Time:2025-05-13 03:22:34 Source:Sanjian Meichen Steel Structure
While steel itself is non-combustible, it loses its structural strength significantly at elevated temperatures (typically around 550°C / 1000°F), which can lead to deformation and collapse during a fire. Therefore, fire prevention and protection measures for steel structures focus on preventing the steel from reaching these critical temperatures or ensuring structural integrity for a sufficient period to allow for evacuation and firefighting.
The primary goal here is to insulate the steel members to slow down the rate at which their temperature rises during a fire.
Spray-Applied Fire Resistive Materials (SFRM): These are cementitious or gypsum-based plasters sprayed directly onto steel members. They are cost-effective but can be fragile and aesthetically unpleasing if left exposed.
Intumescent Coatings: These paint-like coatings swell and char when exposed to heat, forming an insulating layer. They offer a more aesthetic finish and are often used where steel is exposed.
Concrete Encasement: Encasing steel columns and beams in concrete provides excellent fire resistance. This can be done with cast-in-place concrete or precast concrete sections.
Fire-Resistant Boards and Cladding: Gypsum boards, calcium silicate boards, or mineral wool boards can be used to box in steel members, creating a fire-resistant barrier.
Blockwork/Brickwork Encasement: Similar to concrete encasement, masonry can be built around steel members.
Filling Hollow Sections: Hollow structural sections (HSS) can be filled with concrete or other fire-resistant materials to improve their fire performance.
These systems aim to detect a fire early and suppress it or control its spread.
Sprinkler Systems: Automatic sprinklers are highly effective in controlling or extinguishing fires, thereby limiting the heat exposure to the steel structure.
Fire Detection and Alarm Systems: Smoke detectors, heat detectors, and flame detectors provide early warning, allowing for timely evacuation and firefighter response.
Fire Suppression Systems (Gaseous, Foam, etc.): Used in specific areas where water might be unsuitable (e.g., server rooms, areas with flammable liquids).
Fire Resistance Rating (FRR): Structures are designed to achieve a specific fire resistance rating (e.g., 1-hour, 2-hour, 3-hour), which dictates how long the structural elements must withstand fire conditions without collapse. This is determined by building codes based on occupancy, building height, and area.
Compartmentation: Dividing the building into fire-rated compartments using fire walls, fire-rated floors, and fire doors helps contain a fire within a specific area, limiting its spread and impact on the overall structure.
Structural Redundancy: Designing the structure so that the failure of one or a few members does not lead to a disproportionate collapse.
Heat Dissipation: In some designs, exposed steel might be acceptable if analysis shows it can dissipate heat effectively enough to prevent reaching critical temperatures, or if the protected critical members can carry the load.
Ventilation Systems: Smoke control systems (natural or mechanical) help to remove smoke and heat, improving conditions for evacuation and firefighting, and potentially reducing the thermal load on the structure.
Regular Inspections and Maintenance: Ensuring that PFP (e.g., SFRM, intumescent coatings) is intact and undamaged, and AFP systems (sprinklers, alarms) are functional.
Good Housekeeping: Reducing combustible materials (fire load) within the building minimizes the potential fire severity.
Hot Work Permits: Controlling activities that involve open flames or sparks (welding, cutting).
Emergency Planning and Drills: Ensuring occupants know evacuation routes and procedures.
Firefighter Access: Designing the building to allow easy access for firefighters and their equipment.
The choice and combination of these measures depend on various factors, including building codes, the building's use and occupancy, its size and height, and a comprehensive fire risk assessment. Often, a combination of passive and active measures, along with sound design principles, is employed to achieve the required level of fire safety.
