Design of Barrel Trailer for Maximum Collision Protection

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Corey Boone
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1 76 Test 5 The gardrail installation for this test as identical to that sed for tests 3 and 4. In this (essentially head-on) test, a 268-kg (456 -lb) 197-model atomobile impacted the trned-don terminal section at an angle of 5,5 and a speed of 89. km/h (55.3 mph). On impact, the vehicle dep1 essed the rail in a manner similar to that of the vehicle in test 4. lt then contin.ed astraddle of the rail, exhibiting a loamplitde, oscillatory pitching and rolling motion, and eventally stopped on the top of the rail approximately 57 m (188 ft) from the end anchor. The position of the vehicle and the damage to the gardrail are shon in Figre 24. Tenty-six posts ere split, broken, or bent over. The maxim m average. 5-s longitdinal deceleration as approximately 3 g 1 and the peak vales ere all belo 5. 5 g,. The extensive damage to the ndercarriage of the vehicle is shon in Figre 25. The repairs to the gat'drail consisted of replacing 26 posts and eight 7.6-m (25-ft) sections of rail. In some installations, e.g., bridge abtments and other fixed obstacles, the approach length of gardrail may be less than the 57 m (188 ft) traveled by this test vehicle. If a vehicle became captive at the end of the rail, it cold impact the obstacle from hich it as being protected. To obtain some indication of. the potential severity of sch impacts, a crve of velocity ve1 ss distance traveled by the test vehicle as developed from the docmentary movie film and is given in Figre 26. To avoid the possibility of sch head-on impacts, gardrail terminals shold be flared aay from the roaday. CONCLUSIONS A relatively simple method of modifying the trneddon ends of gardrail terminals has been developed. This method shold eliminate or greatly minimize the probability that a vehicle impacting them ill nmp and roll over. The hardare sed in the design are either standard gr. drau components or items that are readily available commej.'cially. Sccessfl crash tests ere condcted as described in the NCHRP Recommended Procedres (4 ). In three of the tests the vehicle impacted the mod!iied terminal section, dep1 essed tbe rail and rode over it itl1ot rolling over. REFERENCES 1. E. F. Norcllin, R. N. Field, and J. J. Folsom. Dynamic Tests of Short Sections of Corrgated Metal Beam Gardrail. lirb, Highay Research Recoi d 259, 1969 pp J. D. Michie a11d M. E. Bronstad. Gardrail Performance: End Treatments. Sothest Research Institte, Ag J. D. Michie and M. E. Bronstad. Gardrail Crash Test Evalation-Ne Concepts and End Designs. NCBRP, Rept M. E. Bronstad and J. D. Michie. Recommended Proced es for Vehicle Crash Testing of Highay Apprtenances. NCHRP, Rept. 153, Pblication of this paper sponsored by Committee on Safety Apprtenances. Design of Barrel Trailer for Maximm Collision Protection F. W. Jng, Research and Development Division, Canada Ministry of Transportation and Commnications, Ontario This reporrdcscribes a Texas type, steel-barrel trailer developed by the Highay Waysid11 Eqipment Research Office and the Eqipment Office of the Ontario Ministry of Transportation and Commnications. When attached 'lo a sign tre!(, the trailer provides maximm crash protection for occpants of impacting atomobiles in rear collisions at impact speeds of p to 1 km/h (6 mph). This means that restrained occpants ill srvive sch collisions ithot serios injries. (Crash protection is expected to be somehat less for anglar impacts.) The trailer can be toed at traveling speed and backed p at slo speed on a closed traffic lane. For fll 1notection of a orking cre, the trailer shold be attached to the kind of heavy sign trck that is presently sed in maintenance operations. Althogh the trailer is an extra piece of eqipment and reqires special driver skill hi backing, it is recommended for se on high-speed highays ith high traffic volmes, ex1,ressays. or free ays. The trailer redces impact severity considerably and is more effective than nontrailer attachments at impact speeds of 8 km/h (5 mph) or less. The first prototype tried on the road has been involved in to collisions. In both instances, the im1)act attenation and redirectionnl capabilities of the steel barrels ere sfficient to prevent injries. The connections beteen the barrel modles. hich ere originally elded, no consist of bolts and hard rbber spacers and are still being developed. In September 1974, a car aveling at an estimated speed of 13 km/ h (8 mph) strck the rear of a sign trck that as protecting a night cre ho ere making illmination meas ements. The driver oi the ca1 as killed instantly, and the trck as seve1 ely damaged (Figre 1). Althogh there ere arning systems in operation and the di iver as exceeding the legal speed limit U1e case nevertheless dl'amatically illstrates the need for greater protection from sch collisions Ior the driving pblic. The solid backs and rigid bmpers of the trcks o in se are road hazards of the greatest severity. Moreover, in the folloing year,.from Decembe to November 1975, there ere 34 collisions ith Ministry of Transportation and Commnications sign trcks in

