Bridge bearings

Bridge bearings

Elastomer bearings

Elastomer bearings are layered products, i. e. they alternate between an elastomer layer and a steel panel as reinforcement for the part.
The entirety is vulcanised to permanently attach the rebar with the elastomer layers.
The main component used in manufacture is polychloroprene rubber, reinforcement is made of enhanced quality steel type S355 J0.
The reinforced elastomer blocks are used in engineering structures to transfer reactions from vertical and horizontal loads to the support parts; they also provide freedom of deformation for stays and the walkway platform, which are a result of temperature changes.

 

Product description

Support for drive-on components of engineering structures: bridges, viaducts, pedestrian flyovers – is constructed in most cases through the use of flexible components. Elastomer bearings are such components. The load resistance is ensured by internal reinforcement with steel panels. These bearings are made of polychloroprene rubber or natural rubber.
Thanks to different types of bearings, it is possible to satisfy all that is required of them in engineering structures.
According to Polish Standard PN-EN 1337-3, structural elastomer bearings possess the CE mark, confirming the adherence to particular requirements of the indicated norm by the manufacturer, in this case the company Gumba GmbH. The CE mark issued to the elastomer structural bearings made by Gumba GmbH by MPA Stuttgart, a notified body within the European Union, unequivocally conforms the adherence to requirements of standard PN-EN 1337-3. This document permits the introduction of the bridge bearings onto the European market, including the Polish market.

Elastomer properties allow, to a certain degree, movement of the material itself and twisting by deformation. As compared to other bearing types, they have a certain particular advantage – in many cases one can forgo expensive structures with slip components. If the shift caused by the properties of the elastomer bearing is not sufficient for a particular case, the scope of functionality may be expanded.

Note:
As a result of errors during design and bearing selection, locking of the structure may occur, as well as pressure of the main structure on the abutments, and following that – cracking of front walls, head walls and lower plinths. Altering bearing dimensions also causes flaws, and as a result, it needlessly increases costs of construction and maintenance of the structure.

Every elastomer bearing has a vulcanised label describing the bearing, which contains the following information (image below):

  • CE certificate number
  • norm according to which the bearing was manufactured
  • manufacturer logo
  • bearing number
structural bearings

 

 

 Bearing types

Considering the anchoring method, one can differentiate between four basic elastomer bearing types: type B(1), type C(2), type B/C(1/2) and type C-PSP(5).

Type B(1) – reinforced, non-anchored bearing, consisting of at least two steel reinforcement plates. Fulfilment of the condition of minimum load and friction prevents this bearing from slipping. Lack of anchoring eases replacement and servicing of these bearings.

 

 

 

 

Type B/C(1/2) – reinforced bearing with single-side anchoring. The vulcanised external rubber prevents this bearing from slipping, and forms the lower support surface of the part. The method of anchoring of the bearing may be freely configured: welded anchors, protective circular plates or threaded holes. For railway bridges, irrespective of the loads, type B/C(1/2) should always be used.

 

 

 

 

 

Type C(2) – reinforced bearing, anchored on both sides. The vulcanised external sheet steel (support surfaces) prevent this bearing from slipping. Similarly to the type described earlier, the method of anchoring of the bearing is freely selectable: welded anchors, protective circular plates or threaded holes. Replacement of this bearing type is quite complicated, and requires additional operations.

 

 

 

 

reinforced bearings

 

 

Type C-PSP(5) – reinforced bearing, anchored on both sides. Vulcanised external ribbed metal sheets (support surfaces) prevent this bearing from slipping. The replacement of this bearing type is quite complicated, and requires not only the grout under the bearing, but also the reinforced concrete part above the bearing, to be removed.

