Structures DNT 7059/01 2023 V/2

Structures 1.1 / [Types and functions] - A structure is something that will support an object or a load. It must be strong enough to support its own weight and any additional compounded weight. All structures are to; - resist forces, not collapse during usage, and hold parts vis-a-vis appropriate position. Natural Structures – are structures which are the result of animals or natural forces. E.g Skeleton Chicken Skeleton Manufactured Structures – are structures which are human made. E.g Bridge Russkiy Bridge, Vladivostok, Primorskiy Krai - Additionally, man made structures derive inspiration from nature. The Esplanade in Singapores’ Central District derived inspiration from the Durian fruit, a pungent fruit predominantly associated with the Southeast-Asian region. This is one example of nature- derived inspiration incorporated into the built environment.

Structures 1.2 / [Loads, Forces, Equilibrium, and Failure] 1 ) Types of Loads Static Load Stationary load Dynamic Load Dynamic load (moving) Dead Load Component 2) Types of Forces Compression A force that tries to squash an object Tension A force that tries to pull something apart Bending A structure subjected to bending is being simultaneously squashed and stretched. - Beam is a member supported at both ends - Cantilever is supported at one end only Torsion A turning or twisting force caused by torque Shear A shear force is created when two opposite forces try to cut or rip something in two Stress Measure of force acting on a unit area of material Strain Measure of the amount of extension per unit area of material 3) Equilibrium The state of equilibrium is achieved when all forces acting on an object are balanced, giving 0 resultant force.

4) Factors Causing Structural Failure Poor selection and application of materials E.g wood used in outdoor construction. When wood comes into moisture w/o sufficient weather-proofing, it detoriates and degrades, causing structural failure as material cannot support stress applied. A lack of understanding of the forces involved in a design E.g the Hotel New World collapse in S’pore was caused by only considering the live weight (weight of occupants) while neglecting the dead weight (weight of structure). This resulted in foundation being insufficient to tolerate stress applied. Failure of a joint E.g failure of column-beam joints Fatigue resulting from changes in the properties of a material over a period of time. E.g the rusting of metal can reduce the ability to withstand stress applied. - In Genoa, rusting and corrosion of rebar in concrete caused bridge structural failure. Excessive loads Stress on structure exceeds the carrying capacity of structure, resulting in structural failure as it is unable to tolerate it. - In Ghana, building collapse due to excessive load of occupants

Incomplete knowledge of the conditions