Concrete Column Fire Resistance (FRP) Rekenmachine

When subjected to fire, reinforced concrete can react in several ways which reduce its structural integrity:

• Cracking and spalling of concrete at the faces of the element.
• Debonding of concrete from reinforcement, reducing composite action (and overall strength).
• Reduction in yield stress and stiffness of reinforcement.

Fire resistance is the ability of a structural element to maintain its integrity when subjected to fire. This is typically described using a Fire Resistance Period (FRP), gemeten in minuten. Building codes mandate minimum FRP values for structural elements depending on the building classification. FRP requirements can range from 30-240 minuten. Some codes split FRP requirements into distinct categories relating to methods of fire suppression. These categories include:

• Structural Adequacy: Ability to maintain structural capacity.
• Integriteit: Ability to prevent the transfer of fire through the element.
• Insulation: Ability to prevent heat transfer through the element.

Depending on the classification, some codes may require different FRP values for each category.

The Fire Resistance Period of a concrete section is influenced by the following factors:

• Grootte: Larger concrete sections typically have a higher FRP.
• Hoes: Increased cover to reinforcement can reduce the potential of concrete spalling/debonding.
• Betonsterkte: Higher concrete strengths have increased fire resistance.
• Load Level: Heavily loaded concrete sections typically have a lower FRP.
• Reinforcement Ratio: Increasing section reinforcement can increase FRP.
• Blootstelling: Elements exposed all sides will have a lower FRP than sections protected on one side.

It is also possible to increase the FRP of concrete elements through the application of protective coatings such as vermiculite or intumescent paint.

FRP is calculated differently depending on the design code adopted. When using IN 1992-1-2, the below process is followed:

1. Determine the isotherm of 500°C for the specified fire exposure, standard fire or parametric fire.
   
2. Calculating new cross-section dimensions by excluding the concrete outside the 500 jij. isotherm.
3. Determine the temperature of reinforcing bars in the tension and compression zones.
4. Determine the reduced strength of reinforcement.
5. Calculate the reduced ultimate load bearing capacity.

When using AS 3600:2018, the process is as follows:

1. Determine effective length and slenderness.
2. Calculate loading eccentricity based on design moment/axial force.
3. Calculate load level and mechanical reinforcement ratio.
4. Use tabulated values to determine minimum section width and reinforcement cover.

De SkyCiv RC brandweerstandscalculator berekent de spreiding van de temperatuur die tijdens de brand is ontwikkeld binnen de wapening en het beton van een element. Vervolgens berekent het de gereduceerde doorsnede van de staven, d.w.z. de doorsnede verkregen door het verwijderen van delen van de doorsnede waarvan wordt aangenomen dat de sterkte en stijfheid nul zijn. It then estimates the axial and flexural force carrying capacity in its combined form and finally compares the capacity with the actual forces to which the member is being subjected.

De volgende ingangen zijn vereist om de module te laten werken:

• Sectietype (rond of rechthoekig).
• Sectie afmetingen.
• Brandwerendheidsduur in uren.
• Verstevigingsindeling (staafdiameter en staafafstand) voor laterale en longitudinale zijden.
• Ontwerpbelastingen (buigen op de hoofdas en secundaire as en axiale kracht).
• Zijdeksel.
• Materiaaleigenschappen voor beton en wapeningsstaal.

SkyCiv offers tools to calculate concrete FRP in accordance with the following codes:

• IN 1992.1.2.2004 - Ontwerp van betonconstructies
• NET ZO 3600:2018 Betonnen constructies