Vibration Isolation in Railway Systems - Light and Heavy Mass Spring Systems

d y n a m i k

Calenberg Taiwan Mass spring system.ppt

Vibration Isolation in Railway Systems

Light and Heavy Mass-Spring-Systems for Ballastless Track

Some Basic Facts

Status December 2005

Dipl.-Ing. Helmut SchmitzGeneral ManagerCalenberg EngineersBearings ManufacturerSalzhemmendorf, Germany

www.calenberg-ingenieure.de

d y n a m i k

Dr.-Ing. Frank Mueller-BoruttauManaging Directorimb-dynamikConsulting engineersInning-Buch, Germany

www.imb-dynamik.de

page 2Presentation Taiwan 2005

d y n a m i kVibration Isolation in Railway Systems -Light and Heavy Mass-Spring-Systems

Vibration Isolation in Railway Systems -Light and Heavy Mass-Spring-Systems

Contents Overwiew

Definition: What is a mass-spring-systemDefinition: Light and heavy mass-spring-systems Where to use a mass-spring-system Dimensioning mass-spring-systems How to lift the concrete componentsTo stick or not to stick?




Definition: What is a mass-spring-system

Definition: Light and heavy mass-spring-systems Where to use a mass-spring-system Dimensioning mass-spring-systems How to lift the concrete componentsTo stick or not to stick?



Definition: What is a mass-spring-systemA mass-spring-system always consists of these 3 components:

massspringsupport (rigid, which is best for vibration insulation, or not rigid)

It works like this:Due to the elasticity the dynamic wheel-rail-forces Fdyn are reduced.The mass „absorbs“ a large portion of the reduced dynamic forcesThe spring transmits only the remaining force to the supportLower dynamic forces on the support means also lower vibration

100 % F dyn

95 % F dyn

5 % F dyn



Definition: What is a mass-spring-systemSince there is a mass, resting on a spring, resting on a support, the mass will show an „eigenfrequency“. An eigenfrequency is the frequency, the mass-spring-system will vibrate with, if you hit it with a hammer like this:

Decaying vibration

time t

disp

lace

men

t s(t)

s(t)exp




Definition: What is a mass-spring-system

Definition: Light and heavy mass-spring-systems

Where to use a mass-spring-system Dimensioning mass-spring-systems How to lift the concrete componentsTo stick or not to stick?



Definition: Light and heavy mass-spring-systems

There are two kinds of mass-spring-systems:

light mass-spring-system

heavy mass-spring-system

Definitions:For a given spring the eigenfrequency of the mass-spring-system depends on the mass. The heavier the mass the lower is the eigenfrequency.

Light mass-spring-system have an eigenfrequency of about 12 Hz up to 18 Hz.

Heavy mass-spring-system have an eigenfrequency of about 5 Hz up to 12 Hz.




Definition: What is a mass-spring-systemDefinition: Light and heavy mass-spring-systems

Where to use a mass-spring-system

Dimensioning mass-spring-systems How to lift the concrete componentsTo stick or not to stick?




A train causes dynamic forces, which in turn causes vibration.A mass-spring-system can reduce the vibration ot the track and of the surroundings by a (very) large amount.Thus the immission acting on the neighborhood is reduced as far as necessary.



Where to use a mass-spring-system In detail:

Basically a mass-spring-system

reduces the vibration of the trackreduces the vibration that enters the supporting structurethus reduces the vibration that is transmitted through the groundthus reduces the vibration to neighboring buildingsthus reduces the vibration acting on • man• buildings • technical installations

Since the vibration of the building is reduced, the noise coming from the vibrating floors, walls and ceilings is also reduced




A mass-spring-system is used for a new track if some of the following conditions are true:

Trains will have wheels with imperfections like out-of-round wheels, wheel flats, corrugation etc. There is no such thing as a perfect wheel. At least not after some operation time.

The track will not always be as perfect as it has been built, but will have defects of the rail head as well as the other components of the track. There is no such thing as a perfect track...




There is • a neighborhood - buildings close to the track -• that must be protected • according to local codes and standards • against vibration and noise, caused by this vibration. (This noise can be

caused by the supporting structure (bridge, elevated track) or by the floor, walls and ceiling of rooms, where people are present.)




Usually mass-spring-systems are used to achieve a high reduction of the

immissions.

A heavy mass-spring-system is even more efficient than a light mass-spring-

system. A heavy mass-spring-system has the highest protection efficiency.

