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- Prestressed Concrete Structures - PCS
- 2018
- PYQ
**Biju Patnaik University of Technology Rourkela Odisha - BPUT**- Civil Engineering
- B.Tech
**2246 Views**- 94 Offline Downloads
- Uploaded 1 year ago

Registration No : Total Number of Pages : 02 B. Tech PECI5415 8th Semester Regular / Back Examination 2017-18 PRESTRESSED CONCRETE BRANCH : CIVIL Time : 3 Hours Max Marks : 70 Q.CODE : C175 Answer Question No.1 which is compulsory and any five from the rest. Use of IS 1343 is allowed. The figures in the right hand margin indicate marks. Q1 a) b) c) d) e) f) g) h) i) j) Q2 a) b) Q3 Q4 a) b) Answer the following questions : Define pressure line. State the various types of high tensile steel used for pre stressing. State Mohr’s theorem used for calculating the deflections in PSC beams. State the formula to calculate the loss prestress due to friction. How can the shear resistance of a pre stressed concrete beam be improved? Distinguish between short term deflection and long term deflection in uncracked members. For long span members, explain, whether the loss due to anchorage slip is higher or lower. What are the various parameters on which, the shrinkage strain of concrete is dependent? State two advantages of continuous members in pre stressed concrete structures compared to single members. What do you mean by concordant cable profile? (2 x 10) Distinguish between pre tensioning and post tensioning process. A prestressed concrete beam of section 150 mm wide by 350 mm deep having an effective span of 6m carries a live load of 3.5 kN/m excluding its dead load and two concentrated loads of 5 kN at 2m and 4m from left end. Find the magnitude of concentric pre stressing force necessary to cause zero tensile stress at the soffit of the beam at the centre of span section. (4) (6) A pre stressed concrete beam of rectangular section, 160 mm wide and 300 mm deep is of 6 m span. The beam is prestressed by a triangular cable profile carrying an effective force of 250 kN with zero eccentricity at ends and e = 75 mm below the neutral axis. If there is a concentrated load of 20 kN at centre in addition to a dead load of 3 kN/m, find the final deflection under pre stress, self weight, live load and effect of creep. The creep coeff. = 1.5 (10) State and explain the stress equations applied for flexural design of a pre stressed concrete member during the first stage. A beam of size 200 mmx350 mm is to support an ultimate shear force of 350 kN. The compressive pre stress at centroidal axis is 4 N/sq mm. Using M35 concrete and cover to tension reinforcement of 40 mm, design the member for shear. Permissible yield strength of steel used for shear is 415 N/sq mm. (3) (7)

Q5 A pre stressed concrete beam 180 mm wide and 300 mm deep of span 10 m is prestressed with wires of 300 sq mm of parabolic cable profile located at zero eccentricity at end and 40 mm eccentricity at centre. The initial stress in the wire is 1250 N/sq mm. Calculate the percentage loss of pre stress if the beam is pre tensioned. Es = 200 kN/sq mm, Ec= 30 kN/sq mm, shrinkage of concrete is 300 x 10-6. creep coeff = 1.6, slip at anchorage = 2 mm and relaxation of stress of steel = 5 per cent. (10) Q6 A pre stressed concrete beam of rectangular section, 150 mm wide and 250 mm deep is to be designed to support two imposed loads of 6 kN, each located at one third points of a beam of length 6 m. If there is no tensile stress in the concrete at transfer and service loads, find the minimum prestressing force and the corresponding eccentricity. (10) Q7 A two span continuous prestressed concrete beam has uniform c/s with width of 150 mm and depth of 250 mm. A cable carrying an effective prestressing force of 300 kN is parallel to the axis of the beam and located at an eccentricity of 75 mm below the neutral axis. Find the secondary and resultant moment developed at the mid support section. If each span length is 5 m, find the resultant stress developed at mid section of the left side beam. (10) Q8 a) b) c) d) Write short answer on any TWO : Concept of load balancing web shear and flexural shear stress distribution in the end block Primary moment and secondary moment (5 x 2)

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