 

 

 

Standard Gumba bearing dimension tables

Minimum pressure
≥ 3N/mm²
 Minimum pressure
< 3 N/mm²
Typ B(1) Typ C (2) i C (5)
 Typ B/C (1/2)
Load
Nz,k		 Bearing
dimensions
a x b
 Elastomer
layer count
n
 Shift
+/-
ex
 Bearing
height
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
Typ 2
d
 Bearing
thickness
Typ 5
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
d
 Elastomer
thickness
t
 Turn
angle
Ø
kN
 mm
 pcs.
 mm
 mm
 mm
 rad/1000
100
150		 100×100
100×150		 1 7 14 10 – – – – – – – 4
2 11 21 15 7 42 32 10 9 31,5 12,5 8
3 14 28 20 11 49 39 15 12 38,5 17,5 12
4 16 35 25 14 56 46 20 15 45,5 22,5 16
5 18 42 30 16 63 53 25 17 52,5 27,5 20
6 – – – 18 70 60 30 – – – 24
300 150×200 1 7 14 10 – – – – – – – 3
2 11 21 15 7 42 32 10 9 31,5 12,5 6
3 14 28 20 11 49 39 15 12 38,5 17,5 9
4 18 35 25 14 56 46 20 16 45,5 22,5 12
5 21 42 30 18 63 53 25 19 52,5 27,5 15
6 23 49 35 21 70 60 30 22 59,5 32,5 18
7 25 56 40 23 77 67 35 24 66,5 37,2 21
8 27 63 45 25 84 74 40 26 73,5 42,5 24
9 28 70 50 27 91 81 45 28 80,5 47,5 27
10 – – – 28 98 88 50 – – – 30
310
630
750
1000		 ø200
200×250
200×300
200×400		 1 9 19 13 – – – – – – – 3 4
2 15 30 21 11 49 39 16 13 39,5 18,5 6 8
3 20 41 29 17 60 50 24 19 50,5 26,5 9 12
4 26 52 37 22 71 61 32 24 61,5 34,5 12 16
5 30 63 45 28 82 72 40 29 72,5 42,5 15 20
6 34 74 53 32 93 83 48 33 83,5 50,5 18 24
7 36 85 61 35 104 94 56 36 94,5 58,5 21 28
8 – – – 37 115 105 64 – – – 24 32
Minimum pressure
≥ 3N/mm²
 Minimum pressure
< 3 N/mm²
Typ B(1) Typ C (2) i C (5)
 Typ B/C (1/2)
Load
Nz,k		 Bearing
dimensions
a x b
 Elastomer
layer count
n
 Shift
+/-
ex
 Bearing
height
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
Typ 2
d
 Bearing
thickness
Typ 5
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
d
 Elastomer
thickness
t
 Turn
angle
Ø
kN
 mm
 szt.
 mm
 mm
 mm
 rad/1000
600
1300		 Ø250
250×400		 1 9 19 13 – – – – – – – 3 4
2 15 30 21 11 49 39 16 13 39,5 18,5 5 8
3 20 41 29 17 60 50 24 19 50,5 26,5 8 12
4 26 52 37 22 71 61 32 24 61,5 34,5 10 16
5 32 63 45 28 82 72 40 30 72,5 42,5 13 20
6 37 74 53 34 93 83 48 35 83,5 50,5 15 24
7 40 85 61 38 104 94 56 39 94,5 58,5 18 28
8 43 96 69 41 115 105 64 42 105,5 66,5 20 32
9 46 107 77 44 126 116 72 45 116,5 74,5 23 36
10 – – – 46 137 127 80 – – – 25 40
900
1800		 Ø300
300×400		 1 9 19 13 – – – – – – – 2 3
2 15 30 21 11 49 39 16 13 39,5 18,5 4 6
3 20 41 29 17 60 50 24 19 50,5 26,5 6 9
4 26 52 37 22 71 61 32 24 61,5 34,5 8 12
5 32 63 45 28 82 72 40 30 72,5 42,5 10 15
6 37 74 53 34 93 83 48 35 83,5 50,5 12 18
7 43 85 61 39 104 94 56 41 94,5 28,2 14 21
8 46 96 69 44 115 105 64 45 105,5 66,5 16 24
9 50 107 77 48 126 116 72 49 116,5 74,5 18 27
10 52 118 85 51 137 127 80 52 127,5 82,5 20 30
11 55 129 93 53 148 138 88 54 138,5 90,5 22 33
12 – – – 56 159 149 96 – – – 24 36
1200 Ø350 1 11 24 16 – – – – – – – 4
2 19 39 27 15 56 46 22 17 47,5 24,5 8
3 27 54 38 23 71 61 33 25 62,5 33,5 12
4 34 69 49 31 86 76 44 33 77,5 46,5 16
5 42 84 60 39 101 91 55 40 92,5 57,5 20
6 50 99 71 46 116 106 66 48 107,5 68,5 24
7 55 114 82 52 131 121 77 53 122,5 79,5 28
8 59 129 93 57 146 136 88 58 137,5 90,5 32
9 63 144 104 61 161 151 99 62 152,5 101,5 36
