Subject: ACTION: Crash Testing of Bridge Railings May 30, 1997

Transcription

1 Subject: ACTION: Crash Testing f Bridge Railings May 30, 1997 Frm: Chief, Federal-Aid and Design Divisin T: Reginal Administratrs Federal Lands Highway Prgram Administratr On August 28, 1986 and n August 13, 1990, the Office f Engineering sent yu listings f bridge railing designs that were cnsidered acceptable fr use n Federal-aid prjects by virtue f their crash test perfrmance. As nted in the transmittal memranda, sme f these railings had been tested under the Natinal Cperative Highway Research Prgram (NCHRP) Reprt 230 and sme under the 1989 AASHTO Guide Specificatins fr Bridge Railings. Since the FHWA has nw adpted NCHRP Reprt 350 as the guideline fr testing all radside hardware, including bridge railings, we reviewed these listings and assigned each railing n the lists a rating that we cnsider apprximately equivalent t ne f the six test levels suggested in NCHRP Reprt 350. These equivalency listings, alng with a third listing which identified additinal bridge railings tested after the 1990 memrandum, were included in a paper we presented t the AASHTO Highway Subcmmittee n Bridges and Structures n May 14, A cpy f this psitin paper, withut the riginally accmpanying lists, is attached fr yur reference. Als attached are revised cpies f the three lists with sketches fr each cited design. We have added several additinal railings t the third list. Please nte that thse railings which were specifically tested t NCHRP Reprt 350 criteria are nw identified in bld type, whereas thse assigned an equivalent test level based n earlier testing guidelines are shwn in regular type. The equivalent test levels are cnservative and may be subject t further evaluatin in sme cases as additinal NCHRP Reprt 350 tests are run n these railings r n similar systems. Recgnizing that these lists are nt ratinally rganized and that the quality f many f the accmpanying sketches is pr, we wish t cnslidate and rerganize the three lists int a single list and prvide a drawing f each bridge rail that is similar in detail t the drawings in the AASHTO- AGC-ARTBA Guide fr Standardized Highway Barrier Hardware (SB-series drawings). T aid us in this effrt we wuld appreciate yur ding the fllwing: Tell us which States within yur regin are currently using which f the railing designs identified n the three lists. Prvide us with a set f drawings f each f the railings n the lists that are used in yur Regin. Where there are duplicatins r slight variatins f nminally the same railing used by different agencies, nly ne drawing fr that type f railing need be sent. Hwever, we wuld appreciate a brief verbal descriptin f any differences and an assessment f their significance. Tell us f any railings nt n ne f the lists that any State within yur Regin plans t use n the NHS after September 30, We wuld als appreciate receiving

2 drawings f these railings and infrmatin n any crash tests that have been run n these designs. Infrmatin n railings develped and tested fr use n Federal Lands Highways will be requested frm that ffice. Respnses by July 15 wuld be appreciated. When we have received the requested infrmatin, a cnslidated listing with drawings will be sent t each field ffice, and we will keep this listing current as additinal designs are tested. Please address any questins regarding this effrt t Mr. Richard Pwers at (202) (riginal signed by Dwight A. Hrne) 4 Attachments Dwight A. Hrne

3 BRIDGE RAILING DESIGN AND TESTING A Discussin with the AASHTO Highway Subcmmittee n Bridges and Structures Technical Cmmittee (T-7) fr Guardrail and Bridge Rail May 14, 1996 Until the late 1980's, designers relied n precedent, the infrmatin cntained in the mst recent editin f the AASHTO Standard Specificatins fr Highway Bridges, and their judgement t design a bridge railing apprpriate fr a given site. The Standard Specificatins, as they still d, called fr the applicatin f a 10-Kip static lad at key lcatins n the railing as well as sme dimensinal requirements fr the penings between rail elements and ther crss sectin gemetry. Full-scale crash testing was nt required, althugh a design that passed crash testing culd be used even if it did nt meet the static lading and/r gemetric design criteria. The test requirements generally accepted by highway agencies at the time were cntained in the Natinal Cperative Highway Research Prgram (NCHRP) Reprt 230, Recmmended Prcedures fr the Safety Perfrmance Evaluatin f Highway Appurtenances, (Tw earlier publicatins with this title, NCHRP Reprt 153,1974, and Transprtatin Research Circular Number 191, 1978, and the Highway Research Bard publicatin, Highway Research Crrelatin Service Circular 482, Prpsed Full-Scale Testing Prcedures fr Guardrails, 1962, als prvided testing guidance.) In the late 1970's and early 1980's, actual tests were run n several cmmnly-used railings that had been designed under the static lading prcedures. The results were unexpected: several f the railings failed quite dramatically and it was shwn that static design ladings were nt sufficient t ensure adequate railing perfrmance. As a result f these findings, Mr. R.D. Mrgan, FHWA s Executive Directr, issued a plicy memrandum n August 28, 1986, that stated that railings n bridges n Federal-aid prjects must be (r have been) crash tested and meet the acceptance criteria in NCHRP Reprt 230 r equivalent acceptance prcedures. Included with that memrandum was a list f 22 railings that were cnsidered crashwrthy based n previus testing. In 1989 AASHTO published its Guide Specificatins fr Bridge Railings, a dcument that nt nly specified tests t be run, but categrized them int three separate perfrmance levels. This publicatin als included a selectin prcedure fr determining an apprpriate perfrmance level fr a given site. The crash test matrix included in the Guide Specificatins differed in several areas frm the NCHRP Reprt 230 test matrices, and its use by State highway agencies was (and remains) ptinal. On August 13, 1990, the FHWA issued a secnd memrandum listing 25 additinal railings that had met the requirements in NCHRP Reprt 230 r ne f the perfrmance levels in the AASHTO Guide Specificatins. This memrandum als stated that the FHWA cnsidered any railing that was acceptable based n NCHRP Reprt 230 testing culd als be cnsidered

