Limiting vertical deflection of gantry girders carrying EOT cranes with capacity less than 500 kN is
- AL/500
- BL/600
- CL/750Correct
- DL/1000
Solution
Concept
Deflection limits for EOT gantry girders
Formula
NONE
Step-by-step solution
1. Gantry girders supporting electric overhead traveling (EOT) cranes must satisfy serviceability deflection limits. 2. For EOT cranes with a capacity of less than 500 kN (50 tonnes), IS 800 limits maximum vertical deflection to Span/750 (L/750). 3. For crane capacities greater than 500 kN, the limit is increased to Span/1000 (L/1000). Answer: C
Explanation
Gantry girders supporting electric overhead traveling cranes undergo dynamic moving loads during operation. For cranes with a capacity under 500 kN, design codes specify a maximum vertical deflection limit of L/750. This constraint ensures smooth crane motion and prevents operational misalignment or excessive vibration.
Why the other options are wrong
A) L/500 is the deflection limit for gantry girders supporting manually operated cranes. B) L/600 is the limit for EOT cranes with capacity greater than 500 kN. D) L/1000 is a stringent limit typically used for heavy industrial or precision crane gantries.
Shortcut
EOT crane gantry girder limit for capacity under 500 kN is L/750 (over 500 kN is L/1000).
Common mistake
Confusing deflection limits for EOT cranes under 500 kN capacity (L/750) with those for higher capacity cranes (L/1000) or manual cranes.
Correct answer: C) L/750