTZE and PLOT ANGLE. Brief descriptions of the functions of these two computer programs are provided as follows. The DGTZE program uses digitized data from vehicle-mounted linear accelerometers to compute occupant/compartment impact velocities, time of occupant/compartment impact after vehicle impact, and the highest 1-ms average ridedown acceleration. The DGTZE program also calculates a vehicle impact velocity and the change in vehicle velocity at the end of a given impulse period. Maximum average accelerations over 5-ms intervals in each of the three directions are computed. For reporting purposes, the data from the vehicle-mounted accelerometers are flltered with a 6 Hz digital filter and acceleration versus time curves for the longitudinal, lateral, and vertical directions are plotted using a commercially available software package (QUATTRO PRO). The PLOTANGLE program uses the digitized data from the yaw, pitch, and roll rate transducers to compute angular displacement in degrees at.67-second intervals and then instructs a plotter to draw a reproducible plot: yaw, pitch, and roll versus time. These displacements are in reference to the vehicle-ftxed coordinate system, with the initial position and orientation of the vehicle-fixed coordinate system being that which existed at initial impact. Anthropomorphic Dummy nstrumentation An un-instrumented Alderson Research Laboratories Hybrid, 5th percentile male anthropomorphic dummy, restrained with lap and shoulder belt, was placed in the driver's position of the vehicle. The anthropomorphic dummy used in the test reported herein is shown in Figure 2. Photo~raphic nstrumentation and Data Processin~ Photographic coverage of the test included two high-speed cameras; one with a field of view perpendicular to and aligned with the test installation and one placed downstream of the test 7

14 Figure 2. Anthromorphic test dummy shown in restrained postion prior to test MAR3. 8

15 article at an angle of approximately 45 degrees. Flash bulbs visible from each camera were activated by pressure sensitive tape switches positioned on the impacting vehicle to indicate the instance of contact with the test installation. The films from these high-speed cameras were analyzed on a computer-linked Motion Analyzer to observe phenomena occurring during the collisions and to obtain time-events, displacements and angular data. A professional Betacam video camera and 35 nun still cameras were used to document the pre-test and post-test conditions of the vehicle and test installation. Test Vehicle Prqpulsion and Guidance The test vehicle was towed into the test installation using a steel cable guidance and reverse tow system. A steel cable for guiding the test vehicle was tensioned along the impact path, anchored at both ends, and threaded through a guide plate attachment anchored to the front wheel of the test vehicle. An additional steel cable was connected to the test vehicle, passed around a pulley near the impact points and attached to a tow vehicle. A 1 to 1 speed ratio existed between the test and tow vehicle for the low-speed crash test. Just prior to impact with the test installation, the test vehicle was released to be free-wheeling and unrestrained. The vehicle remained freewheeling, i.e., no steering or braking inputs, until the vehicle cleared the inunediate area of the test site, at which time brakes on the vehicle were activated to bring the vehicle to a safe and controlled stop. 9

16 CRASH TEST RESULTS Triple 5.9 k~:/m (4. lb/ft) steel U-channel supports anchored in stron~: soil Test MAR3 A 1991 Ford Festiva, shown in Figures 3 and 4, was used for the crash test. Test inertia weight of the vehicle was 82 kg (1,88 lb) and its gross static weight was 896 kg (1,975 lb). The height to the lower edge of the vehicle bumper was 355 mm (14.2 in) and it was 53 mm (2.9 in) to the upper edge of the bumper. Additional dimensions and information on the vehicle are given in Figure 5. The vehicle was directed into the triple 5.9 kg/m (4. lb/ft) steel U-channel sign installation anchored in strong soil, shown in Figure 6, using the cable reverse tow and guidance system, and was released to be free-wheeling and unrestrained just prior to impact. The vehicle impacted the centerline of the sign installation with the centerline of the vehicle at a speed of km/h (21.73 mi/h) and a zero degree heading angle. As the vehicle impacted the sign installation, the supports began to deflect rearward. The outside supports fractured at approximately.27 second and the center support at.37 second. The center support fractured at bumper level and the outside supports failed at the splice connections. As the vehicle continued traveling forward, the supports separated from the vehicle at.245 second. The sign panel was rotating away from the vehicle at 16 degrees per second when separation occurred. The vehicle came to rest approximately 1.8 m (35.5 ft) downstream from the point of impact with the base of the supports under the front of the vehicle. Final rest positions of the vehicle and sign installation are shown in Figure 7. Sequential photographs of the crash test are shown in Figure 8. As shown in Figure 9, the supports were fractured and the support stubs displaced. The center support failed at a height of 46 mm (16. in) from ground level, the outside supports failed at the splice connections. Damage sustained by the vehicle during this test is shown in Figure 1. The vehicle sustained very minor damage to the bumper and the driver's side headlight. The vehicle occupant compartment was not deformed. Data from the accelerometer located at the center-of-gravity were digitized for evaluation of occupant risk and were computed as follows. n the longitudinal direction, occupant impact 1

