CS (Main) Exam:2015 CIVIL ENGINEERING Paper—I

OUESTION PAPER SPECIFIC INSTRUCTIONS

SECTION—A

Q. A rod AB 6 m long is held against sliding by a string AD. The rod weighs 10 kN.Determine the tension in the string AD assuming that all surfaces are smooth. 10

Q. The global stiffness matrix of a structure contains rigid body displacements. Describe how to modify it to account for nodes having zero displacements. Give two approaches. 10

Draw the B.M. diagram for the beam shown in figure when support B settles by 10 mm,
using moment distribution method. 10

Q. The ground water movement at a site takes place through a soil zone comprised of 3 m thick sand with coefficient of permeability 0.01 cm/s (in both directions) overlain by 1 m thick fine gravel with coefficient of permeability 0.1 cm/s (in both directions). Determine the coefficient of permeabilities applicable for horizontal and vertical ground water movements through the layer. 10

Q. At the entry of the pump intake the velocity v varies inversely as the square of the radial distance r from inlet to suction pipe. The velocity is found to be 0.8 ms-1 at a radial distance of 1.5 m. Compute the acceleration of flow at radial distances of 0.5 m and at 1.25 from the inlet assuming the stream-lines to be radial. 10

Q. Material for an earthfill was available from three different borrow pits/sites. In the compacted state the fill measured 1.0 x 105 m3 at a void ratio of 0.75. The corresponding in-situ void ratio and cost (cost of material and transportation) of the material for three sites are as follows

Determine the most economical site for the above earthfill work. 15


Q. Two wheels, placed at a distance of 2.5 m apart, with a load of 200 kN on each of them, are moving on a simply supported girder (I-section) of span 6.0 m. The top and bottom flanges of the I-section are of 200 x 200 mm and the size of web plate is 800 x 6 mm. If the allowable bending compressive, bending tensile and average shear stresses are 110 MPa, 165 MPa and 100 MPa respectively, check the adequacy of the section against
bending and shear stresses, self weight of the girder may be neglected. 20

Q. In order to predict lift and drag forces on a scale model of an aircraft during a section of operational envelope, involves sea level flight at 100 ms”1, where the speed of sound may be taken as 340 ms-1. It is proposed to utilise cryogenic wind tunnel with Nitrogen at 5 atmosphere of pressure
and a temperature of-90°C 7.7 kg n r viscosity 1.2 x Ns for nitrogen). The speed of sound in nitrogen at this temperature is 295 ms-1. Determine the wind tunnel flow velocity, the scale of model to ensure full dynamic similarity and, the ratio of forces acting on the model and prototype.
Mass density of air 1.2 kg m“3 and viscosity 1.8 x 10-5 Ns. 15

Determine the slope at vertical deflections at B and mid span using the moment-area theorem. Take El Const. 15

Design a section of wall of a water tank on uncracked basis to resist a pull of 60 kN and a bending moment of 7.5 kNm/m width producing tension on the water face. Use
M 30 concrete and Fe 415 grade steel.
Effective cover 30 mm
Permissible stress in direct tension in concrete =1.5 MPa
Permissible stress in bending tension in concrete 2 MPa
Modular ratio 9 15

Q. Three pipes are connected as shoW in figure. The characteristics of pipe are as follows

Determine the flow rate in each pipe. Minor losses may be neglected.

q. What is the preconsolidation pressure Describe a method to determine the preconsolidation pressure. 15


Q. An in-situ vane shear test was conducted at the bottom of a borehole in a soft clayey soil. A torque of 155 N-m was required to shear the soil. The vane was 100 mm diameter and 150 mm long. What was the undrained shear strength, Cu of the soil Derive the relevant expression relating to torque vane dimension, and undrained shear strength of the soil. 15

Q. A counterfort retaining wall is shown in figure in plan and sectional elevation. It retains dry earth having a density of 19 kN/m3 and angle of repose of 30°. Design a counterfort in flexure only using the limit state design. Take M 30 grade of concrete and Fe 500 grade steel. 20

Q 5 Determine the diameter of the vertical pipe needed for a flow of a liquid of kinematic viscosity 1.95 x 10"3 m2s“1 at a Reynolds number of 1500. The constant pressure is maintained throughout its length. 5

Q. Prototype data of Tidal Channel are as follows
Length of channel 18 km, Discharge 250 m3s_1
Depth 2.5 Width of the channel 50 m
Model is built with a vertical scale of 1 50 and a horizontal scale of 1 500
Tidal period is 12 hours

