Fire resistance is the ability of the structure to sustain its state for a specific duration in the event of fire. The structure must be engineered and built in a way, that in the event of an outbreak of fire:

1. The bearing resistance of the construction can be assumed for a specified period of time.
2. The generation and spread of fire and smoke within the works is limited.
3. The spread of fire to neighboring construction works is limited.
4. The occupants can leave the works or can be rescued by other means.
5. The safety of rescue teams is taken into consideration.

Human safety is of utmost importance in any structure/building during construction as well as in operational conditions. The structure shall be designed by the engineers in such a way that it shall resist the fire long enough to permit the safe evacuation of the occupants.

If designed properly with some specific considerations, concrete can be stated as a fire-resistant material.

Yes, the encasement of structural steel members with concrete can increase the durability of a structure against fire. However, proper cover around the structural steel member, bonding between structural steel and concrete, and reinforcement arrangement are all parameters that should be designed as per the country-specific design standards to make the encased member fire-resistant.

There are various ways in which concrete members can be engineered to increase fire resistance, these include:

1. Encasement of steel into concrete.
2. Applying protective coating onto the structural steel members.
3. Designing the concrete members (beams, slabs, columns) with appropriate cover based on the fire rating in terms of specific desired duration.

The SkyCiv RC Fire Resistance Calculator calculates the dispersion of the temperature developed during the fire within the reinforcement and concrete of a member. It then calculates the reduced cross-section of the members i.e. the cross-section obtained by removing parts of the cross-section with assumed zero strength and stiffness. Then, it 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.

The capacity estimation can be done for circular and square/rectangular types of concrete cross-sections. The calculator allows the user to enter the reinforcement arrangement in lateral and longitudinal directions based on which the fire resistance capacities are being calculated.

The following inputs are required to run the module:

• Section type (circular or rectangular).
• Section dimensions.
• Fire resistance duration in hours.
• Reinforcement layout (bar diameter and bar spacing) for lateral and longitudinal sides.
• Design loads (bending at the major axis and minor axis and axial force).
• Side cover.
• Material properties for concrete and reinforcing steel.

The fire resistance of reinforced concrete cross sections of walls, columns, and beams is calculated based on EN 1992.1.2.2004 - Design of Concrete Structures.