BEARING INSTALLATION - Voss Engineering, Inc.

1 BEARING INSTALLATION . xpailsioii aiid slide BEARING Upper BEARING Assembly positioned so that tliere is sufficient E assemblies generally coi~sistof upper and lower components. The upper coil1ponent contains a Upper BEARING pad support elemelits are usually fabricated from ASTM. Type A36 steel. Stainless steel contact vertical and llorizontal clearances between the pad and the retainer to allow for pad lateral expansioli and support elemel~tsuch as a steel plate surfaces wheii used, are made from long-term creep sl~ortening. aiid a coiltact element such as a sheet ASTM A240 or Type 304 staililess steel All exposed carbon steel should be of stainless steel or layer of rTFE.

2 The and sliall be at least 14 gage ( ill.) painted to retard corrosion. lower component usually coiisists of a wit11 a surface finish less than steel support elemelit, an ROF inicroiiicl~ (20 microinches, elastoil~ericor preforined fabric pad root-meail-square.) 111 addition to tlie and a contact assembly. The contact surface roughness requirement, other Lateral Cold Flow of PT1;EWith assembly call be a boiided layer of PTFE contact surfaces shall have Laminated Expansion BEARING Pads PTFE, bonded lail1inations of minimuiu Brine11 Hardness of 125.

3 Polyiuer and PTFE or a bonded steel (-70 Rockwell B). As elastomeric pads compress plate recessed to contain a layer of 1 TFE. Stainless steel contact surfaces from applied vertical loads, the pads These assemblies call be illstalled in should be coiltinuously welded to the expand laterally. Wlien tlie concrete to concrete, steel to steel and support element to prevent illfiltration elastomeric inaterial is laminated to a concrete to steel construction. of rnoisture between tlie sheet and plate. low-friction PTFE system, the PTFE. Fig. 34,35 and 36 illustrate some Tlie BEARING area of tlie contact surface inaterial also expands laterally uilless typical methods of BEARING asselnbly sllould be sufficieiltly larger tllaii tlie a special polyineric material separates attacliment.

4 Fig. 35 sliows i ~ ~ e t l ~of o d scontact area of the lower eleineilt to the elastomeric pad from the I'TFE. attacliing bearings in concrete to allow for relative 111ovement between material. This cold flow within tlie concrete constructioi~while Fig. 34 tlie elements. Contact areas of both PTFE can create long-term durability sl~owsinethods used for steel to steel upper aiid lower elemei~tsshould be problems, particularly wllen the PTFE. attacliinent. Sollie iilstallatioiis recluire protected from dirt, abrasion etc. does not recover its lateral cold flow bearings which limit il~ovementto one during INSTALLATION .

5 Wherever strain. During the test program, the direction. Examples of two such possible, the coiltact surfaces shall be lateral cold flow characteristics of PTFE. designs are shown in Fig. 36. oriented so that sliding movements bonded to plain SORBTEX, to Coinbinations of these methods and will cause dirt and dust accuin~~lationSORBTEX wit11 a polymer, to FIBER- others can be used for steel to concrete to fall froin the mating surface. LAST and to FIBERLAST wit11 a applications. polymer were measured. The results Lower BEARING Assembly of these uiiiform coinpression tests are The lower BEARING assembly usually sliowi~iii Fig.

6 A4 (on Pag 22) The test rests on a steel plate cast in concrete data indicate that the polymer layer or is attached to a steel structural dramatically reduces the lateral cold element. Support eleilients of the flow bellavior of the I'TFE wheil BEARING are usually ASTM Type A36 bonded to SORBTEX or FIBERLAST. steel, welded or bolted to the steel The design eilgineer should coiisider plate or structural element. The the expected lateral straiii 111 the BEARING pad/contact surface eleinent design BEARING w l ~ econsiderii~g i~ the can be either unrestrained free standing, use of a polymer substrate.

7 If the restrained free standing, or boi~dedto edge straiii of a FIBERLAST /. the support element, if used. Polymer / PTFE pad under rotation If welding is used to attach elemeilts exceeds about 15 percent, a piece of wit11 bonded PTFE surfaces, provisioils 10 gage stainless steel should be used i n ~ ~be s tmade to ensure that the in place of the polymer. temperature in the boild area does not exceed 300 F (150 'C). When desigiliilg retainers for the lower asseil-tbly,consideration must be given to bulge and long-term creep sliortei~iiigcharacteristics of the BEARING pad.

8 Retainers must be - Cl i~l,/l,'5 of F i x . A / -CWEBC BEHAVIOR. Illlcloic~s~ - - +. References 1 . Fiberlast--The Omni Direction BEARING Pacl of Tomorrow, Voss Engineering, hic., Chicago, Illinois, 1989, 14 pages 2. Standard Specifications for Highway Bridges, Division 1, Section 14 and 15;. Division 2, Sections 25 and 27, American Associa tion of State Highway and Transportatioli Officials (AASIJTO), Fourtee~itliEclition, 1989. 3. National Cooperative Highway Research Program Report 298, r -= - -. - - - "Performance of Elastomeric Bearings, CIII/I c,~<iilc, FIX A2 COEFFICIENT OF FRICTIOW TESTS.

9 Transportation Research Board, October, s / ,I - - _ - - - - S~ics, Mlli7. 1987. 4. I'feifer, D. W. and Iverson, J. I-'., "Liearing Pads for Precast Concrete Buildings," 1'CI Journal, Scptember/October, 1985. 5. "I'CI Design I-Jandbook-Precast ancl I'restressed Co~icrete,"Prestressed Concrete Iiistit~~tc.,Tliircl Edition, 1985 hx c r o r ~ r c / l i ~RMS. s 6. National Cooperative Highway Research I'roject lieport 248, "Elastomcric Bearings-Design,Constr~~ctio~i and Materials," Transportation Research I. Board, August, I982 1 F i t s . A3 SLIDE BEARING FRICTION TESTS S/rc:is Slrc:ss.

10 ~isi - M1111. - - 7. Roeder, C. W. and Stanton, , 0 Voss L I i ~ j i l l117'FE. ~~~l "State-of-the Art Elastomcric Bridge -A- Voss Fil11~r-l1'7-FE. -~. BEARING Design," ACI Str~~ctural Journal, Vol. 88, No. 1, January-Fcbr~~ary,1991. 8. Iverson, James K. and Pfeifer, Donald W., "Criteria for Design of BEARING Pacls," 'i Technical Report No. 4, I'restresseed Concrete I~istitutc,June, 1985. 9. Military Specification MIL-C-882E, 27. January '1989," C:loth, Duck, Cotton or Cotton-l'olyester Blend, Synthetic Rubber 1 I~iipreg~iatedand Lailiinated, Oil Resistant.