Flexible Element

The flexible element is a two-node component for modeling expansion bellows and flexible hoses. Unlike single-node expansion joints (zero-length), this element has finite length with beam properties. Specify bending stiffness four times greater than for zero-length expansion joints.

General Properties

Property	Description
Name	Element identifier. Sort and select elements by name in the project tree
Coordinate Input Method¹	Projections: Input dimensions as projections on global coordinate axes D_X, D_Y, D_Z Spherical: Input element length L and three angles to global coordinate axes j_X, j_Y, j_Z Cylindrical: Input projection on XY plane, Z-axis projection, and two angles to X and Y axes
Stiffness Properties (Ka, Kl, Kt, Kr)	Shear stiffness (Kl) and bending stiffness (Kr) are automatically calculated using: Kl = Kr × 3/L² and Kr = Kl × L²/3 Where: Kr = Bending Stiffness (N·m/rad) Kl = Shear Stiffness (N/m) L = Bellows length (m) Important: Two-node flexible elements require bending stiffness four times greater than zero-length expansion joints. Comparison of flexible element types: Two-node element: Allows deflection (δ) Zero-length element: No deflection (δ=0) For identical applied moment M, rotation angle θ₂ = 4 × θ₁, requiring KR(two-node) = 4 × KR(zero-length) Multiply manufacturer's bending stiffness values by 4 for two-node flexible elements
Thrust Area	Models pressure thrust forces in flexible piping. Set to zero for pressure-balanced expansion joints
Total Weight	Total element weight
Uniform Weight	Distributed weight along element length

Menu and Toolbar Access

To insert a flexible element:

Select the desired node
Use menu: Insert > Flexible Element

To view element properties:

Double-click the element in the 3D view
Select the element and click the toolbar icon