STRUCTURAL MECHANICS PROFESSIONAL ENGLISH IN USE FOR ENGINEERING

 

PROFESSIONAL ENGLISH IN USE FOR ENGINEERING UNIT 32. STRUCTURAL MECHANICS

 

A Statically determinate structures When a structural member – that is, part of a structure – is loaded in a certain direction, the load will cause a reaction. This means that another force, equal to the load, will act in the opposite direction. The reaction will counteract (resist) the load and stop the member from moving. When the loads and reactions acting on a member are equal, we say it is in equilibrium. Structures that are designed not to move – to stay equilibrium – are called statically determinate structures. B Resultant forces and centre gravity Often, a structural member will need to carry different magnitudes, acting in different directions. To calculate the result of these different component forces, an engineer can calculate a resultant force (or resultant). This is a force with a magnitude and direction equal to all the component forces together. C Frames and trusses A frame (or framework) is made from a number of relatively thin members. Examples are bicycle frames and steel-frame buildings. The members of a frame can form a complex shape – often with many triangles – called a lattice. The advantage of triangles is that they are stiff – they strongly resist deformation. Triangular assemblies can therefore be used to stiffen (or brace) structures. EXERCISES 32.1 Complete the explanation using words and expressions from A opposite. You will need to change the form of one word. In (1) ______________, each load acting on the structure is (2) ______________ by a (3) ______________. This means the structure are always remains (4) ______________. 32.2 Complete the text using words and expressions from A, B and C opposite. To analyse the roof structure shown in Diagram 1, an engineer draws Diagram 2 to help make some initial, simple calculations. In Diagram 2, the engineer uses the following assumptions and information. ·   The three (1) ______________ forces from the loads act as a single (2) ______________ force on the top of the frame. 32.3 In Diagram above, which of the members (a-c) are tries, and which are struts? 32.4 Choose the correct words from the brackets to complete the sentences. Look at C opposite to help you. 1. Trusses are (framework/ ties). 2. A connection between members which flaxes is called a (pin joint/ rigid joint)

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