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MECHANICS - CASE STUDY

    Introduction


Basic Steel Frame Structure


Center Column Joint at Top

 

A simple, four bay office building is being considered for additional equipment storage facility at the construction company where you work. The company would like to use the steel I-beams currently in storage at the company for the center columns. The list of available I-beams are given in the table at the left.

What is known:

  • Young's modulus, E, is 200 GPa.
  • Dead load on the roof is 300 kg/m2.
  • Live load on the roof is 250 kg/m2.
  • A factor of safety of 2.5 is required for all loads.
  • Columns are rigidly fixed to the ground.
  • Columns are assumed to be fixed at the top due to the rigid beams.
  • Yield stress in compression is 250 MPa.
   
  Question

 

What I-beam should be specified for the center column to minimize the total weight of the building? Chose only from the list at the left.

   
    Approach

Section Number
W310 x 67 W250 x 58
  x 39   x 45
  x 33   x 28
  x 24   x 22
  x 21   x 18
W200 x 59 W150 x 37
  x 46   x 30
  x 36   x 22
  x 22   x 24

Wide-Flange Beams Available
in the Storage Yard
 
  • Roof loads, dead and live, need to be combined for total design load.
  • Roof load needs to be distributed to each of the columns.
  • Assume failure will be buckling.
  • Use Euler's formula for fixed-fixed columns.

          
     
   
 
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