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.)
BS.5400: Section 9.1 Design load effects (kN)
‘Working stress’ design (kN)
Serviceability Limit State
ULS †
Principal dimensions (mm)
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.)
BS.5400: Section 9.1 Design load effects (kN)
‘Working stress’ design (kN)
Serviceability Limit State
Ultimate Limit State †
Principal dimensions (mm)
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.
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Issue: 06 22/03/11