CTT Pot Bearings

8/12/2019 CTT Pot Bearings

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CONTENTS

1. General page 3

2. Specif ications and designparameters page 4

3. Informat ion required for designof POT bearings page 5

4. Dimensions data sheets

- POT bearing type PU page 6

- POT bearing type PL page 7

- POT bearing type PF page 8

5. Accessories page 9

6. Site installation page 10

7. POT bearings for incrementally

launched bridges page 11

8. Special POT bearings page 12

9. Recent bridge structures page 13

10. Quality control and tests page 15

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Structural bearings are required to connect different parts

of a structure such as bridge decks to piers and

abutments. The most widely-used structural bearings

are plain or reinforced elastomeric bearings, and POT

bearings. They are capable of transmitting forces while

absorbing the structures deformations and rotations.

The strength of reinforced elastomeric bearings is limited

by the shear properties of the elastomeric block,

especially when the three stresses, compression, shear

and bending, occur at the same time. POT bearings

maximise the shear strength of the bearings elastomer

by encasing it in a steel cylinder. They can accept working

loads in the elastomer, which, in turn, allows the

bearings dimensions to be reduced.

POT bearings are divided into three main types,

depending on restrictions to the structures

deformations: type PF (fixed), type PL (free or unguided

sliding), and type PU (guided sliding).

In all types, under vertical load, the upper plate acts on

the elastomer like a piston on a hydraulic cylinder, and

the elastomer itself, perfectly sealed, behaves like a

viscous fluid, offering minimal resistance to rotation

around any horizontal axis. No sliding movement isallowed in type PF (fixed).

Type PL (free sliding) is obtained by dividing the upper

plate into two independent elements: rectangular sliding

plate and circular piston. The sliding ability is achieved

by combining the following three materials into the

sliding system:

ILM bridge pot bearing type

- Polished stainless steel (mirror finishing) welded

to the bottom side of the rectangular sliding plate.

- Circular dimpled PTFE disc recessed to half of its

thickness in the piston. Minimum protrusion is given

to grant full contact with stainless steel at any time.

PTFE displays excellent resistance to fatigue, impact

and ageing.

- Special lubricant grease: silicone base. This grease

fills the dimples in the PTFE disc ensuring a permanent

very low friction system coefficient and preventing

abrasion of PTFE.

The combination of these three materials gives a regular

range of friction coefficient between 1% and 3%.

Type PU (guided sliding) is obtained by assembling a

guide bar, either welded or bolted, on top of the piston.

The guide bar slides along a longitudinal recess in the

sliding plate, thus avoiding transverse movement.

Contact between guide bar and sliding plate consists of

special composite material (DU-metal) fixed to the guide

bar and stainless steel backed to the sliding plate,

ensuring a minimum friction coefficient.

Neoprene bearing

3

1. General


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2. Specifications and design parameters

4

BASIC DESIGN PARAMETERS

UPPER PLATE

Load distribution at 60

The length of the upper plate must

grant a proper load distribution in the

concrete in the event of max. design

movement

L5 = D6 + 2 Ex + 2T5/3+50

Where :

D6 diameter of PTFE discEx Max. design movement

T5 Thickness of upper plate

P.T.F.E.

Average allowable stress at SLS undermax. vertical load D1/50>12mm

DOWELS -STUDS

In order to grant a safety factor not

less than 1,5 against sliding, the

following condition must be verified::

/S*Vmin+n*Hd>Zh

where :

= 0.5 Steel-concrete friction coefficient

S = 1.5 Safety factor

n Number of dowels ( or studs)

Hd Shear capacity of each dowel

MATERIALS

STANDARD SPEClFlCATlONS

TOP PLATE

Quality steel St37 or

St52 according to

DIN 17.100

Stainless steel

according to AISI 304

LUBRICANT

Silicone grease type 300

P.T.F.E.

