Tetron Disc Bearings

The Tetron Disc Bearing Type 3 The design of Tetron Disc Bearings is based upon many years of experience in solving the problems of structural movement in civil engineering and incorporates: Low sliding friction - Very important for slender pier designs. Low rotational resistance - Point of load application moves about 5% of base dimension at full rotation. Unlimited sliding movement - Range of movement unrestricted regardless of size or type. Seizure-free movement -

No lubrication necessary in service .

Material specification of disc bearings Rubber disc: Natural Rubber (+anti-ozonants) to BS.1154 Ring: High grade heat treated steel or solid base plate Side Restraints (D3F only):

Steel to BS EN 10025 S275 Pins for side restraint: Special spring steel – minimum Yield strength 1100 N/mm². Seal and sliding surface: BS EN 10088 Grade 1.4401 or 1.4404 (was 316S31) Top plate, rocker and Base plate:

Steel to BS EN 10025 S275 or BS EN 10025 S355 P.T.F.E.:

BS 6564 Socket head cap screws: BS.4168 Grade 12.9 Recommended HD bolt: BS 3692 Grade 8.8 (zinc plated) Cast-in sockets

Mild Steel to BS EN 10025 S275 or equivalent If extreme corrosion resistance is required, cast iron base plates can be supplied. All materials used comply with the requirements of BS.5400: Section 9.2 1983 All permanently exposed steel parts are fully corrosion protected. Several different treatments are available, full technical data on request.

Components Tetron Disc bases and rockers, and all sliding plates are made of corrosion protected mild steel. Sliding plates are faced with a smooth surface of high quality stainless steel. Sliding surfaces are pure dimpled P.T.F.E. discs incorporating grease pockets which allows a permanent reservoir of lubricant. Elastomer used for rotational purposes in Tetron Disc bearings is high grade natural rubber. A mastic seal is provided around the rocker to prevent ingress of moisture into the base unit. Tetron is a registered trade mark

Side Restraints ('F' Type only)

Stainless Steel Sliding Surface

Filled P.T.F.E. (on edge)

Pure P.T.F.E

Rocker

Elastomeric Disc

Seal

Transit Brackets

Ring

Base Plate

Top Plate

2

General In a bearing that is free sliding in all directions (e.g. the D3E range) positive fixing to the main structure may not be required if the bearing is always subjected to adequate vertical loading. Horizontal movement will occur on the plane of least resistance which is, of course, the bearing sliding surface. Nevertheless, it is prudent to provide fixings to guard against displacement during installation, impact vibration and accidental unloading. In a light structure the bearing fixings must be vibration resistant otherwise they may work loose. Consideration should always be given to the practicability of removing and replacing the bearings, should this prove to be necessary. Most cases of bearing malfunction are attributable to faulty installation and almost all bearing damage occurs during installation or even earlier during handling and storage. Careless handling on site and the ingress of dirt can easily lead to abnormally high frictional resistance. Tetron bearings are normally delivered in a condition to discourage unnecessary dismantling and bolts or straps are used to connect together the upper and lower parts of the bearings. These temporary fixings, as well as excluding dirt during installation, prevent accidental displacement between the parts of the bearings but they must be removed before the bearings are called upon to slide or rotate. However, they are not structural fixings and should be supplemented, for example by wedges, during installation. Bearings should be clearly identified, and Freyssinet can help by marking them with such details as type and location when requested. Marking is particularly important where the top plate is to be offset. Bearings should be transported and unloaded carefully and then stored under cover in clean, dry conditions until required. An inspection should be carried out shortly before installation and bearings that have been damaged in store should not be accepted – almost certainly they will not work correctly, unless they are repaired. As much preparatory work as possible should be carried out, before bringing a bearing to it’s actual location. The seating should be level and this usually necessitates the use of a mortar bedding composed of sand and either cement, polyester resin or epoxy resin, with a cube crushing strength of at least 35N/mm². If the bearing is located directly on steelwork, the seating area should be machined.

