Principles of Crane Stability and Structural Integrity Flashcards
6 cards from real NCCCO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Principles of Crane Stability and Structural Integrity flashcards as text
What is the tipping line of a crane and why is it significant?
Answer: The axis around which the crane would rotate if it tipped over
The tipping line is the axis about which the crane would rotate during a tipover, typically the line between the outermost support points on the side toward the load.
How does increasing the boom radius (working radius) affect crane stability?
Answer: It decreases stability by increasing the overturning moment relative to the restoring moment
Increasing the working radius moves the load farther from the crane's rotation axis, increasing the overturning moment and requiring reduced rated capacities to maintain the required stability safety factor.
What structural component limits the maximum load a crane can lift based on material strength rather than stability?
Answer: The structural limit, governed by the boom chord and lacing member capacity
Structural limits are determined by the capacity of the boom, jib, and other structural members; at shorter radii where stability is not the limiting factor, structural strength of the boom sets the maximum rated capacity.
What effect does operating on a side slope have on crane stability?
Answer: Side slopes reduce stability by shifting the center of gravity toward the downhill side
Operating on a side slope shifts the crane's center of gravity toward the downhill side, reducing stability in the downhill direction and requiring derated capacities or leveling before operations.
What does it mean when a crane load chart lists a capacity with an asterisk (*)?
Answer: The capacity is limited by structural strength rather than stability
An asterisk (*) on most crane load charts indicates that the capacity at that radius is governed by structural strength limits rather than by stability limits.
How does the addition of a jib (fly) to a crane boom affect structural loading?
Answer: A jib increases bending moment at the boom tip and places additional compression loading on the main boom
A jib increases the effective radius and applies concentrated bending and compression loads at the boom tip and main boom head, requiring the crane to use jib-specific load charts with reduced capacities.