Department of Built Environment - PUC PUC Nana Benyi Ansah

PENTECOST UNIVERSITY COLLEGE

FACULTY OF ENGINEERING SCIENCES & COMPUTING

DEPARTMENT OF BUILT ENVIRONMENT

END OF FIRST SEMESTER EXAMINATIONS JUNE 2015

COURSE TITLE: INTRODUCTION TO STRENGTH OF MATERIALS

LEVEL 100 (WEEK END)BSc (Quantity Surveying & Construction Economics)BSc (Construction Technology & Engineering Management)Answer All Questions

Time Allowed - 2 Hrs

INSTRUCTIONS TO STUDENTS

1. Answer questions 1 and 2 and any other 3 questions2. Do not write on the question paper

3. Do not leave your seat unless you are given permission by an invigilator4. All answers should be written in the answer booklet(s) provided5. All rough work should be written in the answer booklet and a line drawn through them to

indicate they are not part of the main answers.6. Write legibly in blue or black ink7. PDAs and mobile phones are not allowed in the examinations

8. You may not leave the examination room until after the first hour9. All announcements would be made when there are 30 minutes of the exam time left.10. At the end of examinations remain seated until your answer booklet(s) have been

collected and you have been asked to leave.

Department of Built Environment - PUC PUC Nana Benyi Ansah

Question One

A long steel wire was rigidly held at its upper end, a small load of mass m, was hanged at itslower end experiencing tension in the fibre of the material. In relation to its load extension,explain the following terminologies:

i) Hookes Lawii) Limit of proportionalityiii) Elasticityiv) Plasticityv) Youngs Modulusvi) Elastic Limit (30 marks)

Question Two

A four legged column concrete stand (section shown below) is to be reinforced to support a

20,000 Litre capacity Polytank. Taking concrete and steel strength as 30N/mm2 and 460N/mm2

respectively, check whether the columns have adequate capacity to carry the Polytank. Ignore the

weight of the tank and assume a column size of 400mm by 400mm with 8no T20 steel. Note: 1

litre of water weighs 1 kg. (10 marks)

Section B: Answer any Three Questions

Question One

An axial blow applied to circular bar A shown below produced an instantaneous extension of0.25mm. Calculate the instantaneous maximum stress and extension in the circular bar B if thesame blow is applied axially. (20 marks)

400

mm

Department of Built Environment - PUC PUC Nana Benyi Ansah

Question Two

A hollow steel tube is to be used to carry an axial compressive load of 160kN. The yield stressfor steel is 250N/mm2. A factor of safety of 1.75 is to be used in the design. The following threeclasses of tubes of external diameter 101.6mm are available.

Class Thickness (mm)Light 3.65Medium 4.05Heavy 4.85

Which section do you recommend? (20marks)

Question Three

A composite bar is rigidly fitted at the supports A and B as shown. Determine the reactions at the

supports when temperature rises by 20 C. Take Ea = 70GN/m2, Es = 200GN/m2, a = 11x 10-6/ C and s = 12x 10-6/ C.

Bar BBar A

300m

m20

0mm

500m

m

25mm

1525

Department of Built Environment - PUC PUC Nana Benyi Ansah

Question Four

A steel bar 300mm x 100mm x 40mm is subjected to a force of 5kN (tensile), 6kN (tensile), and4kN (tensile) along x, y, and z direction respectively. Determine the change in the volume of theblock. Take E = 2 x 105 N/mm2 and Poissons ratio = 0.25. ( 20 marks)

y

z=4kN

x=5kN=6kN

40mm

100mm

300mm

1m 3m

steelAa=600mm2 As=300mmA

B

aluminium

2