Fire in steel framed buildings
These web pages are a guide to the latest thinking in the field of fire safety.
The Approved Document approach to satisfying regulatory requirements in England and Wales in the mid 1980s began a recognition of modern practice that continued into the ’90s with the introduction of the structural codes for fire resistant design embodied in BS5950 Part 8, and the draft Eurocodes 1991-1-2, 1993-1-2 and 1994-1-2. This has further developed with the publication of BS7974, the Code of Practice for Application of Fire Safety Engineering Principles to the Design of Buildings.
Even the basic shape of structural sections, substantially unchanged for over 100 years, is now being enhanced with a shape specially developed for optimum performance in fire in the form of the asymmetric beam. The pace of change will continue through this decade as increasingly sophisticated methods are developed to allow design for fire to move away from consideration only of simple elements towards whole building behaviour in fire.
These web pages are a guide to the latest thinking in the field of fire safety. It is concerned primarily with solutions to structural fire resistance issues in steel-framed buildings. It will be updated frequently to ensure its relevance as a source of information on the fire resistance of buildings.
|
|
BS5950 Part 8: Code of Practice for Fire Resistant Design
BS5950 Part 8, shown below, was first published in 1990 and redrafted in 2003. It brings together in one document all of the methods of achieving fire resistance for structural steelwork.
Cardington fire tests design guidance
Between 1994 and 1996 a series of six fire tests were carried out on an eight storey composite building with metal deck floors at the Building Research Establishment test facility at Cardington in Bedfordshire.
Combining fire resistant design methods
Innovative design solutions for beams and columns can be combined so that whole buildings with fire ratings up to 1 hour can be realised without recourse to site applied protection.
Composite steel deck floors in fire
A composite steel deck floor is designed in bending as either a series of simply supported spans or a continuous slab. Strength in fire is ensured by the inclusion of reinforcement. This can be the reinforcement present in ordinary room temperature design; it may not be necessary to add reinforcement solely for the fire condition.
External steelwork
A number of modern steel buildings have being constructed with the steel skeleton on the outside of the structure. Since an external structural frame will only be heated by flames emanating from windows or other openings in the building facade, the fire that the steelwork experiences may be less severe than in an orthodox design.
Filled hollow sections in fire
Unprotected hollow sections can attain up to 2 hours fire resistance when filled with concrete.
Fire damage assessment of hot rolled structural steel
The assessment of fire damaged hot rolled structural steel is an area in which most engineers and architects have little practical experience. On many occasions fire affected steelwork shows little or no distortion resulting in considerable uncertainty regarding its re-usability.
Off site fire protection
At the time of writing, off-site application of fire protection is thought to have captured over 15% of the total fire protection in steel multi-storey new build in the UK.
Section factor and protection thickness assesment
Fire resistance is expressed in units of time so one of the contributory factors to fire resistance is the heating rate of the member, which governs the time taken to reach its failure (or limiting) temperature.
Single storey buildings in fire
By far the most common structural form for single storey non-domestic buildings are portal frames and the most common scenario in which fire protection is required is a boundary conditions.
Site applied protection materials
Passive fire protection materials insulate steel structures from the effects of the high temperatures that may be generated in fire. They can be divided into two types, non-reactive, of which the most common types are boards and sprays, and reactive, of which intumescent coatings are the best example.
Sprinklers
Sprinklers are designed to suppress automatically small fires on, or shortly after, ignition or to contain fires until the arrival of the fire service.
Steelwork fire resistance
Fire resistance is usually expressed in terms of compliance with a test regime outlined in BS476 Part 20 and 21. It is a measure of the time taken before an element of construction exceeds specified limits for load carrying capacity, insulation and integrity. These limits are clearly defined in the standard.
Structural fire engineering
Fire safety engineering can be seen as an integrated package of measures designed to achieve the maximum benefit from the available methods for preventing, controlling or limiting the consequences of fire.
The Building Regulations and Structural Fire Resistance
The Approved Document approach to satisfying regulatory requirements in England and Wales in the mid 1980s began a recognition of modern practice that continued into the ’90s with the introduction of the structural codes for fire resistant design embodied in BS5950 Part 8, and the draft Eurocodes 1991-1-2, 1993-1-2 and 1994-1-2.
