ctt pot bearings(2)

8/8/2019 CTT Pot Bearings(2)

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CONTENTS

1. General page 3

2. Specifications and designparameters page 4

3. Information 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

2


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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:

v 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.

v Neoprene bearing

3

1. General


4/16

2. Specifications and design parameters

4

BASIC DESIGN PARAMETERS

UPPER PLATE

Load distribution at 60

The length of the upper plate mustgrant a proper load distribution in theconcrete in the event of max. designmovement

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

Where :

D6 diameter of PTFE discEx Max. design movementT5 Thickness of upper plate

P.T.F.E.

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

DOWELS -STUDSIn order to grant a safety factor notless than 1,5 against sliding, thefollowing condition must be verified::

/S*Vmin+n*Hd>Zh

where : = 0.5 Steel-concrete friction coefficientS = 1.5 Safety factorn 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:

Allowable 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 sliding 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 o ad)

Vg: kN Hxg: kN Hyg: kN

Load c as e Vmin.

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

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

AllowablebearIng 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.

v 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-100PU-200

PU-300PU-400

PU-500PU-600

PU-700

PU-800PU-900

PU-1000PU-1200

PU-1400PU-1600

PU-1800PU-2000

PU-2400PU-2800

PU-3000

PU-3500PU-4000

PU-4500PU-5000

TH

8 08 1

8 58 4

9896

102

106119

115122

131198

154153

16118 0

170

192190

196216

L5

393478

538608

665719

768

8 148 57

8 98975

10451110

11711229

13371436

1515

15931705

17931885

B5

293378

438508

565719

768

8 148 57

8 98975

10451110

11711229

13371436

1515

15931705

17931885

oD2

293378

438508

565619

668

714757

7988 75

9451010

10711129

12371336

1415

14931605

1693178 5

DP

256316

360408

450501

536

568599

62868 2

732778

8 218 62

9381008

1064

11201199

12601325

DL

200200

200250

250300

300

300300

300350

350350

350350

350350

350

350350

350350

DM

40

40

4050

5060

60

6060

6070

7070

7070

7070

70

7070

7070

DIMENSIONS IN mmNOTE : 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-200PL-300

PL-400PL-500

PL-600PL-700

PL-800

PL-900PL-1000

PL-1200PL-1400

PL-1600PL-1800

PL-2000PL-2400

PL-2800

PL-3000

PL-3500PU-4000PL-4500

PL-5000

TH

74

798 5

9698

96110

106

119115

122131

136154

153

16118 0

160

17218 6194

216

L5

353

457538

605665

719768

8 14

8 578 98

9751045

11101171

1229

13371436

148 2

159316931793

1885

B5

273

377458

52558 5

63968 8

734

7778 18

8 95965

10301091

1149

12571356

1402

151316161713

1805

oD2

253

357438

505565

619668

714

757798

8 75945

10101071

1129

12371336

1415

151216051693

178 5

DP

228

302360

406450

48 7521

554

58 5613

668717

7648 06

8 47

924994

1050

1118118 41246

1311

DL

150

150200

200200

250250

250

250250

250250

250250

250

250250

250

250250250

250

DM

30

3040

4040

5050

5050

50

5050

5050

5050

50

50

505050

50


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 longitudinal and transversal horizontal loads

BEARING TYPEPU-100

PU-200

PU-300

PU-400PU-500PU-600

PU-700PU-800

PU-900PU-1000

PU-1200

PU-1400PU-1600

PU-1800PU-2000

PU-2400

PU-2800PU-3000

PU-3500PU-4000

PU-4500PU-5000

TH

8 0

8 1

8 5

8 49896

102106

119115

122

131198

154153

161

18 0170

192190

196216

L5

393

478

538

608665719

7688 14

8 578 98

975

10451110

11711229

1337

14361515

15931705

17931885

B5

293

378

438

508565719

7688 14

8 578 98

975

10451110

11711229

1337

14361515

15931705

17931885

oD2

293

378

438

508565619

668714

757798

8 75

9451010

10711129

1237

13361415

14931605

1693178 5

DP

256

316

360

408450501

536568

599628

68 2

732778

8 218 62

938

10081064

11201199

12601325

DL

200

200

200

250250300

300300

300300

350

350350

350350

350

350350

350350

350350

DM

40

4040

505060

6060

6060

70

7070

7070

70

707070

70

7070



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

metallic ruler.

v 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 rulerv


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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 Xaxis of the bearing is aligned in the longitudinal

direction of the bridge and that the X and Ydirections are accurately horizontal. For bearings

allowing horizontal displacements it should bechecked 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 indicatedon the drawings.

w

v

v

v

3. GROUTlNG

Install the form for grouting the space betweenpier and pot bearing. Grout the space between

pier and pot bearing. Fill in the recesses checkingthat the level is the correct.

5. REMOVAL OF FIXING PLATES

Once the formwork has been removed, thebearing is definitively installed. Remove the lateralfixing plates of the bearing in order to allow its

free movement.

4. FORMING OF DECK

The formwork of the deck is placed embeddingthe upper dowels of the bearing.

w


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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 surfacesover 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 relativemovement between sliding plate and pot cylinder.

v POT bearing for ILM bridge

The sliding plate is supplied with a second stainless

steel sheet on top. Inserting neoprene-teflon padsbetween deck and bearings allows the launching

operation to be carried out. Pads, second stainless steelsheet 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 toits 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 thej ob because :

- Temporary launching bearings are not required

- Demolition and replacement of the temporary bearingsby 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 websof 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 slidingplate and pot.

These bearings were installed in the Cartuj aviaduct in Seville (approaches to Alamillo bridge).

w

v

ELIPTIC POT BEARINGS

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

w

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 thecapability to develop alternatives to the standard product,

thus adapting our design to the proj ect requirement.

The pictures below show several special bearingsdesigned 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 INGRANADA. 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-RECONCOSPORTUGAL

OWNER

J AE

CONTRACTOR:

ENGIL - Soares da Cosat

CONSULTANTS:

Ing. Armando Rito

BEARING TYPE:

PL-380, PU-1550,S PU-1450

v

w

v


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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-380, PU-1550, PU-1450

v

w

MADRID-SEVILLE HIGH SPEED

TRAININ ADEMUZ (CORDOBA).SPAIN

OWNER:

M.T.T.C.

CONTRACTOR:

DYCSAEntrecanales y Tavora, s.a.

COMSA

CONSULTANTS:

EPTISA

BEARING TYPE:

PL-400, PPUE-1650, PPLE-1650

w

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 officiallaboratory next to our factory :

- Laboratori General dAssaigs i lnvestigacions LGAI

in Barcelona.

v Testing POT bearings in laboratory

CORROSION PROTECTION

All steel areas in contact with the atmosphere areprotected 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 corrosionprotection following specific requirements such as

metalisation or use of special self-protected steels.

High precision techniques are used in the manufacturingand finishing of POT bearings. Given the loads to be

transmitted and the deformations to be absorbed, thequality of the materials and workmanship are ensured

by Quality Control Plans regularly revised to meet anyparticular specification.

Since early 1997, we have established a quality manualand a manual of procedures in order to be certified ISO-

9002-94.

CTT, acting as a member of the European StandarisationCommitee CEN collaborates in the European Standard

for POT bearings.

v Testing platform general view

v Quality control document


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