10 66 159 115 64 176 166 110 65 167,5 112,5 40
Minimum pressure
≥ 5 N/mm²
 Minimum pressure
< 5 N/mm²
Typ B(1) Typ C (2) i C (5)
 Typ B/C (1/2)
Load
Nz,k		 Bearing
dimensions
a x b
 Elastomer
layer count
n
 Shift
+/-
ex
 Bearing
height
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
Typ 2
d
 Bearing
thickness
Typ 5
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
d
 Elastomer
thickness
t
 Turn
angle
Ø
kN
 mm
 pcs.
 mm
 mm
 mm
 rad/1000
2400 350×450 3 27 54 38 23 81 61 33 25 67,5 33,5 8
4 34 69 49 31 96 76 44 33 82,5 46,5 10
5 42 84 60 39 111 91 55 40 97,5 57,5 13
6 50 99 71 46 126 106 66 48 112,5 68,5 15
7 55 114 82 52 141 121 77 53 127,5 79,5 18
8 59 129 93 57 156 136 88 58 142,5 90,5 20
9 63 144 104 61 171 151 99 62 157,5 101,5 23
10 66 159 115 64 186 166 110 65 172,5 112,5 25
1900
3000		 Ø400
400×500		 3 27 54 38 23 81 61 33 25 67,5 35,5 6 9
4 34 69 49 31 96 76 44 33 82,5 46,5 8 12
5 42 84 60 39 111 91 55 40 97,5 57,5 10 15
6 50 99 71 46 126 106 66 48 112,5 68,5 12 18
7 57 114 82 54 141 121 77 56 127,5 79,5 14 21
8 62 129 93 60 156 136 88 61 142,5 90,5 16 24
9 67 144 104 65 171 151 99 66 157,5 101,5 18 27
10 70 159 115 69 186 166 110 70 175,5 112,5 20 30
11 74 174 126 72 201 181 121 73 187,5 123,5 22 33
12 – – – 75 216 196 132 – – – 24 36
2400
4050		 Ø450
450×600		 3 27 54 38 23 81 61 33 25 67,5 33,5 6 9
4 34 69 49 31 96 76 44 33 82,5 46,5 8 12
5 42 84 60 39 111 91 55 40 97,5 57,5 10 15
6 50 99 71 46 126 106 66 48 112,5 68,5 12 18
7 57 114 82 54 141 121 77 56 127,5 79,5 14 21
8 65 129 93 62 156 136 88 63 142,5 90,5 16 24
9 70 144 104 67 171 151 99 68 157,5 101,5 18 27
10 74 159 115 72 186 166 110 73 172,5 112,5 20 30
11 78 174 126 76 201 181 121 77 187,5 123,5 22 33
12 82 189 137 80 216 196 132 81 202,5 134,5 24 36
13 85 204 148 83 231 211 143 84 217,5 145,5 26 39
Minimum pressure
≥ 5 N/mm²
 Minimum pressure
< 5 N/mm²
Typ B(1) Typ C (2) i C (5)
 Typ B/C (1/2)
Load
Nz,k		 Bearing
dimensions
a x b
 Elastomer
layer count
n
 Shift
+/-
ex
 Bearing
height
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
Typ 2
d
 Bearing
thickness
Typ 5
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
d
 Elastomer
thickness
t
 Turn
angle
Ø
kN
 mm
 pcs.
 mm
 mm
 mm
 rad/1000
2900
3600
4500		 Ø 500
Ø 550
500×600		 3 27 54 38 23 81 61 33 25 67,5 33,5 6 6
4 34 69 49 31 96 76 44 33 82,5 46,5 8 8
5 42 84 60 39 111 91 55 40 97,5 57,5 10 10
6 50 99 71 46 126 106 66 48 112,5 68,5 12 12
7 57 114 82 54 141 121 77 56 127,5 79,5 14 14
8 65 129 93 62 156 136 88 63 142,5 90,5 16 16
9 72 144 104 69 171 151 99 71 157,5 101,5 18 18
10 77 159 115 75 186 166 110 76 172,5 112,5 20 20
11 82 174 126 80 201 181 121 81 187,5 123,5 22 22
12 86 189 137 84 216 196 132 85 202,5 134,5 24 24
13 89 204 148 88 131 211 143 89 217,5 145,5 26 26
14 93 219 159 91 146 226 154 92 232,5 156,5 28 28
15 – – – 94 161 141 165 – – – 30 30
4100
5000
6300		 Ø 600
Ø 650
600×700		 3 35 70 50 32 95 75 45 33 82,5 47,5 6 6
4 46 90 65 42 115 95 60 44 102,5 62,5 8 8
5 56 110 80 53 135 115 75 54 122,5 77,5 10 10
6 67 130 95 63 155 135 90 65 142,5 92,5 12 12
7 77 150 110 74 175 155 105 75 162,5 107,5 14 14
8 86 170 125 84 195 175 120 85 182,5 122,5 16 16
