BCGBC4010A Apply structural principles to residential low-rise constructions

Structural principles - Structural members

Beams

Shear forces
Match the following sentences with the appropriate graph.
Sentences
1.	Simple beam central point load. There is a diagram of a beam of length L with load P applied downwards onto the middle of the beam. Arrows indicating supports are shown at each end of the beam, pointing upwards.
A graph beside this is shown as an example. It shows two rectangles which are the same size and shape as each other. The first rectangle is positioned higher than the second and the two triangles are joined at the bottom right hand corner of the first rectangle and the top left hand corner of the second rectangle. The highest point of the graph is labelled SFmax = P/2. The lowest point is labelled SFmax = - P/2. The middle point of the graph is labeled SF = 0.
2.	Simple beam UDL. There is a diagram of a beam of length L with UDL = W  shown. This is represented as a force applied all along the length of the beam. Arrows indicating supports are shown at each end of the beam, pointing upwards.
3.	Simple beam off-set point load. There is a diagram of a beam of length L. A point load P is applied at a length a from one end of the beam and b from the other end. Arrows indicating supports are shown at each end of the beam, pointing upwards.
4.	Cantilever beam point load. There is a diagram of a beam of length L attached to a support member. A load P is applied downwards at the non-supported end of the beam.
5.	Cantilever UDL. There is a diagram of a beam of length L attached to a support member. A load UDL = W is applied along the length of the beam.
Graphs
A.	A picture of two rectangles, the first rectangle is positioned higher than the second and is longer and thinner. The two triangles are joined at the bottom right hand corner of the first rectangle and the top left hand corner of the second rectangle. The highest and lowest points of the graph are labelled Pb/L and - Pa/L, and the midpoint is labelled SF = 0.

B.	A picture of a rectangle. The lowest point of the rectangle is labelled SF = 0, and the highest point is labelled SFmax = P.
C.	A picture of a shape that is almost a right-angled triangle except that the longest side is curved. The right angle is at the bottom left corner. The lowest point of this graph is labelled SF = 0 and the highest point is labelled SFmax = P.
D.	A picture of two right-angled triangles. The first is positioned higher than the second. The right angle in the first triangle is at the bottom left, and the right angle in the second triangle is at the top right. The bottom right hand corner of the first rectangle connects to the top left hand corner of the second rectangle. The highest and lowest points of the graph are labeled SFmax = P/2 and SFmax = - P/2. The middle point of the graph is labeled SF = 0.
Answers
1.	Simple beam UDL matches diagram D.
2.	Simple beam off-set point load matches diagram A.
3.	Cantilever beam point load matches diagram B.
4.	Cantilever UDL matches diagram C.
The graphs also show the formulas which are used to determine the maximum shear forces SFmax. 
Positive values for SFmax are shown above the baseline (where SF = 0) and negative values for SFmax are below this line.
If you are unsure about any of these graphs and would like to know more, talk to your trainer.

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