There are lateral expansion joint objects in START/PROF that cover all five types:
This expansion joint has 3 or more tie rods and prohibits any movements except linear movement along two lateral axes. Any kind of rotations are prohibited. Typical structure is shown on figures below
Also it could be two bellows or two hinged or gimbal expansion joints with supports, that are placed with a special manner to remove all types of deformations from the expansion joint except lateral deformations. Usually this design is used when the internal pressure is very low or zero.
This expansion joint consist of two angular expansion joints. It is also called Double Hinged Expansion Joint. Allows linear movements along one axis and allows rotation around one axis. Typical structure is shown on figures below
This expansion joint has 2 tie rods and allows linear movements along two lateral axes and rotation around one axis. Typical structure is shown on figures below
This expansion joint consist of two hinged expansion joints. It is also called Double Hinged Expansion Joint. Allows linear movements along one axis and allows rotation around one axis. Typical structure is shown on figure below. In PASS/START-PROF modeled using two hinged expansion joints
This expansion joint has 2 tie rods and allows linear movements along two lateral axes and rotation around two axes. Typical structure is shown on figures below. In PASS/START-PROF modeled using two gimbal expansion joints
Expansion Joint analysis results can be found in Expansion Joint Deformation Table. See also "How to Reduce the Nozzle Loads in START-PROF"
All expansion joint properties can be taken from expansion joints database by pressing the "..." button and selecting the appropriate expansion joint.
Property |
Description |
Name |
Element name. If checked then it shown in 3D view |
Lateral Flexibility |
Lateral flexibility, (1/KL) of whole length of expansion joint (all convolutions). Value must be obtained from manufacturer |
Lateral Stiffness |
Lateral Stiffness, (KL) of whole length of expansion joint (all convolutions). Value must be obtained from manufacturer. In contrast to the finite length flexible element, there's no need to multiply bending stiffness provided by manufacturer by 4, because expansion joint is modeled as zero length. Bending angular stiffness can be calculated by equation:
Kx - Axial stiffness of the bellows Dm - Effective diameter (mean diameter of the bellows) Lb - Corrugated length of bellows Lu - Distance between outermost ends of convolutions |
Stiffness Temp. Factor |
For elevated temperatures material elastic modulus is reducing, therefore the stiffness values should be adjusted. This stiffness temperature correction factor is equal to the ratio of elastic modulus at operating and ambient temperature for bellows material and can be specified for each operating mode depending on the temperature |
Allowable lateral expansion movement |
Allowable lateral expansion movement - maximum allowable transverse linear deformation. Value used for expansion joint deformation analysis. |
Allowable Corr. factor |
Allowable movements are based on a reference number of load cycles and pressure. It should be adjusted to the actual number of cycles and pressure. This allowable correction factor can be specified for each operating mode depending on the pressure |
Length |
Expansion joint length Lu. In the internal second layer hidden model PASS/START-PROF model this type of expansion joint as zero length expansion joint and adds two rigid elements with length Lu/2 on the both sides. Non zero-length expansion joints can be modeled using Flexible Element |
Weight |
Expansion joint weight that is applied on the rigid elements (half on the left and half on the right) |
Type of expansion joint |
Choose the expansion joint type: |
Bending Stiffness |
Bending stiffness KR calculated automatically: |
Allowable Rotation |
Allowable rotation angle - maximum allowable rotational deformation. Value used for expansion joint deformation analysis. Value must be obtained from manufacturer |
Bellows Number |
Choose the number of bellows in expansion joint 1 or 2 |
Bellows Length |
The Lb value |
Tie rod plane |
Choose the plane in which the tie rods are located: Vertical, horizontal, custom. For example this is "Vertical" If custom is selected, then need to specify the angle between the vertical plane and tie rods plane. 0 degree - vertical, 90 degree - horizontal |
Stiffness depends on pressure and rotation |
For angular expansion joint we should also take into account the friction moment in the hinges P – Internal pressure y – Lateral movement KLi – Angular stiffness on i iteration Cl - lateral stiffness (KL) Algorithm is following: Set bellows angular stiffness KL0=Cl+P*Cp, and perform analysis. Get the lateral movement y Set bellows angular stiffness KL1=Cl+P*Cp+(Cl*P)/y, and perform analysis. Get the new lateral movement y Repeat step 2 PASS/START-PROF performs this iteration process automatically. Usually 3 steps (iterations) are enough to achieve convergence. |
Factor Cl (lateral) and Cp (pressure) |
Cl and Cp factors should be provided by expansion joint manufacturer |
To insert a ballasting weight, select the desired node and use the menu option: Insert > Expansion Joint > Lateral