Base Fixings A ‘D3E’ and ‘D3M’ type bearings are free sliding in all directions with a low coefficient of friction, so that theoretically the bases do not require mechanical fixing, (figure 1) but see notes above. All other types of bearings can resist horizontal loading and so their bases should be fixed. There are several ways of achieving this. The fixing bolts and sockets can be attached to the bearing base with a rubber washer between the socket and base. It is then possible to cast in the fixings and grout the bearing in one operation. The bearing may be supported on temporary packs, aligned, levelled and a chemical resin grout poured around the sockets and under the bearing (Fig 2) using some simple shuttering. The fixings should not be over-tightened when the grout has set; otherwise the bearing may be distorted due to compression in the washers. Nevertheless, rubber washers must be used to prevent the sockets carrying vertical loading. This is the preferred method of fixing and ensures bearing removeability. In special cases, a large recess can be left in the abutment into which the bearing base is placed bodily, bedded upon and surrounded with cement/sand or epoxy resin mortar (see fig.3). The recess must be correctly reinforced on all sides. This method does not meet the removeability requirement. Clearly sockets provide the easiest cast-in fixings with removal in view, for all types of bearing.

Figure 1

Figure 2

Figure 3

Top Fixings For similar reasons, top fixings must be provided for all bearings (optional for the ‘D3E’ types). A completed precast concrete structure may be lowered on to a skim of mortar on the top of the bearing, to eliminate soffit irregularities. The mortar mix needs careful control to ensure that it is not totally squeezed out by the weight of the superstructure, which must be supported until it has set. The fixing sockets for the top of the bearing should be ready cast into the soffit, but this requires accurate casting, using a jig drilled mould insert to match the bolting arrangement in the bearing. Alternatively the sockets may be replaced by a single plate cast in flush with the soffit and tapped to receive the bearing fixing bolts. Where a concrete superstructure is cast in-situ, the bearing top plates, with dowels can be built into the soffit shuttering. The area around the mould cut out must be carefully sealed to ensure that concrete does not leak into the working parts of the bearing during placing, and all sliding plates must be propped to prevent them distorting under the weight of wet concrete. A disc type bearing will compress by perhaps 2% of its total height during the casting operation, which must be provided for, to facilitate the removal of the shuttering. Subsidiary spreader plates, with a special taper, may be required to accommodate a superstructure with an inclination or cross fall. When intermediate tapered plates are used, the plane of movement in sliding bearings must be horizontal and may not coincide with the soffit of the superstructure. Great care must be exercised to ensure that ‘D3F’ lateral restraint bearings are correctly orientated. Notes It cannot be stressed too strongly that bearings should not be dismantled on site because the effects of dirt on the sliding surfaces are highly deleterious. Where appropriate, bearings should be requested with top plates pre-set to accommodate anticipated movements to prevent unnecessary dismantling on site. In all cases the transit bolts connecting the bearing top plate to its base must be removed after the mortar has set and before the bearing is called upon to rotate or slide.

3

REMOVEABLE BEARINGS

Removable bearings can be removed from the structure with a minimum of jacking when used in conjunction with cast in sockets or similar devices.

Tetron D3T Fixed (Fixed in all directions, free to rotate in all directions.)

‘Working stress’ design (kN)

BS.5400: Section 9.1 Design load effects (kN)

Serviceability Limit State

Ultimate Limit State †

Principal dimensions (mm)

