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Design methods to enhance the capacity, stiffness, and timber utilization of wood.

Authors
Barczak-TM; Gear-DF
Source
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9494, 1994 Jan; :1-15
Link
NIOSHTIC No.
10012276
Abstract
This U.S. Bureau of Mines report describes methods to enhance the capacity, stiffness, and timber utilization of wood crib supports. Since stiffer supports minimize strata deflections that contribute to roof instability, efforts to maximize crib stiffness while maintaining stability through a wide displacement range should be a design priority. The stiffness and capacity of conventional crib designs, employing alternating layers of wood timbers that are loaded perpendicular to the grain, can be increased by increasing the interlayer contact area or by using higher strength wood. Contact area can be increased by using wider timbers or employing more timbers per layer. Concepts that provide parallel-to-the-grain timber loading will provide substantial increases in crib stiffness and capacity. Two concepts that utilize this principle are examined: (1) an original South African design that constructs wood cribs from preformed layers (mats) of timber where short blocks are oriented vertically between horizontal slabs; and (2) a design that employs full lengths of timber placed vertically in the interior of a conventional crib structure. These designs also provide more efficient timber utilization by providing greater support capacity per volume of wood used in the crib construction.
Keywords
Shoring; Structural-timber; Stiffness; Mechanical-properties; Oak-wood; Poplar-wood; Mine-safety; Strata-control; Roofs; Compressive-properties; Design-criteria; Birch-wood; Hardwoods; Softwoods; Crib-walls; Coal-mines; Wooden-structures; Mining-industry; Underground-mining
Publication Date
19940101
Document Type
Report of Investigations
Fiscal Year
1994
NTIS Accession No.
PB94-127867
NTIS Price
A03
Identifying No.
RI-9494
ISSN
1066-5552
NIOSH Division
PRC
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9494
State
PA
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