17 Figure 3. Vehiclefmstallation geometries before test MAR3 11

18 Figure 4. Vehicle before test M:AR3. 12

19 DATE: 5/9/95 NO t.1AR3 YN NO.:KNJPTOSHBt WCE..._.._Eo r..,d... UODEl.: Eest!vg YEAR: 1991 ODOUETER: 7372 TRE srzf P145/8R12 '. TEST TRE NFLATON~ LF ,9... RF' ,... LR 1.L5.a8.. RR.1_..51aoj3t... OESCR8E AHf DAMAGE TO VEHCLE PROR TO TEST: ENGNE TYPE 4 Cfl ggs ENGNE em: 1. 3 liter TRANSMSSON TVP : _AUTO X. UANUAl. OPTONAL EQUPMENT: MASS - (kg) CURB Ml 525 M2 29 MT 815 TEST NERTAL GROSS STATC Figure 5. Vehicle properties for test :MA.R3. 13

20 Figure 6. nstallation before test MAJ13. 14

21 . s.37 s.73 s.11 s Figure 8. Sequential photographs for test MAR3. (perpendicular and oblique views) 16

22 .147 s.184 s.22 s.257 s Figure 8. Sequential photographs for test MAR3 (continued). (perpendicular and oblique views) 17

23 Figure 9. nstallation after test MARJ. 18

24 Figure 1. Vehicle after test MAR3. 19

25 velocity was 4.91 m/s (16.11 fils) at.171 s, the highest.1-s average ridedown acceleration was -.4 g between.174 and.184 s, and the maximum.5-s average acceleration was -7.5 g between.7 and.57 s. Lateral occupant impact velocity was.58 m/s (1.91 fils) at 1.36 s, the highest.1-s occupant ridedown acceleration was -.66 g between.175 and.185 s and the maximum.5-s average acceleration was -.44 g between.8 and.13 s. These data and other pertinent information from the test are summarized in Figure 11. Vehicular angular displacements are displayed in Figure 12. Vehicular accelerations versus time traces filtered digitally at 6Hz are presented in Figures 13 through 15. The NCHRP Report 35 evaluation criteria and the assessment of the performance of this installation with respect to those criteria are presented in Table 1. 2

26 O.OOOs.73 s.147s.22s 1.8 m ~D±ro=o - 1'-) General nformation Test Agency.... Test No Date Test Article Type Name or Manufacturer Bottom of sign height (m) Support material. Number of supports.. SQil Type and Condition.. Test Vehicle Type Designation..... Model Mass (kg) Curb Test nertial Dummy Gross Sta~ic Texas Transportation nstitute MAR3 5/9/95 Small sign support Marion Steel 2.1 m (7.ftl 5.95 kg/m (4 lb/ft) steel u-channel Three Strong soil, slightly damp Production 82C 1991 Ford Festiva 779 (1717 lb) 82 (1881b) 76 (1681b) 896 (1975 lb) mpact Conditions Speed (km/hl. Angle (deg).. Exit Conditions Speed (km/hl..... Angle (deg) Occupant Risk Values mpact Velocity (m/s) x-direction... y-direction... THV (optional) Ridedown Accelerations (g's) x-direction y-direction. PHD (optional) AS (optional) Max..5-sec Average (g's} x-direction y-direction z-direction (21.73 mi/hl N/A N/A 4.91 (16.11 ft/s).58 (1.91 ft/sl Test Article Deflections (m) Dynamic... Permanent.... Vehicle Damage Exterior VDS... CDC... nterior OCD Maximum Exterior Vehicle Crush (mm).. Max. Occ. Compart. Deformation (mm) Post-mpact Behavior Max. Roll Angle (deg) Max. Pitch Angle (deg) Max. Yaw Angle (deg) N/A N/A 12F-1 12FDLN1 ASOOOOOOO N/A NA Figure 11. Summary of results for test MAR3.

27 (f) OJ OJ L Ol OJ..., MAR3 r- )( -~ Pitch Roll.y_ ~ fi?r.'?[5:'--..-' ' ~~'i ~ y.z ry"~'~ Axes are vehicle fixed. Sequence for determining orientation is: 1. Yaw 2. Pitch 3. Roll N +J c OJ E OJ u ro r-1 Q (f) r L _ Time (Seconds) PA3.9 Figure 12. Vehicle angular displacements for test MAR3.

28 CRASH TEST MAR3 Accelerometer at center-of-gravity 15-6Hz Filter 5-msec Average T - - T - - T - - T - - T - - T - - T - - t-.) w ~ ell -bl) '-" s:: - «i 1-< (!)... (!) C,) C,) < Sl--t--t--t--t--t--t--t-- - ~ ~ :l - v -T--T--T--T--T--T--T t-v \f- - _L - - _L - - _L - - _L Test Article: Marion Triple Sign Support mpacting Vehicle: 1991 Ford Festiva Test nertia Weight: 82 kg (188 lb) Gross Static Weight: 896 kg (1975 lb) Test Speed: km/h (21.73 mi/h) Test Angle: deg Time After mpact (seconds) Figure 13. Longitudinal accelerometer trace for impacting vehi~le during test MARJ.

