Structural Safety

Structural Safety

• Any of the following may affect the safety of a structure:– Dead Loads– Live Loads– Dynamic Loads– Solar Radiation– Rain– Wind– Atmospheric Contaminants– Corrosion– Timber Decay– Vibrations & Sudden Shocks– Subsidence

Dead Loads

• Include the material of which the building is constructed e.g. columns, beams and floors which must not only support the other components of the building, such as dividing walls and partitions, but also their own weight

Live Loads

• The building must support other weights such as people, furniture, equipment and goods

• These loads can be constantly moving and changed day by day

Dynamic Loads

• Dead loads and live loads normally change slowly and are called static loads

• Other loads can change rapidly, like a gust of wind, and such loads are called dynamic

Solar Radiation

• Absorbed when it strikes a material – as material warms up, it expands and cools as it contracts

• Solar radiation causes surfaces to heat up quickly. Rain falling on the heated surface can cause severe shock to the material and may result in tension cracking, especially on roofing membranes

Rain/Snow/Hail

• Moisture is the greatest cause of deterioration in building materials

• Rising damp can cause flaking and cracking• Frozen water can cause stresses and cracks• Moisture can promote rust in metals• Moisture creates an environment for fungal

growth as well as insect attack• Build up of snow or ice on roof structures

can increase the loading

Wind

• Can cause direct physical damage

• Can cause dampness by driving moisture into building fabric

• Wind can lift roofs coverings, especially on tool buildings

Atmospheric Contaminants

• Include:– Sulphur dioxide– Carbon dioxide– Oxygen– Ozone

• Can combine with moisture to form acids that attack certain materials

Corrosion

• Metal combines with oxygen in the air to form rust

• This is accompanied by expansion of metal, which can affect adjacent materials

Timber Decay

• Deterioration of structural timbers can in severe cases lead to building collapse

• This may be due to:– Wet rot– Dry rot– Fungal attack– Insect attack

Vibrations & Sudden Shocks

• Vibrations caused by traffic or machinery can be prolonged and intense, and can affect the foundations of buildings, although modern foundations are designed to withstand ordinary vibrations

• Effects of buildings being struck by heavy lorries, particularly when repetitive, can cause weaknesses

Subsidence

• Buildings constructed over mine tunnels or large holes can cause sever deformation as the ground subsides

• Signs of defects include:– Semi-random cracks in walls– Sagging of arches and beams– Fractures of pipe joints