P.T.F.E. pad with dimples accordingASTM D1457-91 a Type 1

Grade 2BS 3764 Grade A

GUIDE

Quality steel St37 orSt52 according to

DIN 17.100

DU-metal

EXTERNAL SEALING

RING

Spongy neoprene

PISTON

Quality steel St37 orSt52 according to

DIN 17.100

INTERNAL SEALING

RING

Double gasket brass ring

ELASTOMER PAD

Natural rubber accordingAASHTO 50Sh+-5

POT (STEEL RING +

BASE PLATE)

Quality steel St37 or

St52 according to

DIN 17.100

ANCHOR SOCKETS

Galvanized bolts

Steel CK35 according

DIN 17.200


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It should be pointed out that the cost of the POT bearings

varies with the changes in design parameters. Forinstance the allowable bearing pressure on the concrete,

has a maj or influence. It depends on the characteristic

concrete strength, Br and the relation between the

diameters of direct circular loaded area (D2) and circular

enlarged area, with the same centre of gravity, lying totally

within the top support area (D) (see figure). The following

design rules are proposed for the allowable bearing

pressure on concrete :

5

3. Information required for the design of POT bearings

Dimensions given in the section 4 tables are indicative,

representing a presizing of the three different types of POT

bearings. They are given to make the design engineers

work easier and should be used with caution, bearing in

mind that they are calculated from the following assumed

design parameters:

Al lowable concrete pressure

Pier : 20 N/mm 2 Deck : 20 N/mm2

Rotation = 0.01 rad.

Loads and movements

1.- Free sliding type PL

1.1 Hxmax= 3 % of Vmax.

1.2 Hymax = 3% of Vmax.

1.3 Ey= +- 10mm.

1.4 Ex= * 50mm.

2.- Guided slid ing type PU

2.1 Hxmax= 3 % of Vmax

2.2 Hymax = 5% of Vmax

2.3 Ey= 0 always

2.4 Ex= +- 50mm.

3.- Fixed type PF

3.1 Hxmax = 5% of Vmax

3.2 Hymax = 5% of Vmax

3.3 Ey= 0 always

3.4 Ex= 0 always

4.- For every type

4.1 Vg = 70% Vmax

4.2 Vmin = 50% Vmax

4.3 Hxg = 90% Hxmax

4.4 Hyg = 90% Hymax

4.5 Hxmin = 70% Hxmax

4.6 Hymin = 70% Hymin

Our Technical Department is at your disposal to supply any

specific information in order to assist you from the early

design stage. To assess the optimum POT bearing

dimensions for your application and to carry out a detailed

design, we need the following information:

Project: Bearing type :

Loads:

Load c as e Vmax.

Vmax: kN Hx: kN Hy: kN

Lo ad c as e Vg . ( pe rmane nt l oad)

Vg: kN Hxg: kN Hyg: kN

Lo ad c as e Vmin.

Vmin: kN Hx: kN Hy: kNRotation and movement :

Ex+-: mm. Ey +-: mm. Rotation: rad.

Al lowablebearIng pressure on concrete :

Pier : MPa Deck : MPa

1 .- For direct distribution from the pot to the concrete:

b= Br * D < 1, 4 *Br

1, 8 D2

2.- For distribution plates through masonry plates

between pot and concrete:

b= Br * D < 1, 0*Br

2, 1 D2

3.- For distribution through sliding plates:

b= Br * D < 0, 9 *Br

2, 3 D2

Bursting reinforcement to be designed in SLS for a total

force of:

with the allowable stress in reinforcement between

18 0 MPa and 200 MPa according to the steel grade.

