P.E.S. Institute Of Technology – Bangalore South Campus

Department of Science & Humanities

1rd Internal Assessment Test (Scheme & Solutions)

Even Semester – JAN 2018

SUBJECT / CODE: 17CIV23

CONTINUOUS INTERNAL EVALUATION TEST -1

Date : 28/02/2018 Marks:60

Subject & Code : Elements of Civil Engg & Mechanics/ 17CIV23 Section: A,B,C,D & E

Name of faculty : Prof. D Jawahar, Prof. Rashmi B A & Prof. Sachna K G Time : 8:30 to 10:00a.m

Note: Answer FIVE full questions choosing any ONE full question from each part.

PART 1

1 a Explain briefly the scope of civil engineering in

i) Structural Engineering ii) Geotechnical Engineering

iii) Building Materials iv) Transportation Engineering

12

2 a Write short notes on : i) Shoulders ii) Kerbs iii) Traffic separators 6

b Write a note on impact of infrastructural development on the economy of the country. 6

PART 2

3 a Explain any 2 types of dams with neat figure. 6

b Explain any 3 types of bridges with neat figure. 6

4 a State & explain basic idealizations in mechanics 6

b Explain the different types of force systems giving an example for each one of them. 6

PART 3

5 a Find the value of resultant of the system of forces as shown in fig.5.a 8

b Resolve 50N force acting on a block as shown in the fig.5.b.

i) Into horizontal & vertical components

ii) Along the inclined plane & right angles to the plane

4

6 a Two cables attached to the top of tower carries a guy wire AB as shown in fig.6a. Determine the tension in

AB such that the resultant of the forces in all three wires acts vertically down. Also find the resultant force

6

b State & prove parallelogram law of forces. 6

PART 4

7 a

Derive an equation for the centroid of a right angled triangle of base ‘b’ and height ‘h’ from first

principles.

8

b Locate the centroid of the uniform wire bent as shown in the fig 8.b 4

8 a Locate the centroid of the semicircular lamina which is symmetrical about Y –axes from the method of

integration.

7

b Locate the centroid of the plane area as shown in the fig8.b 5

PART 5

9 a Determine the centroid of the shaded area for the lamina shown in the fig.9a. (all the dimensions are in

meter)

12

10 a Locate the centroid of the lamina shown in the fig.10a. with respect to the axes given. 12

Q.

NO

1 A i) Structural Engineering:

Structural engineering is a field of engineering dealing with the analysis and design of

structures that support or resist loads economically.

Structural engineers analyse, design, plan, and research structural components and

structural systems. Their work takes account mainly of technical, economic and

environmental concerns, but they may also consider aesthetic and social factors

ii) Geotechnical Engineering Geotechnical engineering is the branch of civil engineering concerned with the engineering

behavior of earth materials. Geotechnical engineering includes investigating existing subsurface

conditions and materials; determining their physical/mechanical and chemical properties that are

relevant to the project considered,

iii) Building Materials The engineering structures are composed of materials. These materials are known as engineering

materials or building materials or materials of construction. It is necessary for an engineer to

become conversant with the properties of such materials. The materials which are used for

construction should have properties such as weather resistant, strength, durability, permeability,

heat resistant, appearance etc.

iv) Transportation Engineering Transport engineering (or transportation engineering) is the science of safe and efficient movement

of people and goods (transport). It is a sub-discipline of civil engineering

The planning aspects of transport engineering relate to urban planning, and involve technical

forecasting decisions and political factors. Technical forecasting of passenger travel usually

involves an urban transportation planning model, requiring the estimation of trip generation (how

many trips for what purpose), trip distribution, mode choice and route assignment

12

2 a i) Shoulders 1. Shoulders are provided along the road edge to serve as an emergency lane for vehicles

compelled to be taken out of the pavement/ roadway.

2. Shoulders also act as service lanes for vehicles that have broken down.

3. The minimum width of the shoulder recommended by IRC is 2.5m.

4. The shoulder should have sufficient load bearing capacity to support loaded truck even in wet

condition.

ii) Kerbs Kerb indicates the boundary between the pavement and shoulder or Footpath.

