STRUCTURES - SUSPENSION ROOF

Assume:



1  Cable roof structure

2  Parabolic cable by graphic method

 Process:
  Draw AB and AC (tangents of cable at supports)
  Divide tangents AB and AC into equal segments
  Lines connecting AB to AC define parabolic cable envelop

3 Cable profile

 Process:
  Define desired cable sag f (usually f = L/10)
  Define point A at 2f below midpoint of line BC
  AB and AC are tangents of parabolic cable at supports
  Compute total load W = w L

4  Equilibrium vector polygon at supports (force scale: 1” = 50 k)
 Process:
  Draw vertical vector (total load W)
  Draw equilibrium polygon W-Tl-Tr
  Draw equilibrium polygons at left support Tl-H-Rl
  Draw equilibrium polygons at right support Tr-Rr-H
  Measure vectors H, Rl, Rr at force scale

Note:  This powerful method finds five unknowns: H, RI, Rr. Tl. Tr The maximum cable force is at the highest support


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