civils mains 2013 CIVIL ENGINEERING (Paper

TIme Allowed: Three Hours

Maximum Marks: 250

QUESTION PAPER SPECIFIC INSTRUCTIONS

Please read each of the following instructions carefully before attempting questions.
There are EIGHT questions divided into two SECTIONS and printed both in HINDI and in ENGUSH.
Candidate has to attempt FIVE questions in all.
Question No. 1 and 5 are compulsory and out of the remaining, three are to be attempted choosing at least ONE from each section.
The number of marks carried by a question/part is indicated against it.
Answers must be written in the medium authorized in the Admission certificate which must be stated clearly on the cover of this Question-cum-Answer booklet in the space provided. No marks will be given for answers written in medium other than the authorized one.
Wherever any assumptions are made for answering a question. they must be clearly indicated.
Diagrams/Figures, wherever required, shall be drawn in the space provided for answering the question itself.
Unless otherwise mentioned, symbols and notations carry their usual standard meaning.
Attempts of questions shall be counted in chronological order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the answer book must be clearly struck off.

SECTION A

1. Answer all five questions:
<img src='./qimages/92-1.jpg'>
Find the resultant of the force system acting on a lamina of equilateral triangle of sides 200 1Th<1. Find also its direction and position w.r.t. point A as shown in the figure. D and E are the mid- 80 kN points of BC and AC respectively. 10

Design two solid circular shafts to transmit 200 HP each without exceeding a shearing stress of 70 MPa. One of these operates at 20 RPM and the other at 20,000 RPM. Give your inference about the final results from the view point of economy. Do you have any other suggestion to improve the economy further? 10

A body is immersed in an air stream with an ambient velocity of 40 m1s at a pressure of 98·07 kN/m2 and a mass density of 1·20 kg/m). If the velocity of the immersed body is 80 mls at some point, determine the pressure at that point. 10

2·5 em diameter water jet strikes a stationary plate held at right angles to the jet. The jet exerts a force of 784·53 N on the plate. Determine the discharge. Assume the mass unit weight of water as 10 kN/m3 10

A pelton wheel has a mean bucket speed of 10 mls and is supplied with water at a discharge of 0·8 m31s under a head of 40 m. If the bucket deflects the jet through an angle of 1sao. find the power and efficiency of the turbine. Consider the coefficient of velocity as 0·96. 10

Draw free body diagram of the whole system as shown in the figure. Neglecting self-weight of its parts AB, BC, AC and draw FBDs of individual parts also. The wheel at D is frictionless.
<img src='./qimages/93-2a.jpg'>
10

For the semicircular simply supported member shown in the figure, find the value of bending moment as a function of and also draw its bending moment diagram. 15
<img src='./qimages/93-2b.jpg'>
wind velocities were measured above a smooth plane ground surface at 2 m and 4 m heights as 2 and 2·3 mls respectively. Compute the shear velocity. Assume Karman's constant as 0·40 and kinematic viscosity of air as 0·145 centi stoke. What is the velocity at 8 m above the ground surface? Calculate the probable laminar sublayer thickness. 15

Distinguish between surface and form drags due to a fluid flow. Estimate the bending moment at the base of a 30 m smoke stack 2 m in diameter during a 100 km per hour wind. Assume the mass density of the air as 1·24 kg/m3 and the kinematic viscosity as 0·15 centi stoke. 10

What is the maximum height x of a step in
the figure so that a force P will roll" a
cylinder of radius R weighing W over the
step with no slippage at all. The coefficient
of static friction is J.ls' 10
<img src='./qimages/93-3a.jpg'>

A shallow river has a width of 1200 m and conveys a discharge of 2830 m3/s at a mean velocity of 0·90 m/s. It is proposed to construct a river model to a horizontal scale of I 800 and a vertical scale of 1 40. If Manning's n for the river bed material is 0·025, what should be its value in the model? Verify whether the flow in the model is turbulent. Assume kinematic viscosity as 1·1 centi stoke. 10

A 900 mm diameter steel pipe conveys a discharge of 1·5 m3/s. The wall thickness of the pipe is 10 mm and the elastic modulus of the pipe material is 20·7 x 1010 N/m2 and the bulk modulus of water is 21·09 x 108 N/m2• Determine the increase in pressure if the valve at the end of the 3·5 km long pipe is closed in 3·5 sec and 10·0 sec. Assume the mass density of the water as 1000 N/m3• 10
Following are the monthly inflow, Evaporation and rainfall data and the contemplated demand for a proposed reservoir of a hydropower project:
<img src='./qimages/93-3c.jpg'>
The average reservolf area is 30 km2 Estimate the storage that is necessary to meet the demand. 20

Two equal cylinders, E and each weighing 1000 N are placed in a box as shown in the figure. Neglecting friction between the cylinders and the box, estimate reactions at B and C. 10
<img src='./qimages/93-4a.jpg'>

