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Knec Structures I And Construction Materials October/November 2014 Question Paper

Knec Structures I And Construction Materials October/November 2014

Course:Diploma In Civil Engineering Module I

Exam Year:2014

CONSTRUCTION MATERIALS
Oct./Nov.2014
Time:3 hours

THE KENYA NATIONAL EXAMINATIONS COUNCIL
DIPLOMA IN BUILDING TECHNOLOGY
DIPLOMA IN CIVIL ENGINEERING
DIPLOMA IN ARCHITECTURE
MODULE I
STRUCTURES I AND CONSTRUCTION MATERIALS
3 hours
INSTRUCTIONS TO CANDIDATES
You should have a calculator for this examination.
This paper consists of EIGHT questions in TWO sections; A and B.
Answer FIVE questions choosing TWO questions from section A, TWO questions from section B and ONE question from either section A and B in the spaces provided in the question paper.
All questions carry equal marks.
Maximum marks for each part of question are indicated.
Candidates should answer the questions in English.

SECTION A: STRUCTURES
Answer at least TWO questions in this section.
1. (a) Differentiate between the following terms:

Modulus of elasticity and bulk modulus;
Modulus ratio and Poisson’s ratio.
(4 marks)
(b) (i) Sketch and label a stress – strain graph for typical results obtained from a test on a mild steel rod tested under tension to destruction.
(ii) From the graph in (i), define THREE ranges of stress.
(7.5 marks)
(c) A mild steel specimen was tested under tension to destruction from which the following data was collected:

Gauge length--------------------195 mm
Original diameter---------18 mm
Final length--------------205 mm
Diameter at fracture------16.5 mm
Extension at an early load of 48 kN----------0.05 mm
Yield load-----------56 kN
Maximum load----------190 kN

Determine:
Modulus of elasticity for the material;
Yield stress;
Ultimate stress;
Percentage elongation
Percentage area reduction;
Working stress with a factor of safety of 1.75 applied on maximum stress.
(8.5 marks)

2. (a) (i) Derive the temperature stress equation and state its main limitation.

(ii)A hollow circular copper section of external diameter 225 mm and thickness 4 mm is to be used as a strut. It is initially subjected to a pre–compressive force of 175 kN axially. Determine the stress and hence the thrust against the supports at the ends if it undergoes a change in temperature from 20^oC to 125^oC. Take the coefficient of thermal expansion for the material as 11 X 10^-6 per ^oC and E = 105 kN/mm² (11 marks)
(b) For the section shown in figure 1, determine:
(i) I_yy;

(ii) r_yy;

(iii) z_yyB;

(9 marks)

3. (a) Analyse the beam shown in figure 2 for reactions, shear forces, bending moments and hence sketch the shear forces, bending moment‘s diagrams indicating all the critical values.
(10 marks)

(b) (i) Illustrate two end fixity conditions for columns showing how effective lengths are determined in each case.
(ii) Define the term ‘slenderness ratio’.
(iii)Using Rankine’s formula determine the critical buckling load for a 4 m long
Column of equilateral triangular hollow section of slide 120 mm and 5 mm
Thickness one end of the column is held in position and direction while the
Other end is only held in position but not in direction.
Take a = 1/6500
Actual height = 2.5 m
Yield stress = 115 N/mm²
(10 marks)

4. (a) (i) Define the term ‘bending stress’.

(ii)Determine the value of maximum bending stress and the radius of currature
At the point of maximum bending moment for a rectangular cantilever beam
Of width 120 mm, depth 400 mm and span 2.6 m. The beam carries a
Uniformly distributed load (UDL) of 30kN/m together with a point load of
75kN at the free end.
Take E = 185kN/mm²
(6.5 marks)
(b) Using the method of joint resolution, determine the magnitude and nature of forces for all the members of the frame shown in figure 3.
(13.5 marks)

SECTION B: CONSTRUCTION MATERIALS
Answer at least TWO questions from this section
(a) Describe the glass manufacturing process.
(8 marks)
(b) Outline six types of glass, stating their uses.
(12 marks)

(a) Explain the manufacturing process of bricks
(15 marks)
(b) Describe the water absorption test on bricks
(5 marks)
(a) Describe the following types of paints
(i) Distemper;
(ii) Emulsion;
(iii) Oil paint.
(6 marks)
(b) Explain the following paint defects, stating how they can be eliminated:
(i) Blistering
(ii) Bittiness;
(iii) Chalking;
(iv) Cissing.
(10 marks)

(c) (i) Describe bitumen;
(ii) State two properties of bitumen.
(4 marks)

(a) With reference to iron ore, distinguish between magnetic and haematite.
(4 marks)
(b)Explain annealing as a heart treatment process for metals
(4 marks)
(c) Describe the following timber defects:
(i) Knots
(ii) Burl;
(iii) Shake;
(iv) Pitch.
(6 marks)
(d) Explain the production of pozzolanic Portland cement by the dry process.
(6 marks)

Knec Structures I And Construction Materials October/November 2014 Question Paper

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