Fire resistance

Thermal analysis to determine the nature of the heating of the cross-section. The temperature at certain points of the cross-section of the structure is determined to ensure the required ultimate fire resistance in terms of heat-insulating properties of concrete. It is also possible to select reinforcement that ensure the required ultimate fire resistance of reinforced concrete and composite (steel & RC) structures in loss of bearing capacity according to STO 36554501-006-2006 and DSTU-N B EN 1992-1-2: 2012.

Ultimate fire resistance

In LIRA-FEM program, when analysis on ultimate fire resistance of reinforced concrete and composite (steel and RC) structures is carried out, you will receive the temperature distribution along the section according to the specified time period in fire. Then physical and mechanical properties of materials are modified according to obtained temperature fields. The bearing capacity of structural elements is checked in normative load and, if required, appropriate area of reinforcement is added.

Types of sections for which analysis of fire resistance in LIRA-FEM program is available

Analysis of fire resistance is implemented for standard types of sections (rectangle, ring, T-section, asymmetric T-section, I-section, cross, angle), composite (rectangular concrete section with various options for the location of rigid reinforcement and various pipe concrete sections) and plate elements.

Define combustion conditions and thermal properties for materials

The process to define the input data for analysis on fire resistance is quick and simple. It is possible to define appropriate data both in the SAPFIR module (preprocessor) and in the VISOR-SAPR module (FE editor).

Define and visualize edges subject to heating
Temperature of concrete and normative compressive strength of concrete in heating

When the input data is defined, the temperature fields and material properties for concrete and reinforcement in fire are determined for selected section.

Temperature of reinforcement and normative tensile strength of reinforcement in heating

When design model is generated, the user could evaluate the heat-insulating ability of structures (GOST 30247.1) and determine whether the concrete or reinforcement has reached the critical heating temperature.

Temperature distribution over the cross-sectional area when the cross-section is divided into separate FEs and when FE mesh is dense at the edge subject to heating

Temperature accuracy is improved when the mesh is made denser automatically at edges subject to fire.

The FE mesh is generated so that its nodes are located not only within the thickness of the section, but also along its perimeter, as well as along the flanges and webs for structures with rigid reinforcement.

Export *.txt file of problem with analysis on fire resistance to the 'Thermal analysis' system

*.txt file of problem with analysis on fire resistance may be transferred to the 'Thermal analysis' system.

The *.txt file contains all parameters specified for the section and required for the thermal analysis (geometrical dimensions of the section, materials, edges subject to heating, ultimate fire resistance, thermal conductivity coefficient, heat capacity coefficient, density, convective heat transfer coefficient, etc.).

In the 'Thermal analysis' system, it is possible to modify the transferred section, e.g. to define a fire-proof screen.

Results for analysis of reinforcement in plates with account of strength in heating

To ensure the required ultimate fire resistance in terms of loss of bearing capacity, reinforcement is analysed according to STO 36554501-006-2006 (for SP 63.13330.2012/2018) or DSTU-N B EN 1992-1-2:2012 (for DBN B.2.6-98:2009) with the nonlinear deformation theory.

Results for analysis of reinforcement in bars with account of strength in heating

The results of reinforcement selected for fire resistance are presented graphically: mosaic plots for reinforcement in plate and bar elements of the model. Reinforcement selected in analysis on fire resistance is presented as a certain row in the tables of results and in the 'Information about element' dialog box.

Results for analysis of reinforcement with account of fire resistance in the local mode of reinforcement

Analysis on fire resistance may be performed not only in a unified graphic environment, but also in the local mode for analysis of an individual reinforced concrete bar or plate element.

Forces for the element under consideration may be transferred from the VISOR-SAPR module or defined directly in the LARM-SAPR module.

According to the fire resistance data of an element, the cross-section may be transferred from 'VISOR-SAPR' module into the 'Cross-section Design Toolkit' module. The cross-section is transferred as divided into zones depending on the temperature distribution in each of its segment. Each zone has its own nonlinear stress-strain diagram of the main material and reinforcement with account of changes in physical and mechanical properties of concrete and reinforcement in high-temperature fire.

Analysis on heat conduction, steady and transient heat conduction, analysis of RC structure on fire resistance
How to simulate and analyse a large-panel building in LIRA-FEM software with account of fire resistance

Evaluate the software

If you have any doubt, download the Demo version and evaluate the program or contact our Support Team for more details.

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