235423978 iabse bridge bearings pdf

8/20/2019 235423978 IABSE Bridge Bearings PDF

1/86

Structural Engineering Documents

Gunter Ramberger

Structural Bearings

and Expansion Joints

for Bridges

International Association for Bridge and Structural Engineering

Association lnternationale des Ponts et Charpentes

lnternationale Vereinigung fur Bruckenbau und Hochbau

IABSE

AIPC

IVBH


2/86

Copyright

0

002 by

International Association for Bridge and S tructural En gineering

All rights reserved. No part of this book may be reproduced in any form or by any

means, elec tronic or mechanical, including photocopying, reco rding, or by any

information storage an d retrieval system, without permission in writing from the

publisher.

ISBN 3-85748-105-6

Printed in Sw itzerland

Publisher:

ETH H onggerberg

CH-8093 Zurich, Switzerland

IABSE-AIPC-IVBH

Phone: Int. + 41-1-633 2647

Fax: Int. + 41-1-633 1241

E-mail:

[email protected]

Web:

http://www.iabse.ethz.ch


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Dedicated to the com mem oration of the late Prof. Dr. techn. Ferdinand Tschemmernegg,

University of Innsbruck.

Preface

It is my hope that this treatise w ill serve as a textbook for students and as information

for civil engineers involved in bridge construction. My intent was to give a short

guideline on bearings and expan sion joints for bridge designers and not

to

mention all

the requirements for the manufacturers of such products. These requirements are

usually covered by product guidelines, which vary between different co untries.

Not all the references are related to the content of this documen t. They are more o r less

a collection of relevant papers som etimes dealing with spec ial problem s.

I express many thanks to Prof. Dr.-Ing. Ulrike Kuhlmann, University of Stuttgart,

chairperson of Working Com mission

2

of IABS E, wh o gave the impe tus for this work;

to her predecessor of the IAB SE C om mission, Prof. Dr. David A. Nethercot, Imperial

College of Sc ience, Technology an d Medicine, Lo ndon, for reviewing the m anuscript,

and Prof. Dr. Manfred H irt, Swiss Federal Institute of Technology, Lausanne, for his

contributions and comm ents.

I wish to thank J.

S .

Leend ertz, Rijkswaterstaat, Zoeterm eer; Eugen Briihwiler, Swiss

Federal Institute of Technology, Lausanne; Prof. R. J. Dexter, University

of

Minneso-

ta; G. W olff, Reissner

&

Wolff, W els;

0.

Schimetta

t,

Am t der

00

Landesregierung,

Linz; Prof. B. Johan nsson, LuleA Tekniska U niversitet, for amendm ents, corrections,

remarks and comments. I thank also my assistant Dip1.-Ing. Jorgen Robra for his

valuable contributions

to

the paper, especially for the sk etches and drawings, and my

secretaries Ulla S am m and Ba rbara Bastian for their expert typing of the manuscript.

Finally, I would like to thank the IA BS E for the publication of this Structural Engi-

neering Document.

Vienna , April

2002

Gunter Ramberger


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Table of

Contents

1.

Bearings

1.1 Introduction

1.2 The role of bearings

1.3 General types of bearings and their movem ents

1.4 T he layout

of

bearings

1.5 Calculation of bearing reactions and bearing m ovem ents

1.6 Construction of bearings

1.7 Materials for bearings

1.8

Analysis and design

of

bearings

1 .9

Installation of bearings

1.10 Inspection and maintenance

1. 1 Replacement of bearings

1.

2

Codes and standards

1.13 References

2. ExpansionJoints

2.1 Introduction

2.2 The role of expansion joints

2.3

Calculation

of

movements

of

expansion joints

2.4 Construction of expansion joints

2.5 M aterials for expansion joints

2.6 Analysis and design

of

expansion joints

2.7

Installation of expansion joints


2.9 Rep lacem ent of expansion joints

2.10 References

7

7

7

9

16

19

29

33

37

38

39

41

42

51

51

51

58

70

72

84

86

87

88

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7

1 Bearings

1.1

Introduction

All bridges are subjected to movements due to temperature expansion and elastic

strains induced by various forces, especially due to traffic loads. In form er times our

bridges w ere built of stones, bricks or timber. Obviously, elongation and shortening

occurred in those bridges, but the temperature gradients were small due to the high

mass of the stone bridges. Timber bridges w ere sm all or had natural joints, so that the

full elongation values we re subdivided into the elongation of eac h part. O n the other

hand, the elongation and shortening of timber bridges du e to change of moisture is of-

ten higher than that due to therm al actions. With the use

of

constructional steel and,

later on, of reinforced and prestressed concrete, bridge bearings had to b e used. T he

first bearings were rocker and roller bearings made of steel. Numerous rocker and

roller bearings have operated effectively for more than a century. W ith the develop -

ment of ageing-, ozone- and UV -radiation-resistant elastom ers and plastics, new ma-

terials for bearings becam e available. Various types of bea rings we re developed with

the advantage of an area load transmission in contrast to steel bearings with linear or

point load transmission, w here elastic analysis leads theoretically to infinite compres-

sion stresses. For the bearings the problem s of m otion in every direction and of load

transmission were solved, but the problem of insufficient durability still exists. W hilst

it is reasonable to assu me the life of steel bearings to be the same

as

that of the bridge,

the life of

a

bearing with elastom er or plastic parts can b e shorter.

1.2 The role of bearings

Th e role of bearings is to transfer the bea ring reaction from the superstructure to the

substructure, fulfilling the design requiremen ts concerning forces, displacem ents and

rotations. The bearings should allow the displacements and rotations

as

required by

the structural analysis with very low resistance du ring the whole lifetime. Thus, the

bearings should withstand all external forces, thermal actions, air moisture changes

and weather conditions of the region.

1.3

Normally, reaction forces and the corresponding m ovements follow

a

dual principle

a non zero bearing force corresponds to a zero movem ent and vice versa. An exception

is given only by friction forces which are nearly co nstant during the mo vem ent, and by

elastic restraint forces which are generally proportional to the displacem ent.

Usually, the bearing forces are divided into vertical and horizontal com ponents.

Bea rings for vertical forces normally allow rotations in on e direction, some types in

all directions. If they also transmit horizontal forces, usually vertical forces are com-

bined.

General types of bearings and their movements


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1. Bearings

A special type of bearing transmits only horizontal forces, while allowing vertical

displacements.

The following table (Table

1.3-

1 ) shows the common types of bearings, including the

possible bearing forces and displacements. Friction and elastic restraint forces are not

considered.

Symbol Function

Construction

Point rocker bearing

Pot bearing; Fixed

elastomeric bearing;

Spherical bearing

All translation

fixed

Rotation all

round

Constr. point rocker

sliding bearing;

Constr. pot sliding

bearing; Const.


Constr. spherical

sliding bearing

Free point rocker

bearing; Free pot

sliding bearing; Free


Free spherical sliding

bearing; Link bearing

with universal joints

(tension and

compression)

Horizontal

movement in

one direction

Rotation all

around

Horizontal

movement in

all directions

Rotation

all

round

Line rocker bearing

Leaf bearing

(tension and

compression)

Roller bearing; Link

bearing (tension and

compression);

Constant line rocker

sliding bearing

Free rocker sliding

bearing; Free roller

bearing; Free link

bearing

All translation

fixed

Rotation

about one axis

Horizontal

movement in

one direction

Rotation

about one axis

Horizontal

movement i n

all direction

Rotation

about one axis

All horizontal

tranal. fixed

Rotation all

round

+

~

HoriLontal force

bearing

Horizontal

movement

in

one direction

Rotation all

round

Guide bearing


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1.4

The

layout of

bearings

9

Tuble 1.3-1 82

1.4

The

layout

of

bearings

1.4.1 General

Bearings can be arranged at abutments and piers (fig. 1.4.1-1

;

fig. 1.4.1-2) under the

webs of the main girders, under diaphragms (fig. 1.4.1-3), and under the nodes

of

truss bracings. The webs and the diaphragms of concrete bridges have to be properly

reinforced against tensile splitting; steel bridges need stiffeners

in

the direction of the

bearing reactions to transfer the concentrated bearing loads to the superstructure and

the substructure. Abutments and piers also have to be properly reinforced under the

bearings against tensile splitting.

77

Fig. I .4. I

-

I : Bearings at a n abutment

,

I ~- ~

I

Fig. 1.4.1-2: Bearings

at

u pier

I7

Fig. 1.4.1 3: Bearing at a single pier


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10 1 .

Bearings

Th e layout of the bearings should correspond to the structural analysis of the who le

structure (super- and substructure together ).

If

the settlem ent and the deflection of the

substructure can be neglected the structural analysis of the superstructure, including

the bearings, can be separated from that of the substructure. Som etimes the mod el for

the analysis, especially of the su perstructure, will be simplified by assum ing the fol-

lowing: bearings are situated directly

on

the neutral axis of the girder

(fig. 1.4.1-6),

he

motion of the bea rings occurs w ithout restraint, b earings have no clearance, etc. In this

case we must consider the correct system (fig.

