Gimbal Expansion Joint

For a Gimbal Expansion joint of properties

Axial stiffness : Rigid
Lateral Stiffness : Rigid
Bending Stiffness : 263.18 kg/m deg
Torsional Stiffness: Rigid
Weight : 450 Kg
Length : 1000 mm Flexible Element length 50 mm

I have given Input as below

Node From 20 to 30 : 475 , Force at Node 20 - 225 kg
Node From 30 to 40 : .....( Not given any values ) + above expansion joint properties
Node From 40 to 50 : 475, Force at Node 50 - 225 kg

1) Is it correct to give Input as like above

Use the Caesar "help" and select the "Application Manual" 5-16 and 5-23 cover Gimbal bellows.

I saw the Application Guide but it doesn't cover how to give the Bellow weight for Hinged type one. Is it not necessary to consider weight for this kind of bellow ?

Take the weight, divide it by 2, and put the result on the adjacent two elements.

I gone through Application Manual on page 5-17 ( Hinged Joint ) as per the drawing the hinge axis is on X, the rotation is stopped in X direction so the restraint could be RX but u've specified that portion as RY. Please clear.

I'm rite or wrong ?

The example on page 5-17 is missing some information. All restraints should be present except for the Rx, which is the hinge axis. So, for this example, on the element from 45 to 46 there should be X, Y, Z, and Rz restraints. Then on element 40 to 45, there should be an Ry restraint as in the example. I will have the manual corrected.

Thanks for ur reply sir

I have one more doubt. On Page 5-24 in Application Guide for Gimbal Joints no restraints shown. Is it not necessary for gimbal joints ?

No, you don't need any restraints. All degrees of freedom are rigid except for bending, in which you input the manufacturer's rotational stiffness values. That then takes care of all six degrees of freedom.

Sir I am not clear with some aspects in Hinged joints

1. As like in Application Manual for Hinged Joint, Torsion should be Rigid, then RX,RY,RZ are Restrained, but u said RX restraint not to give ? can we give rotation for Metallic Bellows.. ?

2. Why we should have to specify RX,RY,RZ restraints even after feeding the value
Torsion- Rigid.

Richard Ay why no replies from ur end ?

Loren is on vacation.

The example on page 5-24 is a zero length bellows element, thus all stiffnesses are provided. There are no CNODES necessary here, which is why there are no other restraints needed.

The Application Guide shows different ways of defining constraints for these expansion joint assemblies. In some models, the hardware is modeled as restraints with CNodes (page 5-17) and in others, through the expansion joint stiffnesses directly (page 5-24).

Gimballed joints (5-24) have two rotational (bending) degrees of freedom and can be defined without adding restraints. Single hinges (5-17) have only one rotational (bending) degree of freedom so some restraint must be added to lock up the second local bending term defined in the XJ parameters.

Pick a method, use it, then confirm the proper operation of your model by reviewing the results. If your model doesn't respond properly, fix the model.