Cribtest

BRANCH CORPORATION
(802) 368-7112
branch@ sover.net

Destructive testing of box cribbing used in the Emergency Services: This testing is not for the purpose of defining the best material used for cribbing but rather to show how different types of material behaves when loaded to there limits. In this way Rescuers can best stabilize an emergency scene.

We have chosen a scenario and will attempt to follow the recommendations of E.S.R. and F.E.M.A..

Scenario: An emergency requiring large amounts of cribbing capable of holding heavy loads has accrued. A call is sent out to available sources for 4" X 4" stock. One is to a local lumber yard that can supply units of P.T. southern yellow pine. another is to a soft wood mill that has units of eastern spruce and yet another is to a hard wood mill that has maple.
Samples were collected and brought to a *100 ton press where 4 point box cribs were constructed with approximately 32 square inches of support. They were then pressed to failure and analyzed and examined during the process.

Units are usually bound in 4 ft. x 4ft. x 8 ft. long. Most yards have fork lifts to facilitate loading. Don't over look the use of dump trucks for delivery.

In order to establish how each type of material would behave it was decided to use the weakest link theory. A box crib consisting of dry maple, pine, spruce, and wet maple was pressed. No pressures were recorded.

Now we had a idea what to expect.

There has been some concern that dry Hardwood would fail catastrophically under a destructive load. This piece of dry (11% moisture content) Maple was pressed until it could no longer hold a load of 60.tons. No catastrophic failure accrued.

Pressure treated southern yellow pine compressed 3 1/2 in. before failure at 20 tons. At 21 tons the entire stack could no longer hold the maximum load and would collapse if the load was increased.

Eastern spruce compressed 3" in before failure at 20 tons. At 21 tons the stack could no longer hold the maximum load and would collapse if the load was increased.

Semi dry soft maple compressed 1 1/2 " and held 60 tons. Pressure was increased but held at 60 tons. The stack was able to hold 60 tons as it was compressed. This ability will be explored further.

New red maple compressed 1 1/2 " and held 63 tons, (126.000 lbs.).

More information will be posted as it becomes available.

* The press had two hydraulic gages installed one new and one shop certified. the pressing was conducted in public , Chief David Emery of Brattleboro VT. fire department was present. Bob Jamrog PME.Ret. G.M. systems consultant. The 100 ton pres was operated by Lester Dunklee.

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