- 3 3 A Horizontally Placed Structural Steel Beam Of Channel Section Shown In Figure Q3 Is Subjected To A Bending Moment 1 (124.02 KiB) Viewed 30 times
3 3. A horizontally placed structural steel beam of channel section shown in Figure Q3 is subjected to a bending moment, with the plane of bending perpendicular to the web as indicated. The material has a yield strength of 240 MNm Assume the material from which the channel section is made has an elastic- perfectly plastic stress-strain curve. 10 mm 8 mm 68 mm 1 1 150 mm Figure Q3 ) (a) Explain briefly what the 'elastic-perfectly plastic' assumption means and why this is acceptable for this type of analysis. [2 marks] (b) Determine the position of the neutral axis for elastic bending. [4 Marks] (c) Determine the position of the neutral axis for fully plastic bending. [2 marks] (d) Calculate the limiting bending moment that would cause plasticity to penetrate fully across the section as in (c) above. [8 Marks] (e) Sketch the bending stress distribution across the section from the top surface to the bottom surface when the bottom surface has just begun to yield. Show the position of the neutral axis clearly on your sketch. (No calculations are necessary). [4 Marks] (f) The beam is simply supported at the ends and loaded resembling a 4- point bend test configuration. When plasticity is about to fully penetrate as in (d) above at the mid-section between the two loads, the beam is now completely unloaded. What will be the residual stresses generated at the top and bottom surfaces at the mid-section? Identify whether tensile or compressive. [Note: You are given that the second moment of area about the centroidal axis is 1.06 x 106 mm“). [5 Marks] Total (25 Marks)