PART 3:
ESTABLISHING THE RESCUE SCENE

 

CONSTRUCTION TYPES

There are common methods of building construction. These are defined by the Building Code of Australia (BCA). Understanding construction methods can help rescue teams consider risks posed by each form of construction.

Common methods of construction:

  • Timber
  • Light frame (ordinary construction/brick veneer)
  • Besser block
  • Reinforced masonry
  • Unreinforced masonry
  • Concrete tilt-up
  • Reinforced concrete and steel construction

Each type of construction has particular risks.

The following table describes the collapse risks associated with some of the construction methods.

Timber Construction

Masonry chimneys can crack and collapse into or out from the structure
House sliding off foundation
Racking of walls (out of plumb)
Displaced walls
Timber houses with cradling space, can slide from foundations
Openings can become misshaped (rectangular to parallelograms)
Masonry veneers can fall off the walls

There is an extreme risk from fire in these structures due to the abundance of fuel. Because of their relatively lightweight and small size few people are seldom comprehensively entrapped within timber residential collapsed structure.

Light Frame Construction

Masonry chimneys can crack and collapse into or out from the structure
Chimneys can separate from the walls
House sliding off foundation
Racking of walls (out of plumb)
Displaced walls
Brick skin can collapse from external influences i.e. car into house etc.
Openings can become misshaped (rectangular to parallelograms)
Masonry veneers can fall off the walls

There is an extreme risk from fire in these structures due to the abundance of fuel. Because of their relatively lightweight and small size few people are seldom comprehensively entrapped within brick veneer residential collapsed structure.

Concrete Tilt-up

More common in the newer style of factory/warehouse complex, although can date back to 2000.

The walls can separate from the roof and floors. They are formed up on site and craned into position. The use of right angle intersections acts as primary stabilisation (until roof ties are put into place) along with 45 degree screw jacks.

Panels have a silicon base bonding material adhered between them.

During fires, the metal ties weaken and break, causing a ‘pack of cards’ style collapse.

Reinforced Masonry – Older style office blocks and residential buildings

Columns break at intersections with floor beams. Inadequate reinforcement bar and ties do not confine the concrete when subjected to high shear and tension stresses.

Short columns in the exterior walls get high shear and tension stresses directed into them by surrounding massive concrete.

Bending and punching shear failure at intersections of a slab (waffle) and columns.

Unreinforced masonry infill may fall off and often become displaced from surrounding frames.

Weak concrete and poor construction can make all the above conditions worse and is more likely to lead to larger collapse.