9 93 190 140 91 215 195 135 92 202,5 137,5 18 18
10 99 210 155 98 235 215 150 98 222,5 152,5 20 20
11 105 230 170 103 255 235 165 104 242,5 167,5 22 22
12 109 250 185 108 275 255 180 109 262,5 182,5 24 24
13 113 270 200 112 295 275 195 113 282,5 197,5 26 26
Minimum pressure
≥ 5 N/mm²
 Minimum pressure
< 5 N/mm²
Typ B(1) Typ C (2) i C (5)
 Typ B/C (1/2)
Load
Nz,k		 Bearing
dimensions
a x b
 Elastomer
layer count
n
 Shift
+/-
ex
 Bearing
height
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
Typ 2
d
 Bearing
thickness
Typ 5
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
d
 Elastomer
thickness
t
 Turn
angle
Ø
kN
 mm
 pcs.
 mm
 mm
 mm
 rad/1000
5800
6600
8400		 Ø 700
Ø 750
700×800		 3 35 70 50 32 95 75 45 33 82,5 47,5 6 6
4 46 90 65 42 115 95 60 44 102,5 62,5 8 8
5 56 110 80 53 135 115 75 54 122,5 77,5 10 10
6 67 130 95 63 155 135 90 65 142,5 92,5 12 12
7 77 150 110 74 175 155 105 75 162,5 107,5 14 14
8 88 170 125 84 195 175 120 86 182,5 122,5 16 16
9 98 190 140 95 215 195 135 96 202,5 137,5 18 18
10 105 210 155 103 135 215 150 104 222,5 152,5 20 20
11 112 230 170 110 255 235 165 111 242,5 167,5 22 22
12 118 250 185 116 275 255 180 117 262,5 182,5 24 24
13 123 270 200 121 295 275 195 122 282,5 197,5 26 26
14 127 290 215 126 315 295 210 127 302,5 212,5 28 28
15 131 310 230 130 335 315 225 131 322,5 227,5 30 30
7500
8500
9600		 Ø 800
Ø 850
800×800		 3 41 79 59 38 104 84 54 40 91,5 56,5 6 6
4 54 102 77 50 127 107 72 52 114,5 74,5 8 8
5 67 125 95 63 150 130 90 65 137,5 92,5 10 10
6 79 148 113 76 173 153 108 77 160,5 110,5 12 12
7 92 171 131 88 196 176 126 90 183,5 128,5 14 14
8 104 194 149 101 219 199 144 103 206,5 146,5 16 16
9 115 217 167 113 242 222 162 114 229,5 164,5 18 18
10 124 240 185 122 265 245 180 123 252,5 182,5 20 20
11 131 263 203 129 288 268 198 130 275,5 200,5 22 22
12 138 286 221 136 311 291 216 137 298,5 218,5 24 24
13 144 309 239 142 334 314 234 143 321,5 236,5 26 26
14 149 332 257 147 357 337 252 148 344,5 254,5 28 28
Minimum pressure
≥ 5 N/mm²
 Minimum pressure
< 5 N/mm²
Typ B(1) Typ C (2) i C (5)
 Typ B/C (1/2)
Load
Nz,k		 Bearing
dimensions
a x b
 Elastomer
layer count
n
 Shift
+/-
ex
 Bearing
height
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
Typ 2
d
 Bearing
thickness
Typ 5
d
 Elastomer
thickness
t
 Shift
+/-
ex		 Bearing
thickness
d
 Elastomer
thickness
t
 Turn
angle
Ø
kN
 mm
 pcs.
 mm
 mm
 mm
 rad/1000
9500
12000		 Ø 800
900×900		 3 41 79 59 38 104 84 54 40 91,5 56,5 5 5
4 54 102 77 50 127 107 72 52 114,5 74,5 6 6
5 67 125 95 63 150 130 90 65 137,5 92,5 8 8
6 79 148 113 76 173 153 108 77 160,5 110,5 9 9
7 92 171 131 88 196 176 126 90 183,5 128,5 11 11
8 104 194 149 101 219 199 144 103 206,5 146,5 12 12
9 117 217 167 113 242 222 16 115 229,5 164,5 14 14
10 128 240 185 126 265 245 180 127 252,5 182,5 15 15
11 137 263 203 135 288 268 198 136 275,5 200,5 17 17
12 145 286 221 143 311 291 216 144 298,5 218,5 18 18
13 152 309 239 150 334 314 234 151 321,5 236,5 20 20
14 158 332 257 156 357 337 252 157 344,5 254,5 21 21
15 163 355 275 162 380 360 252 163 367,5 272,5 23 23
16 168 378 293 167 403 383 270 391 390,5 290,5 24 24
bearings

