--- title: "Components of a suspension bridge" subject: "Theory of Structures I" chapter: 7 key: "semester_4/theory_of_structures_i:suspension-components" source: https://www.bctengineer.com/q/semester_4/theory_of_structures_i/suspension-components site: BCT Engineering --- # Components of a suspension bridge Theory of Structures I · Chapter 7: Suspension Cable Systems - Asked in: 2074 Bhadra, 4 marks - Video: [Suspension Bridge | How Do Suspension Bridges Work | Design Factors of Suspension Bridges | Lec -08](https://www.youtube.com/watch?v=pSD5j2rg6Kk) — STRUCTURE-TECH - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/theory_of_structures_i/suspension-components - Whole chapter: https://www.bctengineer.com/md/semester_4/theory_of_structures_i/chapter-7 ## Question Enlist the different components of a suspension bridge. ## Short answer The main components include main cables, towers, saddles, suspenders (hangers), stiffening girder, deck and floor system, anchorages, side spans and back stays, wind cables and ties, and bearings. The main cables carry the load in tension over saddles on towers; suspenders transfer deck loads; the stiffening girder distributes loads; anchorages resist horizontal pull. ## Answer The main parts of a suspension bridge are: 1. **Main cables:** two or more parabolic (or catenary) cables of high-tensile steel wire that carry the whole load in tension and pass over the towers to the anchorages. 2. **Towers (pylons):** steel or reinforced concrete columns that support the cables through saddles at their tops and transfer the vertical load to the foundations. 3. **Saddles:** castings at the tower tops (and at the splay points) on which the cable rests; they allow the cable to slide or roll and so keep the tower free from bending. 4. **Suspenders (hangers):** vertical ropes or rods that transfer the load from the deck or stiffening girder to the main cable. 5. **Stiffening girder (or truss):** a beam or truss along the deck that distributes concentrated loads, reduces local deflection and prevents the cable from changing shape under moving loads (three-hinged, two-hinged or unhinged). 6. **Deck (roadway) and floor system:** floor beams and slab that carry the traffic. 7. **Anchorages (anchor blocks):** massive concrete blocks or rock anchors at the ends of the cables that resist the horizontal pull and any uplift. 8. **Side spans and back stays:** cable portions from the tower to the anchorage. 9. **Wind cables, wind ties and bracing:** lateral cables and bracing that resist wind forces. 10. **Bearings and expansion joints:** at the towers and abutments for movement of the deck. ```text tower tower || main cable || anchor || .--------.______.--------.|| anchor block<--||-' | | | | | | | '-||-->block || hangers (suspenders) || ======||=== stiffening girder + deck ===||====== || || ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the function of the main cables of a suspension bridge? A. To carry the whole load in tension and pass over the towers to the anchorages B. To resist wind only C. To distribute concentrated loads along the deck D. To act as compression members between towers Answer: A. The main cables are high-tensile parabolic or catenary cables that carry the load in tension to the anchorages. (Key point: Role of the main cables) 2. Why is a stiffening girder provided along the deck? A. To anchor the cable ends B. To connect the cable to the tower C. To distribute concentrated loads, reduce deflection and stop the cable changing shape under moving loads D. To increase the cable sag Answer: C. The stiffening girder spreads concentrated loads to the hangers and limits local deflection and shape change of the cable. (Key point: Purpose of the stiffening girder) 3. What do the saddles and the anchorages do? A. Saddles anchor the cable; anchorages support the deck B. Saddles carry the traffic; anchorages carry the hangers C. Saddles stiffen the girder; anchorages are wind ties D. Saddles let the cable slide or roll at the tower top so the tower is not bent; anchorages resist the horizontal pull and uplift Answer: D. Saddles keep the tower free from bending; anchor blocks hold the cable ends against the horizontal pull and uplift. 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