CE 1402– PRESTRESSED CONCRETE STRUCTURES

DURATION: 3 Hrs         DATE: 09.10.2013                 MAX.MARKS:100

PART-A                                         10 x 2 = 20

1. Give applications of pre stressing.
2. Explain the need of high tensile steel for pre stressing.
3. What are the various types of system in pre stressing?
4. Give a short note on End zone Reinforcement.
5. Sketch the arrangement of tendons & anchorages in circular pre stressing of concrete pipe.
6. Sketch the correct arrangement of sheet cage in anchorage zone.
7. Sketch the loop reinforcement, hair-pin bars in anchorage zone.
8. Give the advantages of pre stressed units.
9. List out the advantages of PSC bridges.
10.  Give the span limitations for T-beam slab deck & box girder bridges.

                                                 PART-B                                                  5x 16 = 80

    

11.                     a. Explain the following systems of pre stressing

i)                    Freyssinet’s system  (8)

ii)Gifford Udall system   (8)                (OR)

11    b.i) Explain the factors influencing deflections? (8)

         ii) What is the necessity of using supplementary or un tensioned reinforcement in pre stressed concrete members? (8)

        12  a.i) Explain briefly about strain compatibility method. (8)

                 ii) The Pre tensioned pre stressed concrete beam having a rectangular section 150mmx350mm has a effective cover of 50mm, fck= 40N\mm²                            ,fp= 1600N\mm², area of pre stressing = 461N\mm². Calculate the ultimate flexural strength of the section. Using IS1343  (8)                                     

                                                                           (OR)                        

            b.i)The end block of the post tensioned concrete beam 300mm wide & 300mm deep. This subjected to concentric anchorage force of 832.2KN by a festinate system anchorage of area 11720mm2. Design and detail the anchorage reinforcement of end block.(8)

              ii) The end block of a p.s.c beam rectangular in section 100mm wide and 200mm deep. The p.s force of 100KN is transmitted to concrete by a distribution plate 100mm wide and 50mm deep concentrically loaded at the ends. Compute the position and magnitude of maximum tensile stress and bursting tension( guyon’s method)  (8)

                                           

13.a)  i) Explain the general features of pre stressed concrete tanks.(8)

                ii) Explain the junctions of tank wall and base slab with neat sketch.(8)

                                                                           (OR)

b) A cylindrical pre stressed concrete water tank of internal diameter 30m is required to store water over a depth of 7.5m. The permissible compressive stress in concrete at transfer is 13N/mm² and the minimum compressive stress under working pressure is 1N/mm², the loss ratio is 0.75, wires of 5mm dia with an initial stress of 1000N/mm² are available for circumferential winding and freyssinet cables made up of 12 wires of 8mm dia stressed to 1200N/mm² are to be used for vertical pre stressing. Design the tank walls assuming the base as fixed. The cube strength of concrete is 40N/mm². For the thickness of wall is 150mm.(16).

14a) i) Explain the types of composite construction with neat sketch.(8)

ii)                  Explain the precast pre stressed concrete stresses at serviceability limit state.(8)

(OR)

               b) i) Explain the advantages and dis advantages of composite construction?(8)

                   ii) Clearly explain the creep and shrinkage effects in composite construction.(8)

    15a) i) Explain the advantages of pre stressed concrete bridges.(8)

           ii) Explain the post tensioned pre stressed concrete bridges decks with neat sketch.(8)

                                                                               (OR)

                    b) i) Explain the process of cantilever method of construction of p.s.c bridges with                     sketches.(8)

               ii) Explain clearly the general aspects of design of pre stressed concrete decks.(8)