The tables for reinforced elastomer bearings apply to standard-construction Gumba bearings. They apply to initial dimensions, which only allow a general and fast estimation of the bearing size. The values provided in them are characteristic values for the Serviceability Limit State (SLS). In order to conduct more precise dimensioning of the structural bearings, please contact our representatives in the retail branches, employees of the technical department or alternatively use the software available at the manufacturer’s website at www.gumba.de. The software allows optimum bearing selection. It includes only known bearing dimensions with layered structures according to Gumba standards and regular bearing dimensions according to norm EN 1337-3.

 

Calculation basis according to EN 1337-3.

Designing and manufacture of elastomer bearings is based on Polish Standard PN-EN 1337-3, which is harmonised with the Construction Directive 89/106/EEC. This norm covers i. e. reinforced elastomer bearings with a surface area of up to 1200 x 1200 mm2, used between temperature values between -25 °C and +50 °C.
Below, the recommended course of calculations, the expansion of which is found in the norm indicated earlier on, is presented.
Remarks and further hints concerning the presented calculation phases are found in standard PN-EN 1337.
For the calculation of values related to elastomer bearings, characteristic load values need to be applies. The proof takes place at the Ultimate Limit State (ULS) for joint deformation stemming from load and shift.
The table above contains information necessary to dimension bearings according to standard PN-EN 1337-3. The table also contains necessary shore conditions. It may serve the determination and description of structural bearing parameters designed for a particular structure.

Note:
According to Polish Standard PN-EN 1337-3, the bridge structure designer presents all necessary data allowing the selection of structural bearings for such a structure. It is not possible for the bearing manufacturer to calculate this data.

Elastomer bearing calculations

The bearings must correspond to the following requirements:
1. Maximum calculational deformation
At any given point of the bearing, the sum of deformations (Ɛt,d) caused by effects of calculational load (Ed) is given by the formula:

Ɛc,d – calculational deformation caused by compressive calculational loads
Ɛq,d – calculational shear deformation caused by calculational horizontal shifts
Ɛɑ,d– calculational deformation caused by the calculational twist angle
KL – load type coefficient

  •   Calculational deformation caused by compressive calculational loads

Nz,d – vertical force calculational value
G – nominal value of the ordinary non-dilatational strain modulus for an elastomer bearing
Ar – reduced effective area of the elastomer bearing

A’- effective area of a reinforced bearing (surface area of reinforcement sheet steel)
A’ = a’·b’ (for cuboid bearings without openings)
a’ – effective width of reinforced bearing (reinforcement sheet width)
b’ – effective length of reinforced bearing (reinforcement sheet length)
vx,d – maximum horizontal relative shift of a bearing part towards dimension a of the bearing caused by all effects of calculational load
vy,d – maximum horizontal relative shift of a bearing part towards dimension b of the bearing caused by all effects of calculational load