2 77 three major districts in Ontario (Toronto, Ottaa, and Hamilton). Becase of these accidents, the Highay Wayside Eqipment Research Office and the Eqipment Office have initiated the development of a protective trailer for sign trcks. P1 ototypes have been designed and bilt, and their operations tested. The attachment of a barrel trailer can redce the probability that a straight or anglar rear or side collision ill be fatal or reslt in serios injries from abot.7to.33 (!). DESCRIPTION OF TRAILER Figre 2 shos the first prototype trailer in operation. Details of the design are shon in Figres 3 and 4. The trailer is made of 18-gage paint drms,.9 m (3 ft) high and.6 m (2 ft) in diameter, ith 355-mm (14-in) holes on theil tops and bottoms. The barrels are tied together ith adjstable steel cables and elded together by means of flat steel connectors that arch over the rims (bt this design is no being changed by the sbstittion of bolted connections). A cable sspension, hich as added before major se, is spported on top of the barrels by a stirrp. The trailer has the folloing operational feat-es. 1. It can be plled on smooth or moderately rogh roads at a normal traveling speed ithot toching the Figre 1. Damage to trck after fatal accident. Figre 4. Cable sspension of barrels on first trailer. Figre 2. Operational test of crash trailer. Figre 5. Testing of open paint drms. Figre 3. Design featres of first trailer.

3 78 grond if the distance of the barre ls from the grond is 2 mm (8 in) or more hen the trailer is standing on a horizontal plane srface. 2. It can be backed p easily by a skilled driver at a speed appropriate for setting markers. The com1ection to the trck dring the backing p operation is flexible, and the angla1 -impact behavior of the design in tllis sitation cannot be predicted ithot field testing. DESIGN FOR IMPACT ATTENUATION The trailer can be connected more rigidly for nondriving or stationary conditions by tatly engaging the chains. ln this sitation, the impact behavior can be predicted fairly accrately if the crash prope1 ties are knon and the hitch onnections are sfficiently strong. Ths, design calclations are presented for a straight rear impact. Crshing Force of Barrels Althogh the1 e a.re data for crsh forces of steel crsh testing for static forces or a slo loading rate as performed. The testing procedre is shon Jn Figre 5. Typical c1 shing forces and deformations of barrels are shon in Fire 6. The reslts of actal Figre 6. Typical force deformation of steel drm. DEFORMATION, millimetres Imm) , # 18 ( 12 mm) PAINT DRUM, 14 in or 356 mm Hole c -" 3 :;!. 5, 2 OL--'-.,.,._--, DEFORMATION, inches Figre 7. Average crshing force of steel drms (static load). HOLE DIAMETER d, mil\imelres (mm l z 7 c 6 l 5 UJ a: OL--'----''----'---'-'--'-.._-'----'O I HOLE DIAMETER IN INCHES (d)

