22. Describe the difference in both the behaviour and appearance of similar bars of cast and wrought iron -
(a) When broken under a tensile stress suddenly applied.
Draw, to a scale of ¾" to a foot, showing the use of diagonal bond in both courses, to strengthen the wall. (12.)
Draw to twice the size, showing the members in tension by single, those in compression by double, and those under compression and bending stress by triple lines ; the stresses due to their own weight to be neglected.
Draw a similar diagram, supposing the same load to be along the bottom instead of the top of the girder, omitting any bars you consider superfluous, and making any other alterations you think necessary.
(14.) *26. Section of part of a single floor with common joists 9" x 2½".
*28. Line diagram of part of an iron roof truss for a 38 feet span, the rise being ¼ the span, and the camber of tie rod 1/30 the span. Draw a line diagram of the complete truss, to a scale of 1/96. Give an elevation of the joint at A, ½ full size, with any details required to fully explain its construction, aa being angle irons 2½ x 2½" x 3/8" ; and bb (not continuous), as well as c, to be of 1¼" round iron. (16.)
*29. Plan of part of the top of a wall at the angle of a building, showing the wallplates to carry a hipped roof.
Draw, to a scale of ¾" to a foot, adding an angle tie and dragon beam. Give a vertical section through the dragon beam, showing its connection with the angle tie and the foot of the hip rafter. (16.) 30. Two iron plates 10" x ½" are to be connected by a riveted lap joint.
Show by another plan a similar joint, but with the rivets arranged so as to weaken the plates as little as possible. (17.)
3l. Elevation of a brick archway.
Draw, to a scale of 1/48, showing the centering you would use in its construction. Full details to be given, with the scantlings, including supports. (17.)
32. Give a horizontal section, to a scale of l½" to a foot, through a cased window frame for 2 ¼" double hung sashes ; the wall being of stone, 24" thick, finished inside with lath and plaster on battens, and square boxed shutters for a 4 feet opening. (18.)