The cable takes _______ shape while it resists the loads
- AParabolic curve
- BVermicular curve
- CSemi-circular curve
- DFunicular curveCorrect
Solution
Concept
A cable carries load in pure tension, so it takes the funicular shape of the load acting on it.
Step-by-step solution
1. A cable has no bending stiffness, so it can resist only tension. 2. Under any load, it takes the shape of the bending moment diagram of that load. This shape is the funicular (string) polygon or curve. 3. So the cable takes a funicular curve.
Explanation
A cable cannot take bending, so it changes its shape to match the load. This shape is called the funicular curve. A parabola is only one special case, for uniform load along the span.
Why the other options are wrong
A: Parabola forms only under UDL along the horizontal span, so it is not the general answer. B: 'Vermicular' means worm-like. It is not an engineering term for cables. C: A semi-circle is not the natural shape of a cable under load.
Shortcut
Cable shape = shape of the BM diagram of the load = funicular curve.
Common mistake
Choosing parabolic, which is correct only for uniformly distributed load on the horizontal span.
Correct answer: D) Funicular curve