4(b)For the beam shown in the figure, compute the deflection of end B by force method. 15
<img src='./qimages/93-4b.jpg'>

It is required to choose a suitable turbine for hydropower generation for the following data:
Available head 300 m and discharge 6·25 m3/s. A runner speed of 200 rpm and maximum overall efficiency of 85% can be adopted. Determine the diameter of the runner. Assume the specific weight of water as 10,000 N/m3• 12
A discharge of 1·0 m3/s is to be pumped to a height of 40 m using centrifugal pumps of specific speed of 50. The pumps run at 1500 rpm and have an overall efficiency of 75%. Determine the number and arrangement of pumps. 13

SECTION
<img src='./qimages/93-5a.jpg'>
A built-up column consists of three ISWB 450 0·794 kN per m connected effectively to act as one column. (See above figure.) Determine the safe load carrying 'capacity of built-up section if the unsupported length of column is 4·25 m. Properties of ISWB 450 0·794 kg per m. Area 101·15 sq cm In 35057·6 cm4 Iyy 1706·7 cm4 tw thickness of web 9·2 fy 250 M.Pa yield stress. 10
<img src='./qimages/93-5a1.jpg'>

<img src='./qimages/93-5b.jpg'>
Draw the bending moment diagram and shear
2m 2m 2m force for the beam as shown in the figure. 10

What will be the gross and net safe bearing pressure of sand having rp 36° and effectiveunit weight of 18 kN1m3 under m wide strip footing a square footing of 1 m size? Assume the footings are placed at a depth of 1m below ground surface and the water table is at a great depth. Also, assume a factor of safety of 3·0. Use Terzaghi's theory. Given rp= Nq 47 and Ny 43. 10

In a variable head permeability test the initial hydraulic head is 45 cm and it drops 1 em in 5 minutes. Calculate the time required for the head to drop further by 10 em i.e. from 44 cm to 34 em. 10
In unconfined compression test, a soil sample fails at 160 kN/m2 stress. The failure plane makes an angle of 50° with the horizontal. Calculate the values of cohesion and angle of internal friction of the soil. 10

A simply supported I beam (ISMB 350) is to carry an imposed load of 20 kN/m. The beam ends are resting on 250 mm thick walls with bearing plates (smooth) with clear span of 6·25 m. The beam is laterally restrained and is made of MILD STEEL. The beam supports a floor slab. Check the beam section against bending, shear deflection. The section properties of ISMB 350 are Ixx 13630-6 x 10" mm4 Weight 524 N per m tw Thickness of web 8·1 mm; Area 6671 sq mm D Depth of the beam 350 rum Assume allowable bending stress, allowable shear stress as per code. 20

A masonry retaining wall has to retain sand with a unit weight of 15 kN/m3 Angle of internal friction 300 • Assume sand to be dry and the height retained is 4·2 m. The top width of the wall is 300 rum. Bottom width is 2100 mm. Check whether the resultant of the forces is within the middle third of the base. Calculate the stabili ty factors of the wall. The back of the wall adjoining the soil is vertical. The top level of sand is horizontal. Unit of weight of masonry is 24 kN/m3. 15

<img src='./qimages/93-6c.jpg'>
For sub-soil conditions shown in the figure draw total, effective and neutral stress diagram up to a depth of 8 m. Neglect capillary rise. Take 10 kN/m3• 15

A slab is reinforced with 10 rum diameter bars at 200 rum c/c located at an effective depth of 125 rum. M 20 concrete and Fe 415 steel are used. Find the Moment of resistance of the slab using either working stress method or limit state of strength (ultimate limit state of stress) method as per I.S. code. (I.S. codes are not applied during examination). What shall be the overall depth of slab? Modular ratio is 13·33. 20

A 30 cm diameter concrete pile, is driven to a depth of 20 m in a deep deposit of clay having unconfined compressive strength of 90 kNIm2• What is the design carrying capacity of pile Assume adhesion factor =0·8 and factor of safety =3. 15
A point load of 200 kN acts on the surface of a homogenous soil mass of large extent. Find the stress intensity at a depth of 10 m directly under the load. at a horizontal distance of 5 m and depth of 10 m. Use Boussinesq equation. 15

A prestressed concrete beam of 300 mm wide x 500 mm overall depth is prestressed with a net force of 750 kN at an eccentricity of 100 mm below from the centroid of gross section. The effective simply supported span of beam is 7 m. It is subjected to an imposed load of 20 kN per metre in addition to the dead load. Evaluate the stresses at top and bottom fibres at the centre of span due to effect of prestress, dead load and live load. Unit weight of prestressed beam is 24 kN per m. Calculation of equivalent area of concrete is not necessary. 15
Analyse the continuous beam by moment-distribution method and draw the bending moment diagram showing salient values. 20

A normally consolidated clay has a compression index =O·2. Initial void ratio of this clay layer is 0·9 and thickness 3 m. Ifthe initial soil stress is 10 kNIm2, how high can the stress become before the ultimate settlement is 2 cm 15