After superimposing the thermal load cases with the internal pressure load cases, you gain the corresponding combinations. You can create other manual piping and result combinations in parallel with the automatic load combination.
Automatic Load Combination
Wie für RFEM steht auch für RF-PIPING die automatische Kombination der Lastfälle zur Verfügung. Dieses Feature wird standardmäßig aktiviert und erzeugt die empfohlenen Last- und Ergebniskombinationen für die Rohrleitungsbemessung. Die entsprechende Einwirkungskategorie muss dabei den Lastfällen zugeordnet werden, um korrekte Kombinationen zu erzeugen. Hier wurden speziell für Lasten auf Rohrleitungen neue Einwirkungskategorien implementiert.
Druck-Temperatur-Bedingungen werden als Sätze mit erstem (zweitem, drittem, ...) Lastfall der Kategorie „Druck“ und als erster (zweiter, dritter, ...) Lastfall der Kateogire „Temperatur“ erzeugt. Standardmäßige Einstellungen können im Dialog „Gruppierung von thermischen und Innendruck-Lastfällen für Betriebskombinationen“ eingesehen bzw. geändert werden. Dieser Dialog ist im Register „Rohrleitungs-Kombinationen“ des Dialogs „Lastfälle und Kombinationen bearbeiten“ zugänglich. Der genannte Dialog wird automatisch angeboten, um jede Änderung eines Lastfalls der Kategorie „Druck“ oder „Temperatur“ zu kontrollieren.
Druck-Temperatur-Bedingungen werden als Sätze mit erstem (zweitem, drittem, ...) Lastfall der Kategorie „Druck“ und als erster (zweiter, dritter, ...) Lastfall der Kateogire „Temperatur“ erzeugt. Standardmäßige Einstellungen können im Dialog „Gruppierung von thermischen und Innendruck-Lastfällen für Betriebskombinationen“ eingesehen bzw. geändert werden. Dieser Dialog ist im Register „Rohrleitungs-Kombinationen“ des Dialogs „Lastfälle und Kombinationen bearbeiten“ zugänglich. Der genannte Dialog wird automatisch angeboten, um jede Änderung eines Lastfalls der Kategorie „Druck“ oder „Temperatur“ zu kontrollieren.
Author
Mr. Sühnel is responsible for the quality assurance of RSTAB; he also participates in product development and provides technical support for our customers.
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Knowledge Base
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Piping systems are exposed to a variety of loads. One of the most decisive is internal pressure. This article will, therefore, deal with the stresses and deformations resulting from a pure internal compression load in the pipe wall or for the pipe.
The RF-PIPING and RF-PIPING Design add-on modules allow you to design piping systems according to EN 13480-3 [1], ASME B31.1 and B31.3. In the case of the European standard, the determination of pipe stresses is based on the formulas of Section 12.3 Flexibility Analysis. Depending on the stress type, one or more resulting moments is applied without regard to each other. This differentiation occurs when determining the stresses due to occasional loads, for example.
You can now use axial expansion joints in RF‑PIPING. These are applied to absorb movements of extension and compression in the axis direction due to the thermal expansions of the piping.
For stress calculations, some standards use the "wall thickness analysis". We get the wall thickness by subtracting corrosion, abrasion allowance, manufacturing allowances (threading, grooving, and so on), and mill tolerances from the nominal wall thickness. All necessary values can be entered in the "Piping Cross‑Section" dialog box, "Stress Analysis Parameters" tab.
After activating the RF‑PIPING add‑on module, a new toolbar is available in RFEM and the project navigator and tables are extended. The piping system is now modeled in the same way as the members. Pipe bends are defined simultaneously by tangents (straight pipe sections) and radius. Thus, it is easy to subsequently change bend parameters.
It is also possible to extend the piping subsequently by defining special components (expansion joints, valves, and others). The implemented libraries of structural components facilitate the definition.
Continuous pipe sections are defined as sets of piping systems.
For piping loads, member loads are assigned to the respective load cases. The combination of loads is included in piping load combinations and result combinations.
After the calculation, you can display deformations, member internal forces, and support forces graphically or in tables.
Pipe stress analysis according to standards can then be performed in the RF‑PIPING Design add‑on module. You only need to select the relevant sets of piping systems and load situations.