1.4.1-5)

at least for the design of the

bearings and take into account the influence of the simplifications on the structure.

&

Fig.

I

.4.1 4: Reality

A

Fig. I .4.1 5: Correct system

On the abutm ents or separating piers

i t

is normal to use at least two vertical bearings

to avoid torsional rotations. At interm ediate piers one o r more vertical bearings may

be used. If more than one bearing is used the rotational displacement at the pier is re-

strained. M ore than three vertical supports of the superstructure lead to statically in-

determinate bearing conditions, but even the sim plest bridge has at least four vertical

bearings. If the torsional stiffness of the superstructure is low (e.g. open cross sec-

tions)

i t may b e neglected and the layout with four bearings becomes isostatic. If the

torsional stiffness is not negligible (e.g. box girders) we have to take it into acco unt for

the structural analysis, especially for skewed and curved bridges. On a bridge with n

> 3 vertical supports, n - 3 bearing reactions can be cho sen freely within a reasonable

bandw idth. This possibility can be used to prestress the su perstructure and to distri-

bute the bearing reactions as desired.

If the bearings are situated (nea rly) in a plane we need at least one horizontally fixed

and one horizontally mo veable bearing. Th e moving direction mu st not be orthogo nal


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.4

The

layout of bearings

11

to the polar line from the fixed to the moveable bearing. If m ore than two b earings in

the horizontal direction are necessary, the basic principle should be that an overall

uniform extension, caused by temperature or shrinkage, shall be possible without

restraint.

In general, there a re two possibilities for the arrangem ent of the bearings:

a)

arrangem ent in

a

horizontal position (fig.1.4.1-7)

b) arrangement in a position parallel to the road or rail surface (fig. 1.4.1-8).

I

1 - - - _- - - - - a

Fig.1.4.1 -7: Horizontal arrangement

of

the bearings case a)

- I f=-- I ,,displaced bridge (

Fig. 1.4.1-8: Inclined arrangement ofthe bearings case b)

Case

a)

has the advantage that only vertical bearing reactions and

no

permanent hori-

zontal reactions result from vertical loads, but it has the disadvan tage that bridges w ith

inclined gradients require a step at the expansion joint due to m ovem ents in the sup er-

structure. Th e greater the elonga tion or shortening, the greater the step required.

Case b)

has

the advantage that the slope of the ex pansion joint is independent of the

movement of the bridge. The inclination of the surface of support gives the direction

of the normal force. Besides vertical reaction forces, also horizontal reaction forces

result from vertical loads. Permanent horizontal actions can lead to

a

displacement

by creep

of

the concrete and the soil and, thus, to crooked piers.


10/86

12 1. Bearings

1.4.2

For single span girders the layout of the bearings is straightforward. One fixed and one

moveable bearing is provided on each abutment, all other bearings are just vertical

supports, moveable in any horizontal direction. For wide bridges the horizontally

fixed bearings are located in or near the bridge axis.

The layout

for

different types of bridges

Formerly, the “classical” arrangement of the bearings for a bridge with two main gird-

ers consisted of one fixed and one lengthwise moveable bearing at one abutment and

one lengthwise moveable and one free bearing at the other abutment (fig.1.4.2-

1).

This

layout has the advantage that longitudinal horizontal forces (braking and traction

forces) can be distributed into the two bearings at the abutment, but it has the

disadvantage that horizontal forces in the cross direction (wind) and temperature dif-

ferences cause horizontal restraint forces, provided that bearings have no clearance on

the abutments.

The author prefers the statically determinate system with

only one lengthwise re-

strained bearing at the abutment concerned because the actual clearance of a bearing

is not determinable

in

reality (fig.

1

‘4.2-2).

.

-

-

++-

LA-

:”.

;c

11, I,

I

Fig. 1.4.2-1: “Classical” layout

Fig. 1.4.2-2: Horizontally statically determinate system better than classical layout)

.

_ - - - -------- - - -

-

Fig. 1.4.2-3: System with separated vertical and horizontal bearings statically deter-

minate system)


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1.4

The

layout of bearings

13

For skewed or horizontally curved single span bridges we have to decide whether the

horizontal force should be combined with the higher or with the lower vertical reac-

tion force. For all bearing constructions i t is easier to transfer horizontal forces in com-

bination with a high vertical force. In this case the resultant force stays nearer to the

centre, its angle to the vertical is smaller and leads to smaller bending moments in sub-

and superstructure (fig. 1.4.2-4).

I

I

I

Fig. 1.4.2-4: Inclination of the resu ltant o rce

Thus, the horizontally constrained bearings for skewed bridges should be placed at the

obtuse corners of the bridge, for curved bridges at the outer side (fig. 1.4.2-5).

Fig. 1.4.2-5: Skewed bridge

Fig. .4.2-6: La yo utfo r continuous girders


12/86

14

1. Bearings

For straight continuous girders normally tw o bearings are used at every abutm ent and

pier. If the torsion al stiffness is high (box girder) the interm ediate piers can be reduced

to a round column with on e bearing on the axis under the diaphragm. Constrained

bearings in the cross direction are the rule at all piers. If the horizontal bend ing stiff-

ness is very high we can transfer the horizontal forces only

at

the abutments. The same

considerations are suitable

also

for skewed and curved bridges (fig. 1.4.2-6).

Bearings for horizontal forces and guide bearings which transfer only horizontal

forces may be used in combina tion with leaf or link bearings w hich cannot transmit

horizontal forces.

The movement of an expansion joint must be linked by a guide like a constraint bear-

ing. Th e main m ovement of an expan sion joint should be in the axis of the traffic way.

Generally, this direction does not coincide w ith the direction of the polar line from the

fixed bearing to the moveable bearing at the abutment (fig.1.4.2-7). If all other

bearings have the sam e angle between the polar line and the moving direction there

results

a

layout of the bearings w ith no restraints

on

uniform elongation or shortening

(e.g. caused by therm al actions or shrinkage ), as show n below (fig.1.4.2-8).

Fig.1.4.2-7: Layout for curved bridges

Fig.

1.4.2-8:

Layout for curved continuous girders

no

constraint under overall tem-

pe ra tu re)

Fig. 1.4.2-9: Geometrical situation


13/86

I .4

The layout of bearings

15

Th e elongation is

A,,

=

k . ,


14/86

16

I .

Bearings

I

A

Fig. 1.4.3-1: Prying effect due to a eccentric loading

b) A similar situation occurs for a continuous girder with chequer pattern loading.

~

~

Fig. 1.4.3-2: Prying effect due to chequer pattern loading

c) It is not generally known that a skewed bridge with horizontally fixed bearings only in

one line exhibits the same effect under vertical loading, as the following figure shows:

Fig. 1.4.3-3: Prying for ces f o r a skewed bridge w ith vertical loading

Similar effects can occur for curved bridges. For the correct analysis of the bearing

reactions it is always necessary to model the bearings at the very point where they

are actually situated, and in combination with the substructure. The deflection of the

substructure can influence the constraint bearing reactions significantly.

1.5

Calculation of bearing reactions and bearing movements

1.5.1 Actions

According to Eurocode 1 (ENV 1991)the actions can be subdivided into:

permanent actions,

- variable actions,

extraordinary actions.


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1.5Calculation of bearing reactions and bearing movements 17

The bridge should take up the desired shape under all permanent loads, at the average

temperature (+lo C in most of the European countries) and, if time-dependant

displacements occur, at the time t = 00 at which time all moveable bearings should be

in the zero adjustment (null position). Variable actions and extraordinary actions lead

to deviation from this form.

Variable actions to consider are:

- raffic loads, considering the applicable dynamic coefficients

oads due to traffic loads, i.e.

nosing forces

centrifugal forces

braking forces

traction forces

wind on construction

wind on traffic loads

wind loads

settlements of abutments and piers

- hermal actions '

uniform temperature

vertical temperature gradient

horizontal temperature gradient

temperature differences between individual parts of the bridge (e.g. stay

cables, pylon and stiffening girder)

creep and shrinkage of concrete

earthquake actions

vehicle impact

derailment

rupture of the conductor line

others

Extraordinary actions to consider are:

1.5.2 Bearing reactions

For permanent actions such as self-weight of the construction, dead load and pre-

stressing, the bearing reactions can be calculated as one load case.

For the analysis of the bearings it is necessary to consider different combinations of

the bearing reactions:

maximum vertical force and the adjacent horizontal force,

minimum vertical force and the adjacent maximum horizontal force,

maximum horizontal force and the adjacent maximum vertical force,

maximum horizontal force and the adjacent minimum vertical force.

The simplest way to obtain these combinations is to calculate the variable actions, es-

pecially the traffic load, according to the influence line. One should bear in mind that

horizontal actions such

as

centrifugal forces or braking forces are proportional to the

vertical traffic load, but other loads, such

as

wind or traffic or traction forces for rail-

ways, are not.


16/86

18 1. Bearings

To obtain the extreme bearing reaction it is necessary to consider that all bridges are

three-dimensional and not merely plane systems.

