An over-braced jib crane, as shown in Figure Q1, is made from 2 steel bars. The lower jib bar is pin-jointed to the wall mounted face plate (C). The upper jib brace bar is pin-jointed to the
wall mounted face plate (A) and pin-jointed to the lower jib beam at the maximum span where
the load is applied (B). The jib is designed to carry a maximum mass of 500.
a) Using the displacement based finite element analysis and assuming the mass being
applied at the farthest position only (B):
i) Simplify the structure and label nodes and elements of the structure, (4 marks)
ii) Develop the element stiffness matrices, (8 marks)
iii) State the boundary conditions, (4 marks)
iv) Assemble the necessary terms of the structural stiffness matrix, (4 marks)
v) Calculate the unknown displacements, (6 marks)
vi) Calculate the stress in the upper brace bar, (5 marks)
b) Explain briefly, how you would modify your calculations, if the load was carried at the midspan of the lower jib bar. (4 marks)
The following values are given: = 200, = 0.3
ௌ௘௖௧௜௢௡ଵ = 0.001ଶ
, ௌ௘௖௧௜௢௡ଶ = 0.000