Bridge trackwork: Wooden sleepers placed on girder bridges are typically fabricated from which durable timber species for long service life?

Introduction / Context:
Bridge track flooring often uses timber sleepers mounted on steel girders to carry rails. The choice of timber must resist decay, moisture, and mechanical wear while holding spikes/fastenings securely. This question asks which species is generally selected for bridge sleepers in railway practice.

Given Data / Assumptions:

• Application: Sleepers on steel or composite girders of bridges.
• Required properties: High durability, dimensional stability, resistance to rot and insects, good spike-holding.

Concept / Approach:
Teak is renowned for natural oils, high durability, and excellent resistance to weathering and insects. It maintains fastenings securely and withstands cyclic loading and moisture at bridge locations. While Sal is strong and used widely for plain track sleepers, teak is typically preferred on bridges where longevity and fastening reliability are paramount.

Step-by-Step Solution:

Verification / Alternative check:
Standard railway specifications and bridge maintenance manuals commonly reference teak (or pre-stressed concrete in modern practice) for severe exposure locations; among the timbers listed, teak scores highest for durability class and dimensional stability.

Why Other Options Are Wrong:

• Sal: Strong and common for track, but less weather-resistant than teak on bridges.
• Deodar and Chir: Softer and less durable; not preferred for high-duty bridge sleepers.
• Bamboo: Not a standard sleeper timber for bridges.

Common Pitfalls:

• Confusing general track sleeper timber (Sal) with the higher durability demands on bridges.
• Ignoring the importance of fastener retention under vibration and moisture.

Final Answer:
Teak