Section 4195. Bearing Pads

4195.01 LEAD.

Furnish sheet lead for bearing areas meeting the requirements of ASTM B 29.

 

4195.02 NEOPRENE BEARING PADS.

 

A. Fabricate the elastomer portion of the pad from new neoprene. Cast pads under heat and pressure. They may be individually molded to the size and shape specified in the contract documents, or they may be cut from pressure cast stock. Ensure cut edges are at least as smooth as ANSI 250 finish. Variations in dimensions shown are not to exceed the values in Table 4195.02-1:

 

Table 4195.02-1: Maximum Dimension Variations

 

Nonlaminated

Laminated

Thickness

+ 1/16 inch

(2 mm)

+ 1/8 inch

(3 mm)

Width

- 1/8 inch, + 1/4 inch

(-3 mm, + 6 mm)

- 1/8 inch, + 1/4 inch

(-3 mm, + 6 mm)

Length

- 1/8 inch, + 1/4 inch

(-3 mm, + 6 mm)

- 1/8 inch, + 1/4 inch

(-3 mm, + 6 mm)

 

B. Furnish pads in one piece, not laminated in any manner, unless specified otherwise in the contract documents.

 

C. If pads are laminated, they are to have alternate laminations of neoprene and rolled steel sheets molded together as a unit. Unless required otherwise, meet the following requirements for pads:

 

1. The thickness of metal laminations: in the range of 14 gage to 1/8 inch (1.5 mm to 3.5 mm) inclusive.

 

2. Outer laminations of neoprene: 1/4 inch (6 mm).

 

3. Edges of all metal laminations covered by a minimum of 1/8 inch (3 mm) of neoprene, except at laminate restraining devices and around holes that will be entirely closed on the finished structure.

 

D. For the neoprene in laminated pads, meet the requirements in Table 4195.02-2, as specified by the Engineer. Compounds of nominal hardness between the values shown may be used, and test requirements interpolated. For homogeneous pads, the neoprene is to meet the requirements of Table 4195.02-2, using a durometer hardness of 70 unless the Engineer specifies otherwise.

 

Table 4195.02-2: Neoprene Requirements

ASTM
Standard

Physical Properties

50 Duro.

60 Duro.

70 Duro.

D 2240

Hardness

50 + or - 5

60 + or - 5

70 + or - 5

D 412

Tensile Strength, minimum psi (MPA)

 

 

Ultimate elongation, minimum %

2250

(15.5)

 

 

 

400

2250

(15.5)

 

 

 

350

2250

(15.5)

 

 

 

300

D 573

70 hr.

212F

(100C)

Heat Resistance

Change in durometer hardness, maximum points

Change in tensile strength, maximum %

Change in ultimate elongation, maximum %

 

+15

 

 

 

-15

 

 

 

-40

 

+15

 

 

 

-15

 

 

 

-40

 

+15

 

 

 

-15

 

 

 

-40

D 395

Method B

Compressive Set

22 hours @ 212F (100C), maximum %

 

35

 

35

 

35

D 1149

20% strain

Ozone

100F 2F (38C 1C),

100 hours

100 pphm ozone in air by volume

 

No
Cracks

 

No
Cracks

 

No
Cracks

D 429, B

Adhesion

Bond made during vulcanization
minimum lbs. per inch (N/mm)

 

40 (7)

 

40 (7)

 

40 (7)

D 746

Procedure B

Low Temperature Test

Brittleness at -40F (-40C)

No

Failure

No

Failure

No

Failure

Ensure laminates are fabricated from rolled mild steel sheets conforming to ASTM A 1011/A 1011M, Grade 33; Grade 36, Type 1 and 2; or Grade 40, unless the Engineer specifies otherwise.

 

E. When test specimens are cut from a finished product, a 10% variation in physical properties will be allowed.