UNIVERSITY OF ZAMBIA
SCHOOL OF ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING
MEC 3351 – STRENGTH OF MATERIALS I
PREP SHEET
Assignment 1 - Direct Stress
Assignment 2 – Shear Stress
Due Date: 15th August, 2024
Prepare to ALL questions but you will be advised to answer THREE selected questions (TWO
questions from SECTION A and ONE from SECTION B) in class on the due date. PRINT OUT
THIS ASSIGNMENT SHEET FOR YOUR USE ON THE APPOINTMENT DAY.
SECTION A – Direct Stress:
1. A prismatic bar shown in Figure Q1 is fix at both ends and is loaded by an axial load P acting at a
distance a from one of the supports. The material of the prism is homogenous throughout its entire
volume with an elastic modulus of E. Determine the resultant reactions at the supports A and C.
Figure Q1
2. Two vertical rods, one of steel and the other of copper, are suspended from a horizontal ceiling,
the horizontal distance between them being 80cm as shown in Figure Q2. Each rod is 2.5m
long and 12.mm in diameter. A horizontal cross-piece connects the lower ends of the bars.
a. Where should a load of 10kN be placed on this cross-piece so that it remains horizontal
after being loaded?
b. Also determine the stress in each rod.
Take Esteel=2.0 x 106 kg/cm2 and Ecopper=1.1 x 106 kg/cm2. Neglect bending of the crosspiece.
Figure Q2
3. A rod of square section of side D at one end tapers to a square section of side d at the end. If
its length is l, find the increase in length if it is subjected to an axial pull P.
Figure Q3
4. A bracket is riveted to a column by 6 rivets of equal size as show in Figure Q4. It carries a load
of 60 kN at a distance of 200mm from the centre of the column. If the maximum shear stress
in the rivet is limited to 150 MPa, determine the diameter of the rivet.
Figure Q4
5. A bracket in the form of a plate is fitted to a column by means of four rivets A, B, C, D in the
same vertical line as shown in Figure Q5. Determine the diameter of the rivets which are made
of steel having a yield stress in shear of 240 MPa. Take a factor of safety of 1.5.
Figure Q5