4 acceptable at least as a PL-1 Attachment 1 railing as described in the Guide Specificatins. In additin, it indicated that any SL-1 railing (as develped by Suthwest Research Institute and reprted in NCHRP Reprt 239, Multiple- Service-Level Highway Bridge Railing Selectin Prcedures, Nvember 1981) culd als be cnsidered equivalent t a PL-1 railing. NCHRP Reprt 230 was superseded by NCHRP Reprt 350, Recmmended Prcedures fr the Safety Perfrmance Evaluatin f Highway Features, in This dcument includes six different Test Levels, all f which differ in sme ways frm the previus Reprt 230 basic test matrix as well as frm the Perfrmance Levels cntained in the Guide Specificatins. N selectin prcedures fr the use f a specific test level are included in Reprt 350. And finally, t add t the cnflicting guidance fr selecting an apprpriate bridge railing, AASHTO issued its 1994 LRFD [Lad and Resistance Factr Design] Bridge Design Specificatins as an alternate t the lng-standing Standard Specificatins fr Highway Bridges. Sectin 13 f the new publicatin cntains recmmendatins n railing designs and a crash test matrix that differs frm NCHRP Reprt 350 and the AASHTO Guide Specificatins. FHWA s current psitin can be summarized as fllws: All bridge railings installed n NHS prjects let t cntract after August 16, 1998, shall meet the acceptance criteria cntained in NCHRP Reprt 350 r an FHWA recgnized successr t thse criteria. The minimum acceptable bridge railing will be a TL-3 (MSL-2 until August 1998) unless supprted by a ratinal selectin prcedure. Acceptability under NCHRP Reprt 350 and a ratinal selectin prcedure are defined belw. Railings that have been fund acceptable under the crash testing and acceptance criteria in NCHRP Reprt 230, the AASHTO Guide Specificatins fr Bridge Railings, r the AASHTO LRFD Bridge Design Specificatins will be cnsidered as meeting the requirements f NCHRP Reprt 350 withut further testing as indicated in the fllwing table. RAILING LEVEL EQUIVALENCY TABLE BRIDGE RAILING TESTING CRITERIA ACCEPTANCE EQUIVALENCIES NCHRP Reprt 350 TL-1 TL-2 TL-3 TL-4 TL-5 TL-6 NCHRP Reprt 230 MSL-1 MSL-2* MSL-3 AASHTO Guide Specificatins PL-1 PL-2 PL-3

5 AASHTO LRFD Bridge Specificatins PL-1 PL-2 PL-3 * This is the perfrmance level usually cited when describing a barrier as tested under NCHRP Reprt 230. It is clse t a TL-3 but adequate TL-3 perfrmance cannt be assured withut a pickup truck test. The FHWA strngly suggests that the AASHTO adpt the test level definitins in NCHRP Reprt 350. The FHWA strngly recmmends that all future testing f bridge railings be cnducted in accrdance with the recmmendatins in Reprt 350 r an FHWA-recgnized successr t Reprt 350. The FHWA strngly encurages the AASHTO t supprt the nging NCHRP effrts t develp railing level selectin prcedures and, after apprpriate review and, if needed, adjustment, adpt railing level selectin prcedures. Until the AASHTO adpts a new railing level selectin prcedure the FHWA will accept the prcedures in the Guide Specificatins fr Bridge Railings r a ratinal, experiencebased, cst-beneficial, cnsistently-applied prcedure prpsed by a State. Exceptins t the items in this psitin, which are expected t be rare, will be cnsidered n their merits n a case-by-case basis. Attached is a list f the railings that are cnsidered acceptable under the guidelines in NCHRP Reprt 350 r the presumed equivalent guidelines indicated in the Railing Level Equivalency Table. This list will be supplemented with sketches f each railing sn. Omissin f a railing frm this list may be the result f an versight r a judgement that a particular railing is unlikely t be used. Therefre, the list shuld nt be cnsidered all-inclusive. As is currently the case, any railing that is essentially the same as ne that was successfully tested, even thugh nt identical, may ften be cnsidered acceptable as well. J. H. Hattn FHWA HNG-10 7 May 96 3

