Bearings, expansion joints and hydraulicequipments for bridges

Autor(en): Ramberger, Gnter

Objekttyp: Article

Zeitschrift: IABSE congress report = Rapport du congrs AIPC = IVBHKongressbericht

Band (Jahr): 15 (1996)

Persistenter Link: http://dx.doi.org/10.5169/seals-816

PDF erstellt am: 23.04.2015

NutzungsbedingungenMit dem Zugriff auf den vorliegenden Inhalt gelten die Nutzungsbedingungen als akzeptiert.Die ETH-Bibliothek ist Anbieterin der digitalisierten Zeitschriften. Sie besitzt keine Urheberrechte anden Inhalten der Zeitschriften. Die Rechte liegen in der Regel bei den Herausgebern.Die angebotenen Dokumente stehen fr nicht-kommerzielle Zwecke in Lehre und Forschung sowie frdie private Nutzung frei zur Verfgung. Einzelne Dateien oder Ausdrucke aus diesem Angebot knnenzusammen mit diesen Nutzungshinweisen und unter deren Einhaltung weitergegeben werden.Das Verffentlichen von Bildern in Print- und Online-Publikationen ist nur mit vorheriger Genehmigungder Rechteinhaber erlaubt. Die Speicherung von Teilen des elektronischen Angebots auf anderenServern bedarf ebenfalls des schriftlichen Einverstndnisses der Rechteinhaber.

HaftungsausschlussAlle Angaben erfolgen ohne Gewhr fr Vollstndigkeit oder Richtigkeit. Es wird keine Haftungbernommen fr Schden durch die Verwendung von Informationen aus diesem Online-Angebot oderdurch das Fehlen von Informationen. Dies gilt auch fr Inhalte Dritter, die ber dieses Angebotzugnglich sind.

Ein Dienst der ETH-BibliothekETH Zrich, Rmistrasse 101, 8092 Zrich, Schweiz, www.library.ethz.ch

http://retro.seals.ch

507

Gnter RAMBERGERo.Univ.-Prof.Institute for Steel StructuresTechnical University ViennaVienna, Austria

Gnter Ramberger, born 1942, got his master degreein civil engineering 1966 and his doctor degree 1970from the Technical University Vienna. After 12 yearsas a designer for bridges at a steel construction firm atDsseldorf, Germany, he returned 1981 as Fll Professorto the Technical University Vienna.

Bearings, expansion joints and hydraulic equipments for bridges

1. Introduction

The target of this paper is to give a very short state-of-the-art-report on bearings, expansionjoints and hydraulic equipments for bridges as an introductory report for the following papers.

2. Bearings

The task ofbearings is to transfer the bearing reactions from the superstructure to thesubstructure flfilling the design requirements due to displacement and rotation. According toforce transmission, displacement and rotation we distinguish between the following types ofbearings (table 1). In table 1 the forces and the adjacent displacements are dual values.

The force can be transmitted theoretically through a contact point, a contact line or a contactarea. In the first two cases the theoretical stresses are infinite, so we need steel parts to takeover the Hertz-compression, in the third case in addition to steel, elastomeric parts arepossible.

To allow rotation with only small resistance we know the rolling ofa plate on a sphere in alldirections or on a cylindrical body in one direction or the rotation by different compressions ofan elastomeric body.For displacements with no or only small resisting forces we can use the elastic deformation ofan elastomeric body or the sliding between two elements, mostly polytetrafluorethylen (PTFE)and stainless steel or polyamide. In combining these elements we get all different types ofbearings (fig. 1).

Bearings, especially bearings with plastic parts are wearing parts ofa bridge. The exchange ofbearings in the lifetime ofa bridge is to be taken into aecount. If this exchange is to be madeunder traffic or not, depends on the individual Situation, on the intervals between traffic events(for railway bridges) and in the duration ofthe exchange works. In recent times in the mostcases an exchange ofthe bearings under (partly) traffic loads should be considered for thedesign ofa bridge. For the exchange ofa bearing the bridge must be lifted by hydraulic jacks atforeseen points. There must be enough space to adjust the necessary jacks and stiffeners andreinforced areas to transfer the forces in sub- and superstructure. The connection ofthebearings with sub- and superstructure should be simply to release. Bolted connections fulfil this

508 BEARINGS, EXPANSION JOINTS AND HYDRAULIC EQUIPMENT FOR BRIDGES

,,M,/Mv

's// yAr /Mx / % / X/ .// / tc

G. RAMBERGER 509

.2

o

cotex

Standard typeReinforcedelastomeric bearing

Anehored elast. bearing

Combinations

Elastomeric bearingwith fixing device.all translations fixed movement in one dir.

