Calendar: 1868-1869 Page 502

504 APPLIED SCIENCES horizon by means of bracket at distance of ft from the inner edge of wall which is ft thick and 30 ft high find the pressure when it is just on the point of overthrowing the State and prove the proposition known as the Triangle of Forces Explain clearly how it may be employed to determine practi- cally the strains on the several pieces of jointed framework under given external pressures section of an iron roof of given weight is supported on two pillars 40 ft apart by means of primary truss of two rafters and tie-rod the middle point of each rafter is supported by secondary truss consisting of strut two ties and strut- brace perpendicular to the rafter the top of the roof is 10 ft above the pillars find by diagram of forces or otherwise the strains along the several pieces Explain the principle of the method of sections and illus- trate it by means of "Warren Girder" with every joint loaded pointing out which pieces are ties and which struts What is meant by the line of resistance in structure In straight arch with the load equally distributed horizontally show that the form of the line of resistance is parabola with its axis vertical wall of brickwork ft thick at the top and 10 ft thick at the bottom and sloping inwards is to be built round reservoir find the depth in order that the line of resistance may cut the base in within the extrados when the reservoir is full If is the weight of cubic foot of earth and φ its natural slope and χ its depth show that the greatest pressure produced against vertical retaining wall by earth which is on level If the specific gravity is 15 the height 20 ft and the natural slope 30 find the pressure on each foot of the length of the Prove the following construction for finding this pressure From the foot Β of the wall BG draw line making an angle wall with its summit is wx2 tan2 wall