4 79 tests are plotted in Figre 7 (the all thickness of the barrels sed in these tests cold be measred only approximately). The design criteria are given belo (1 km/ h =,6 mph and 1 kg= 2.2 lb). Property Impact speed, km/h Impact angle, Range of atomobile eights, kg Dynamic Eqations Criterion 1 8 to 2 The folloing eqations, hich may be sed for the design, are derived from the physical las of momentm and energy conservation: v=mv/(m+m) s = v 2 /2gf x (m + M)/M' e = Y,mV 2 - (m + M)v 2 here v impact velocity of atomobile, Figre 8. Velocity after impact. 5 4 mph,_ ;f 3! ffi t;: " 2 g "' > IO 15 1 m/sec MASS OF TRUCK AND TRAILER M IOOO kg lb) 2 kg (4,49 lb) 3 kg (6,614 lb) 4 kg (B,BIB lb) kg (11,52 lb) (I) (2) (3) v velocity of total mass after imµi.ct, M mass of trck and trailer, M' mass of trck only (eight on braking heels), m mass of atomobile, s skidding distance after impact, g acceleration of gravity ( 9.81 m/ s 2 (32.2 ft/ s 2 )], f coefficient of friction (assmed to be. 7), and e energy absorbed by crshing material. These eqations are independent of the crshing material and its attenation mechanics. Their soltions Figre 1. Dissipated impact energy 'ID :; E , x <> -" :;; ;!';,... >- "' 3 "' 15 2 z z 2 if) iii!!] (/) i5 1 1 V= 1 km/h (62,137mph)CAR SPEED 1. 2, 3, 5 tooo 15 MASS OF CAR Figre 11. Average atomobile deceleration kg (11,52 lb) 4 kg (B,818 lb) 3 kg (6,614 lb) 2 <g (4,49 lb) 1 kg (2,25 lb) 1 M MASS OF TRU CK ANO TRAILER 4. 5.o. lb kg IOOOkg 1, 2, 3, 2 kg 4, 5, lb. GAGE # 18 DRUM WITH 355 mm (14 in. ) HOLE GAGE # 18 DRUM WITH 39 mm ( 16 in,) HOLE MASS Of CAR Figre 9.,_ ;f ::': t.. mph 25 2 IS 1 Skidding distance after impact. M/HC 1 5 K=m+M M' i " MASS OF TRUCK ONLY I "' z "'.. _J a: Cl 1 s OL-.1...L.--L------'---' kg I lb SKIDDING DISANCE S MASS OF CAR

5 BO Figre 12. Design layot and anglar impact force components. TRAILER BARRIER SIGN TRUCK t (m+mtlv, (COM PO NENT I "' / _.,,,.,,.../!' AFTER IMPACT / / m, v,, EFORE IMPACT COMPONENT Note: V V' V cy' and are zero for straight rear hit, and VT is zero if trck is stationary Figre 13. Damaged crash trailer after glancing-blo collision ith atomobile. Figre 14. Wrecked crash trailer after anglar rear collision ith trck. crshing the steel drms. In this design there are nine ros of drns ith for drms in each ro. For a drm made of.12-mm (18-gage)steel ith45- mm (16-in) holes In its top and bottom, the static average crshing force for 65 percent of the total diameter [ 381 mm {15 in)) is approximately 24 kn (54 lb). A dynamic factoi of 1.5 mst also be applied (2, 3). Ths the enei gy-absorbing capacity.for one drm is at least E 1 = 1.5 x.381 x 24 = J (4) and, for a ro of for drms, 4E 1 = (m x G x g) x D = (dynamic force x distance) (4a) are plotted in Figres B, 9, and 1 for an impact speed of 1 km/h (62.14 mph). Crsh Design We can assme that the energy (e) is dissipated by here G = mltiple of g for average deceleration and D = crshing distance or stroke of one drm. 'I'here Iore, e have G " 4E i/mgd = [ (4 x )/ (9.81 x.381)] x 1/ m or Gm = 14 68/ m. The corresponding expression for drms ith 355-mm (14-in) holes is G = 18 35/ m; Le., an energy absorption of J / drm. These estimated average decelerations are plotted In Figre 11 for a ide range of atomobile eights. What nmber of drms shold be sed in the design? For a total mass (M) of 5217 kg (11 5 lb) the dissipation energy is 555 J for a 2-kg (44-lb) atomobile (from Figre 1). The nmbe1 of drms (11) is then 1116 = (555 / ) = 4.4 = 4 and =

81 Figre 15. Modified crash trailer. (555 / 17 145) = 32.4 = 32, be1 e llto and ni are the nmbel's of drms having 45-mm (16-in) and 355-mm (14-in) boles respectively.