The influence lines (influence surfaces) of the bearing reactions can be found as the

displacement curves (displacement surfaces) of the system, due to unit displacements

F

=

1

or cp =

1,

acting at the position and in the direction of the required force. If these

analyses are performed on

a

three dimensional model, the definitive influence area

will result directly (fig.1

S.2-1;

fig.1S.2-2) . If plane models are used for the analyses,

special care is necessary, particularly with continuous girders with open or box sec-

tions. The following examples demonstrate the difference:

Fig. .5.2-1:

Influence area for the verticul bearing reaction

A, box

section.

Fig. .5.2-2: ZnJuence areafor the vertical bearing reaction A, open section.

1.5.3 Bearing displacements

As already mentioned, the zero adjustment (null position) of every bearing has to be

defined. The displacements are measured from that position. Thus, for concrete and

composite bridges it is usual to consider displacements under time-dependent actions

such as creep and shrinkage from the time of installation of the bearing to the time de-

fined for the null position (normally t =

w ,

from which position the displacements due

to variable actions are measured.

To obtain the maximum displacements and rotations, again we can use influence lines.

The influence line of a displacement can be calculated as the displacement curve due

to the corresponding unit force P = I.

To take into account the imperfections due to installation, the temperature difference

for the calculation of bearing displacements should be assumed higher than for the

structural analysis of the bridge, or some additional displacement should be consi-

dered.


17/86

I .6 Construction of

bearings

1.6 Construction of bearings

Fig. 1.6 1gives un overview fo r the most comm on bearings.

19


18/86

20 1. Bearings

1.6.1

Elastomeric bearings

Elastomeric bearings are the simplest types of bearings. In the basic mode they con-

sist merely of an elastomeric block (usually rectangular or round). The elastomeric

works as a soft part between sub- and superstructure and allows movements in all di-

rections by elastic displacements or rotations. Under vertical loads the elastic block

bulges, leading to vertical displacements.

A

solution to this problem was found by re-

inforcing the elastic block by thin horizontal steel plates, vulcanized to the elastomer

(fig. 1.6.1

1).

The reinforcing plates prevent the block from bulging, thus leading to

very small vertical displacements, but they do not hinder horizontal displacements in

every direction and also allow small rotations in all directions. Every displacement

and rotation leads to restraining forces and moments which have to be taken into

account on the whole structure.

These restraining forces are possible if the friction between bearing and sub- and

su-

perstructure is sufficient. The friction forces F depend on the compressive force C and

the friction coefficient p with F = C

.

p. If displacements take place under a small

compressive force, sliding between bearing and sub- or superstructure can occur. To

avoid this it is necessary to use elastomeric bearings with resistance to sliding. This

can be achieved by applying vulcanized plates on the bottom and on the top of the

bearing, which can be connected to the sub- and superstructure by bolts, pins or ap-

propriate shapes (fig.

1.6.1-2).

Fig. .6.1-1: Elastomeric hearing una nch ore d)

Smaller, short time, horizontal forces can be transmitted by the restraining forces. If

these forces are higher or if they are permanent loads a restraining steel construction

is required. In these case the elastomeric bearing transmits the vertical force and

allows rotations, while horizontal forces in one or two directions are transmitted by

the steel construction (fig. 1.6.1-3 ; fig.1.6.1-4).

Fig. 1.6.1-2: Elastomeric bearing an ch ored )


19/86

1.6Construction of bearings 21

I

Fig. 1.6.1 3: Elastomeric bearing constraint

Combination: elastomeric bearing and steel construction fixed in one direction.

Fig. 1.6.1 4: Fixed e lastom eric bearing

Combination: elastomeric bearing and steel construction fixed in two directions.

1.6.2

Steel bearings

Steel bearings are the oldest type of bearings. They have been used for more than 100

years. The principle is simple: a flat plate rolls on another steel plate with a curved sur-

face. If this surface is part of a sphere, theoretically we obtain a point tangency. If this

surface is part of a cylinder, theoretically we obtain a linear tangency. In the first case

we speak of point rocker bearings, in the second case of line rocker bearings. These

bearings allow rotations in all or in one direction, but they do not allow displacements

Under minimal vertical reactions in combination with horizontal loads point rocker

bearings and line rocker bearings can exhibit damage of their connections, because of

tension. In combination with sliding elements these bearings are very sensitive to this

phenomenon, and it causes partial uplift and excessive wear as a result.

Linear tangencies can be found also in roller bearings consisting of a roll and a lower

and an upper plate (fig. 1.6.2-5). These bearings allow rotations in one direction and

displacements in one direction.

The problem with these bearings is a point or linear concentration of the bearing

force, which theoretically leads to infinite stresses. In 188

1,

the physicist Heinrich

Hertz found the solution of this problem: caused by the elastic deformation the theo-

retical point of tangency yields to a circle, the theoretical line of tangency yields to a

rectangle. The infinite stresses decrease to high but finite stresses, the so called Hertz

compression stresses over a very small contact zone. If the radius of the sphere or of

the cylinder decreases the Hertz stresses increase. From the local stress concentration

the stresses have to be distributed to the contact zones between bearing and sub- and

superstructure. Therefore, steel bearings normally need thicker plates for the stress

distribution than other types of bearings which transfer the bearing reactions over an

area.

(fig. 1.6.2-1

;

fig.1.6.2-4).


20/86

22

1. Bearings

Point rocker bearings are used for bearing reactions in the range 500 and 2500 kN, line

rocker bearings and roller bearings for loads in the range 200 and

20

000 kN.

Fig.1.6.2-I: Fixed point rocker bearing

Fig. 1.6.2-2: Point rocker bearing constraint in one direction

Fig. 1.6.2-3: Free point rocker bearing

Fig. 1.6.2-4: Line rocker bearing


21/86

.6 Construction

of

bearings

23

i

Fig. 1.6.2-5: Roller bearing left side without guide rail; right side with guide rail)

The contact zones of steel bearings cannot be protected against corrosion. Therefore

corrosion-resistant layers of high alloyed steel should be used for the contact areas.

This can be done by building up a surface by forging or by welding. Between the mild

steel and the hardened high alloyed steel of the surface there should be a welded or

forged tough buffer zone. The thickness (in mm) of the hardened layer both on the

roller (radius R in mm) and of the plate should be t

2

0,14 .R - 2.

1.6.3 Pot

bearings

These bearings were invented in the 1950s. They combine the two desirable proper-

ties: rotation capacity with a very small resistance and transmission of the bearing

reaction over a defined area.

The pot bearing consists of a steel pot, filled with an elastomeric disc and a lid or a

piston to the top (fig. 1.6.3-

1).

When subjected to high compression forces, the unrein-

forced elastomeric disc behaves similarly to a liquid. Rotations can occur due to the

nearly constant volume of the elastomer (v

= 0,5).

Of great importance is the sealing

between the elastomeric pad and the lid: if this sealing has a defect the elastomeric pad

escapes like a viscous liquid.

The standard type of pot bearing allows only rotation (fig. 1.6.3-2). Vertical forces are

transmitted to the pad, horizontal forces from the lid to the pot. To release one sliding

direction, an additional construction becomes necessary (fig. 1.6.3-3 and fig. 1.6.3-5).

This sliding construction consists of three components: a polytetrafluorethylene

(PTFE) disc, a surface of polished stainless steel connected to a sliding plate of struc-

tural steel and lubrication grease. PTFE is a plastic with high mechanical and chemi-

cal resistance, great toughness and very small friction when combined with polished

stainless steel. The PTFE disc is

5

to

6

mm thick, where half a thickness is enclosed by

the lid. This disc has small round pockets on the surface for the lubrication grease

(normally silicon grease) to reduce friction and wearing.

To constrain the movement in one direction an additional guide is used for the lid. This

guiding device allows movements

in

only one direction (fig. 1.6.3-3).

Pot bearings are used for vertical bearing forces from 1000 kN up to 100000 kN.

Depending on the standard applied the allowable compression between lid and elas-


22/86

1. Bearings

4

tomeric pad sho uld not exceed 4.0 kN/cm2. The allowable compression for the PTFE

is 3 kN/cm2 or permanent loads and 4.5 kN/cm 2 for sho rt term loads (traffic, wind e tc.).

Pot

bearings have the advantage of

a

very high vertical stiffness (nearly incompres-

sible elastomeric part). It

is

comparatively independent of the size of bearing and the

applied load . Th is characteristic is imp ortant for the bearing

of

high velocity railway

bridges. Bearings with low vertical stiffness can lead to dam age of the rails.

Fig.1.6.3-1: Function

of

a pot bearing

astom ere disc

Lid

Sealing

Pot - wall

Pot

-

bottom

Fig.

