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Longman Sales
Mr. Haroon Riaz Sheikh
87-Circular Road, Lahore, Pakistan.
+92 42-37664166
+92 300-8444061 |
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Steel Reinforced Laminated Bearing Pads:
Steel Reinforced Laminated Type: Laminated pads consisting of alternating steel Laminates and internal elastomer laminates bonded together, with top and bottom layers of steel reinforcement uniformly covered with ¼ inch of elastomer. Exposed sides shall be covered with 1/8 inch of elastomer.
A. American Association of State Highway & Transportation Officials (AASHTO)
REFERENCES:
1. AASHTO M251: Plain & Laminated Elastomeric Bridge Bearings.
B. American Society for Testing & Materials (ASTM):
2. ASTM A236/ A36M: Specification for Carbon Structural Steel.
3. ASTM A570/A570MS: Specification for Steel, Sheet and Strip, Carbon Hot Rolled Structural Quality.
4. ASTM A611: Specification for Steel, Sheet, Carbon Cold Rolled, Structural Quality.
5. ASTM D395: Test Methods for Rubber Property Compression set.
6. ASTM D412: Test Methods for Vulcanized Rubber and Thermoplastic Rubbers and Thermoplastic Elastomers.
7. ASTIM D429: Test Methods for Rubber property Adhesion to Rigid substrates .
8. ASTM D518: Test Methods for Rubber Deterioration Surface cracking.
9. ASTM D573: Test Methods for Rubber Deterioration in an Air Oven.
10. ASTM D1149: Test Methods for Rubber Deterioration Surface O-Zone Cracking in a Chamber.
11. ASTIM D2240: Test Method for Rubber property- Durometer Hardness.
12. ASTIM D4014: Specification for Plain and Steel Laminated Elastomeric Bearings for Bridges.
A. As used in these Specifications, the word “ Elastomer” or “Elastomeric” means “Rubber” the words are interchangeable.
MATERIALS:
Elastomeric Compound / Elastomer: Virgin crystallization resistant polychloroprene as the raw elastomer. Physical requirements of the elastomeric compound including the followings:-
1. Physical Properties:-
a. Hardness: ASTM D2240, Type: D durometer 60, plus or minus 6.
b. Tensile Strength: ASTM D412, 2500 psi minimum.
c. Ultimate Elongation: ASTM D512, 350 percent minimum.
2. Heat Resistance: ASTM D573 48HRS AT 212 DEGREE F.
a. Change in durometer hardness: plus 15 points max.
b. Change in tensile strength: minus 15 percent max.
c. Change in ultimate elongation: minus 40 percent max.
3. Compression Set: ASTM D395, Method B, 22 hours at 212 degree F. 35 percent max.
4. O-Zone Cracking: ASTM D1149, 100 pphm O-Zone in air by volume 20 percent strain, 104 plus or minus 2 degree F, 100 hours mounting procedure. A in accordance with the ASTM D518: no cracks.
5. Adhesion: ASTM D429, Method B, bond made during vulcanization 40 pounds per sq. inch.
6. Steel Laminates: Steel for internal reinforcement laminates shall conform with the following requirements as indicated:-
a. Steel 3/16 inch thick and Over: Steel plate conforming to ASTM A36/A36M.
b. Steel Under 3/16 inch Thick: Steel sheet conforming to ASTM A570/A570 Grade “c” or “D” or ASTM A611, Grade C or D.
c. Adhesive: Adhesive for the installation of bearing pads to concrete and steel bearing surfaces shall be a solvent free adhesive as appropriate for this particular installation.
a. Plain elastomer bearing pads and laminated steel bearing ads shall conform to the applicable requirements of ASTM D4014, Laminated fabric bearing pads shall conform to the applicable requirements of AASHTO M251.
b. Pads ½ inch or less in thickness shall be either all elastomer or laminated Pads over ½ inch thick shall be laminated. Stacking of individually laminated pads to attain thicknesses over ½ inch is not acceptable.
c. Plain elastomer bearing pads shall be molded individually or cut from previously molded strips of slabs or extruded and cut size. Cutting shall produce a smooth surface and no heating of the elastomer.
d. Laminated pads shall have reinforcement every ½ inch through the entire hickness. Reinforcement shall be parallel to the top and bottom surfaces of the ad. Elastomer and reinformcement together shall not exceed ½ inch in thickness per lamination.
e. Laminated bearing pads shall be molded as a single unit under pressure and heat. Bonding of elastomer to reinforcement laminates shall be carried out during molding. Elastomer at outer edges of bonds to external load plates shall be shaped to avoid stress concentrations.
f. Internal steel laminates shall be free of sharp edges. Top and bottom steel laminates shall be covered uniformly with ¼ inch of elastomer. Slides shall be covered uniformly with 1/8 inch of elastomer.
g. External load plates shall be protected from rusting.
h. Comply with ASTM D4014 for fabrication tolerances.