What are 2 methods of determining the minimum surface area needed for blocking and cribbing under a crane's outriggers?

• A. Multiply the crane's outrigger float area by 3 and divide the maximum capacity of the crane by 5 (for square feet)
• B. Multiply the outrigger float area by 2 and divide the maximum capacity by 3
• C. Add 5 square feet to the outrigger area
• D. Use a fixed 12 square feet per outrigger

Answer: (A)

When determining the minimum surface area for blocking and cribbing under outriggers, you must account for both the outrigger footprint and the crane’s loading. The recommended method uses two parts: first, take the outrigger float area and multiply it by three to add a safety margin around the contact area. Second, take the crane’s maximum capacity and divide it by five to convert that capacity into an additional area expressed in square feet. Add these two results together to get the required minimum surface area. This combines real-world footprint with capacity-based needs, covering both bearing requirements and load effects, including dynamic factors. The other approaches either rely on a fixed value, apply a single factor, or ignore the crane’s capacity, which can lead to undersized or unnecessarily large blocking.