Question

Problem 1: 8 kN 1.5 m 1.5 m 8 kN Last week we determined the couple moment, or pure moment, acting on the beam was M- 30.4 kN-m CW a. Draw a FBD of the beam with reactions at A&B. A is a pin, B is a roller. Try to guess intuitively which way the vertical components of A & B are pointing. Do not show the 8 kN forces in your FBD. Only show the couple moment, or pure moment. b. Does it matter where you place the couple (pure) moment? Why? C. Use ΣFxs 0 to determine Ax d. Use EFy = 0 to make a relation between Ay and By e. If you were given that Ay 3 kN, compute how far apart the supports are. Figure not necessarily drawn to scale i.e. What is the distance between point A and point B? Compute this value. Does the distance from A to C have to equal the distance from D to B? Can the distance from C to D vary if all else remains the same? f. g.

Answer 1

FBD of the beam with reactions at A and B place of pure couple moment is important because pure bending zone deepens upon the place of couple \r\n Sigma Fx = 0 Ax + 48 - 48 = 0 Ax = 0 Sigma Fy = 0 Ay + By = 0 Given Ay = 3 KN Sigma MB = 0 +ve direction Ay(L) - (6.4 times 7) = 0 3L - 44.8 = 0 3L = 44.8 L = 44.8/3 L = 14.933 m No The distance from A to C is not equal to the distance from D to B yes The distance from C to D varies only when the force of couple changes