Hi,everyone.
I have a doubt about EJMA Expansion joint Rating in Caesar2:
1:
The differenct between 1st Input and 2st input is only Z Rotation , 1st Inpu is at the ‘’from’’ End , 2st input is at the “to” end,but the result is very different.
In my opinion ,the two case is equivalent.
Can everyone give me the reason?

Data ：
1st Input
EJMA EXPANSION JOINT RATING
Node Number for "FROM" end ..................... 10.000
Node Number for "TO" end ....................... 20.000
Number of Convolutions ......................... 12.000
Flexible Joint Length .....................(mm.) 112.950
Effective Diameter ........................(mm.) 126.700

X Coordinate of "from" end ................(mm.) 0.000
Y Coordinate of "from" end ................(mm.) 0.000
Z Coordinate of "from" end ................(mm.) 0.000

X Coordinate of "to" end ..................(mm.) 112.950
Y Coordinate of "to" end ..................(mm.) 0.000
Z Coordinate of "to" end ..................(mm.) 0.000

X Displacement of "from" end ..............(mm.) 0.000
Y Displacement of "from" end ..............(mm.) 0.000
Z Displacement of "from" end ..............(mm.) 0.000
X Rotation of "from" end ..................(deg) 0.000
Y Rotation of "from" end ..................(deg) 0.000
Z Rotation of "from" end ..................(deg) 0.000

X Displacement of "to" end ................(mm.) 0.000
Y Displacement of "to" end ................(mm.) 0.000
Z Displacement of "to" end ................(mm.) 0.000
X Rotation of "to" end ....................(deg) 0.000
Y Rotation of "to" end ....................(deg) 0.000
Z Rotation of "to" end ....................(deg) 3.000

OUTPUT:

AXIAL DISPLACEMENTS
(TOTAL)
Axial Displacement (mm.) 0.000
Axial Displacement due to Lateral (mm.) 0.000
Axial Displacement due to Rotation (mm.) 3.317
Axial Displacement TOTAL (mm.) 3.317

2st input
EJMA EXPANSION JOINT RATING
Node Number for "FROM" end ..................... 10.000
Node Number for "TO" end ....................... 20.000
Number of Convolutions ......................... 12.000
Flexible Joint Length .....................(mm.) 112.950
Effective Diameter ........................(mm.) 126.700

X Coordinate of "from" end ................(mm.) 0.000
Y Coordinate of "from" end ................(mm.) 0.000
Z Coordinate of "from" end ................(mm.) 0.000

X Coordinate of "to" end ..................(mm.) 112.950
Y Coordinate of "to" end ..................(mm.) 0.000
Z Coordinate of "to" end ..................(mm.) 0.000

X Displacement of "from" end ..............(mm.) 0.000
Y Displacement of "from" end ..............(mm.) 0.000
Z Displacement of "from" end ..............(mm.) 0.000
X Rotation of "from" end ..................(deg) 0.000
Y Rotation of "from" end ..................(deg) 0.000
Z Rotation of "from" end ..................(deg) 3.000

X Displacement of "to" end ................(mm.) 0.000
Y Displacement of "to" end ................(mm.) 0.000
Z Displacement of "to" end ................(mm.) 0.000
X Rotation of "to" end ....................(deg) 0.000
Y Rotation of "to" end ....................(deg) 0.000
Z Rotation of "to" end ....................(deg) 0.00

OUTPUT:

AXIAL DISPLACEMENTS
(TOTAL)
Axial Displacement (mm.) 0.155
Axial Displacement due to Lateral (mm.) 19.893
Axial Displacement due to Rotation (mm.) 3.317
Axial Displacement TOTAL (mm.) 23.365

2:

a single hinged joint is always defined using a zero length expansion joint with rigid axial,transverse,and torsional being input,the bending stiffness is set equal to the bending stiffness of the hinge from the manufacturer’s catlog.
The other method to model a finite length expansion with the correct connecting relativity between those hinged plate and bar.
The special is that the transverse stiffness must be left blank,and the bending stiffness must be 4 times the bending stiffness from the manufacture’s catlog.

There is no any difference in The result of force,displacement in the piping system between this two method.

Ok,now ,my question arise.

