Question

Horizontal stadia sights. An automatic level with an internal focusing telescope was set up somewhere at mid-length of a long-span steel bridge. The rod readings tabulated below were observed on s stadia rod held successively at the vicinity of the concrete abutments in the southern and northern approaches of the bridge. If the stadia interval factor of the instrument is 97.5, determine the length of the bridge.

Table 3. ROD POSITION HAIR READINGS Middle 1.68 2.02 Upper 2.98 3.54 At southern approach At northern approach Lower 0.38 0.49

NOTE: Please illustrate.

Answer 1

- 43.54 2.98 2.68 2002 to.ug 0.38 Now South DI - Dr & Since the bridge will be kat and horizontal through out. 20 ut is a case of horizontal sights. ki multiplying constant / stadia interval factor = 975 وما) Total length of bridge = DitDz. B. Horizontal distance between the axis of telescope and Stadia rod A = OA = Di & B= OB=D2 Di= KS, tC & D2 = KS₂ te czo if not given, Si= 2.98 -0.38 = 2.60 (stadia intercept) 52= 3.54-0.49 = 3.05 Cestadia untercept) now, Length of Bridge = ksi+ KS2. = (37.5 x 2.60) + (97.5X3-05) = 550.875 nenits Please rate the answer