Fire Behaviour Elements of Structure and Fire Development

Aim To give students an understanding of the effects of elements of structure on the development of fire.

Learning Outcomes At the end of the session students will be able to: Describe the positive and negative effects of elements of structure upon fire development.

Elements of structure Elements of structure are designed to maintain the physical integrity of a building to enable people to use it safely In the event of a fire, the structure should remain stable to allow people time to escape.

Elements of structure of a building. Roof members are not elements of structure Any gallery Separating or compartment walls External walls Columns or beams Structure enclosing protective shaft Lower floor not part of structure Floor Any part of structural frame Any load bearing walls

Columns Steel Iron Wood Concrete. Behaviour in fire depends on their material

Fire resistance of columns The applied load Type and strength of concrete Dimensions Method of reinforcement Resistance to collapse. Depends on;

Beams As they support a larger area of load, if they do fail, the area of collapse could be larger. React similarly to columns in fire however,

Floors Wooden - usually domestic, some older industrial Concrete - used in modern modular buildings Steel grid can support concrete slabs or hollow block planks - both with steel reinforcement Top surface of concrete skim.

Hollow block and plank flooring. Concrete ribs R.C. edge beam Concrete topping Hollow clay floor blocks Filler tiles Rib reinforcement Reinforcement Voids Ceiling finish

Hollow block and plank. Typical hollow floor unit details Internal support Void Floor finish Cement/sand screed Grouted joints Floor finish Cement/sand screed Typical channel section floor unit details

Pre cast concrete slab.

Roofs Fire can spread through roof voids Natural venting through the roof will alter the fire development Roof collapse will affect the floors below. Not strictly an element of structure but does have an effect on fire development

Roofing connectors Nailed-on joints.

Sandwich panels Rapid and sudden collapse Fire can spread inside the panels Fire can be hidden behind panels. Made of two layers of sheeting with a ‘sandwich’ of insulation in between these are in common use in commercial buildings and can cause problems in fires

Modern building using sandwich panels. Rails Purlins

Sandwich panel construction.

Confirmation Assessments will be based on this lesson and the corresponding study note Learning Outcomes Describe the positive and negative effects of elements of structure upon fire development.

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