S – shape coefficient

A’- effective area of a reinforced bearing (surface area of reinforcement sheet steel)
A’ = a’·b’ (for cuboid bearings without openings)
a’ – effective width of reinforced bearing (reinforcement sheet width)
b’ – effective length of reinforced bearing (reinforcement sheet length)
lp – circumference of bearing without load
lp=2·(a’+b’)
te – effective thickness of individual elastomer layer at compression

  • Calculational shear deformation caused by calculational horizontal shifts.

vxy,d – maximum resultant horizontal relative shift of bearing part obtained from vector sum of  vx,d and vy,d
Tq – total elastomer thickness at non-dilatational strain with upper and lower cover

  • Calculational deformation caused by calculational twist angle

a’ – effective width of reinforced bearing (reinforcement sheet width)
ɑa,d – turn angle about bearing width a
b’ – effective length of reinforced bearing (reinforcement sheet length)
ɑb,d –  turn angle (if applicable) about bearing width b
ti – individual elastomer layer thickness

 2. Maximum extension pressure in reinforcement sheets

  • Reinforcement plate thickness

 

Kp – correction coefficient
Kp = 1,3
Nz,d – calculational value of vertical force
t1, t2 – elastomer thickness on both sides of metal sheet
Kh – extension pressure coefficient caused in the reinforcement steel sheet
Kh =1 (without openings)
Kh = 2 (with openings)
Ɣm – partial safety coefficient, Ɣm= 1,0
Ar – reduced effective elastomer bearing area
fy – steel yield strength

3. Limit conditions

  • Twist limit condition

For reinforced bearings, the limit turn should not be reached when total vertical compression ∑Vz,d meets the following conditions:
For parallel wall bearings:

 

For circular bearings:

 

∑vz,d – total vertical compression causing ɑa  and ɑb
Nz,d – vertical force calculational value

ti – individual elastomer layer thickness
A’ – effective reinforced bearing area (surface area of reinforcement sheet steel)
G – nominal value of the ordinary non-dilatational strain modulus for an elastomer bearing
S1 – thickest layers shape coefficient
Eb – volumetric strain modulus Eb = 2000 MPa
a’ – effective width of reinforced bearing (reinforcement sheet width)
ɑa,d – turn angle about bearing width a
b’ –  effective length of reinforced bearing (reinforcement sheet length)
ɑb,d –  turn angle (if applicable) about bearing width b
Kr,d – twist coefficient
Kr,d = 3
D’ – effective bearing diameter
ɑd – twist angle about diameter D of circular bearing

  •  Dent stability

In reinforced elastomer bearings, the load should conform to the following formula:

 

Nz,d – vertical force calculational value
Ar – reduced effective area of the elastomer bearing
a’ – effective width of reinforced bearing (reinforcement sheet width)
G – nominal value of the ordinary non-dilatational strain modulus for an elastomer bearing
S1 – thickest layers shape coefficient
Te – sum total of all elastomer layers

  • No-slip condition

Non-anchored bearings must conform to the following formula:

and under fixed loads

 

Nxy,d – resultant force of all horizontal forces
Nz,dmin – minimum vertical calculational force related to Nxy,d
Ar – reduced effective area of the elastomer bearing
µe – friction coefficient according to the following formula:

Kf = 0,6 for concrete
Kf = 0,2 for all other surfaces including resin mortars and grout
σm – average load tension resulting from Nz,dmin

 4. Forces, moments and deformations acting on structures

  • mutual contact surface pressure

All that is required is a test whether the average pressure on the surface does not exceed the base layer material strength.

  • result force of resistance against horizontal shift

A – total flat bearing area
G – nominal value of the ordinary non-dilatational strain modulus for an elastomer bearing
vxy,d – maximum resultant horizontal relative shift of bearing part obtained from vector sum of vx,d and vy,d
Te – sum total of all elastomer layers

  • Rotation resistance

Parallel wall bearings

G – nominal value of the ordinary non-dilatational strain modulus for an elastomer bearing
ɑ – bearing angle of rotation
a’ – effective reinforced bearing width (reinforcement sheet width)
b’ – effective reinforced bearing length (reinforcement sheet length)
n – elastomer layer count
ti – individual elastomer layer thickness
Ks – resistance moment coefficient

Circular bearings

G – nominal value of the ordinary non-dilatational strain modulus for an elastomer bearing
ɑ – bearing angle of rotation
D’ – effective bearing diameter
n – elastomer layer count
ti – individual elastomer layer thickness

