1. General
This article explains where it is necessary to ensure that steel structures, such as columns and beams, maintain the required Fire Resistance Level (FRL) according to the NCC-2022. The FRL of any steel structure in buildings must comply with the specified requirements, with certain concessions permitted in specification 5 of NCC-2022. These concessions are related to steel columns and beams in car parks. If mandated by the NCC-2022, Passive Fire Protection of steel using calcium silicate boards, fire-resistant sprays, or paints.
2. C2D9(2) Lightweight Construction
If lightweight construction is used to protect steel structures and is not in contact with the steel members, any void must be filled solid up to a height of 1.2 meters from the floor and protected from vehicle movement by steel or other suitable coverings.
3. C34D17 Columns Protected with Lightweight Construction to Achieve FRL
A column protected with lightweight construction that passes through an element required to have an FRL must be protected with a prototype assembly of construction that has achieved the required FRL.
Note: The requirement to protect steel members for a length of 300mm on both sides applies only to steel columns that cross building elements with an FRL. This requirement does not apply to every steel member crossing a building element with an FRL. However, Passive Fire protection of steel is critical.
4. Specifications 5 of NCC-2022
4.1 S5C3 Fire Protection for Support of another Part
4.1.1. The supporting structure must have an FRL as specified for different building elements for each type of construction. For example, if the type of construction is A and the building class is 5, columns supporting the floor above must have an FRL of 120/120/120 for the floor and an FRL of 120/-/- for the load-bearing columns. These columns should be protected with lightweight construction, calcium silicate boards, fire-rated sprays, or paints to achieve an FRL of 120/-/-.
4.1.2. If the supporting part is located in the same fire compartment as the part to be supported, with respect to structural adequacy, the greater FRL shall apply to both parts.
Explanation: This clause requires that in type A, B, or C construction, all building elements must have the same FRL with respect to structural adequacy. This means the columns, fire walls, or floors must have the same structural adequacy
4.1.3. The requirements described above in 4.1.2 do not apply to the following members:
4.1.3.1. Elements providing lateral support to external walls that meet the following requirements:
4.1.3.1.1. S5C24(1)(b) – In type C construction, where an external wall requires an FRL from the external side only.
4.1.3.1.2. C2D12 – Concrete external walls that could collapse as a whole in buildings with a rise in stories of no more than 2.
4.1.4. Elements providing support in car parks and complying with the following:
4.1.4.1. S5C19 – Concessions for car parks in type A construction.
4.1.4.2. S5C22 – Concessions for car parks in type B construction.
4.1.4.3. S5C25 – Concessions for car parks in type C construction.
4.1.5. Roofs providing lateral support if they meet the following requirements:
4.1.5.1. In type A construction, where the roof requires an FRL as per table S5C11g, the concessions of S5C15 apply for buildings with:
4.1.5.1.1. A sprinkler system as per specification 17.
4.1.5.1.2. A rise in stories of 3 or less.
4.1.5.1.3. An effective height of less than 25 meters and ceilings below the roof are RISF for 60 minutes.
Explanation: If the same roof is in a class 2 or 3 building and provides lateral support, it must have the same FRL as the element it supports
4.1.6. A column providing lateral support to a wall, where the column complies with S5C6 – General concessions for columns other than those used in fire walls and common walls. According to S5C6, columns other than those in fire walls or common walls do not need an FRL if the building is only 1 story or 2 stories, but the story above is only part of the floor area of story 1.
4.2 S5C11 Type A Fire Resisting Construction
4.2.1. The FRL for external columns also applies to internal columns less than 1.5 meters from a window and exposed to a fire source feature.
4.2.2. Table S5C11 should be consulted for the required FRL for any structural member.
4.2.3. For car parks, the following concessions apply to columns:
4.2.3.1. If the column supports the roof only (not used for car parking) and is more than 3 meters from a fire source feature, FRL is -/-/-.
4.2.3.2. Any other column that does not support any part of the building not used for car parking:
4.2.3.2.1. 60/-/- or
4.2.3.2.2. ESMA less than 26 sqm/tonne.
4.2.3.3. Any other column not covered by 4.2.3.1 and 4.2.3.2: 60/-/-.
4.2.4. For beams in car parks, the following concessions apply:
4.2.4.1. Steel beams in contact with concrete:
4.2.4.1.1. 60/-/- or
4.2.4.1.2. ESMA less than 30 sqm/tonne.
4.2.4.2. Any other beam: 60/-/-.
4.3 S5C21 Type B Fire Resisting Construction
4.3.1. Table S5C21 specifies the required FRL for any steel members.
4.3.2. For car parks, the following concessions apply to columns:
4.3.2.1. If the column supports the roof only (not used for car parking) and is more than 3 meters from a fire source feature, FRL is -/-/-.
4.3.2.2. Any other column that does not support any part of the building not used for car parking:
4.3.2.2.1. 60/-/- or
4.3.2.2.2. ESMA less than 26 sqm/tonne.
4.3.2.3. Any other column not covered by 4.3.2.1 and 4.3.2.2: 60/-/-.
4.3.3. For beams in car parks, the following concessions apply:
4.3.3.1. Steel beams in contact with concrete:
4.3.3.1.1. 60/-/- or
4.3.3.1.2. ESMA less than 30 sqm/tonne.
4.3.4. Any other beam: 60/-/-.
4.4 Type C Construction;
For type C construction, the criteria for steel columns and beams in car parks differ from those for type A and B. In type C, steel columns and beams require an FRL value only if the distance from a fire source feature is less than 1.5 meters
5. Conclusion
CYBIL CONSULTS provides the best services for passive fire protection of steel with calcium silicate boards. We not only protect the steel but also ensure that structural steel achieves the right level of fire resistance. Cybil Consults uses Australian-made products from the best manufacturers in Australia, such as Pronate and Trafalgar. We also ensure that we use products tested according to the guidelines of AS 1530.4 and comply AS 4100
