Download BUILDINGS AND STRUCTURES

Buildings and Structures 1
Elements of Structure and
Causes of Collapse
Aim
To provide students with information to
allow them to deal with incidents involving
buildings and structures safely and
effectively.
Learning Outcomes
At the end of the session students will be able to:
• State the main elements of a structure
• Describe the principal causes of collapse
• Recognise the common signs of collapse.
Elements of structure(1)
• Any member forming part of the structural
frame of a building
• Any beam or column not being a member
forming part of a roof structure only
• An external wall
• A separating wall.
Elements of structure(2)
• Compartment wall
• Structure enclosing a protected shaft
• Load bearing wall or load bearing part
of a wall
• A gallery.
Types of load
The function of each element of a structure in
most buildings is to carry loads placed upon
them, these loads are principally;
• ‘Dead’ load
• ‘Imposed’ load
• ‘Wind’ load.
Dead load
• The weight of all parts of the building
itself that is imposed on the
elements. These are constant.
Imposed load
• Consists of people, furniture, machinery
etc, normally found in the building when
it is occupied.
Wind load
• The load due to the effects of wind
pressure or suction.
Collapse of buildings
• During firefighting operations the risk of
collapse must always be considered and
watched for
• The principal causes of collapse are;
Overloading
Expansion.
Collapse of buildings
Overloading(1)
• Heavy machinery on upper floors can
pose a danger in the event of walls or
supports becoming weakened, water
deployed in these areas should be
removed as soon as possible.
Collapse of buildings
Overloading(2)
• Another consideration is the weight of
the water applied to floors. The existing
‘Imposed’ load coupled with the
additional weight of water which may
weigh several tonnes may load the
structure beyond its capacity.
Collapse of buildings
Expansion(1)
• Occurs in two ways either involving the
contents of a building or involving the
structure of the building itself.
Collapse of buildings
Expansion(2)
• Water directed on absorbent materials
causes the material to expand which
can exert pressure to walls, ceilings and
floors. Examples of such materials are;
• Tea, hops, wool, jute, paper, wood and
pulp.
Collapse of buildings
Expansion(3)
Other expansion hazards include;
• ‘Curtain’ walls expanding, displacing glass
panes or facing panels
• Expansion of steel joists pushing walls out of
perpendicular
• Heating of one side of wall only.
Common signs of collapse
• Cracked or dropped arches over doors,
windows or other openings
• Spalling of stonework, falling of cornices
• Sagging floors or beams, or gaps
between floors and walls
• Displacement of steel or cast iron pillars
supporting joists or beams.
Signs of collapse.
Column
buckling
Bulging wall
Dropped arch
Floor sagging and pulling out wall
Cracks in wall
Displaced column
Confirmation
Assessments will be based on this lesson and
the corresponding study note
Learning outcomes
• The main elements of a structure
• The principal causes of collapse
• The common signs of collapse.
THE END