1.6.3-2:

Fixed

pot

bearing

Fig. 1.6.3-3:

Pot

bearing constraint in one direction


23/86

1.6Construction

of

bearings

25

Fig.1.6.3-4: Members of a pot bearing

Anchoring plate

Sliding plate

Polished stainless steel

PTFE (Polytetrafluorethylen)

Lid

Pot -wal l

Sealing

Elastomere disc

Pot - bottom

Fig.1.6.3-5: Free pot bearing

1.6.4 Spherical bearings

The basic type of spherical bearing consists of three main parts: the pan, the part of a

sphere and the upper plate made of constructional steel (fig.1.6.4-1). To allow dis-

placements between the parts, sliding surfaces are necessary. The pan has a PTFE

plate on the upper surface, the part of the sphere has a chrome-plated polished surface

on the underface and a PTFE plate also on the upper surface, and the upper plate has a

polished stainless steel plate

on

the underface. The PTFE plates are chambered over

half the thickness and have lubrication pockets with silicon grease, like the sliding

plates for pot bearings.

The friction resistance of the sliding parts causes reaction moments due to rotations.

They must be taken into account to consider additional design stresses of the bearing

material.

The vertical bearing reaction is transferred over the compressed areas of the PTFE.

The basic model

is

a moveable bearing (fig. 1.6.4-4).To constrain horizontal displace-

ments an additional construction to connect the upper plate with the pan becomes

necessary (fig.1.6.4-2; fig.1.6.4-3).

British and Italian bearings have one sliding plane only and a deeper concave part to

take over horizontal forces (fig. 1.6.4-5). The construction must be checked for uplift

and exceeding the stresses in the contact area. In the bearings with two sliding planes

the centre of rotation is between the contact areas of the sliding surfaces, whereas in

Italian and British bearings it is somewhere in the bridge structure or in the pier or the

abutment.


24/86

26 1.

Bearings

Like pot bearings, sp herical bearings are used for vertical forces in the range of 1000

to

100

000

kN.

Polished Sliding plate

hart

of

sphere

PTFE Chro me plated

polished surface

Fig.1.6.4-1: Members of a spherical bearing

Fig. 1.6.4-2: Fix spherical bearing

I

I

I

Fig. 1.6.4-3: Spherical hearing constraint in one direction

I

1

I

Fig. 1.6.4-4: Free spherica l bearing


25/86

1.6Construction of bearings

27

Fig. 1.6.4-5: Italian and British spherical bearing

one

s lid in g s u f a c e )

1.6.5

Leaf and link bearings

All

the above mentioned bearings are able to transfer compression forces. If tensile

forces as well as compressive forces must be transferred, leaf and link bearings are

used. These bearings can only transmit forces in the direction of the leaf. To transfer

forces in the crosswise direction, separate bearings must be used.

A

leaf bearing consists of a foot plate, one or two lower leafs with pin holes and two

or one upper leaf with foot plate and pin holes, connected by a pin. Leaf bearings al-

low free rotation in one direction. Pin and pin holes must have a fit less than

0.3

mm,

as in

cases of greater slackness and changing forces the pin will punch the hole. Pin

plate and pin should be of different types of steel to avoid seizure. Pin plates are made

of structural steel, pins often of tempered steel.

For link bearings a pendulum is linked to the foot leaf and to the upper leaf by pins.

Link bearings allow rotation and displacement in one direction. For pin holes and pins

the same rules apply as given for leaf bearings.

Link bearings with universal (Cardan) joints are used only in special cases. They

allow rotation and displacement in all directions.

Displacements

6

of link bearings are always combined with a small displacement 6,

,

with

R

equal to the distance between the

n

the perpendicular direction.

6,

=

__

2 R

axes of the pins. Therefore this distance should not be too small.

62

1.6.6

Disc bearings

Disc bearings were introduced in the late 1960s.The vertical loads are transferred by

an elastomeric disc made of polyether-urethane polymer. In contrast to a pot bearing a

transverse extension of the elastomeric disc is possible. Bearing capacity and func-

tioning is comparable with an elastomeric bearing. Rotations around the horizontal

axis are transferred by differential deflection of the disc. The rotations cause a shift of

the axis of the load from the centre of bearing, which must be considered in the design.

Horizontal forces are transferred by a shear-restriction device which allows vertical

deformation and rotation. The basic type is a fixed bearing. Free bearings are con-

structed by additional sliding elements and (if necessary) guiding systems.


26/86

28

1. Bearings

Fig. I 6.6- : ixed bea ring

I

Fig. 1.6.6-2: Uni-directional guided

-top plate

bearing

assembly

base plate

Fig. I 6.6-3: Multi-directional non-gu ided

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27/86


29


1.7.1 Steel

Structural steel

Structural steel is used for all parts of bearings which are not under extraordinary

local stress or do not require special properties against corrosion. Structural steel for

bearings can be:

Non-alloy structural steels according to EN 10025

- Fine-grained structural steels according

to E N

101 13

Quenched and tempered steels according to EN I0082

Eurocode 3 may be used for the design

of

all bearing components made from struc-

tural steel according to EN 10025 and EN 10113 and for all connections (bolts, welds

etc.). Quenched and tempered steels are used mostly for non-welded parts under high

pressure (parts with Hertz compression, bolts of leaf and link bearings). In contact

areas with Hertz compression layers of corrosion-resistant hard steel can be applied

by forging or by welding. In the case of hard-surface welding a tough intermediate

(puffer) layer must be welded between the steel and the hard-surface.

Stainless steel

Stainless steel according to EURONORM 88-2 or I S 0 683 can also be used for bear-

ings. For design one should use EC 3 , part 1-4. Concerning stainless steel for sliding

plates see 1.7.3.

1.7.2 Elastomeric parts

Elastomeric parts of bearings consist normally of natural or artificial (chloropren) rub-

ber (NR or CR, respectively). Artificial rubber has the same good properties as natu-

ral rubber, and in addition it has a higher resistance against ozone, ultraviolet radiation

and ageing and is more rigid. The characteristic mechanical property is the shear modu-

lus G between 0.7 and 1.15 N/mm2 at room temperature, decreasing with increasing

temperature. When undergoing stress changes the volume of rubber is nearly constant.

So we have a Poisson’s ratio

v

= 0.5 and a Young’s modulus of elasticity E =

2 .

1

+v) .

G -- 3 .

G . The fracture strain of rubber lies between 250 and 500 %. Rub-

ber creeps under stress by up to 50 % of the elastic strain, but creeping ends within

some days or weeks. Rubber does not break under compression, it can only break

under tensile or shear stresses. Compressing a rubber pad changes its shape. The

changing of the shape depends on the possibility of displacement at the compressed

areas. If the compressed areas are fixed to a rigid surface, the displacement remains

small. Thus we obtain the inequality A , > A ,

>

A3 (fig.1.7.2-1).

Fig.

.7.2- : Vertical displacemen ts depending o n the lateral expansion

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28/86

30

1.

Bearings

Fig. 1.7.2-2: Stress distribution

If the surface

of

the rubber is fixed to a rigid body shear stresses develop between the

two surfaces under compression (fig. 1.7.2-2). Under compression we obtain

a

virtual

modulus of elasticity

E,

Lllmpr which depends not only on the shear modulus G but also

on the thickness of the part between two plates. For rectangular parts a good approxi-

mation for E, o,npr is given by

conipr =G (: )

.

(1 0,6

g)

for b 2 a

The maximum stresses under compression between two rigid bodies are

F

ab

with o = -,

F:

compression force.

For bending, the effective modulus of elasticity E,

bcndlng

is lower than E,


29/86

1.7

Materials

for bearings

31

the maximum (3 is not in the middle of one half but nearer the outer side; thus we

finally obtain: a + < El o m p r . This is described very well by the

following approximate formula:

1

- -

2

El

-

for

b

2 a

Under the rotation

a

we obtain a curvature p = =

a b

with I =

_ _ _ _ _

12

a Mi?

and a restraining moment

bending ' I

d

Fig.

1.7.2-3:

Rotution estraining mom ent

Fig. 1.7.2-4: Displacement estruining~forces

1.7.3 Sliding elements

For sliding elements in constructional bearings it is normal to use PTFE, also known

by the registered trade names Teflon and Hostaflon. PTFE is a so called thermoplast.

For bearings

it

is used in the original (virgin) condition, i. e. not sintered and without

fillers. A s a counterpart to this rather soft material polished stainless steel plates are

normally used, and sometimes acetal resin plates or hardened chromium-plated steel

plates. Chromium-plated steel plates are not resistant to fluorine ions and are rather

prone to corrosion than stainless steel plates. They are allowed for convex elements

only.

The combination of a soft and a hard part has the advantage that there is no danger of

cold welding which can occur on polished metal or plastic surfaces under high pres-

sure. To minimise the friction silicon grease should be used to provide lubrication. To

keep this grease between the two surfaces the

PTFE

has lubricant pockets on its sur-

face, so that a permanent lubrication takes place over several years. The PTFE plates

for bearings are normally

5

to 6 mm thick, the depth of lubricant pockets is 2 mm. Un-


30/86

32

1 . Bearings

der pressure the PTFE yields. To keep the PTFE in the desired shape it is necessary to

keep about half the thickness in a ith sharp edges. Over the sharp edges

we obtain a small bulge. It is also possible to glue PTFE to

a

steel surface. In this case

the PTFE is about 2.5 mm thick.