Elastomeric pdReinforcing platesAnchor plateDowels

v/ ,'///r/7//////yy//y/.r^\\ys^\\\\\\\\\\\\\*VZ&I illinmnn r i ss s rr7.K\\KK\K\\\\\;\..\\y.rsr

Pot bearing

TFE \Guide rails

Horizontal force bearing

l

Roller beanng

Link beanng

P,

$,

Link bearing withuniversal (cardan) joints

}

Guide bearingY/////////a

K\\\^k\\\\\N K\\\\^s\\\\\\\\l

Fig. 1: Types ofbearings

510 BEARINGS, EXPANSION JOINTS AND HYDRAULIC EQUIPMENT FOR BRIDGES

3. Expansion jointsExpansion joints in bridges are used to bridge the necessary gap between bridge and abutmentfor the movement due to temperature and various other causes. They should be constructedsuch that they satisfy the following conditions:-

allow the movements ofthe bridge in horizontal and vertical direction,-

withstand the loading, that means that the serviceability limit State, the ultimate limit Stateand the fatigue limit State are not exceeded during the life time ofthe joint,

- are silent and have a good riding quality for all types of road users,-

resist corrosion, also under gritting sand and de-icing agents,- are easy to inspect, to maintain and to repair,- are of long durability (desirable: the life time ofthe expansion joint is that ofthe bridge).Various types of expansion joints have been developed for small and large movements. Figure2 shows some examples for movements between 100 and 200 mm. Most of these jointscan also be used for small movements (~ 20 mm), especially the seal joints, which need in thiscase no rails and no control device for the spacing. Comparing these types we can say that alltypes with plastic elements allow movements in all directions, but these elements must beexchanged after a relatively short period. It is very important that the time for repair andmaintenance is short to shorten up the time for traffic interruption. Expansion joints with onlysteel elements are normally robust, but are in the rule not watertight and allow no movementsacross the axis ofthe bridge. Due to the displacements caused by traffic loads the singularplates of rolling leafjoints are not fll in contact, so that chatter is nearly unavoidable.

According to the condition mentioned above the steel elements ofan expansion joint shouldhave the same durability as the bridge itself. Failures and cracks due to fatigue can often befound in different parts of expansion joints. To improve the durability fll scale fatigue tests onexpansion joints had been carried out during the last years. The first problem is the testing withrealistic loads. The load models for the design ofa bridge are not applicable because they donot contain the realistic wheel loads combined with horizontal forces which depend not only onbreaking or acceleration forces but also on the geometry ofthe expansion joint and whichinduce sometime stresses ofthe same rnge as the vertical forces. On the other hand it isimpossible to simulate the realistic elasticity ofthe bridge's end. In spite of all imponderabilitiesthe fatigue-tests showed the weakest points and how to construct expansion joints with ahigher durability.

Beside the Joint itself the connection to the bridge and to the abutment is ofthe sameimportance. Only a good construction combined with good workmanship will bring thedesired success and avoid defects. It is recommended that the manufacturer ofthe expansionjoint installs it or at least surveys the work and confirms that it is in order.

G. RAMBERGER 511

1. Multiple seal expansion joints1.1 Rails supported by beams,

spacing controlled by Springs

SBi1.2 Rails supported by beams,

spacing controlled byhorizontal parallel linkages

HH h-M

2S**l%\44.rr,^,

TTII II II I

liiln^n ^yHHl

1nid^ir1 :^ v_j_L ll'^KIf.

e^tt ij l ij_'l I1 "Li jlL iL

LjU- I

1.3 Rails supported by folding trellis linkages

KSE

gviiiiwwi

') Lt=Bir1^^.^

o XrOQ

fecjj Rrpoi5cU

ga

fflilfflltt

2. Cantilever toothed jointorfinger joint

3. Rolling leafJoint

!HS

^5= =5=*pl, :lI

4. Elastic cushion joint

Tl

I a j sa s ; a s*=

F/'g. 2: Types qfescpansion joints

512 BEARINGS, EXPANSION JOINTS AND HYDRAULIC EQUIPMENT FOR BRIDGES

4. Hydraulic equipments

Hydraulic equipments for bridges are only used for special cases but gain more importance inrecent times. They are used to control the movement ofa bridge and to distribute (horizontal)forces on several piers and abutments. They work like fixed bearings for short time forces(breaking forces, impact forces) and like moveable bearings for long time effects (temperature,creeping and shrinking). The function ofa hydraulic equipment in principle is given in figure 3.

Piston

Throttle valveXSSxv\\\

V44C444P

Hydraulic jack cylinderHydraulic liquid

Fig. 3: Hydraulic equipment

Normally the piston is in the middle ofthe cylinder. Under slow motion the equalization ofpressure takes place over the throttle valve nearly without resistance. At movements with highspeed the throttle valve blocks the transportation ofthe liquid and the piston is fixed. Hydraulicequipments are used for railway bridges to transfer the breaking forces on both abutments andfor Symmetrie cable stayed bridges to keep the main girder in a Symmetrie position.

5. References

[ 1 ] Lee, DJ.: Bridge Bearings and Expansion Joints, E & FN SPON, 2nd edition,London 1994

[2] Eggert H, Grote J., Kauschke W.: Lager im Bauwesen, Verlag von Wilhelm Ernst &Sohn, Band 1, Berlin 1974

[3] Eggert H.: Vorlesungen ber Lager im Bauwesen, Verlag von Wilhelm Ernst & Sohn,Berlin 1980

[4] Descriptive literature published by several producers ofbearings and expansion joints

Bearings, expansion joints and hydraulic equipments for bridges