If many buildings that must be protected do have wooden floors, a heavy mass-

spring-system must be used.




Definition: What is a mass-spring-systemDefinition: Light and heavy mass-spring-systems Where to use a mass-spring-system

Dimensioning mass-spring-systems

How to lift the concrete componentsTo stick or not to stick?



Dimensioning mass-spring-systems

Light mass-spring-systems, sketch 1 cross section

mass

spring

support



Dimensioning mass-spring-systemsLight mass-spring-systems, sketch 2 ground plan



Dimensioning mass-spring-systemsLight mass-spring-systems

The concrete slab thickness is at least 0.2 m and will not exceed about 0.35 m.The width is about 2.7 mThe length of a concrete slab varies: it might be about 6 m, or even continuous. However a section length of about 10 to 15 m should be avoided due to disadvantegous slab eigenfrequencies.Theelastic layer is usually covering the whole footprint of the slabs.The elastic layer stiffness is selected appropriately to the eigenfrequency the mass-spring-system shall have.(Light mass-spring-system have an eigenfrequency of about 12 Hz up to 18 Hz.)The elastic layer should have the optimal amount of damping:• to reduce the slab vibrationsas well as • supplying the necessary insertion loss for the higher frequencies



Dimensioning mass-spring-systemsHeavy mass-spring-systems, sketch 1 cross section

mass

spring

support



Dimensioning mass-spring-systemsHeavy mass-spring-systems, sketch 2 ground plan strip bearings



Dimensioning mass-spring-systemsHeavy mass-spring-systems, sketch 3 ground plan round discrete bearings



Dimensioning mass-spring-systemsKeep in mind: the slabs must be restricted in such a way that the longitudinal and transverse forces can be borne. Use camplates or other horizontal bearings.




Definition: What is a mass-spring-systemDefinition: Light and heavy mass-spring-systems Where to use a mass-spring-system Dimensioning mass-spring-systems

How to lift the concrete components

To stick or not to stick?



How to lift the concrete componentsYou will use the lifting method in combination with discrete bearings preferably.Now how to lift the slabs?It depends:

It is very easy if the longitudinal sides are free. Then you can lift it with jacks that can be applied from the sides.

If the sides are NOT freely accessible:You must install some manholes for example like this:



How to lift the concrete componentsThe manholes must be shaped such that you can

lift the structure with mechanically or hydraulically acting jacksand

insert the bearings simultaneouslyOr: you can lift the slabs with jacks applied at the longitudinal sides. You must have holes shaped appropriately such that the jacks can be inserted and the slab can be lifted with the slabs.



How to lift the concrete componentsThe manholes must be shaped such that you can

lift the structure with mechanically or hydraulically acting jacksand

insert the bearings simultaneouslyOr: you can lift the slabs with jacks applied at the longitudinal sides. You must have holes shaped appropriately such that the jacks can be inserted and the slab can be lifted with the slabs.




Definition: What is a mass-spring-systemDefinition: Light and heavy mass-spring-systems Where to use a mass-spring-system Dimensioning mass-spring-systems How to lift the concrete components





If you require that the elements must be replaceable, you can NOT stick the elements to either the support or the slab. If a replaceability is not required there is no need to stick the elements either to support or slab: the rubber surface of top and bottom side of the bearings tolerate a certain roughness of the concrete surfaces. If the roughness exceeds the acceptable limit some viscoplastic sheets are used to smooth the surfaces. Thus it is inhibited that the rough concrete surfaces damage the rubber surfaces.Usually the horizontal forces are borne by special stop units. Thus only neglectable horizontal forces are acting upon the bearings.

Thus it follows: you will not stick (glue, cement) the bearings to the concrete.Only exception: You use precast concrete troughs or precast slabs (for example on an elevated track), where you will pour the in situ concrete later. Then you might want to stick the bearings to the concrete floor. Thus they can not be misplaced accidentally.

d y n a m i k

Calenberg Taiwan Mass spring system.ppt

This presentation was prepared by

Dipl.-Ing. Helmut SchmitzManaging DirectorCalenberg EngineersBearings ManufacturerSalzhemmendorf, Germany

www.calenberg-ingenieure.de

d y n a m i k

Dr.-Ing. Frank Mueller-BoruttauManaging Directorimb-dynamikConsulting engineersInning-Buch, Germany

www.imb-dynamik.de

For further information please contact the authors

State December 2005

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Vibration Isolation in Railway Systems - Light and Heavy Mass Spring Systems