The friction coefficient increases with decreasing temperature and with decreasing

compression. The static friction coefficient (first movement) is higher than the dy-

namic coefficient. After movement has taken place the dynamic friction coefficient re-

mains at this value and returns to the static value after a few hours. This might depend

on the orientation of the large polymer molecules; during movement they are orientat-

ed into the direction of motion within

a

very thin surface layer. When the motion is

stopped, the orientation is lost within a few hours. Fig. 1.7.3-1 shows the design val-

ues of the friction coefficient pLdetween PTFE and stainless steel, depending on the

compression force (EN 1337-2).

I

I

I I

I I

I

I

I

I

0.00

Fig.1.7.3 : Friction coejficient depending on the compression orce

I I I I I I

-

0 .0

0.5 1

o

1.5

2.0

2.5

3.0

p

[kNicm']

The design value of the ultimate compression load is

f ,

=

6 , 5 ( 1

0,02. 6 - 30'C)) kN/cm2 for 6 2 30'C ,

6 : maximum temperature of the bearing.

The wearing of the PTFE depends on

a )

the product of compression and velocity of the displacement

b) the total amount of sliding during the life-time

c) the lubrication of the surface (a loss

of

lubrication leads to extremely high wearing)

d) the roughness and the hardness of the stainless steel surface

e) the contact pressure near the edge of PTFE (ironing effect)


31/86

.8

Analysis and design

of bearings

33

For slow movements caused by thermal actions we obtain long sliding movements but

at a low velocity. Quick movements caused by traffic loads have short sliding move-

ments but they occur at high velocity. Wearing is mostly caused by the second case.

For the stainless steel plate, austenitic steel X6CrNiMo17122 according to EU-

RONORM 88-2, surface n (IIIc), should be used. The stainless steel plate must cover

the PTFE plate completely in all situations. The thickness of the plate should be at

least

of

1 .5 mm. The connection to the carrying plate of mild steel can be welded or

glued. For 2.5 mm thick plates the connection can be riveted or bolted.

1.8 Analysis and design of bearings

1.8.1 Hertz

compression

For the design of bearings the following problems should be addressed: compression

between two spherical bodies, compression between a spherical and a flat body, com-

pression between two cylindrical bodies, compression between a cylindrical and a flat

body along a generator line.

As

already mentioned, Heinrich Hertz obtained the solu-

tion under the following assumptions (1881):

1. The two bodies consist of isotropic, homogeneous and infinitely elastic materials.

2. Only normal stresses (no shear stresses) occur at the contact areas.

3. The radius (width) of the contact areas is small compared with the radii of the

Hertz found the following maximum compression stresses

max

(T and widths b on the

contact areas:

involved bodies.

Spherical body on spherical body

=

1,109

1 1

f 7

3 F ( I - v 2 )

.

1

3 E - * -

=

2E

1

Cylindrical body on cylindrical body


32/86

34

1 . Bearings

with

1 1

+

~ ~

rl r2

Fig. I .8. I - I b: Arrangement of the radii

F bearing reaction

1

length of the cylinder

r, , r2

radii of the bodies in contact

E

Young's

modulus Fig.1.8.1 2:

Stress

distribution

V

max (3

b

Poisson's ratio (v

=

0.3 for steel)

maximum normal stress at the contact area

half the width of the contact zone

For the usual rocker or roller bearings the max (3 beneath the vertical bearing reaction

greatly exceeds the material yield strength (fig. 1.8.1-2).However, at the contact zone

we have not only vertical but also horizontal compression stresses. According to the

von Mises criterion the comparison stress

Ov =

d0i2 +

O2

+ Oj3

-

3~(32 -

reaches

the material yield strength f,. In the present three-dimensional compression regime,

(3 will be less than (3, and yielding will not begin until o1 f,. On the other hand, the

maximum strain does not occur at the surface in the middle of the compression zone,

so that the hardness of the surface is

not

the only criterion for the assessment of Hertz

compression.

I

2

- O3Oi and yielding begins when

EN 1337-4 roller bearings gives for the design line load pd of a roller bearing

(cylindrical body on flat surface):

pd

5 1 8 . R .

f 2

E d

with

f,

R

radius of the cylinder

Eddesign value

of

the modulus of elasticity

tensile strength of the material


33/86

1.8

Analysis a nd design of bearings

a c

h c ,

35

a

Com pared to Hertz's form ula with

m a x o , = 0 . 4 1 8 .

R

we find

m a x o , 1 0 . 4 1 8 . f i . f "

=

1 , 7 7 . f u

=oRd

EN 1337-6 ocker bearings

-

gives for the design load Fz,d f a point rock er bearing

(sphere against plane surface) Fz,d 1 7 0 .R 2

f .

Ed

Com pared to Hertz's formula with

we find

m a x o , 1 0 .3 8 8. .1 /17 0 .f , = 2,15f ,

= o R d .

For cylindrical rocker bearings the same formulae as for roller bearings are used.

1.8.2

A

special problem of all leaf and link bearings con cerns the design of the pin an d the

pin plate. Eurocode 3, part 1- 1, gives simple but satisfactory design rules. Th e design

values

of

the shear force and the bending m oment for the pin can be foun d using the

simple m odel of distributing the force of each pin plate uniformly over the pin.

Pin and pin plate for leaf and link bearings

In the case of fig. 1.8.2-1 we obtain the shear force and the ben ding m om ent according

to fig. 13. 2 -2 and fig. 1.8.2-3.


34/86

36

1.

Bearings

ig. 1.8.2-2: Shear force

Fig. 1.8.2-3: Bending moment

For normal bridge bearings we have: c

=

0, a

= .

The design values for the resistances are

b

2

d 2 n

4

Shear: F,,,

=

0.6. A . fupY M p

=

0.6. . fupYMp

=

0.47

1.

d’f,,

/ Y M p

The combination of shear and bending has to fulfil the inequality

In this inequality, the central pin plate is controlling.

The bearing resistance of plate (thickness t and yield strength f,) and pin is:

F,,,,

=

1 .5 .t .d . f y/YM

f,, field strength of the pin

fUp ensile strength of the pin

yMp 1.25 according

to

EC 3-1- 1

The bearing capacity of the pin plate at the hole

is

achieved under one

of

the following

conditions (EC 3 - 1- 1 gives two possibilities):


35/86

1.9 Installation of bearings

a) Depending on the pin plate thickness t:

t = min (2a, b),

e

>--

Sd '

Y M p

d

7

- 2t fy

3

FSd '

Y M p

e, 2

2t . f,

3

b) Depending on the geometry of the pin plate:

37

d

= e 2+ -

3

1.9

Installationof bearings

Concerning the installation of bearings, the need for a later simple replacement must

be taken into account. So it should be common practice to put every bearing between

a

lower and an upper steel cover plate. These cover plates are anchored or connected

both with the substructure and the superstructure. These cover plates are connected to

the bearings during the installation but remain fixed to the structure while the bearings

are replaced (fig.1.9-1). Thus, the connection between bearing and cover plates should

be constructed in order to allow a simple release. Bolted connections are often used

but after many years often the bolts can hardly be unscrewed. According to the

author s experience, fastening the bearings with small fillet welds that can be ground

off and remade during the replacement process is simpler.

Fig. 1.9-1: Fixing of a bearing

Generally, bearings should not be built directly on the construction beneath. To guar-

antee that the area below a bearing is fully sealed a layer of mortar or of a similar prod-

uct is used. So the height of the bridge at the abutments or piers can be adapted easily

and very exactly. It is useful to fix the bearing to the bridge so that there is no clear-

ance at the upper plate and to adjust the bridge by hydraulic jacks. In this situation the


36/86

38

1. Bearings

bearings should be adjusted exactly. Thus, the lower plate will get exactly the desired

inclination (horizon tal or parallel to the gradient, see fig.1.9-1) and all m oveable bear-

ings will have the desired pre-adjustment, which depends on the temperature of the

bridge and the expec ted shrinkage and creep. The installation of the bearings should

be don e early in the mo rning when the bridge has a (nearly) constant tempe rature. T he

designer has to provide a table w ith the pre-adjustment of every bearing depen ding on

the measured bridge temperature.

For good functioning, careful handling of the b earings during installation is very im-

portant. Th e bearings must be kept free of dirt, mortar, water and dust, especially from

all moving parts. Many b earings, such as pot bearings and sph erical bearings, are pro-

tected against dust by rubber bulges, but others are not protected a t all. These have to

be cleaned to remove m ortar and sand after the installation.