Technical departement in the factory


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4. Dimensions data sheets

6

POT bearing type PU

This type of bearing :

- Allows longitudinal movements

- Constrains transversal movements

- Bears horizontal transversal loads

BEARING TYPE

PU-100

PU-200

PU-300

PU-400

PU-500

PU-600

PU-700

PU-800PU-900

PU-1000

PU-1200

PU-1400

PU-1600

PU-1800

PU-2000

PU-2400

PU-2800

PU-3000

PU-3500

PU-4000

PU-4500PU-5000

TH

8 0

8 1

8 5

8 4

98

96

102

106119

115

122

131

198

154

153

161

18 0

170

192

190

196216

L5

393

478

538

608

665

719

768

8 148 57

8 98

975

1045

1110

1171

1229

1337

1436

1515

1593

1705

17931885

B5

293

378

438

508

565

719

768

8 148 57

8 98

975

1045

1110

1171

1229

1337

1436

1515

1593

1705

17931885

oD2

293

378

438

508

565

619

668

714757

798

8 75

945

1010

1071

1129

1237

1336

1415

1493

1605

1693178 5

DP

256

316

360

408

450

501

536

568599

628

68 2

732

778

8 21

8 62

938

1008

1064

1120

1199

12601325

DL

200

200

200

250

250

300

300

300300

300

350

350

350

350

350

350

350

350

350

350

350350

DM

40

40

40

50

50

60

60

6060

60

70

70

70

70

70

70

70

70

70

70

7070

DIMENSIONS IN mm

NOTE : The dimensions given in the tables are indicative. Design and dimensions may be modified by CTT without prior notification.

DL

TH

DL


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7

BEARING TYPE

PL-100

PL-200

PL-300

PL-400

PL-500

PL-600

PL-700

PL-800

PL-900

PL-1000

PL-1200

PL-1400

PL-1600

PL-1800

PL-2000

PL-2400

PL-2800

PL-3000

PL-3500PU-4000

PL-4500

PL-5000

TH

74

79

8 5

96

98

96

110

106

119

115

122

131

136

154

153

161

18 0

160

17218 6

194

216

L5

353

457

538

605

665

719

768

8 14

8 57

8 98

975

1045

1110

1171

1229

1337

1436

148 2

15931693

1793

1885

B5

273

377

458

525

58 5

639

68 8

734

777

8 18

8 95

965

1030

1091

1149

1257

1356

1402

15131616

1713

1805

oD2

253

357

438

505

565

619

668

714

757

798

8 75

945

1010

1071

1129

1237

1336

1415

15121605

1693

178 5

DP

228

302

360

406

450

48 7

521

554

58 5

613

668

717

764

8 06

8 47

924

994

1050

1118118 4

1246

1311

DL

150

150

200

200

200

250

250

250

250

250

250

250

250

250

250

250

250

250

250250

250

250

DM

30

30

40

40

40

50

50

50

50

50

50

50

50

50

50

50

50

50

5050

50

50

DIMENSIONS IN mm


POT bearing type PL


- Allows longitudinal and transversal movements

- Does not resist any horizontal load (except friction)


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8

POT bearing type PF


- Constrains longitudinal and transversal movements

- Bears longi tudinal and transversal horizontal loads

BEARING TYPE

PU-100

PU-200

PU-300

PU-400PU-500

PU-600

PU-700

PU-800

PU-900

PU-1000

PU-1200

PU-1400

PU-1600

PU-1800

PU-2000

PU-2400

PU-2800PU-3000

PU-3500

PU-4000

PU-4500

PU-5000

TH

8 0

8 1

8 5

8 498

96

102

106

119

115

122

131

198

154

153

161

18 0170

192

190

196

216

L5

393

478

538

608665

719

768

8 14

8 57

8 98

975

1045

1110

1171

1229

1337

14361515

1593

1705

1793

1885

B5

293

378

438

508565

719

768

8 14

8 57

8 98

975

1045

1110

1171

1229

1337

14361515

1593

1705

1793

1885

oD2

293

378

438

508565

619

668

714

757

798

8 75

945

1010

1071

1129

1237

13361415

1493

1605

1693

178 5

DP

256

316

360

408450

501

536

568

599

628

68 2

732

778

8 21

8 62

938

10081064

1120

1199

1260

1325

DL

200

200

200

250250

300

300

300

300

300

350

350

350

350

350

350

350350

350

350

350

350

DM

40

40

40

5050

60

60

60

60

60

70

70

70

70

70

70

7070

70

70

70

70

DIMENSIONS IN mm



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9

5. Accessories

ANTIDUST SKIRTS

These devices are installed in order to avoid the dust on the sliding parts of the bearing,

that could affect the friction coeficient.