Compute the average velocity in ms-1 and tidal period in the model. 5

Q. A particle moves on a vertical line with an acceleration a . At t — 2 sec, its displacement is 8 m and velocity is 6 m/s. Determine its displacement, velocity and acceleration at time t 4 sec. a acceleration and v velocity. 10

Q. A horizontal shaft 12 m in length is fixed at its ends. When viewed from its left end, axial couples of 50 kNm clockwise and 75 kNm counterclockwise act at 5 m and 9 m from the left end respectively. Determine the end fixing couples and the position where the shaft suffers no angular
twist. 10

Q. An infinite natural slope with angle of slope 15° (inclination measured from horizontal) has a saturated unit weight of 18 kN/m3 and an effective angle of internal friction, § Determine the factor of safety against failure of the slope when the slope is completely dry or submerged but without seepage, when seepage occurs at and parallel to the surface of the slope. 10

Design a welded lap joint to join two plates of size 300 x 10 mm and 280 x 10 mm in Fe 410 grade steel to mobilise the tensile strength of the plates using field weld.
Yield strength of material 250 MPa
ymo 1.1
Partial safety factor for field weld 1.5

Q.6(a) A beam has a cross-section shown in figure. It is subjected to a vertical shear force of 10 kN at a given section. Determine the shear stress distribution on the section. 15

Q.6(b) A booster pump is installed in the pipeline between two reservoirs. If the energy added by the pump is 20 determine the flow rate in the pipeline in m3s_1.

Length of the pipeline 1500 m
Coefficient of friction 0.02
Diameter of the pipeline 300 mm
WSEL of A 200 m WSEL of B 185 m 5 10

Q. Compute the shear stress acting on the river bed for the data given

Discharge 5000 m3s“1, River bed slope 1 2500
Depth of flow 4.50 m
Assume the river to be wide. 4

A hydraulic jump has an energy loss of 9.0 m and the downstream Froude number is 0.12.
Determine the initial depth and the discharge intensity. 6

Q. State the Abram’s law on water-cement ratio. 5
Name the various grades of ordinary Portland cement. 5
(iii) Define characteristic strength of reinforcing steel. 5
State any five applications of prestressed concrete. 5

Q. For the sluice gate shown in Figure, if Cv 0.98 and Cc 0.62, what is the height of the opening Given 2.006 m g 9.81 Also determine the flow per unit width. 5

Q. The uniform flow depth is 1.5 m in a trapezoidal channel of bottom width of 20 m with a side slope of The bed slope is 1 x 10-4. Manning roughness coefficient is 0.2. The downstream control raises the water surface by 3 m. Classify the profile. 5

Q. Following data are given for a rectangular channel

Width 9m n 0.017, S0 1 4000
D/S depth is 6.80 U/S depth is 3.6865 m
Discharge 48.748 m3s_1.
Using single step method compute the length of profile. 5

Q. A pile, group consists of nine friction piles driven into a deep layer of clay soil. The diameter of each pile is 0.4 the embedded length is 12 m and center to center spacing of the piles is 1.2 m. The soil has cohesion, c 50 kN/m2, unit weight, y — 18 kN/m3. Determine the block capacity of the pile group using a factor of safety 3.0, group capacity based on individual pile failure criterion and design capacity of the pile groups (Assume adhesion factor a 0.8) 20

Q. A radial flow turbine has the following dimensions
Outer periphery radius 0.5 m
Inner periphery radius r2 0.3 m
The angle made by the relative velocity at the inlet is 80°.
The width of the flow passage between the two sides of the turbine is 0.25 m.
The flow of 4 m3s_1 goes through the turbine when the speed is 300 rpm.
Find the blade angle P2 such that water exit radially.
Find the torque exerted by the water in the turbine and the power thus developed.
Find the head utilised by the runner and the power resulting therefrom.
Assume no shock at the entrance and blades are of negligible thickness. 15

Q. For the earth retaining structure shown in the figure, determine the total active thrust on the wall, and the point of application of the thrust above the base of the wall. Given

Q. For the truss shown in fig. draw the influence lines for force in members U3L3, U3L2 and L,Lr. The load moves on the bottom chord. 15


Q. A bracket connection shown in figure, consists of a joist cutting welded to the flange of a column by shop fillet welds 8 mm on flanges and 6 mm on the web. Determine the safe service load ‘W’, the bracket can support at a distance of 200 mm from the face of the column if the steel grade is Fe 410.

Partial factor of safety on shop weld 1.25
Yield strength of steel 250 MPa
20