Max. load

Max. load

All Vertical

Permanent

Horizontal

Vertical

Horizontal

Bearing

Type

A B C D E F G K

vertical

horizontal

Vertical

D3T 50

58 235 170 195 120 170 130 M12

500

100

500

300

100

750

160

D3T 80

75 340 235 280 155 235 175 M20

800

150

800

500

200

1200

260

D3T 100

80 355 250 295 170 250 190 M20

1000

150

1000

650

220

1500

290

D3T 125

83 375 270 315 190 270 210 M20

1250

190

1250

800

250

1900

320

D3T 160

92 395 290 335 210 290 230 M20

1600

220

1600

1000

280

2500

370

D3T 200

97 460 335 385 240 335 260 M20

2000

250

2000

1350

320

3300

430

D3T 250

97 485 360 410 270 360 285 M20

2500

280

2500

1600

360

4000

520

D3T 325

116 575 410 475 280 410 310 M20

3250

300

3250

2100

390

5500

560

D3T 400

127 615 450 515 330 450 350 M24

4000

360

4000

2600

450

7000

580

D3T 500

132 680 515 580 390 515 410 M30

5000

500

5000

3200

630

9000

800

D3T 650

141 770 570 645 420 570 440 M30

6500

600

6500

4200

700

12000

1000

D3T 800

156 835 635 710 490 635 510 M30

8000

650

8000

5200

800

15000

1100

D3T 1000

175 950 710 805 540 710 560 M30

10000

700

10000

6500

890

18000

1200

D3T 1250

179 1015 785 870 620 785 640 M30

12500

900

12500

8000

990

22000

1500

D3T 1600

203 1140 870 970 680 870 700 M30

16000

1000

16000

10000

1100

25000

1700

D3T 2000

203 1260 985 1090 780 985 800 M30

20000

1300

20000

13000

1500

33000

2200

D3T 2500

232 1425 1100 1220 875 1100 895 M42

25000

1600

25000

16000

1900

40000

2700

D3T 3000

257 1550 1230 1350 1000 1230 1030 M42

30000

2000

30000

20000

2200

50000

3400

4

† Note – it may not be

possible to achieve the

maximum vertical

and

horizontal

design load

effects simultaneously.

Tetron D3E Free Sliding (Free sliding in all directions, free to rotate in all directions.)




ULS †


Bearing

Type

A B* C* D* E* F G

Max. rotation

(Radians)

Max. load

Vertical

All Vertical

Permanent

Vertical

Vertical

D3E 50

60 235 170 195 120 170 130

0.026

500

500

300

750

D3E 80

73 340 235 280 155 235 175

0.026

800

800

500

1200

D3E 100

78 355 250 295 170 250 190

0.026

1000

1000

650

1500

D3E 125

82 375 270 315 190 270 210

0.026

1250

1250

800

1900

D3E 160

86 395 290 335 210 290 230

0.026

1600

1600

1000

2500

D3E 200

92 460 335 385 240 335 260

0.026

2000

2000

1350

3300

D3E 250

99 485 360 410 270 360 285

0.024

2500

2500

1600

4000

D3E 325

112 515 375 455 280 410 310

0.022

3250

3250

2100

5500

D3E 400

128 555 420 495 330 450 350

0.022

4000

4000

2600

7000

D3E 500

128 620 465 560 390 515 410

0.020

5000

5000

3200

9000

D3E 650

137 675 510 615 420 570 440

0.018

6500

6500

4200

12000

D3E 800

147 740 575 680 490 635 510

0.016

8000

8000

5200

15000

D3E 1000

162 815 635 755 540 710 560

0.016

10000

10000

6500

18000

D3E 1250

168 910 700 840 620 785 640

0.014

12500

12500

8000

22000

D3E 1600

183 1000 780 925 680 870 700

0.012

16000

16000

10000

25000

D3E 2000

193 1155 875 1055 770 985 800

0.012

20000

20000

13000

33000

D3E 2500

213 1270 970 1170 865 1100 895

0.012

25000

25000

16000

40000

D3E 3000

228 1440 1080 1310 950 1230 1030

0.012

30000

30000

20000

50000

•

Dimensions B, C, D & E are for zero movement, and specified movement has to be added to above in increments of 100mm.

5

Tetron D3F Sliding Guided (S

liding, guided in one direction, free to rotate in all directions.)




