Cable is a tension member that does not resist shear force and bending moment with its zero stiffness along transverse direction. When we are dealing with a parabolic shaped cable, the geometry, namely span and sag are used to determine the curve function.
With this function, we can derive the function for inclination angle at any point on the curve. Then, we also need to determine the constant horizontal component along the cable. With these functions, we can proceed with the determination of tension force developed in cable.
The following shows the procedure to analyse a cable. Watch the video above for full details.
Cable overview
A 20m span cable with 1.5m sag is subjected to 5kN/m UDL.
Curve function
The parabolic curve function is determined using half of the span.
Reactions
The reaction forces can be determined easily for symmetrical loading case.
Horizontal component
Constant horizontal component is calculated based on UDL, span and sag.
Force polygon
Tension in cable can be calculated using one simple formula.
Internal forces
Tension in cable for every 1m interval is calculated.
The cable tension is the maximum at support and minimum at the lowest point.
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