The gap between the lower plate of the bearing and the substructure is normally 3 to 5

cm thick and m ust be com pletely filled with a mortar bedding. This can be don e in dif-

ferent ways:

by a fresh mortar bedding, chambered in the centre where the bearing is set. The

excess of mortar will com e out on all sides and m ust be removed.

by a special joint filling mortar which must be m ixed in a pan type concrete m ixer

with a prec ise quantity of water. This m ortar is liquid at first and shou ld be poured

in a formw ork around the bearing only from one side, so that the air can escape o n

the other side . T he sp ecial mortar fills the gap without air bubbles, it sets and hard-

ens very quickly

so

that after one day the mortar bedding can b e fully loaded an d

the formw ork removed. If the ga p is less than 1 cm a two-component epoxy resin

should be used instead of mortar. Initially this resin is a lighter fluid than mortar,

thus com pletely filling even very sm all gaps.

- by boxing up earth-dam p mortar in the gap with a wooden stick also from on e side

to avoid air bubbles. Th is method will be difficult for the lower plates with a short

side larger than half a m etre.

All mortars should be non-shrinking.


Visual tests of all bearings sho uld be do ne by qualified personnel at regular intervals.

Th e following properties of the bearings have to be checked:

a) sufficient ability to allow m ovem ent, taking into account the temperature of the

su-

b) correct positioning of the bearings them selves and of parts of the bearing relative to

c) uncontrolled m ovement of the bearing

d) fracture, cracks and deform ations of parts of the bearings

e) cracks in the bedding o r in adjacent parts of sub- and superstructure

f

condition of the anch orage

g) condition of sliding or rolling surfaces

h) condition of the anticorrosive protection, against dust, and of the sealings.

For the different types of bearings the follow ing checks are of im portance:

perstructure

each other


37/86

1.1 1 Replacement of bearings

39

Elastomeric bearings:

Displacem ents and rotations, cracks in the elastomer.

Roller and rocker bearings:

Displacem ents and rotations, adjustment of the

guiding device, no gap in the contact line.

Pot bea rings : Sufficient mesh of the lid in the pot, tight sealing of the elastomer

in the pot (if the sealing has a defect, the elastomer com es out like a pancake )

Sliding devic es PT FE and stainless steel: Thickn ess of the PTF E, clean surface of

the stainless steel.

The result of an inspection should be recorded

in

a report. EN 1337-10gives an ex-

amp le for such a report.

For maintenance the bearings should be cleaned, lubricated (if necessary and pos-

sible) and coated with paint. Sm all defects should be repaired a s far as possible.

1.11

Replacement of bearings

The replacem ent of bearings is a normal m aintenance operation for bridges. Thus, a

bridge designer has to provide measures so that a replacement can be carried out

easily. Th e ow ner

of

a bridge has to d efine in the tender if the rep lacem ent of the bear-

ings must be ca rried out under full traffic, restricted traffic or without traffic, depend-

ing

on

the importance of the bridge and the possibility of a traffic ban or a traflk

diversion.

In case of a replacement under traffic the jacking equipment should allow the same

movem ents as the bearing. To allow rotations the ja ck s around one bearing should be

connected to a single hydraulic circle. Tha t means that the security devices m ust have

a

sufficient clearance. Translations are possible by means of additional sliding con-

structions.

- -

I

i

\ /

-

_m_

reinforcement against splitting tension

Fig.1.

I

- I : Stif fened areas o r hydraul ic a cks

To replace a bearing, the bridge has to be lifted by one or more hydraulic jacks. F or hy-

draulic jack s, adequately stiffened areas to transm it the hydraulic ja ck forces to the

sub- and superstructure are required. Concrete parts m ust be reinforced against split-

ting tension, steel parts need stiffeners (fig. 1.11-2). Thus, the construction drawings

must show in which areas or at which points hydraulic jack s can b e set, what are the

maximum lifting forces and up to which level the bridge may safely be lifted. This


38/86

40 1. Bearings

kN

500

1000

2000

SO00

data is of particular importance if the bridge is supported in a statically indeterminate

way at one abutment or pier, in which case the lifting force depends on the height of

lift. High stresses can be induced in the cross girder or diaphragm by the lifting device.

In such cases it may be necessary to lift the whole cross section uniformly with two or

more hydraulic jacks even for exchanging only one bearing. If more than one jack is

used the forces can be controlled by hydraulic connection of some or of all jacks: all

connected jacks have the same pressure. Hydraulic jacks need some clearance for the

installation. For lifting by a few millimetres up to two centimetres flat piston jacks can

be used. The following table gives a guide for the required clearances:

Normal hydraulic jack Flat piston jack

mm mm

300

150

360 180

450 200

600 250

I Force I Required clearance

I

Required clearance

Table 1.11 1:Required clearance for hydraulic jacks

There are flat jacks with a height of 80 mm and a lifting force up to

SO00

kN. But their

stroke is only 20 mm and there is no security device. This kind of jack should be ap-

plied for special cases only. New bridges should be constructed for normal hydraulic

jacks.

In all situations, during the replacement of a bearing the hydraulic jack should be se-

cured by a mechanical device such as an adjusting nut for the piston or lining plates to

avoid dropping in case of pipe rupture or rupture of the piston sealing which some-

times can occur (fig.l.11-3 and tig.l.11-2).

I I

pipe or

I

I

L

- - - - _ _ _ _

c =

Fig. 1.1 1-2: H ydra ulic jac k with lining plates


39/86

1.12 Codes

and

standards

41

Fig.

1. 1-3:Hydraulic ja ck with thread and

nu1

If the replacement of a bearing takes a long time so that displacements of moveable

bearings will occur, the hydraulic jacks have to be equipped with a sliding device,

normally PTFE plus a sliding plate of stainless steel.

Particular care is required when replacing bearings which transmit horizontal forces:

if

the friction between the jack and the surface of sub- and superstructure is not suffi-

cient

i t

is necessary to restrain the movement of the bridge by appropriate devices. If

the replacement is done under traffic, in most cases, and especially for railway

bridges, these devices have to transmit all horizontal forces due to a possible loss of

friction.

1.12 Codes

and standards

The first attempts to standardize bearings in national codes were made decades ago. In

Europe several codes and national standards are available. The best known national

standards in Europe on this topic are

Germany: DIN 4141 Lager im Bauwesen (structural bearings),

United Kingdom: BS 5400

Teil 1 bis 14.

Steel, Concrete and Composite Bridges.

Section 9.1 Code of Practice for design of bridge bearings

Section 9.2 Specification of materials, manufacturing and installa-

tion of bridge bearings

New European Standards about bearings are the following

EN 1337 “Structural bearings” with the parts

EN 1337-1 General design rules

EN 1337-2 Sliding elements

EN 1337-3 Elastomeric bearings

EN 1337-4 Roller bearings


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42

1. Bearings

EN 1337-5 Pot bearings

EN 1337-6 Rocker bearings

EN 1337-7

EN 1337-8

EN 1337-9 Protection

EN 1337- 10 Inspection and maintenance

EN 1337-

1

1 Transport, storage and installation

Spherical and cylindrical PTFE bearings

Guided bearings and Restrained bearings

A recomm endable American Standards about bearings is the following:

AA SHO -LRFD : Am erican Association of State Highway Officials ( I 994).

1.13 References

Books and special chapters about bearings for bridges:

Eggert H., J. Grote, W. Kauschke: Lager im Bauwesen. Verlag von Wilhelm

Ernst & Sohn , Berlin, Munchen, Dusseldorf 1974 .

Lee D.J.: Bridge Bearings and Expansion Joints. Second edition by E

&

FN Spon,

London, G lasgow, New York, Tokyo, Melbourne, M adras 1994.

Eggert H., W. Kauschke: Lager im Bauwesen. 2. Auflage, Ernst & Sohn, Berlin 1995.

Rahlwes K., R. Maurer: Lagerung und Lager von Bauwerken in: Beton-Kalender

1995, Te il2, Ernst & Sohn , Berlin.

Papers:

Albrecht, R.: Zur Anw endung und Berechnung von Gummilagern. Der Deut-

sche Baumeister 1969, Heft 4, Seite 326, und H eft 6, Seite 563.

Andra, Beyer, Wintergerst: Versuche und Erfahrungen mit neuen Kipp- und

Gleitlagern. Der Bauingen ieur 5 (1 962 ).

Andra, W. und Leonhardt, F.: Neue Entwicklungen fur Lager von Bauwerken,

Gumm i- und Gumm itopflager. Die Bautechnik 39 (1 969), Heft 2, Seite 37 bis

50.

Bayer, K.: Auflager und Fahrbahnubergange fur Hoch- und Bruckenbauten aus

Kunststoff. Verein Deutscher Ingenieure VDI im Bildungswerk BV 1956 (Vor-

tragsveroffentlichung).

Beyer, E. und Wintergerst, L.: Neue Briickenlager, neue Pfeilerform. D er Bau-

ingenieur 35 (1960), Heft 6, Seite 227 bis 230.

Eggert, H.: Briickenlager. Die Bautechnik 50 (1973), S . 143/144.

Bub, H.: Das neue Institut fur Bautechnik. Strasse und Autobahn, Band 20

(1969), Seite

189.

Burkhardt, E.: Gepanzerte Betonwalzgelenke, Pendel- und Rollenlager. Die

Bautechnik 17 (1939), Seite 230.

Cardillo, R. und K ruse, D.: Paper (61/WA-335) AS M E (1961).

