Figure 1 shows an oil platform idealised as a space frame. Each beam member is of thin-walled
circular (tubular) cross-section with an average diameter D =2 m and thickness t= 0.05 mm. The
members are made of steel with Young’s modulus E = 2 x 1011 N/m2
and Poisson’s ratio υ=0.3.
The space frame is subjected to equal forces P at each of the four nodes shown in the figure and P is
given as 4 MN.
(A) Analyse the space frame in figure 1 using beam elements in commercial FEA tool (Abaqus or
Ansys) to determine translational and rotational displacements in all directions. Also report
the maximum and minimum stress in the members of the space frame. [30 marks]
(B) Show, through further analysis, on how to improve the design of the platform (i.e., minimise
the deflections and stresses). You need to show three cases of design improvements and
discuss your results, arguments and insights. [50 marks]
(C) For one case of your choice, conduct the analysis using three-dimensional (solid) elements
and report your findings and observations. [20 marks]
Figure 1: A space frame representing an oil platform
(A) Analyse the space frame in figure 1 using beam elements in commercial FEA tool (Abaqus or
Ansys) to determine translational and rotational displacements in all directions. Also report
the maximum and minimum stress in the members of the space frame. [30 marks]
(B) Show, through further analysis, on how to improve the design of the platform (i.e., minimise
the deflections and stresses). You need to show three cases of design improvements and
discuss your results, arguments and insights. [50 marks]
(C) For one case of your choice, conduct the analysis using three-dimensional (solid) elements
and report your findings and observations. [20 marks]
Note: For circular cross-sections, cross-sectional area A = πDt, second moment of area I= πD3
t/8,
polar moment of inertia J=2I, and shear modulus G= E/2(1+ υ). Appropriately assume any other
properties or parameters that you think are missing and justify accordingly.