The Ks resistance moment coefficient is determined using the following table.

b/a
 0,5
 0,75
 1
 1,2
 1,25
 1,3
 1,4
 1,5
Ks 137 100 86,2 80,4 79,3 78,4 76,7 75,3
b/a
 1,6
 1,7
 1,8
 1,9
 2
 2,5
 10
 X
Ks 74,1 73,1 72,2 71,5 70,8 68,3 61,9 60

 

 

ASSEMBLY RECOMMENDATIONS

General information

Apart from co-operation with design agencies and contractors concerning selection and design of structural bearings, Betomax offers supervision, and, since 2010, also installation of structural bearings. We currently utilise two specialised teams of structural bearing installation specialists. Installation covers arrangement of the bearing on the support structure, levelling and adjusting the bearing with respect to axes, execution of formwork, grouting using low-contraction mortar and protecting the bearing after installation. Our teams are equipped with specialised tools required for correct bearing installation. they utilise the following measurement devices: high-precision levels, electronic levelling instruments, infra-red thermometers and power tools required at installation. The installation concludes with the issue of a bearing installation protocol transferred to the site contractor.
We co-operate with the largest construction companies operating in Poland, i. e. Skanska, Strabag, Polimex Mostostal, Budimex. We have participated in the construction of the first sections of Polish highway A1 and several sections of highway A2. For the installation of structural bearings, we adhere to the current standard PN-EN 1337-11, complying with the strictest EU requirements, as proven by the respect of our satisfied customers.

elastomer bearing

The installation of a bearing is preceded by creation of image documentation and its transfer to the construction site. After it is approved, preparatory works may commence. The first stage is the execution of lower plinths. The plinths are executed individually for every bearing, considering the hints included in assembly drawings transferred by Betomax. The plinth needs to be reinforced and covered by formwork up to an appropriate height. In case of anchored bearings equipped with studs, openings need to be left clear in the plinth. After appropriate concrete strength is reached, the installation of the bearing may commence. The part on which the grout shall be executed must be prepared accordingly. The bearings are arranged according to the axes indicated by the geodesic services. Then, the bearings are levelled, and their arrangement is checked and approved by a geodesic specialist. A further step is preparing the formwork, after which the grout may be executed. The grout is introduced in a manner ensuring removal of air from under the bearing, so as to avoid emergence of so-called air bubbles under the bearing. Depending on the grout type, after appropriate resistance strength is reached, the load bearing structure of the element may be executed. For transport and assembly, the bearings are protected by assembly securing screws, which must be removed when the structure starts transferring loads and working by itself.

Assembly work

1. Preparation of plinth surface by graining 2. Cleaning of lower plinth surface
3. Assignment of bearings 4. Layout and levelling of elastomer bearing
5. Grout execution 6. Securing the bearing

Structural bearing replacement

Extensive investments related to the construction of new road sections and engineering structures are currently carried out in Poland, along with repairs and upgrades of existing structures and roads. In case of existing structures, old, used-up bearings needs to be replaced with new products. Viaducts and bridges often rest on corroded roller bearings which do not work properly, with the entire structure at risk of failure. Betomax offers assistance in the selection of appropriate solutions and in the installation of new bearings. The first stage is designing appropriate bearings, which shall ensure the transfer of vertical loads, horizontal forces and thermal deformations of the existing structure. The above solutions must be accepted by the design office executing the site upgrade design. The replacement of the delivered bearings itself entails lifting the existing structure by hydraulic motors to an appropriate height, thus ensuring the space necessary for removal of the current bearings, in most cases by chiselling them away, and the installation of new bearings.
Professional evaluation of the condition of elastomer bearings requires to a great extent knowledge and experience, and must be conducted by qualified personnel. If divergences are found, consultations with the bearing manufacturer are recommended.
During the inspection of a bridge, structural bearings are also controlled. During an inspection, among others, the following factors are analysed:

  • elastomer bearing position
  • elastomer bearing contact area size with surrounding surfaces
  • quality of elastomer bearing surface (springing effects, cracks)
  • allowable horizontal shift
  • allowable rotation
  • slip surface quality
  • corrosion protection quality

Below may be found a few examples of upgrade works completed. Photographs provided by Other Montagen.

before after before after
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