Classification of kerbs

1. Class 1 or Low or Mountable Kerbs

2. Class 2 or Low speed barrier or Urban parking kerb 3. Class 3 or High speed barrier

iii) TRAFFIC SEPARATORS: Traffic separators are provided to separate the traffic moving in

opposite directions. It avoids head on collision between vehicles moving in opposite directions.

Traffic separators may be in the form of pavement marking or parking strips whose width may

vary from 3 to 5m.

6

b Impact of infrastructural development on the economy of the country. Infrastructure plays a key role in a country’s growth. It provides a basis for social, economic and

spatial development; it makes it possible for consumers to receive products, for employees to get

to work, and so on. It helps improve a country’s prosperity and enhance its competitiveness. There

is also a relationship between regional development and infrastructure, as various studies have

6

shown. International organizations such as the World Bank acknowledge how important

infrastructure is to regional development.

3 a Gravity dams: These are dams which are built of rigid materials like concrete & stone masonry.

The cross sections of such dams are very large & also have enormous self-weight. The destabilizing

forces like hydrostatic pressure, wind pressure, uplift pressure, and wave pressure are resisted by

the self-weight of the dam only.

Arch dams: These are dams which are also constructed of rigid material like concrete or

stone masonry. These dams are curved in plan. The cross section of such dams is slender

when compared to gravity dams. These dams transfer the water pressure, wind pressure etc.

to the banks of the river by arch action.

6

6

4 a Particle: A particle is a body of infinitely small volume and the entire mass of the body is

assumed to be concentrated at a point.

Continuum: the body is assumed to consist of continuous distribution of matter.

Rigid body: It is one, which does not alter its shape, or size or the distance between any two

points on the body does not change on the application of external forces.

Point force

6

b 1) Collinear forces: It is a force system, in which all the forces have the same line of action. Ex.:

Forces in a rope in a tug of war

2) Coplanar parallel forces: It is a force system, in which all the forces are lying in the same

plane and have parallel lines of action.

Ex.: The forces or loads and the support reactions in case of beams.

6

3) Coplanar Concurrent forces: It is a force system, in which all the forces are lying in the

same plane and lines of action meet a single point.

Ex.: The forces in the rope and pulley arrangement.

4) Coplanar non-concurrent forces: It is a force system, in which all the forces are lying in

the same plane but lines of action do not meet a single point.

Ex.: Forces on a ladder and reactions from floor and wall, when a ladder rests on a floor and

leans against a wall.

5) Non- coplanar parallel forces: It is a force system, in which all the forces are lying in the

different planes and still have parallel lines of action.

Ex: The forces acting and the reactions at the points of contact of bench with floor in a

classroom.

6) Non- coplanar concurrent forces It is a force system, in which all the forces are lying in

the different planes and still have common point of action. Ex.: The forces acting on a tripod when a camera is mounted on a tripod.

5 a

8

b

4

6 a

6

b Parallelogram law of forces: This law states “If two forces acting at a point are represented both in

magnitude and direction by the two adjacent sides of a parallelogram, then the resultant of the two

forces is represented both in magnitude and direction by the diagonal of the parallelogram passing

through the same point.”

Let F1 and F2 be two forces acting at a point O and be the angle between them. Let OA and OB

represent forces F1 and F2 respectively both in magnitude and direction. The resultant R of F1 and

F2 can be obtained by completing a parallelogram with OA and OB as the adjacent sides of the

parallelogram. The diagonal OC of the parallelogram represents the resultant R both magnitude

and direction.

6

7 a

Let us consider a right angled triangle with a base b and height h as shown in figure. Let G be

the centroid of the triangle. Let us consider the X- axis and Y- axis as shown in figure. Let us

consider an elemental area dA of width b1 and thickness dy, lying at a distance y from X-

axis.

W.K.T

8

b

4

8 a

Let us consider a semi-circle, with a radius „r‟. Let „O‟ be the centre of the semi-circle .let „G‟ be

centroid of the semi-circle. Let us consider the x and y axes as shown in figure. Let us consider an

elemental area „dA‟ with centroid „g‟ as shown in fig. Neglecting the curvature, the elemental area

becomes an isosceles triangle with base r.dθ and height „r‟.

Let y be the distance of centroid “g” from x axis.

7

b

5

9

12

10

a

12