Problem 1:
The Figure 1 below shows a tension member made up from two 125x75x10 UA using Grade 300 Steel. The members are connected together with M20 bolts (assume 2mm over size bolt holes). Also note that there are the same sized bolt holes along the non-connecting leg of the angle.
a. Calculate the member yield.
b. Locate all the possible fracture paths (show on a diagram).
c. For each of the fracture paths calculate section fracture values.
d. What is the final maximum allowable tension in the compound member?
e. Calculate the minimum size of the 16 mm Grade 250 steel cleat plate required to carry the calculated load in part (d). Round your answer up the near multiple size of 10 mm (i.e. 90, 100,...etc.)
Problem 2:
You have been asked to design a strut (Figure 2) for a new version of the Airbus A380. You are only required to consider the compression capacity of the strut. A detailed load analysis has determined an applied axial load of 1000KN with a load factor = 2.0, to account for the expected fatigue and impact loading, giving a final design load N*=2000KN.
The strut is a 2000mm long hot rolled cruciform profile using a high alloy aluminium. A cruciform profile is required for logistical reasons and is to have all legs the same length. The strut is pined supported each end so that there is no eccentric loading.
The material properties are:
Fy = 655MPa, Fu = 683MPa, Density = 2830kg/m3
Assume that AS4100 is appropriate for the design (In real life a high level finite element analysis and design approach would likely be used).
a) The load factor for the design is 2.0. Referring the Limit State theory explain how this factor contributes to a safe design.
b) Explain why the minimum second moment of areas axis are parallel to each leg and not rotated at an angle around the centroid (descriptive and a diagram do use not maths).
c) There are two variables controlling the shape T=thickness, D=length of the legs. As weight is critical devise a method to estimate to minimum weight of the strut.
Notes:
You must show the full computations for at least two combinations of T and D (with one of the computations for your final answer) for assessment. However you may use a spreadsheet or short hand presentation for any subsequent trials.
Your final answer should include the strut dimensions and weight to the nearest 10g and the load carried (must exceed 2000KN).
d) Outline your method (or a method that could be used) to minimize the strut weight.
[The student(s) that achieves the lowest conforming strut weight will be acknowledged on the Unit site]
