With this module you can conduct a structural analysis for fire scenarios based on the general calculation method for 2D and 3D beam structures. Steel, reinforced concrete and composite sections are used in this analysis based on the following standards:

• EN 1992-1-2: 2004
• EN 1993-1-2: 2005
• ENV 1994-1-2: 1997

The analysis consists of a thermal calculation and a mechanical calculation.
The calculation steps are outlined below. For more detailed information, refer to this excerpt from the user manual.

Thermal Calculation

The temperature distributions in the sections are determined as part of a nonlinear time-step integration.

Various materials such as reinforced concrete, steel or insulation can be used within a section. If necessary, user-defined curves can be specified for the thermal properties of these materials.

The time increment and duration can be specified by the user and then incorporated into the thermal analysis and the subsequent mechanical analysis. The result is a temperature profile for all specified times.

Time-temperature curve at a selected section point

Mechanical Analysis

As part of the mechanical analysis, a nonlinear time-step calculation is performed based on the 'General Calculation Method' defined in Chapter 4.3 of the EN 1992-1-2 and EN 1993-1-2 standards.

The thermal strains and stress-strain curves in the section are determined using the temperature profiles from the thermal analysis.

Related stress-strain curves for concrete with quartz additives

The example below was taken from Upmeyer, Dissertation Universität Hannover 2001 and is based on a fire test conducted in Brauschweig in 1995.

   Composite frame with dimensions, load and sections

The fire stress occurs according to the unit temperature-time curve. Flame is applied to the frame member from the bottom and to the frame strut from all sides.

Temperature profile of the used sections at time t=90 min

Geometric and physical nonlinearities are included in the time-step calculation process. At the end of the calculation, the time-dependent deformations, internal forces and support reactions are available.

The time displacement curve depicted below matches the test results very well. Even the calculated failure time of 149 min differs only slight from the test result (150 min).

Superelevated deformation figure of the frame shortly before failure (t=148 min)

Time-displacement curve uz in the horizontal frame member (1)

Time-displacement curve ux in the frame strut (2)

Thermal Analysis

• Thermal actions as per EN 1991-1-2
• User-defined fire curves
• Optional consideration of moisture content in concrete
• Optional consideration of reinforcement layers
• Non-uniform temperature load
• Heat transfer to connected components
• Radiation and convection on internal boundaries
• User-defined calculation increments

Mechanical analysis

• Temperature-dependent material properties
• Consideration of different fire scenarios
• Nonlinear time-step calculation of the structure

References:

Eurocode 1: Einwirkungen auf Tragwerke (Actions on Structures) –
Teil 1-2: Allgemeine Einwirkungen –
Brandeinwirkungen auf Tragwerke (Part 1-2: General Actions – Fire Actions on Structures);
German Version EN 1991-1-2:2002. Beuth Verlag GmbH, Berlin, Germany, 2003.

Eurocode 2: Bemessung und Konstruktion von Stahlbeton- und Spannbetontragwerken (Design and Construction of Reinforced and Prestressed Concrete Structures) –
Teil 1-2: Allgemeine Regeln –
Tragwerksbemessung für den Brandfall (Part 1-2: General Rules – Structural Fire Design);
German Version EN 1992-1-2:2004. Beuth Verlag GmbH, Berlin, Germany, 2006.

Eurocode 3: Bemessung und Konstruktion von Stahlbauten (Design and Construction of Steel Structures) –
Teil 1-2: Allgemeine Regeln –
Tragwerksbemessung für den Brandfall (Part 1-2: General Rules – Structural Fire Design);
German Version EN 1993-1-2:2005 + AC:2005. Beuth Verlag GmbH, Berlin, Germany, 2006.

Eurocode 4: Bemessung und Konstruktion von Verbundtragwerken aus Stahl und Beton (Design and Construction of Composite Steel and Concrete Structures) –
Teil 1-2: Allgemeine Regeln –
Tragwerksbemessung für den Brandfall (Part 1-2: General Rules – Structural Fire Design);
German Version ENV 1994-1-2. Beuth Verlag GmbH, Berlin, Germany, 1997.

A Heat Transfer Textbook
J.H.Lienhard IV and J.H.Lienhard V, Phlogiston Press Cambridge, Massachusetts, U.S.A., 2008.

Leitfaden Ingenieurmethoden des Brandschutzes (Engineering Guide for Fire Protection)
Technical Report vfdb TB 04/01, Eds. Dietmar Hosser, Altenberge, Braunschweig, Germany, 2006.

Bemessung von Tragsystemen mehrgeschossiger Gebäude in Stahlbauweise für realistische Brandbeanspruchung (Design of Load-Bearing Systems for Multi-Floor Building with Steel Construction for Realistic Fire Stress)
J. Zehfuß, Dissertation, TU Braunschweig, Germany, 2004.

Brandschutzbemessung im Massivbau - insbesondere Stahlbetonstützen (Fire Safety Design in Solid Constructions with Emphasis on Reinforced Concrete Columns) -
Dr.-Ing. Ekkehard Richter, Institut für Baustoffe, Massivbau und Brandschutz (iBMB)
Technische Universität Braunschweig, Germany, 2007.

Tragverhalten stählerner Rahmensysteme bei Brandbeanspruchung (Load Performance of Steel Frame Systems Under Fire Stress)
A. Rubert und P. Schaumann, Stahlbau 9/1985, Wilhelm Ernst & Sohn.

Nachweis der Brandsicherheit von kammerbetonierten Verbundbauteilen über Grenzbrandlasten (Fire Safety Check of Concrete-Encased Composite Components For Ultimate Fire Loads)
J. Upmeyer, Dissertation, TU Hannover, Germany, 2001.

Brandbeständigkeit von Faser-, Stahl- und Spannbeton (Fire Resistance of Fiber, Reinforced and Prestressed Concrete),
Bundesministerium für Verkehr, Innovation und Technologie, Straßenforschung Heft 544, Vienna, Austria, 2004.