They are recommended either for both free sliding and guided sliding types. They are

manufactured from neoprene strips bolted to the upper plate of the bearing through a

metallic ruler.

Antidust skirts

RULER MEASURING MOVEMENTS

This device is designed to measure then movements of the bearing, and consequently,

the movements of the deck visually.

A metallic or aluminium ruler is connected to the upper plate and a rod is welded, by

means of a support, to the masonry plate or to the pot.

The proj ection of the rod on the ruler indicates the movement of the deck.

Measurement ruler


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6. Site Installation

10

2. LEVELLING OFTHE BEARING

Place the pot bearing in its position levelling it with

timber wedges. It is important to ensure that the X

axis of the bearing is aligned in the longitudinal

direction of the bridge and that the X and Y

directions are accurately horizontal. For bearings

allowing horizontal displacements it should be

checked that the arrow painted on the slide plate

is pointing in the correct direction.

1. PREPARATION OF THE PIERS

Build the piers leaving on them the required

recesses according to the dimensions indicated

on the drawings.

3. GROUTlNG

Install the form for grouting the space between

pier and pot bearing. Grout the space between

pier and pot bearing. Fill in the recesses checking

that the level is the correct.

5. REMOVAL OF FIXING PLATES

Once the formwork has been removed, thebearing is definitively installed. Remove the lateral

fixing plates of the bearing in order to allow its

free movement.

4. FORMING OF DECK

The formwork of the deck is placed embedding

the upper dowels of the bearing.


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11

7. POT bearings for incrementally launched bridges

POT bearings for incrementally launched bridges have a

dual function. First, they provide low friction sliding surfaces

over piers as the deck is launched during construction.

Thereafter, they become permanent bearings for the

completed bridge. A POT bearing serving both functions is

shown in the picture above.

During construction, a fixing device avoids relative

movement between sliding plate and pot cylinder.

POT bearing for ILM bridge

The sliding plate is supplied with a second stainless

steel sheet on top. Inserting neoprene-teflon pads

between deck and bearings allows the launching

operation to be carried out. Pads, second stainless steel

sheet and fixing device are removed after launching. To

achieve this, the deck is lifted by means of hydraulic j acks

placed on top of the piers.

Once this operation is achieved, the deck is lowered to

its final position, the j acks are removed and the sliding

plate is connected to a previously embedded steel platein the deck.

Finally, the fixing devices used for transportation are

released, thus the bearing is in its final service position.

For the correct design of these bearings, it is very

important to know the loads during launching, because,

they have maj or influence in the actual length and

thickness of the sliding plates.

Although the cost of this type of bearing is higher than

the standard ones, their use represents a saving for the

j ob because :

- Temporary launching bearings are not required

- Demolition and replacement of the temporary bearings

by permanent ones, are costly and time consuming

are avoided.


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8. Special POT bearings

12

DOUBLE POT BEARINGS

Bearings with double pot and single upper plate.

They are designed for an ILM bridge. The aim was

to center the loads during launching under the webs

of the concrete deck.

These bearings were installed in the High speed

railway Madrid-Sevilla at Ademuz (Cordoba).

BEARINGS WITH "SPRINGS"

These bearings incorporate external springs that

control the relative movements between sliding

plate and pot.

These bearings were installed in the Cartuj a

viaduct in Seville (approaches to Alamillo bridge).

ELIPTIC POT BEARINGS

The pot has an elliptical shape. These bearings werespecially designed for the Aruca-Las Palmas j unction

in the Canary islands.

CTT manufactures special tailor-made POT bearings

designed to fit the technical specifications and requirements

of individual proj ects.