29 CRASH TEST MAR3 Accelerometer at center-of-gravity 15-, , , , ~------, ~------~------~ N ~ ~ ~... ~ [) Q) ~ ~ [) ~ :l -5 - T l_ T l_ T T l_ T l_ T l_ T l_ 6Hz Filter -- T T T l l l_ T T 5-msec Average Test Article: Marion Triple Sign Support mpacting Vehicle: 1991 Ford Festiva Test nertia Weight: 82 kg (188 lb) l_ -1 - Gross Static Weight: 896 kg (1975 lb) f-- -- Test Speed: km/h (21.73 mi/h) Test Angle: deg _L_ -15 _l --+--~~-7:---~-~~~-;;--~ Time After mpact (seconds) T Figure 14. Lateral accelerometer trace for impacting vehicle during test MARJ.

30 CRASH TEST MAR3 Accelerometer at center-of-gravity 15-6Hz Filter 5-msec Average T--T-- T --T- - T--T--T-- N V i 5 ~--t--t--t--t--t--t--t-- g ~ ~. n ~ A A 1-< Q)... Q) - j -511~~ +v- _ _L - - _L - - _L - - _L Test Article: Marion Triple Sign Support mpacting Vehicle: 1991 Ford Festiva Test nertia Weight: 82 kg (188 lb) Gross Static Weight: 896 kg (1975 lb) Test Speed: km/h (21.73 mi/h) Test Angle: deg Time After mpact (seconds). Figure 15. Vertical accelerometer trace for impacting vehicle during test MARJ.

31 Table 1. Assessment of compliance with NCHRP Report 35 evaluation criteria for test MARl Test No. : MARl Test Date: 2/16/95 Test Agency: Texas Transportation nstitute Structural Ad~g,uac~ Evaluation Criteria Test Results Assessment B. The test article should readily activate in a predictable The sign supports fractured near bumper level and at the splice. Pass manner by breaking away, fracturing, or yielding. Occupant Risk D. Detached elements should not penetrate the occupant The sign supports yielded and did not present a hazard to other compartment, or present an undue hazard to other traffic, travel lanes. There was no deformation of or intrusion into the Pass pedestrians, or personnel in a work zone. Deformations of occupant compartment. the occupant compartment that could cause serious injuries should not be permitted. N '1 F. The vehicle should remain upright during and after collision The vehicle remained upright and stable throughout the test period. Pass although moderate roll, pitching and yawing are acceptable. H. Occupant impact velocities should satisfy the following: Occupant mpact Velocity Limits (m/s) Longitudinal occupant impact velocity: rnls (16.11 ft/s) Pass Component Preferred Maximum Lateral occupant impact velocity:.58 m/s (1.91 ft/s) Longitudinal and Lateral 3 5. Occupant ridedown accelerations should satisfy the following Occupant Ridedown Acceleration Limits (G's) Longitudinal Occupant Ridedown Acceleration: -.4 g's Pass Component Preferred Maximum Lateral Occupant Ridedown Acceleration: -.66 g's Longitudinal and Lateral 15 2 Vehicle Trajectorx K. After collision it is preferable that the vehicle's trajectory not The vehicle trajectory was judged to be acceptable. Pass intrude into adjacent traffic lanes.

32 CONCLUSONS AND RECOMMENDATONS A triple 5.9 kg/m steel U-channel sign support installation was crash tested and evaluated in this study. Performance evaluation summary of the low-speed crash test performed was presented in Table 1. Triple 5.9 kglm (4. lb/ft) steel U-channel sign installation The 5.9 kg/m (4. lb/ft) steel U-channel triple support sign installation performed satisfactorily in the crash test conducted in strong soil. n summary, the 5.9 kg/m (4. lb/ft) steel U -channel support installation yielded to the impacting vehicle by the center support fracturing at bumper level or approximately 46 mm (16. in) up from the bottom of the support. The outside upports fractured at the splice connection. n addition, the left ground support was displaced approximately 63.5 mm (2.5 in), the center ground support was displaced 19. mm (.75 in), and the right ground support was displaced 6.4 mm (.25 in). The installation did fail at the lap splice connection in this test as well as at bumper level on the center support. The detached elements of the sign installation were safely displaced away and did not present secondary hazards to other motorists. The vehicle sustained minor damage in the low-speed test. The occupant compartment integrity was not compromised. Additionally, the vehicle remained stable throughout the collision sequence without exhibiting any instability or tendency to roll over in this installation configuration. The occupant impact velocities and ridedown accelerations were well within the current recommended limits of5. m/s (16.4 fils) and 2 g's, respectively. This sign installation is considered acceptable for low-speed impacts according to the criteria presented in NCHRP Report

33 REFERENCES 1. "Standards Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, American Association of State Highway and Transportation Officials (AASHTO), Washington, D.C., Ross, Jr., H. E., Sicking, D. L., Zimmer, R. A., and Michie, J. D., "Recommended Procedures for the Safety Performance Evaluation of Highway Features," NCHRP Report 35, Transportation Research Board, National Research Council, Washington, D. C.,