Cichocki, F.: Bremsableitung bei Briicken. Der Bauingenieur 36 (1961), Seite

304 bis 305.


41/86

1.13

References 43

Clark, E. und Moutrop, K.: Load Deformation Characteristics of Elastomer

Bridge Bearing Pads. University of Rhode Island, May 1962.

Desmonsablon, Philippe: Le calcul des piles ddformables avec appuis en

caoutchouc. Annales des Ponts et Chaussdes, Paris 4/1960.

Eggert, H.: Bauwerksicherheit bei Verwendung von Rollen- und Gleitlagern.

Strasse Brucke Tunnel 1971, Heft 3, Seite 71.

Eggert, H.: Die baurechtliche S ituation bei Lagern fu r Briicken und H ochbau-

ten. Der Stahlbau 39 (1970), Heft 6, Seite 189.

Einsfeld, U.: Erlauterungen zu den Richtlinien von unbewehrten Elastomer-

lagern. Mitteilungen Institut fur Bautechn ik 6/1972 .

Franz: Gumm ilager fur Brucken. VD I-Zeitschrift, Bd. 101/1959, Nr. 12, Seite

47 1 bis 478.

Gent, A.: Rubber Bearings for Bridges. Rubber Journal and International Plas-

tics 1959.

Grote, J.: Neoprenelager

-

einige grundsatzliche Erwagungen. Kunststoffe im

Bau 7/1968.

Grote, J.: Unbewehrte Elastomerlager. Der Bauingenieur 44 ( l969 ), Seite 121.

Grote, J.: Vermeidung von Rissen und Dehnungsschaden durch gum mielasti-

sche Lagerungen. Kunststoffe im Bau 11/1968.

Hakenjos, V.: Untersuchungen uber die Rollreibung bei Stahl im elastisch-plas-

tischen Zustand.

Technisch-wissenschaftliche

Berichte der Staatlichen Materi-

alpriifungsanstalt an der Technischen Hochschule Stuttgart 19 67, Heft 67/05.

Heesen: Gepanzerte Betonwalzgelenke, Pendel- und Rollenlager. Die Bau-

technik, Jahrgang 25

(1

948), Seite 26 1.

Hutten, P.: Beitrag zur Berechnung der Lagerverschiebungen gekrummter,

durchlaufender Spannbeton-Balkenbriicken. D issertation T H Aachen 1970.

Jorn, R.: Gum mi im Bauw esen. Elastische Lagerung einer Pumpenstation. D er

Bauingenieur 3 6 (1961), Heft 4, Seite 1371138.

Keen : Creep of Neop rene in S hear Under Static Conditions, Ten Years, Trans-

actions of the ASM E, Juli 1953.

Leonhardt und Andra: Stutzungsprobleme der Hochstrassenbriicken. Beton-

und Stahlbetonbau 55 (1960), Heft 6.

Leonhardt, F. und Reimann, H.: Betongelenke, Versuchsbericht, Vorschlage

zur Bemessung und konstruktiven Ausbildung. DAfStb, Heft 175. Berlin:

Verlag Ernst & Sohn 1966,und Leonhardt, F. und R eimann , H.: Betongelenke.

Der Bauingenieur 41 (1966), Seite 49.

Leonhardt, F. und Wintergerst, L.: Uber die Brauchbarkeit von B leigelenken.

Beton- und Stahlbetonbau 1961, Heft 5, Seite 123 bis 131.

Maguire, C . und Assoc.: Elastomeric B ridge Bearings Pads 1959.

Massonnet: Zuschrift zu B. Topaloff, Gum milager fur Briicken. Der Bauinge-

nieur 39 (1964), Seite 428.

Monnig, E. und Netzel, D.: Zur Bemessung von Betongelenken. Der Bauinge-

nieur 44 (1969), Seite 433 bis 439.

Morton, M.: Rubber Technology. Reinhold Publishing Co. 1959.

Mullins, L.: Softening of Rubber by Deformation. Rubber Chemistry and

Technology (Feb. 1969).


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44 1. Bearings

[351

[361

[371

[431

[441

[491

[531

Nordlin, E., Stoker,

S .

and Trinble, R.: Laboratory and Field Performance

of

Elastomeric B ridge Bearing Pads, Highway Research Board (1968).

Pare u. Keiner: Elastomeric Bridge Bearings. Highway Research Board Bull

242, 1960.

Payne

u.

Scott: Engineering Design with Rubber

Rejcha, C.: Design of Elastomer Bearings. Journal of Prestressed Concrete

Institute O ct. 1964, Vol. 9, Nr. 5 .

Resinger, F.: Langszwangungen ine Ursache von Bruckenlagerschaden. Der

Bauingenieur 46 (1971), Seite 334.

Rieckmann, H.-P.: Einfluss der Lagerkonstruktion auf die Knicklange von

Pfeilern. S trasse Briicke Tunnel 1970, Seite 36 bis 42 und Seite 270 bis 272.

Sasse, H.-R. und Schorn, H.: Bewehrte Elastomerlager Stand der Entwick-

lung. Plastik-Konstruktion 1971 , Heft 5 , Seite 209 bis 227.

Schonhofer: Neugestaltungen auf dem Gebiet des Auflagerbaues und auf ver-

wandten G ebieten. W erner-Verlag, Dusseldorf 1952.

Sedyter: Uber die Wirkungsweise von Bleigelenken. Beton und Eisen 1926,

Seite 29.

Shen , M. K .: Uber d ie Losung d es Balkens mit unverschieblichen Auflagern.

Der B auingenieur 39 (1964 ), Seite 100.

Suess, K. und Grote,

J.:

Einige Versuche an Neoprenelagern. D er B auingenieur

38

(1963), Heft 4, Seite

152

bis 157.

Thielker, E.: Elastomeric Bearing Pads and Their Application in Structures,

Paper 207 of Leap Conference (1964 ).

Thul, H.: Bruckenlager. Der Stahlbau 38 (1969), S eite 353.

Topaloff, B.: Gumm ilager fur Briicken Berechnung und Anw endung. Der

Bauingenieur 39 (19 64), Seite 50 bis 64.

Topaloff, B.: Gum milager fur Brucken. Beton - und Stahlbetonbau 5 4 (1959),

Heft 9.

Uetz, H. und Breckel, H.: Reibungs- und Verschleissversuche mit Teflon.

Sonderheft der Staatl. Materialprufungsanstalt an der T H Stuttgart, 7.12.1 964,

Seite 61/76.

Uetz,

H.

und H akenjos, V.: Reibungsuntersuchungen mit Polytetrafluorathylen

bei hin- und hergehender Bewegung. D ie Bautechnik 44 (1967), Heft 5, Seite

159 bis 166.

Uetz, H. und Hakenjos, V.: Gleitreibungs- und Gleitverschleissversuche an

Kunststoffen. Kunststoffe, 59. Jahrgang 1969, Heft 3, Seite 161 bis 168.

Weiprecht,

M.:

Auflagerung von Briicken. Elsners Taschenbuch fur den B au-

technischen E isenbahndienst, 1967, Seite 23

1

bis 277, Abschnitt E Brucken-

und Ingenieurhochbau.

Zies, K.-W.: Stabilitat von Stutzen mit Rollenlagern. Beton- und Stahlbetonbau

65 1 970), Seite 297.

AA SHO -LRFD : American Association of State Highway Officials (1994).

Dupont de Nemours Co.: Design of Neoprene Bridge Bearing Pads, Wilming-

ton

(

1959).

CNR-UNI 10018-68 (Italian Standards for rubber bearings).


43/86

1.13

References 45

Ministry of Transport: Provisional Rules for the Use of Rubber Bearings in

Highway B ridges, M emo . 802, Lond on (1962).

Mitteilungen, Institut fur Bautechnik, 1970, Heft 2 und 4, und 1971, Heft 4

und

6.

Ohn e Verfasser. Auflager aus Teflon. Ausziige aus d em Journal of Teflon 1964,

1965 und 1966, Druckschrift der Du Pont de Nemours International S.A.

Geneva, Switzerland.

Ohn e Verfasser. Bruckenlager. Beratung sstelle fur Stahlverw endung, Dussel-

dorf, Merkblatt 3 39 ,2 . Auflage

1968.

OR E Office de Recherches et d’Essais: Verwendung von Gum mi fur Brucken-

lager, Frage D 60, Utrecht (1962 , 1964, 1965).

W iedem ann, L.: Zusatzliche R ichtlinien fur Lager im Brucken- und Hochbau.

M itteilungen Institut fur Bautechnik 3/1973,

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73. Verlag Ernst

&

Sohn.

Eggert: Vorlesungen uber Lager im Bauwesen. Wilhelm Ernst & Sohn

1980/1981.

Kauschke, W.: En twicklungsstand de r Gleitlagertechnik fur Briickenbauwerke

in der Bundesrepublik Deutschland. Bauingenieur 64

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bis 120.

Batterm andK ohler: Elastomere Federung, Elastische Lagerungen. W. Ernst &

Sohn, Berlin, M unchen 1982.

