---
title: "Classification of bridges by superstructure and span; sketch"
subject: "Transportation Engineering II"
chapter: 5
key: "semester_7/transportation_engineering_ii:bridge-classification-superstructure-span-sketch"
source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/bridge-classification-superstructure-span-sketch
site: BCT Engineering
---

# Classification of bridges by superstructure and span; sketch

Transportation Engineering II · Chapter 5: Introduction to Bridge and Tunnel Engineering

- Asked in: 2068 Baisakh, 8 marks
- Video: [Types of Bridges || Types of Bridges Based on Span, Materials, Structures, Functions || in hindi 🔥🔥](https://www.youtube.com/watch?v=GZxQopCVDSg) — Civil Notebook
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/bridge-classification-superstructure-span-sketch
- Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-5

## Question

Classify the bridges according to types of super structure and span length. Make a sketch of a bridge section (longitudinal and cross) and plan indicating its elements.

## Short answer

Bridges are classified by superstructure as slab, girder, truss, arch, cable-stayed, suspension, and rigid frame/box culvert. By span length, culvert up to 6 m, minor bridge 6–60 m, major bridge above 60 m, long-span above about 120 m. A sketch shows deck, girders, bearings, piers, abutments, wing walls, foundations, kerbs, footpath, railings, HFL and scour levels.

## Answer

#### Classification by superstructure (type of structure)
| Type | Description |
|---|---|
| Slab bridge | RCC slab spans, up to about 10 m |
| Girder bridge | RCC T-beam girders with deck slab up to about 25 m; PSC/steel girders up to about 40 m; more with PSC box girders |
| Truss bridge | Triangulated steel members, 40–100 m or more |
| Arch bridge | Masonry/RCC/steel arch that carries the load mainly in compression |
| Cable-stayed | Deck supported by inclined cables from towers, about 100–1000 m |
| Suspension | Deck hung from main cables over towers; the longest spans (above about 500 m) |
| Rigid frame/box culvert | Deck and piers/walls cast monolithically as a frame |

#### Classification by span length (IRC / DoR practice)
- **Culvert:** total length up to 6 m (IRC definition).
- **Minor bridge:** total length from 6 m to 60 m.
- **Major bridge:** total length above 60 m.
- **Long-span bridge:** individual spans above about 120 m.
- Some textbooks instead take minor bridges as about 8–30 m and major bridges as above 30 m.

#### Sketch of bridge sections and plan

```text
 LONGITUDINAL SECTION
       Deck slab + wearing coat       Railing
  ___________________________________  ___
 |==================================|
  Abutment  Bearing  Girder  Pier   Abutment
  |  |       ^   ^                  |  |
  Wing   HFL ~~~~~~~~~~~~~~~~~~~~~~~~  Wing
 wall    Foundation level below scour
 CROSS SECTION
  Kerb  Carriageway  Kerb  Footpath
 |_|______________|__|_|
   ===== deck slab ======
    [girder] [girder] [girder]
 PLAN
 ----------------------------------
  W.wall |  carriageway          | W.wall
 ----------------------------------
```
Elements shown: deck slab, girders, bearings, piers, abutments, wing walls, foundations, kerbs, footpath, railings, and the HFL and scour levels. Approach slabs are placed behind each abutment, at the ends of the deck.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which superstructure type is suited to the longest spans (above about 500 m)?
   A. Truss bridge
   B. Girder bridge
   C. Suspension bridge
   D. Slab bridge
   Answer: C. A suspension bridge hangs the deck from main cables on towers and is used for the longest spans, above 500 m. (Key point: Superstructure types and spans)

2. A simple RCC slab bridge is normally used for spans up to about:
   A. 10 m
   B. 40 m
   C. 100 m
   D. 200 m
   Answer: A. Slab bridges are economical only for short spans, up to about 10 m; girders take over beyond that. (Key point: Slab bridge)

3. According to the IRC classification given, a bridge of total length 45 m is a:
   A. Culvert
   B. Minor bridge
   C. Major bridge
   D. Long-span bridge
   Answer: B. Minor bridges are 6 m to 60 m; culverts are below 6 m and major bridges above 60 m. (Key point: Classification by span length)

4. Which set of elements transmits load from the girders down to the ground in the sketched bridge?
   A. Railing, kerb, footpath
   B. Bearings, piers and abutments, foundations
   C. Wearing coat, approach slab, wing wall
   D. Deck slab, railing, HFL marker
   Answer: B. Girders pass reactions through bearings to the piers and abutments, then to the foundations below scour level. (Key point: Bridge elements in the sketch)

## Related in Transportation Engineering II

- [Classification of bridges by structure, material, loading](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Abridge-classification-structure-material-loading) — Transportation Engineering II, chapter 5

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