- Graphical input of piping systems and piping components
- Illustrative visualization of piping systems and piping components in RFEM graphic window
- Comprehensive libraries for piping cross‑sections and materials
- Comprehensive libraries for flanges, reducers, tees, and expansion joints
- Consideration of piping structure (insulation, lining, tin‑plate)
- Automatic calculation of stress intensification factors and flexibility factors
- Specific piping action categories for load cases
- Optional automatic combinatorics of load cases
- Consideration of material properties (modulus of elasticity, coefficient of thermal expansion) either during operating temperature (default setting) or during reference (assembly) temperature of material
- Consideration of strain and uplift due to pressure (Bourdon effect)
- Interaction between the supporting structure and the piping system
- Response spectra in accordance with different standards
- The following standards are implemented:
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EN 1998-1:2010 + A1:2013 (European Union) -
DIN 4149:1981-04 (Germany) -
DIN 4149:2005-04 (Germany)
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IBC 2000 (USA) -
IBC 2009-ASCE/SEI 7-05 (USA)
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IBC 2012/15 - ASCE/SEI 7-10 (USA)
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IBC 2018 - ASCE/SEI 7-16 (USA)
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ÖNORM B 4015:2007-02 (Austria) -
NTC 2018 (Italy) -
NCSE-02 (Spain) -
SIA 261/1:2003 (Switzerland) -
SIA 261/1:2014 (Switzerland)
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SIA 261/1: 2020 (Switzerland)
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O.G. 23089 + OG 23390 (Turkey) -
SANS 10160-4 2010 (South Africa) -
SBC 301:2007 (Saudi Arabia) -
GB 50011 - 2001 (China) -
GB 50011 - 2010 (China)
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NBC 2015 (Canada) -
DTR BC 2-48 (Algeria) -
DTR RPA99 (Algeria)
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CFE Sismo 08 (Mexico) -
CIRSOC 103 (Argentina) -
NSR - 10 (Colombia) -
IS 1893:2002 (India) -
AS1170.4 (Australia) -
NCh 433 1996 (Chile)
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- The following National Annexes according to EN 1998‑1 are available:
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DIN EN 1998-1/NA:2011-01 (Germany)
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ÖNORM EN 1991-1-1:2011-09 (Austria)
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NBN - ENV 1998-1-1: 2002 NAD-E/N/F (Belgium) -
ČSN EN 1998-1/NA:2007 (Czech Republic) -
NF EN 1998-1-1/NA:2014-09 (France) -
UNI-EN 1991-1-1/NA:2007 (Italy)
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NP EN 1998-1/NA:2009 (Portugal) -
SR EN 1998-1/NA:2004 (Romania) -
STN EN 1998-1/NA:2008 (Slovakia) -
SIST EN 1998-1:2005/A101:2006 (Slovenia) -
CYS EN 1998-1/NA:2004 (Cyprus) -
NA to BS EN 1998-1:2004:2008 (United Kingdom) - NS-EN 1998-1:2004 + A1:2013/NA:2014 (Norway)
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- User-defined response spectra
- Direction-relative response spectrum approach
- Relevant mode shapes for the response spectrum can be selected manually or automatically (5% rule from EC 8 can be applied)
- Generated equivalent static loads are exported to load cases, separately for each modal contribution and separately for each direction
- Result combinations by modal superposition (SRSS and CQC rule) and direction superposition (SRSS or 100% / 30% rule)
- Signed results based on the dominant eigenmode can be displayed
After modeling piping systems in RFEM using RF‑PIPING and defining loads as well as load and result combinations, you can carry out pipe stress analysis in the RF‑PIPING Design add‑on module.
You can select all or only some pipelines and loads, load or result combinations for piping design. The material library provides various materials according to EN 13480‑3, ASME B31.1‑2012, and ASME B31.3‑2012 standards.
After the calculation, the results are displayed in clearly arranged windows; for example, by cross‑section, by pipeline, or by members. You can also display the design ratio graphically on the entire model in RFEM. This way, you can quickly recognize critical or oversized areas of the cross-section.
In addition to the input and result data, including design details displayed in tables, you can add all graphics into the printout report. This way, comprehensible and clearly arranged documentation is guaranteed. You can select the report contents and extent specifically for the individual designs.
How do I activate pipeline modeling?
Is it possible to analyze and design piping systems with Dlubal Software?
Why is it not possible to load the OPE combinations in the RF‑PIPING Design add-on module?
I design pipelines using the RF-PIPING Design add-on module. I have created a new prestress load case and loaded the piping with longitudinal displacement.
Is it possible to add this new load case to combinations that are generated automatically?
Is it possible to add this new load case to combinations that are generated automatically?
Is it possible to automatically generate zones in RWIND 2?
How can I create a response spectrum according to ASCE 7‑22?
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