Ground Bearing Pressure and Outrigger Setup Flashcards
7 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 7 Ground Bearing Pressure and Outrigger Setup flashcards as text
When calculating ground bearing pressure under an outrigger float, you divide the outrigger load by which value?
Answer: The float contact area
Ground bearing pressure (GBP) equals the outrigger reaction load divided by the contact area of the outrigger float or pad.
A crane is set up on asphalt in summer heat. What is the primary concern regarding outrigger pads?
Answer: Asphalt can soften and allow pads to sink or shift under load
Hot asphalt loses bearing capacity and can deform under concentrated outrigger loads, causing the crane to shift or tip.
Which outrigger configuration provides the greatest crane lifting capacity?
Answer: All outriggers fully extended and set
Full outrigger extension maximizes the tipping fulcrum distance, providing the greatest load chart capacity.
What term describes the tendency of a crane to rotate about its tipping axis when a load is lifted?
Answer: Overturning moment
The overturning moment is the rotational force created by the load and boom weight acting against the crane's stability.
Before placing timber cribbing under outrigger pads, what must be confirmed about the cribbing material?
Answer: It must be sound, free of rot, and of adequate dimensions to distribute load
Deteriorated or undersized cribbing can fail under load; sound lumber of correct dimensions is required to safely spread the outrigger load.
A crane manufacturer's load chart specifies 'on outriggers, fully extended.' Using mid-range outrigger extension means:
Answer: The operator must use a reduced capacity or a separate mid-extension load chart if provided
Load charts are configuration-specific; lifting at mid-extension without an applicable chart or derating violates safe operating procedures.
When outriggers are deployed over a utility vault or underground structure, the primary hazard is:
Answer: Collapse of the underground structure under the concentrated outrigger load
Underground vaults, culverts, and utilities may not support the concentrated point loads from crane outriggers and can collapse suddenly.