Photo of Structural engineering for steel structures

Why use Structural Fire Engineering

The purpose of Structural Fire Engineering is to design a building structure with a suitable fire resistance in order to protect the means of escape for occupants and fire fighters. Adequate fire protection will enable fire services to carry out search and rescue and minimize the impact to users of neighbouring properties as part of the criteria to satisfy the functional requirement of the building regulations..

How it works

At BB7, we deliver structural fire engineering by optimizing the passive fire protection, while maintaining the load carrying capacity of the structure throughout the duration of the fire. It also provides suitable compartmentation to control fire spread within the building and to adjacent buildings. The process of structural fire engineering design includes the assessment of fire severity in a compartment, thermal response and structural responses of the building elements.

Every building or compartment is different. Therefore, instead of using a standard fire used in BS476 fire test environment across all types of constructions, BB7 assess the realistic fire behavior in individual building/ compartment on a case-by-case basis. We consider the different usages of the compartment and the rate at which the fire develops due to the help of available ventilation. Our fire severity assessment means that building which would be required to be two-hour fire resistance by the prescriptive based design could be justified to have a fire severity equivalent to 90 minutes.

The temperature rise in the building elements depends on how fire develops in the compartment, but also the size and location of the elements. Typically concrete is a good thermal insulator to the steel reinforcement bars which largely dictate the load carrying capacity of the reinforced concrete element. As opposed to concrete, structural steel elements normally require fire protection to achieve a defined level of fire resistance by keeping their temperature below a critical level. However, this critical “limiting temperature” depends on many factors such as the way the individual structural is loaded and the level of applied load.

Traditionally structural fire resistance is associated with the load bearing capacity of individual element when tested in accordance with the relevant part of BS476. However, failure of an individual element does not normally lead to the failure of the building structure. This is benefited by load redistribution through continuity between structural members. Structural fire engineers therefore assess the load bearing capacity of a wider part of the building structure or even the entire building structure..

With the use of detailed analysis and design technique, it has become more feasible to design certain types of buildings to omit fire protection to all or some of the secondary steel beams. This can lead to substantial cost-saving in fire protection, particular for multi-storey structural steel buildings with floor constructed in composite profile decking.

How BB7 can help

At BB7, our chartered structural and fire engineering consultants are highly experienced. We can apply advanced fire engineering and structural engineering techniques, including computational modelling, to provide the most effective design in terms of safety and cost. The types of structures we work with include pre-stressed or reinforced concrete, steel & concrete composite, multistory building or low-rise steel portal frames.

What BB7 provides:

  • Assessment of fire severity in building/compartment to establish a realistic fire resistance requirement

  • optimization of fire protection to building structures for new or existing buildings

  • structural fire resistance assessment for existing buildings

Tim Liu
Tim Liu, Associate Director, BB7
BSc (Eng), MPhil, PhD, CEng, MIStructE, PE, MASCE
timliu@bbseven.com

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