Civil Engineering Reference
In-Depth Information
resist the passage of a fi re would rapidly collapse. There
have been some notable instances where the lack of fi re
resistance in the structural elements of buildings has
led to rapid fi re spread and rapid collapse of a building
resulting in signifi cant loss of life.
It is therefore vital that the structural elements
within all buildings are designed and constructed in a
way that:
There is a British Standard test for fi re resist-
ance contained in BS 476 Fire resistance of
elements of structure. To pass the test, ele-
ments of structure must maintain their integ-
rity and stability when exposed to fi re for a
given period of time.
Part 20 of BS 476 categorises the elements
of construction into three main groups:
➤
Limits and contains fi re spread
(a) Load-bearing elements that have a fi re
resistance
(b) Non-load-bearing elements that have a
fi re resistance
(c) Elements that make a contribution to the
fi re resistance of a structure.
➤
Ensures structural stability for appropriate periods of
time
➤
Ensures adequate means of escape in case of fi re.
The Building Regulations Part B - Section 2 outlines
the minimum periods of fi re resistance for the structural
elements of buildings. The period of fi re resistance is
given in time. The minimum period that an element of
structure can have is 30 minutes; this can be raised to
4 hours in certain circumstances.
9.4.3
Classes of building construction
The Building Regulations categorise buildings into one
of the following into three classes of construction:
Class 'A' - complete non-combustible construction,
i.e. elements of structure, fl oors, walls. Supporting
structure of brick or concrete
Class 'B' - traditional construction, i.e. non-combustible
walls with combustible fl oors
Class 'C' - combustible construction, i.e. timber fl oors
and walls.
Figure 9.7
Vertical compartmentation in a multi-storey
building
Figure 9.8
Structural beams having undergone fi re tests
