Finite Element Analysis of Substructures in ROHR2 -

Optional program module

ROHR2fesu is an additional module in the program system ROHR2 for detailed analysis of local segments in pipes and vessels.
ROHR2fesu offers the easy-to-use modeling of substructures by nearly any circle and elliptic geometry using shell elements, fully integrated in the ROHR2 framework. This enables to carry out detailed analysis of critical segments inside the framework of the entire model. The shell element substructure analysis is carried out using FE-method.
The mesh generator of ROHR2fesu automatically integrates intersections of branches, trunions, and nozzles with and without reinforcement. ROHR2fesu allows controlling the mesh resolution in a simple way.
ROHR2fesu has been verified extensively by comparison against reference solutions of standard problems.

ROHR2fesu offers:

  • Complete integration of the FE structures into the connecting framework
  • easy-to-use parameter controlled model generation and meshing
  • short calculation time
  • automatic stress analysis and documentation
  • stress analyses following EN 13445, Appendix C, ASME Section VIII, Div. 2, Part 5 and AD S4

ROHR2 optional program module

ROHR2fesu is available as an additional program to the ROHR2 single user license and to the ROHR2 network license. The system requirements correspond to those of the program ROHR2. Running ROHR2fesu always requires the installation of ROHR2.

Tasks of ROHR2fesu

The task of ROHR2fesu is the modeling and calculation of shell-substructures for the detailed analysis of stiffness and stresses in concentrated segments of the piping structure.
The determination of the substructure in the framework is made on the basis of a stiffness matrix.
The results of a ROHR2fesu calculation are a stiffness matrix and loads at nodes from element loads and extra loads (e.g. loads concentrated on the sub structure) at connection points.
The load cases and load case combinations of the ROHR2 framework model used to determine the element stresses within the shell structure.

The main focus of the ROHR2fesu application

The main focus of the ROHR2fesu application is on problems in piping and vessel models where stiffness and/or stress analysis needs to be performed, as there are:

  • Intersections of piping elements generally
  • Special components for which internal pressure design stress codes are available but no calcula-tion norms for external  forces and moments
  • Components where the standards of k- and i-factors are unsatisfactory
  • Special components without k- and i-factors defined in the stress codes
  • Analysis of local stress utilization, e.g. for life-time analysis
  • Optimization of details in pipe and vessel constructions
  • Nozzle and cams at vessel with or without reinforcement
  • Big diameter tubes with miter bends
  • Calculations with to measured pipe segments (as-built), e.g. bends
  • Damage analysis at corroded or eroded pipes
  • Detail analysis of bend deformation due to internal pressure or bending in oval bends

Of course the standard pipe components (e.g. acc. to EN 13480) can be modeled and calculated in ROHR2fesu.
Stress analyses following  EN 13445, Appendix C, ASME Section VIII, Div. 2, Part 5 and AD S4 can be carried out.

Integration into ROHR2

ROHR2fesu is fully integrated into the ROHR2win user interface.

Select the segment, to be analyzed detailed, in the framework. From framework details (geometry, dimensions, component type like bend or head) a coarse model of the substructure is generated from the selected segment. This model can be completed in ROHR2fesu by details which are missing in the framework. The substructure is shown in the containing piping framework using the system lines or as simple shell model. By a double-click on the substructure in the framework, ROHR2fesu is launched to change the model or for analysis or documentation of the substructure.

The assignment of operation data (pressure, temperature, medium density) at each load case in the framework is done analogue to the ROHR2 framework.

ROHR2 calculation of the connecting framework

The stiffness of substructure is considered in the framework by a stiffness matrix resulting from the FE-analysis.

ROHR2fesu calculation of the substructure

Loads at the connection points in the framework are automatically taken over into the calculation of the substructure. Loads from the substructure are taken over in the framework analysis.

Super elements

The kinds of super elements, offered by ROHR2fesu:

SE components pipe Cone: centric, eccentric, elliptical
Bend, circular bend, miter bend, measured bend, creased bend
SE-component rectangular duct
SE-components Boden Spherical slice, toroidal slice - concave/convex, elliptic slice
SE-components Punkt Transition element
Finite Element Analysis of Substructures in ROHR2 - Examples

Simple sloping branch

A simple (sloping) branch is created by two superelements of the type Centric Cone. For the intersection it must be defined properties like rounding radius, projection or reinforcement.


Norm-Tee with conical transitions

The cylindrical bases of the norm tee are created by superelements type Cylinder. The conical transitions in the cen-ter of the tee are superelements of the Centric cone with different dimensions at the beginning and at the end. The intersection requires the input of a fillet.


Spherical fitting

The cylindrical bases as well as the conical transitions are made by superelements of the type Centric Cone. The sphere is created by the superelement Spherical Slice (in the special form complete sphere).


Support at bend

The support and the cylindrical bases are created by the superelement of the type Centric Cone.
The bend is created by a superelement of the type bend (here round bend).


Branch in eccentric reducer

The nozzle and the cylindrical bases are created by a superelement of the type Centric cone (cylinder). The reducer is created by a superelement of the type Eccentric Cone.



The cylindrical bases are created by superelements of the type Centric Cone (cylinder).
The two “reducers” are made by superelements type Eccentric cone.

Finite Element Analysis of Substructures in ROHR2 - Complex Systems