This part of BS 5950 has been prepared by Subcommittee B/525/31, Structural use of steel. It supersedes BS 5950-8:1990, which is withdrawn.
This new edition has been prepared following the developments in fire engineering and the issue of a number of new and related standards adopting European and international standards for materials. The principal change in this edition is the introduction of a more comprehensive set of elevated temperature properties for hot finished steel, normal weight concrete, lightweight concrete and hot rolled and cold worked reinforcing bars. These properties are in agreement with those given in the Eurocodes and have been introduced to enable the fire engineering design of steel structures.
Other changes include the renaming of “Strength reduction factors” to “Strength retention factors” and the inclusion of strength retention factors for normal and lightweight concretes, bolts and welds.
The load factor for non-permanent imposed loads in offices for general use at the fire limit state has also been changed from 0.8 to 0.5. Furthermore, the load factor of 0.0 for wind loads used in the design for boundary conditions to control external fire spread has been added.
The material strength factor of concrete has been reduced from 1.30 to 1.10 and a material strength factor of 1.0 has been added for cold-worked reinforcing steel. The section factor was defined as Hp/A in the 1990 edition of BS 5950-8. In this edition, European terminology has been used and the section factor is now defined as Am/V. However, the numerical values are unaltered. The subclause on castellated sections has been edited to clarify its scope of application.
BS 5950 is a document combining codes of practice to cover the design, construction and fire resistance of steel structures and specifications for materials, workmanship and erection. It comprises the following parts:
— Part 1: Code of practice for design — Rolled and welded sections;
— Part 2: Specification for materials, fabrication and erection — Rolled and welded sections;
— Part 3: Design in composite construction: Section 3.1: Code of practice for design of simple and continuous composite beams;
— Part 4: Code of practice for design of composite slabs with profiled steel sheeting;
— Part 5: Code of practice for design of cold formed thin gauge sections;
— Part 6: Code of practice for design of light gauge profiled steel sheeting;
— Part 7: Specification for materials, fabrication and erection: cold formed sections and sheeting;
— Part 8: Code of practice for fire resistant design;
— Part 9: Code of practice for stressed skin design.
This part of BS 5950 gives recommendations for evaluating the fire resistance of steel and steel/concrete composite structures. Methods are given for determining the thermal response of the structure and evaluating the protection required, if any, to achieve the specified performance, although it is recognized that there are situations where other proven methods may be appropriate.
It has been assumed in the drafting of this British Standard that the execution of its provisions will be entrusted to appropriately qualified and experience people; also that construction, the application of any fire protection and supervision will be carried out by capable and experienced organizations.
As a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading.
This part of BS 5950 gives recommendations for:
— steel beams, columns and tension members designed to BS 5950-1;
— steel/concrete composite beams designed to BS 5950-3;
— concrete-filled steel hollow sections designed to BS 5400-5;
— composite floors designed to BS 5950-4.
For each type of member, recommendations are given for the load carrying capacity and, where appropriate insulation performance, for a given fire exposure assuming they act in isolation and restraint to thermal expansion is ignored.
These recommendations are based on:
a) fire resistance derived from standard fire tests;
b) fire resistance derived from calculations.