6 EQUIVALENT TEST LEVELS FOR CRASH-TESTED BRIDGE RAILINGS - PART NCHRP 239 SL-1 Thrie beam, wd psts TL NCHRP 239 SL-1 Thrie beam, steel psts TL Texas Type 6 (tubular w-beam) TL Aluminum Tru-beam (mdified AASHTO BR5) TL AASHTO BR2 (Califrnia Type 9) TL Ohi Bx Beam Rail (w-beam backed with bx beam) TL Mdified Kansas Crral (pen cncrete beam and pst) TL Oklahma Mdified TR-1 (pen cncrete beam and pst) TL Oregn 2-Tube Curb-Munted Rail TL Nrth Carlina Standard 1 Bar Metal Rail TL Texas T101 Bridge Rail TL Nebraska Tubular Thrie Beam TL Califrnia Type 20 (NJ Safety Shape with Rail) TL Nevada Safety Shape Parapet (NJ Shape with Rail) TL New Jersey Cncrete Safety Shape TL F Prfile Cncrete Safety Shape TL NJ Turnpike Heavy Vehicle Barrier TL Texas T5 Mdified TL-6 Attachment 2

7 EQUIVALENT TEST LEVELS FOR CRASH-TESTED BRIDGE RAILINGS - PART Oregn Side-Munted Thrie Beam TL Texas T202 Cncrete Beam and Pst TL Federal Lands Mdified Kansas Crral TL Nebraska Cncrete Beam and Pst TL Iwa Cncrete Beam and Pst TL Califrnia Type 115 TL Washingtn 10 gage Thrie Beam Retrfit TL Califrnia Thrie Beam TL Glu-Lam Wd Rail n Timber Deck TL Texas 411 Aesthetic Cncrete Baluster TL Texas T421 Aesthetic Steel Pipe Bridge Rail TL Aesthetic Stne Masnry-Faced Cncrete TL Missuri Thrie Beam and Channel TL Wyming Curb-Munted 2-Tube (Tw Designs) TL-3 ( see Acceptance letter B-37) TL Michigan 10 gage Retrfit n curb/sidewalk TL Iwa Cncrete Blck Retrfit TL in Vertical Cncrete Parapet TL Pre-cast NJ r F-Shape blted t deck (see Acceptance letters B-5 and B-5A) TL Illinis Rail n Curb TL in Vertical Cncrete Parapet TL in F Shape Cncrete Barrier TL Texas Type HT (Mdified T5) TL Mdified Texas C202 Bridge Rail TL-5 Attachment 3

8 EQUIVALENT TEST LEVELS FOR CRASH-TESTED BRIDGE RAILINGS - PART 3 Railings fr Timber Bridges: 3-1 Timber rail-system 1 TL Timber rail-system 2 TL Timber rail-system 3 TL Steel System-Thrie beam n steel psts TL Curb System- Glu-Lam timber rail w/ curb TL She Bx System-Glu-Lam rail w/ut curb TL TBC-8000-Thrie-beam w/ stiffened steel psts TL GC-8000 Glu-Lam timber rail w/ curb TL-4 (see Acceptance letter B-31 fr 3-4 thrugh 3-8 designs) Railings fr Cncrete Bridges: 3-9 Texas C411 42" Cncrete Baluster Rail TL BW Parkway Smth Stne Bridge Rail TL West Virginia W-beam Retrfit Railing fr Cncrete Baluster designs TL Fthills Parkway Aluminum Bridge Rail TL GW Parkway Steel Tri-Rail n curb TL Natchez Trace Cncrete Bridgerail (pst and beam) TL Washingtn, D. C. Histric Bridgerail (curb-munted retrfit) TL BR27D-tw steel rails n 18" cncrete parapet w/ curb and sidewalk TL BR27D-flush-munted TL BR27C-single steel rail n 24" cncrete parapet w/ curb and sidewalk TL BR27C-flush-munted TL Nebraska Open Cncrete Bridgerail (mdified frm earlier TL-2 design) TL Missuri 30" NJ Cncrete Barrier (t test effect f 3" verlay n standard height) TL Illinis Side-munted railing TL New England Transprtatin Cnsrtium (NETC) 2-rail curb-munted railing TL-4 (see Acceptance letter B-50) 3-24 Delaware Thrie-beam Retrfit Railing (curb-munted) TL Wyming 2-tube steel railing n curb TL-4 (see Acceptance letter B-37) 3-26 Minnesta Cmbinatin Bridge Rail TL Single Slpe Cncrete Bridge Rail TL-4 (see Acceptance letter B-45A) Attachment 4