Maharashtra State Board of Technical Education 2011-4th Sem Diploma Civil Engineering for in Subject :- -mechnics of structure(12083) - Question Paper
MSBTE ques. paper for Diploma in Civil Engineering
Fourth Semester
Subject :- -mechnics of structure(12083)
12083
3 Hours/100 Marks Seat No
Instructions : (I) AB questions are compulsory.
(2) Answer each next main question on a new page.
(3) Illustrate your answers with neat sketches wherever necessary.
(4) Figures to the right indicate full marks.
(5) Assume suitable data, if necessary.
(6) Use of Non-programmable Electronic Pocket Calculator is permissible.
(7) Mobile Phone, Pager and any other Electronic Ojrmtunication devices are not permissible in Examination Hall.
Marks
1. A) Attempt any six of the following : (6x2=12)
a) Define stress and state Hookes law.
b) Define Poissons ratio. Give its expression.
c) Define modulus of rigidity along with expression.
d) State the relation between three elastic constants E, G and K.
p.T.a
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Marks
e) Differentiate between pure bending and ordinary bending.
f) State the flexural formula. Write the meaning of the symbols used in it
g) Draw shear stress distribution diagram for T-section and locate the position of maximum shear stress.
h) Define strain energy.
B) Attempt any two of the following : (2x4=8)
a) The average shear stress across a certain rectangular cross section is 200 N/mm2. Calculate the maximum shear stress at this section.
b) A square rod 10 mm x 10 run in cross-section and 1000 mm long is fixed at both ends. Determine end reactions due to rise in temperature of 50C. Take E = 2x 10s MPa and = !2xlO"6/',C.
c) A circular hole 25 mm diameter is to be punched in a mild steel plate 3 mm thickness. If the shearing stress developed in the metal is 200 MPa, find the required force to punch the hole.
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Marks
2. Attempt any four of the followii : (4x4=16)
a) A wooden tie 8 m, 100 mm wide and 140 mm thick is subjected to an axial pull of 60 kN and elongation is 3 mm. Calculate value of modulus of elasticity for the material.
b) A mild steel stepped bar 6 m length is 25 mm in diameter of 2m length and 15 mm diameter for remaining length. It is subjected to a tensile load of 70 kN. Calculate the change in length if its modulus of Elasticity is 200 kN/mnr.
c) A reinforced concrete column 500 mm x 500 mm in section is reinforced with 4 steel bars of 25 mm diameter one in each comer. The column is cairying a load of 200 kN. Find the stresses in concrete and steel bars.
Take E for steel = 210 GN/rrr and E for concrete = 110 GN/nr.
d) A metal bar 50 mm x 50 mm section, is subjected to an axial compressive load of 500 kN. The construction of a 200 mm gauge length is found to be
0.5 mm, and the increase in thickness is 0.04 mm. Find the value of Youngs modulus and Poissons ratio.
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Marks
e) A bar of 2 m length, 20 mm breadth and 15 mm thickness is subjected to a tensile load of 30 kN. Find the final volume of the bar. If the Poissons ratio is and Youngs modulus is 120 GPa.
3. Attempt any four of the following : (4x4=16)
a) A bar of 30 mm diameter is subjected to a pull of 60 kN. The measured extension on gauge length of 200 mm is 0.09 mm and the change in diameter is 0.0039 mm. Calculate the value of modulus of elasticity and modulus of rigidity.
b) A timber beam 200 mm wide and 400 mm deep is simply supported over a span of 4 m. It carries a full span uniformly distributed load of 19 kN/m. Find the maximum bending stress induced in the section. Draw bending stress distribution diagram.
c) A beam of symmetrical section is 300 mm deep and it has moment of Ineitia of 16 x 107 mm4 about its principle axis. If the bending stress is not to exceed 120 N/mm2 determine the radius to which the beam can be bent and the moment of resistance the beam can resist at this stress. Take E = 200 GPa.
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Marks
d) A beam of rectangularcioss section 100 mm wide x 200 mm deep is subjected to a shear force of 20 kN. Find the shear stress at the top layer at neutral axis and the average value of shear stress. Show the stress distribution diagram.
e) Calculate the resilience and modulus of resilience of a bar 1000 mm long,
60 mm wide and 40 mm thick subjected to a tensile load of 110 kN applied gradually. Take E = 210 GPa.
4. Attempt any two of the following : (2x8=16)
a) Draw SF and BM diagrams for the simply supported beam loaded as shown in below figure indicating all the values at impoitant points.
b) A cantilever of 2.5 m length carries point k>ad at 20 kN at its free end and
u.dJ. of 5 kN/m for a distance of lm from free end. Draw S.F. and B.M. diagram.
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Marks
c) Draw the SJ7. and B.M. diagram for the beam as shown in below figure and the zero S.F. and point of contraflexure.
5. Attempt any two of the following : (2x8=16)
a) Find polar moment of Inertia and radius of gyration of a hallow rectangular section external size 300 mm x 200 mm and internal size 250 mm x 150 mm.
b) Find the moment of Ineitia of a T-section with flange 250 mm x 25 mm and web 150 mm x 25 mm about an axis passing through the e.g. of the section and parallel to xx-axis.
c) An 1-section is made up of three rectangles, top flange 120 mm x 20 mm thick, web 180 mm x 20 mm and bottom flange 200 mm x 40 mm thick. Find the moment of ineitia of the section along horizontal axis through e.g. of the section.
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