Gerb: Schwingungsisolierungen. Berlin, 9. Auflage 1992, Eigenverlag (gegen

Schutzgeb uhr erhaltlich).

Grote, J. und Kreuzinger, H.: Pendelstutzen mit Elastomerlagern. Der Bau-

ingenieur 53

(1978),

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Kann ing, W.: Elastomer-Lage r fur Pendelstutzen - Einfluss der Lager auf die

Beanspruchung der Stutzen. Der B auingenieur 55

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M auredR ahlwes: Lagerung und Lager von Bauwerken. Betonkalender 1995,

Ernst & Soh n, Teil 11.

Weihermuller, H. und Knoppler, K.: Lagerreibung beim Stabilitatsnachweis

von Bruckenpfeilern. Bauing enieur 55

(1980),

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Andra, W.: Der heutige E ntwicklungsstan d des Topflagers und seine Weiter-

entwicklun g zum Hublager. Bautechn ik (1984), Seite 222 bis 230.

Eggert, H.: 7 Grundsatze bei der Lagerung von Brucken.

9.

IVBH-Kongress

Am sterdam 1972, Schlussbericht. Internationale Vereinigung fur Briickenbau

und Hochbau, Zurich, Schweiz.

Deinha rd, J.M., Kordina, K., M ozahn, R ., Storkebaum , K.-H.: Der Schadens-

fall an der Mainbrucke bei H ochheim . Beton

-

Stahlbetonbau , 72 (197 7), Seite

1 bis 7.

Eggert, H. und Wiedemann, L.: Nutzungsgerechte Lagerung von Stahl- und

Verbundbrucken und unterhaltungsgerechte Konstruktion von Bruckenlagern.

IVBH Sym posium Dresden 1975. Vorbericht.

Eggert, H.: Lager fur Brucken und Hochbauten . Bauing enieur 53 (1 978), Seite

161

bis

168,

und Z uschrift 54 (1979), Seite 200.

Konig, G. et. al.: Spannbeton: Bew ahrung im Bruckenbau. Analyse von Bau-

werksdaten, Schaden und Erhaltungskosten. Springer-Verlag Berlin, Heidel-

berg, New York, London, Paris, Tokio 1986.


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Pfohl, H.: Reaktionskraft am Festpunk t von Briicken aus Bremslast und Bewe-

gungswiderstanden der Lager. Bauingenieur 58 (1983), Seite 453 bis 457.

Eggert, H. und Hakenjos, V.: Die Wirkungsw eise von Kalottenlagern. Der Bau-

ingenieur 49 (1974), Heft

3 ,

Seite 93/94.

Lehm ann, Dieter: Beitrage zur Berechnung der Elastomerlager. Die Bautech-

nik I (1978), Seite 19 bis 22, I1 (1978), Seite 99 bis 102, I11 (1978), S eite 190

bis 198, IV ( l97 9), S eite 163 bis 169.

Kordina, K. und Nolting, D.: Zur Auflagerung von Stahlbetonteilen mittels

unbewehrter Elastomerlager. Der B auingenieur 56 (1981), Seite 41 bis 44 .

Kordina, K. und Osterath, H.-H.: Zur Auflagerung von Stahlbetonteilen mittels

unbewehrter und bewehrter Elastomerlager. Der Bauingenieur 59

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984),

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Kessler, E. und Schw erm, D.: Unebenheiten und Schiefwinkligkeiten der Auf-

lagerflachen fur Elastomerlager bei Stahlbetonfertigteilen. Fertigteilbau-

forum 13/83, Seite

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bis 5 (Betonwerk + Fertigteil-Technik).

Kessler, E.: D ie Anwendung unbewehrter E lastomerlager. Betonwerk + Fertig-

teil-Technik, Heft 6 (1987), Seite 419 bis 429.

Bundesminister fur Verkehr: Sch lden an Brucken und anderen Ingenieurbau-

werken. Dokum entation 1982. Verkehrsblatt-Verlag, Dortmund.

Bundesminister fur Verkehr: Bericht uber Schaden an Bauwerken der Bundes-

verkehrswege. Januar 1984. Eigenverlag BM V.

Beyer, E. und Eisermann, G.: Nachstellbare B ruckenlager. Erfahrungen beim

Bauvorhaben

Dusseldorf-Hauptbahnhof.

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Dickerhoff, K.J.: Bemessung von Bruckenlagern unter Gebrauchslast. Disser-

tation Universitat Karlsruhe 1985.

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lage Mai 1991. Herausgeber: Osterreichische D onaukraftwerke AG.

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chanics. Sept. 1998.

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bearings. Civil Engineering and Public Works Review 61(7 14),

67-72.

Leonhard t, F. und Andra, W. (1960): S tutzprobleme der Hochstrassenbrucken.

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Tanaka, R., Natsukaw a, K. and Ohira, T. (1984): Therm al behaviour of multi-

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Emerson M. (1977): Temperature differences in bridges: basis of design re-

quirements. TRRL Laboratory R eport 765. Transport and Road Research Lab-

oratory, Crow thorne.

Emerson M. (1968): Bridge temperatures and movements in the British Isles.

RRL Report LR 228, pp.38. Road Research L aboratory, Crowthorne.

Emerson M. (1973): The calculation of the distribution of temperature in

bridges. TRRL Report LR 561. Transport and Road Research Laboratory,

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Emerson M. (1976): Bridge temperatures estimated from the shade tempera-

ture. TRRL R eport LR 696. Transport and Road R esearch Laboratory, Crow-

thorne.

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1001 Stephenson, D.A. (1961): Effects of differential temperature on tall slender co-

lum ns. Concrete and Constructional Engineering, 56(5), 175-8: 56(1 ) , 401-3.

[ 1011 Garrett, R.J. (1985): Th e distribution

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the Hong Kong Institution of Eng ineers, May, 35-8.

[

1021 ComitC Euro-International du BCton (1984). Design manual on structural

effects of time-dependent behaviour of concrete (Bulletin No. 142). George

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[

1031 ComitC Euro-International du BCton (1985). Manual of Cracking and Defor-

mations. Bulletin 158E, Lausanne.

[ 1041 Neville, A.M ., Dilger, W.H. and Broo ks, J.J. (1983): Cre ep of Plain and S truc-

tural Concrete. Construction Press, London and New York.

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1051 Mattock A.H . (1961 ): Precast-prestressed concrete bridge 5.Creep and shrink-

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Geological Sciences: National Environmental Research Council

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1071 Dollar, A.T.J., Abedi, S .M .H., Lilwall, R.C. und W illmore, R.L. (1975): Earth-

quake risk in the UK. Proceedings of the Institution of Civil Engineers, 58,

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1081 ICE and SECED (1 985): Earthquake engineering in Britain. Proceedings of

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1091 Lee, D.J. (1 97 1): Th e Theory and Practice of Bearings and Expanison Joints fo r

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[ 1101 Buchler, W. (1987): Design of Pot Bearings, American Concrete Institute

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1 131 Taylor, M.E. (1970): PTFE in highway bridges. TRR L Report LR 4 91, Trans-

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1141 Eggert, H., Kauschke, W.: Lager im Bauw esen, Ernst

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[ 1 151 Hakenjos, V.: Lager im Bauwesen mit Komponenten aus Kunststoff verdran-

gen hochbeanspruchbare stahlerne Rollenlager. 13th H.F. Mark-Symposium

on 19- 10-94 in Vienna.

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161 Marion i, A.: Apparecchi di appoggio per ponti

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strutture. ITEC , M ilano 1983

[

1 171 Campbell, T. I. and Kong, W. L.: T FE S liding Surfaces In Bridge Bearings. Re -

port ME-87-06, Ontario Ministry of Transportation and Communications,

Downsview, Ontario, 1987.

[ I 181 Crozier, W. F., Stoker, J. R., Martin, V. C. and Nordlin, E. F.: A Laboratory

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191 Gent, A. N.: Elastic Stability of Rub ber Com pression Springs. ASM E, Journal

of Mech. Engr. Science, Vol. 6, No . 4, 1 964 .

[I201 Jacobsen,

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K. and Taylor R. K.: TFE Expansion Bearings for Highway

Bridges. Report No. RDR-3

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[

1211 McEw en, E. E. and Spencer, G . D.: Finite Element Ana lysis and Experim ental

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st World Cong ress on B earings and Sealants, ACI Publication SP-70, Niagara

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[ 1221 Nordlin, E. F., Boss, J. F. and Trimble, R. R.: Tetrafluorethylene (TFE) as a

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1261 Roeder, C . W ., Stan ton,

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F. and Feller, T.: Low Temperature Performance of

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[ 1271 Roeder, C. W. and Stanton, J. F.: Failure Modes of Elastomeric Bearings and

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[1291 Roeder, C. W., and Stanton, J. F.: Elastomeric Bearings: A State of the Art.

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way Bridges. Proceedings of 2nd World Congress on Bearings and Sealants,

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Stanton, J. F. and Roeder, C . W.: Elas