Ultimate Limit State †


Bearing

Type

A B C* D* E* F G K

Max. load

Vertical

Max. load

horizontal

All Vertical

Permanent

Vertical

Horizontal

Vertical

Horizontal

D3F 50

79 260 170 195 120 170 130 M12

500

100

500

300

100

750

150

D3F 80

103 345 235 280 155 235 175 M20

800

150

800

500

200

1200

260

D3F 100

108 360 250 295 170 250 190 M20

1000

150

1000

650

220

1500

290

D3F 125

117 405 270 315 190 270 210 M20

1250

190

1250

800

250

1900

300

D3F 160

121 425 290 335 210 290 230 M20

1600

220

1600

1000

280

2500

310

D3F 200

129 475 335 385 240 335 260 M20

2000

250

2000

1350

320

3300

410

D3F 250

129 500 360 410 270 360 285 M20

2500

280

2500

1600

360

4000

510

D3F 325

138 565 410 475 280 410 310 M20

3250

300

3250

2100

390

5500

520

D3F 400

158 605 450 515 330 450 350 M24

4000

360

4000

2600

450

7000

580

D3F 500

158 680 515 580 390 515 410 M30

5000

500

5000

3200

630

9000

720

D3F 650

167 745 570 645 420 570 440 M30

6500

600

6500

4200

700

12000

900

D3F 800

177 810 635 710 490 635 510 M30

8000

650

8000

5200

800

15000

920

D3F 1000

192 905 710 805 540 710 560 M30

10000

700

10000

6500

890

18000

1200

D3F 1250

198 970 785 870 620 785 640 M30

12500

900

12500

8000

990

22000

1400

D3F 1600

213 1070 870 970 680 870 700 M30

16000

1000

16000

10000

1100

25000

1600

D3F 2000

227 1215 985 1090 780 985 800 M36

20000

1300

20000

13000

1500

33000

1800

D3F 2500

267 1360 1100 1220 875 1100 895 M42

25000

1600

25000

16000

1900

40000

2200

D3F 3000

282 1490 1230 1350 1000 1230 1030 M42

30000

2000

30000

20000

2200

50000

2800

Rotation as for D3E type

•

Dimensions C & E are for zero movement, and specified movement has to be added to above in increments of 100mm.

6

† Note – it may not be

possible to achieve the

maximum vertical

and

horizontal

design load

effects simultaneously.

PRINCIPAL MOVEMENT (cm)

LATERAL MOVEMENT (cm)

MOVEMENT (cm)

BEARING

OR

BEARING

NOTES

1. Base contact stress of the bearings illustrated approaches 20N/mm².

2. Sliding plate dimensions of 100mm. The bearings may then be described in a code, for example, thus:

3. The height ‘A’ is nominal; manufacturing tolerances give a variation of ± 3mm on tabulated figure.

4. The size of fixing bolts listed in the tables assumes assistance from friction due to the minimum vertical load normally present in service.

5. Larger capacity bearings are available – details on request.

Standard Fixing Socket for removable bearings D3E, D3F and D3T

Available as an extra from Freyssinet Ltd.

Bolt

Ø'A'

'B'

M12

25

60

M16

40

70

M20

40

100

M24

40

160

M30

50

220

M36

70

220

M42

90

220

M48

100

250

M56

100

350

M64

120

400

7

Bearing Base or Top Plate

3mm Natural Rubber

Mild Steel Socket

Bolt I.S.O. metric

(Grade 8.8, 10.9 or 12.9)

Zinc plated.

LATERAL MOVEMENT (cm)

PRINCIPAL MOVEMENT (cm)

BEARING

SMALL BEARINGS - SIMPLIFIED FIXING

A simplified method is often preferred for the smaller sizes of disc bearing where cast-in sockets are not specified.

Tetron D3M Free Sliding (Free sliding in all directions, free to rotate in all directions.)

‘Working Stress’

design (kN)

Bearing Type

A B* C* D

Max. load vertical

Max. rotation

(Radians)

D3M 30

53 160 200 160

300

0.028

D3M 50

56 170 220 170

500

0.028

D3M 80

69 235 290 235

800

0.026

D3M 100

79 250 305 250

1000

0.026

D3M 125

83 270 325 270

1250

0.026

D3M 160

87 290 345 290

1600

0.026

D3M 200

96 335 390 335

2000

0.026

D3M 250

100 360 435 360

2500

0.024

•

Dimensions, B & C care for zero movement, and specified movement has to be added to above in increments of 50mm.

•

The D3M free sliding bearing is intended to locate by friction only, so adequate vertical loading must always be present to prevent slip.

NOTES

1. Sliding plate dimensions shown are for zero movement . Add to these the amount of sliding required in increments of 50mm. The bearing may then be described in code, for example, thus:

2. Base contact stresses are approximately 20 N/mm² at maximum rated load.

3. The height ‘A’ is nominal; manufacturing tolerances give a variation of ± 3mm on tabulated figures.

8

General arrangement drawings

We suggest that before detailing general arrangement drawings are obtained with the latest information on dimensions and material specifications as the information in this publication is subject to change and updating.

Production & Overseas Units D1 – D3 Stafford Park 15 Telford Shropshire TF3 3BB Tel: +44 (0) 1952 201901 Fax:+44 (0) 1952 211919

Head Office

Innovation House Euston Way Town Centre

Telford Shropshire TF3 3DE

Tel: +44 (0) 1952 201901 Fax:+44 (0) 1952 201753

Issue: 06 22/03/11

Documents

Tetron Disc Bearings