The first method is easy to get the hinged rotation displacement according to the zero length element;
The second method is also easy to get this displacement according to the hinge point;
But if you use the Caesar’s EJMA expansion Joint rating to get the expansion joint’s displacement in the second method ,you will find that the dispalcement is not olny rotation ,and including lateral.
In our opinion ,the hinged expansion is only carrying the rotation displacement,but the EJMA expansion Joint rating get the different result.
Is that if a expansion joint with extern restraint can not be calculated by this program?
does the Erating correctly consider the relation of rotation and lateral?
does it caculate the displacement for expansion repeatedly ?

can anyone help me?

Hi,Richard Ay.
this question troble me a long time
can you give me some suggestion.
i think you will help me if do a test at the Erating tool in the caesar.

We are looking at this issue.

Lanxuedream – Just a simple question, on the defined length example 2, did you model it with two restraints which are pinned (X,Y,Z,Rx,Ry) at the centerline of the bellows?
Dan Edgar, PE
Principal Engineer
Senior-Flexonics, Pathway Div

HI,Dan Edgar
Thank you very much
but I have modeled it with what you show in the graphic.
i think i have understand the relation between the nodes.
my quesiton is how to calculate the expansion axial displacement total.
in singal hinge expansion ,in our opinion ,there is only angle displacement,but if you use the expansion jonit rating module(in the caesar paragram) using the displacement in the caesar report,you will find that there is a lateral dispalcement,because when a hinge expansion joint to bend rotate,in the coodinates system will produce a movement at the end point (if the form point is anc),the expansion joint rating module not olny take this movement to caculate the lateral displacement ,but also take the bending angle to caculate the bend displacement,and the add this to the total displacement.i don't think this is right.can anyone help me.

Hi,Richard Ay.

what is your company's opinion?

lanxuedream,

I think you do not need to consider this lateral movement by rotate of hinge expansion joint. You need to consider lateral movement if you have a lateral deflection.

Attached file is a typical lateral deflection.

Lanxuedream – Erate is set up to extract input from the CAESAR II program which uses end deflections. If you’re going to manually input deflections, you’ll have to translate the rotation from the center line of the bellows to the from / to end. At the end of the bellows, angular rotation is actually a combination of Axial, Lateral and Angular deflection.

The other thing to be aware of is that ERate was written to calculate the effective movement per convolution as the result of axial, translational and rotational movements. This is because at the time CAESAR II was written the number one EJ vendor’s catalog published selection tables based upon this value. This vendor has now gone out of business and all of the vendor’s I’m aware of publish rated movements for the entire bellows element. So, in the case of a hinge joint, Erate is not much use because it gives you the movement at the from/to ends instead of the centerline movements and the effective axial movement is not of much use.

hi,Dan Edgar
your reply give me a great help, I am very pleased to be able to know you.

about the expansion ,i have other quesitions in the following:
1:
In the calculation of the expansion joint column instability, or planar instability ,Why do not need to consider the displacement stress which is forced by the change of Temperatures in the piping system?
because:
in the following ,the displacement is take to the calculation in the instability of the underground piping system:
When the pipeline is buried, the soil limits the heating of the pipeline, this force will be considered in the calculation of the pipe column instability

2:
When the calculation of the expansion joint column instability, it is assumed that both ends are fixed.
When both ends are not fixed support, the critical buckling pressure is multiplied by a reduction factor.
my question is that :
When we use a classic three-hinge expansion joints in the piping system, if the buckling pressure of hinge expansion joints need to reduce,because the ends of the hinge expasion are not anc,can to be rotate.
if not,can you give me some reason.
in my opinion,it is not need to reduce ,it think that are fixed .

3: when to design a expansion ,when to use as-formed condition,when to use heat-treated condition?

i have a certain understanding about your company's product, in particular, the FCC's expansion section

Lanxuedream – These are very detailed questions regard bellows design which we should probably take off line. Please send me an e-mail at: pipesol@connectnet.com and I will address them there.

hi,Dan Edgar


I try to send e-mail to you,but it can't arrive.

if is the email adress right?

Lanxuedream - You can go to my profile and click on my e-mail address and send me a message that way. I tried it and it worked. Sorry about the difficulties.