Concept Notes (Deep Explanation + Examples)
🔹 Introduction
A suspension bridge is a type of structure where the deck (roadway or walkway) is hung below suspension cables on vertical suspenders. These bridges are one of the most efficient and elegant structures for spanning large distances — even beyond 2,000 meters.
In ECET, questions from suspension bridges often appear under the Theory of Structures unit, especially testing concepts of tension, cable shape, and load distribution.
🔹 Basic Concept
In a suspension bridge, the main cables pass over towers and are anchored at both ends to massive anchor blocks. The deck is supported by hangers (suspenders) attached to these cables.
When loads act on the bridge deck:
- The deck transfers the load to hangers.
- Hangers transfer the load to main cables.
- The main cables transfer the load to towers and anchorages.
Thus, the cables carry tension, while the towers carry compression.
🔹 Real-World Example
- Howrah Bridge (Kolkata) – technically a cantilever suspension-type bridge.
- Golden Gate Bridge (San Francisco) – classic example of a full suspension bridge.
- Bogibeel Bridge (Assam) – hybrid truss and suspension design.
At a construction site, engineers check:
- Cable tension using tension meters
- Deck alignment using surveying instruments
- Anchorage strength using concrete and steel testing
🔹 Shape of Cable
Under uniformly distributed load (UDL) on the horizontal span, the shape of the cable is a parabola.
If the load is uniformly distributed along the cable length, the shape becomes a catenary.
In ECET, most questions assume UDL on the span → Parabolic cable.
🔹 Key Components of a Suspension Bridge
- Towers or Pylons – Transfer compression to the ground.
- Main Cables – Carry the major tension force.
- Suspenders (Hangers) – Connect deck and cable.
- Deck or Roadway – Supports vehicular or pedestrian load.
- Anchorages – Massive blocks holding the cable ends firmly.
🔹 Diagram (Explained in Words)
Imagine a horizontal roadway suspended by vertical cables (hangers) from two curved cables draped over tall towers on both ends. The cables go down to anchor blocks embedded in the ground — these hold the entire system in tension.
🔹 Analysis of Cable Under UDL
If span = 
,
Dip (lowest point to tower top) = 
,
and total uniform load per unit horizontal length = 
,
then the maximum tension in cable and horizontal tension are given by:
🔹 ECET-Important Points
✅ Cable shape is parabolic under UDL on span.
✅ Horizontal tension inversely proportional to dip latex[/latex].
✅ Increasing dip reduces cable tension.
✅ Towers experience axial compression.
✅ Cables experience pure tension.
✅ Neglect bending in cables (flexible members).
✅ Suspension bridges are ideal for long spans (>500 m).
⚙️ 3️⃣ Formulas (Plain LaTeX Only)
🔟 4️⃣ MCQs (GATE + ECET Mix)
1️⃣ The shape of a cable under uniformly distributed load on the span is:
A) Catenary
B) Parabolic
C) Circular
D) Elliptical
2️⃣ In a suspension bridge, the cable carries:
A) Compression only
B) Tension only
C) Bending only
D) Shear only
3️⃣ The deck of a suspension bridge is supported by:
A) Towers
B) Cables directly
C) Suspenders
D) Anchorages
4️⃣ The horizontal tension in a parabolic cable is given by:
A) 
B)
C) 
D) 
5️⃣ Increasing the dip of the cable will:
A) Increase tension
B) Decrease tension
C) Not affect tension
D) Make it unstable
6️⃣ The maximum tension in the cable occurs at:
A) Midspan
B) Support
C) Quarter span
D) Anywhere
7️⃣ The shape of a cable under its own weight is a:
A) Parabola
B) Catenary
C) Circle
D) Straight line
8️⃣ The towers of a suspension bridge carry mainly:
A) Tension
B) Bending
C) Compression
D) Shear
9️⃣ The load on the cable of a suspension bridge is transferred finally to:
A) Deck
B) Hangers
C) Anchorages
D) Towers only
10️⃣ The main function of anchorages is to:
A) Support the deck
B) Prevent vibration
C) Hold cable ends firmly
D) Reduce wind load
✅ 5️⃣ Answer Key (WordPress Table Format)
Q.No Answer
1 B
2 B
3 C
4 B
5 B
6 B
7 B
8 C
9 C
10 C
🧠 6️⃣ Explanations (Step-by-Step)
1️⃣ Correct: B → Under uniform load on the span, the cable takes a parabolic shape.
Common mistake: Students confuse with catenary (used for self-weight loads).
2️⃣ Correct: B → Cable carries tension only as it’s flexible and cannot resist compression or bending.
3️⃣ Correct: C → Deck is supported by vertical suspenders connecting it to the main cable.
4️⃣ Correct: B → Formula for horizontal tension under UDL is .
5️⃣ Correct: B → Increasing dip decreases tension because 
.
6️⃣ Correct: B → Maximum tension occurs at the supports, not midspan.
7️⃣ Correct: B → Under self-weight, cable follows a catenary curve (not parabolic).
8️⃣ Correct: C → Towers experience compression due to the downward and inward pull of cables.
9️⃣ Correct: C → Final load is transferred to anchorages via the cables.
10️⃣ Correct: C → Anchorages resist the pull of the cables and keep the system in equilibrium.
🎯 7️⃣ Motivation / Why Practice Matters (ECET 2026 Civil)
Suspension bridges combine structural beauty and engineering logic — they test your understanding of forces, geometry, and materials.
In ECET, mastering this topic strengthens your base in Theory of Structures, improves your accuracy in cable and arch questions, and helps you score easily in one-go questions.
Stay consistent — one concept daily brings you closer to your ECET 2026 Civil Top Rank! 💪
📲 8️⃣ CTA
Join our ECET 2026 Civil WhatsApp Group for daily quizzes & study notes:
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