A suspension cable, supporting loads will be under ............

1. Solution to Provided MCQ

Question: A suspension cable, supporting loads will be under ............ A) tension B) bending C) compression D) compression and bending

• Correct Option: A) tension
• Justification: A suspension cable is a flexible structural element with negligible flexural rigidity ($EI \approx 0$). Because it is flexible, it cannot resist bending moments, and due to its slenderness, it cannot resist compression without buckling. Therefore, a cable adjusts its shape under external loads to resist them purely through axial tension,.

2. & 3. Additional High-Yield MCQs

1. The amount of bending moment induced in a cable is: A) unity B) zero C) two D) all of the above

• Correct Answer: B) zero,

2. The maximum tension in a cable occurs: A) at the highest point in the cable B) at the lowest point in the cable C) at the centre point of the cable D) at all points in the cable

• Correct Answer: A) at the highest point in the cable,

3. A cable subjected to UDL over its entire span assumes a shape of: A) semi-circle B) an isosceles triangle C) parabola D) none of the above

• Correct Answer: C) parabola,

4. Three hinged arch is a ..... structure: A) indeterminate B) determinate C) both (a) and (b) of above D) none of the above

• Correct Answer: B) determinate,

5. The moments in the arch will be zero, if: A) ends are hinged B) ends are fixed C) the arch axis coincides with the line of thrust D) the arch axis is parallel to the line of thrust

• Correct Answer: C) the arch axis coincides with the line of thrust,

4. Core Theoretical Concepts: Cables and Arches

• Cable Behavior: Cables are flexible members that carry loads exclusively through axial tension. They do not resist bending moment or shear force.
• Cable Geometry: The shape of a cable is determined by the applied load:
  • Under a Uniformly Distributed Load (UDL) along the horizontal span, a cable takes the shape of a parabola.
  • Under its own weight (uniform load along the curve), it takes the shape of a catenary.
• Maximum Tension: In a suspension cable, the tension is maximum at the supports (the highest points) where the vertical reaction is maximum, and minimum at the lowest point (the dip) where the vertical component of force is zero.
• Three-Hinged Arch: This is a statically determinate structure consisting of two curved members hinged at the supports and at the crown. Being determinate, it can be analyzed using only the equations of equilibrium.
• Linear Arch (Line of Thrust): This is the theoretical shape an arch would take to support a given load system purely in compression. If the actual physical axis of the arch coincides with this line of thrust, the bending moment is zero at every section,.
• Horizontal Thrust: Both arches and suspension cables generate a horizontal force (thrust for arches, pull for cables) at the supports. For a parabolic arch or cable with span $L$ and rise/dip $h$ carrying a UDL $w$, the horizontal thrust is $wl^2/8h$.