Fire Resistance

May 24, 2019
Fire Resistance

In analysis of reinforced concrete structures on fire resistance, the following building codes are supported:
  • STO 36554501-006-2006 Regulations to ensure fire resistance and fire durability of RC structures
  • DSTU-N B EN 1992-1-2:2012

The following types of sections may be analysed:

  • - rectangular bar
  • - T-section (flange at the top)
  • - T-section (flange at the bottom)
  • - I-section
  • - ring
  • all types of composite (steel and RC) sections.

Analysis on fire resistance may be carried out either in VISOR-SAPR module or in LARM-SAPR (local mode of reinforcement).

When structures are analysed on fire resistance, the program selects and checks reinforcement with account of reduction in strength and strain parameters of concrete and reinforcement as a result of defined fire load.

To define parameters for analysis on fire resistance, follow these steps:

Step 1.

For analysis of RC structures, select building code defined for this type of analysis (SP or DBN).

Fig.1. How to select building code for RC analysis

Fig.1. How to select building code for RC analysis

Step 2.

When you define materials for analysis of RC structures, select the Account of fire resistance check box.

Fig.2. How to take account of fire resistance when defining materials

Fig.2. How to take account of fire resistance when defining materials

Step 3.

To define combustion conditions, click appropriate button ( )

Then in the Combustion conditions dialog box, specify parameters for fire resistance of an element.

Fig.3. How to generate combustion conditions for an element

Fig.3. How to generate combustion conditions for an element

In the Combustion conditions dialog box, the following values should be defined:


Ultimate fire resistance

When you select ultimate fire resistance, you automatically define the time during which fire load is acting on the structure. It is possible to define the standard value for ultimate fire resistance or select the User-defined option and input any value manually.

Fig.4. Ultimate fire resistance
Fig.4. Ultimate fire resistance

Edges subject to heating

To select sides that will be subject to fire load, just select appropriate check boxes.

Fig.5. Edges subject to heating.jpg
Fig.5. Edges subject to heating

Properties of thermal conductivity

There is an option to define the following thermal conductivity properties for concrete and stiff reinforcement (if it is defined in the section):

- heat conductivity coefficient

- heat absorption coefficient

- unit weight

- coefficient for convective heat transfer

Thermal condition

You could either select one of the standard graphs of fire spreading or indicate a user-defined one. Standard graphs of fire spreading depend on the building code. For STO, only Standard graph is provided, for Eurocode and DBN graphs for Standard, Exterior and Hydrocarbon fire.

Step 4.

Analysis results.

To display analysis results for fire resistance, on the RC ribbon tab, on the Reinforcement panel, click appropriate button.

To display contour plots of temperature, in the Information about element dialog box, on the Fire Resistance tab, select appropriate check box.

Then the Fire resistance of an element dialog box (see Fig.7) is displayed on the screen. Use this dialog box to display contour plots of temperature at the time point that was specified with ultimate fire resistance. For example, if the ultimate fire resistance was defined as R90, it means that analysis results will be displayed for distribution of temperature at the 90th minute of combustion.

In the new Fire resistance of an element dialog box it is possible to display:

1. Distribution of the temperature along the section.

2. Changes in physical properties of concrete and reinforcement depending on heating temperature in the section, namely ultimate strength in compression / tension and modulus of elasticity.

Fig.6. Information about element dialog box

Fig.6. Information about element dialog box

Fig.7. Contour plots of temperature for beam section (combustion from three sides)

(combustion from three sides)

To display reinforcement that was selected for elements in analysis on fire resistance, on the Results (RC) menu, click Fire Resistance Reinforcement.

Fig.8. How to display reinforcement selected for fire resistance

Fig.8. How to display reinforcement selected for fire resistance

It is also possible to preview the fire resistance reinforcement in the Information about element dialog box. On the last tab in this dialog box Reinforcement FE (see Fig.9) reinforcement selected in analysis on fire resistance.

Fig.9. How to preview reinforcement in the Information about element dialog box

Fig.9. How to preview reinforcement in the Information about element dialog box

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