6 81 Figre 15. Modified crash trailer. (555 / ) = 32.4 = 32, be1 e llto and ni are the nmbel's of drms having 45-mm (16-in) and 355-mm (14-in) boles respectively. The final design has 37 drms ith 45-mm (16-in) holes. This design pe1 mits tole1 able average decelerations for lap and sholder-belted drivers in the range of atomobile eights indicated in Figre 11 1 and drivers of heavier atomobiles old need only lap belts to have the same degree of protection that lap and sholder-belted d1 ive1 s have in smalle1 atomobiles. The design layot is shon tn Figre 12. The ave1 age crshing force and therefo1 e the ave1 age deceleration are the same for both lo and high impact speeds. Feer barrels ai e crshed by lighter atomobiles. The ti ck skids a longer distance after impacts from heavier vehicles (Figre 9). Anglar Impact Lack of knoledge abot the parameters of the system (sch as the mass moment of in.ertia of the trck and trailer combination) makes it impessible to evalate the anglar-impact behavior of the design. Bt, it can be anticipated that less energy ill be absorbed by crshing as ene1 gy is dissipated by the friction that ill accom - pany rotation 1 spinning of the system. The ave1 age deceleration ill depend on the 'impact angle and the point of contaet. COLLISIONS WITH THE FIRST PROTOTYPE TRAILER The first prototype, as shon in Figres 2, 3, 4, and 13, as sed in the smmer of 1975 to protect the operation of a lo-speed paint striper. Within 3 months, the1 e ere to collisions. The first collision occrred on the Qeen Elizabeth Way, eastbond, at 5:25 a.m. on Jne The driver of the sign trck gave the folloing 1 eport. The trck as traveling at a speed of 1 to 13 km/ h (6 to 8 mph) in the center lane behind the striper, hich as painting the to broken lines simltaneosly. The traile1 as hit a glancing blo by a compact atomobile having an estimated speed of 15 to 113 km/ h (65 to 7 mph). Only one barrel and its attached light fixt1 es ere damaged. The atomobile, hich had several occpants, as redirected, crossed to lanes, and di ove on ithot stopping. If the trailer had not been attaclied, the atomobile old probably have crashed into the right reai corner of the trck. This means that considerable accident costs and possibly hman lives ere saved in this accident. The damage to the trailer is shon in Figre 13. The second collision occrred in the right-hand lane of Highay 4, northbond, at 1:2 p.m. on Jly 14, Th.e sign trck ith the trailer attached as traveling at a speed of abot 16 km/ h (1 mph) behind the striper. The trailer as hit at a slight angle by an empty 27-kg (3-ton) trck traveling at abot 1 km/ h (6 mph). The driver of the impacting trck applied the brakes before the crash and ths the trck impact speed as pl'obably redced. The barrels on the right-hand side of the trailer ere flly or partially crshed, and the trailer as pshed nder the sign trck. The damage to the trailer as beyond repair (Figre 14). The driver of the impacting tre k as nin - jred althogh he old probably have sffered injries if his trck had hit the right-hand corner of the sign trck. FURTHER DEVELOPMENTS The trailer design as modified after an evalation of the accident performance of the first prototype. The modifications ai e shon in Figre 15. A cable sspension spported by a stirrp as monted on top of the bar1 els to increase stability dring rogh driving operations, and a bolted connection that ses steel ashers and hard i bber spacers beteen the barrels ts being developed. At the present stage of development of the trailer, several qestions remain nansered: 1. What are the exact barrier-resistance characteristics for a straight rear impact? 2. What is the behavior of the ti auer at an anglar impact of 15 or 25? 3. What is the performance of bolted connections beteen barre ls? Testing nder controlled conditions and spplementary compte1 simlations ill be necessary before these qestions can be ansered. This topic has been discssed by Jng and Billings (!, REFERENCES 1. J. C. Glennon. Roadside-Safety Improvement Programs on Freeays: A Cost-Effectiveness Priority Approach. NCHRP, Rept. 148, M. C. White and T. J. Hirsch. Highay Crash Cshions. Texas Transportation Institte, Texas A&M Un.iv., College Station, Nov E. L. Marqis, T. J. Hirsch, and J. F. Nixon. Crasb-Cshion Trailer for Highay Maintenance Operations. Texas Transportation Institte, Texas A&M Univ., College Station, Jan F. W. Jng and A. M. Billing. Impact Design of Crash Cshions for No11stationary Barriers. Ontario Ministry of Transportation and Commnications, RR 25, Jan F. W. Jng and A. M. Billings. Impact Design o.f Crash Cshions for Nonstatlonary Barriers. TRB, Transportation Research Record 594, 1976, p. 26. Pblication of this paper sponsored by Committee on Safety Apprtenances.

Techniques for Controlling Rail Corrugation

Techniques for Controlling Rail Corrugation 32 Transportation Research Record 16 Techniqes for Controlling Rail Corrgation SO'N T. LAMSON ABSTRACT Corrgation on lo rails in crved track is a common and significant problem on North American railays.