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Unit 3: Civil structures

11 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

What types of load act on a civil structure and how do engineers account for them?

Identify and quantify the dead, live and environmental loads acting on a civil structure and combine them to find the total design load on a structural element

Structural loads. Covers dead loads, live loads, environmental and dynamic loads, point versus distributed loads, and how to combine self-weight and imposed load into a total design load with worked arithmetic.

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How do engineers describe and compare the properties of materials when selecting one for a civil structure?

Define and compare the mechanical properties of engineering materials, including strength, stiffness, ductility, hardness and toughness, and justify a material selection for a structural application

Material properties. Defines strength, stiffness, ductility, hardness, toughness and density, distinguishes them clearly, and shows how to justify a material choice for a civil structure with a worked comparison.

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How do engineers classify civil structures and decide which structural form suits a given problem?

Classify civil structures by form and load path, and explain how the choice of structural form responds to the function, site and social or environmental context of a project

Classifying civil structures. Covers mass, framed, shell and suspension forms, the idea of a load path, and how function, site and social or environmental context drive the choice of structural form.

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How do engineers measure the mechanical properties of a material before they trust it in a structure?

Describe the standard destructive and non-destructive tests used to measure tensile strength, hardness, impact toughness and other mechanical properties, and interpret the data they produce

Material testing. Covers the tensile test, hardness tests, impact (toughness) testing and non-destructive testing, what property each measures, and how to read the data, with a worked calculation from tensile test results.

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How do engineers leave a margin between the load a structure carries and the load that would break it?

Apply the factor of safety to relate the maximum (failure) stress of a material to the allowable working stress, and select or verify a member size against the expected load

Factor of safety. Covers the definition as failure stress over working stress, why a margin is needed, typical values, and how to size a member so its working stress stays below the allowable limit, with worked arithmetic.

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How do engineers quantify how a material deforms under load using stress, strain and stiffness?

Calculate stress, strain and Young's modulus for a material under axial load, and interpret the elastic region, proportional limit and Hooke's law from a stress-strain diagram

Stress-strain relationship. Covers axial stress and strain, Young's modulus as a measure of stiffness, Hooke's law, the proportional limit and elastic region, with worked numbers and unit handling.

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What can engineers read from the stress-strain curve of a material?

Interpret a stress-strain diagram to identify the proportional limit, yield point, ultimate tensile strength and fracture, and distinguish elastic from plastic behaviour and ductile from brittle materials

Interpreting stress-strain diagrams. Covers the elastic and plastic regions, proportional limit, yield point, ultimate tensile strength, fracture, and how ductile and brittle curves differ, with a worked reading of curve values.

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How do engineers describe the internal effects of bending in a loaded beam?

Determine the shear force and bending moment at points along a simply supported beam under point and distributed loads, and relate maximum bending moment to the risk of structural failure

Beam bending. Covers shear force and bending moment, how to find them at a section, the meaning of maximum bending moment, and how bending stress and deflection link to material choice, with worked numbers.

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How do engineers represent and resolve the forces acting on a static civil structure?

Apply the conditions of static equilibrium to determine unknown forces acting on a structure, using free-body diagrams and the resolution of forces into perpendicular components

Statics for civil structures. Covers force as a vector, resolving forces into perpendicular components, drawing free-body diagrams, and applying the three equilibrium conditions to find unknown reactions and member forces.

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How do engineers find the reaction forces at the supports of a loaded structure?

Calculate the moment of a force about a point and apply moment equilibrium together with force equilibrium to determine the support reactions of a simply supported structure

Moments and reactions. Covers the moment of a force, the principle of moments, pin and roller supports, and using moment equilibrium to solve for the reactions of a simply supported beam, with worked arithmetic.

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How do engineers find the internal force in each member of a loaded truss?

Analyse a statically determinate pin-jointed truss using the method of joints to find the magnitude and nature (tension or compression) of the force in each member

Analysing pin-jointed trusses. Covers two-force members, the assumption of pin joints, the method of joints, and how to classify each member force as tension or compression with worked arithmetic.

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