CTT offers a wide range of technical solutions for the design

of special POT bearings; our technical department has the

capability to develop alternatives to the standard product,

thus adapting our design to the proj ect requirement.

The pictures below show several special bearings

designed for specific j obs.


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13

9. Recent bridge structures

4TH BRIDGE OVER GUADIANA RIVER

IN BADAJOZ. SPAIN

OWNER:

J unta de Extremadura.

CONTRACTOR:

UTE Puente de Badaj oz

DYCSA-FCC

CONSULTANTS:

FCC Construccion. Servicio Tecnico.

D. J os Ignacio Gonzalez Esteban,

D J os Luis Alvarez Poyatos

BEARING TYPE:

PL-1000, PL-500, PU-1000, PU-500

VIADUCT OVER GOR RIVER IN

GRANADA. SPAIN

OWNER

Direccion general de carreteras

J unta de Andalucia

CONTRACTOR:Entrecanales y Tavora

CONSULTANTS:

Direccion general de carreteras

BEARING TYPE:

PL-350, PUE-1150, PLE-1100

BRIDGE OVER VAROSA RIVER

LANCO REGUA-RECONCOS

PORTUGAL

OWNER

J AE

CONTRACTOR:

ENGIL - Soares da Cosat

CONSULTANTS:

Ing. Armando Rito

BEARING TYPE:

PL-38 0, PU-1550,S PU-1450


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14

ACCESS TO ALAMILLO BRIDGE IN

SEVILLE. SPAIN

OWNER:

J unta de Andalucia

CONTRACTOR:

U.T.E. Alamillo

DYCSA-FCC

CONSULTANTS:

FCC

BEARING TYPE:

PL-38 0, PU-1550, PU-1450

MADRID-SEVILLE HIGH SPEED

TRAININ ADEMUZ (CORDOBA).

SPAIN

OWNER:

M.T.T.C.

CONTRACTOR:

DYCSA

Entrecanales y Tavora, s.a.

COMSA

CONSULTANTS:

EPTISA

BEARING TYPE:

PL-400, PPUE-1650, PPLE-1650

LAHORE-ISLAMABAD MTY.

PAKISTAN

OWNER:

National Hghway Authority Pakistan

CONTRACTOR:

DAEWOO Corporation (Korea)

MTY CONSULTANTS:

SMEC (Australia)

ILM BRIDGES CONSULTANTS:

CTT-Stronghold (Spain)

Mr. Wolfgang Buchler (Switzerland)

BEARING TYPE:

PL-1000, PUE-1600, PLE-1000


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15

10. Quality control and tests

TESTING

The quality and behaviour of CTT POT bearings is

regularly checked by several tests :

- vertical load tests

- vertical and horizontal load tests

- friction tests

- rotation test

These tests are generally carried out in an official

laboratory next to our factory :

- Laboratori General dAssaigs i lnvestigacions LGAI

in Barcelona.

Testing POT bearings in laboratory

CORROSION PROTECTION

All steel areas in contact with the atmosphere are

protected with the following standard corrosion protection:

- surface conditioning by sand blasting according to

SIS-055900, grade Sa 2 1/2

,

- two layers of epoxy primer (cathodic protection),- one finishing layer of acrylic resin and chloride

plasticizer paint.

The minimum total thickness of the three-layer protection

is between 100 n and 120 n.

POT bearings are supplied with different corrosion

protection following specific requirements such as

metalisation or use of special self-protected steels.

High precision techniques are used in the manufacturing

and finishing of POT bearings. Given the loads to be

transmitted and the deformations to be absorbed, the

quality of the materials and workmanship are ensured

by Quality Control Plans regularly revised to meet any

particular specification.

Since early 1997, we have established a quality manual

and a manual of procedures in order to be certified ISO-

9002-94.

CTT, acting as a member of the European Standarisation

Commitee CEN collaborates in the European Standard

for POTbearings.

Testing platform general view

Quality control document


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CTT Pot Bearings