Details:

Personal Author:
Mangelsdorf, C. P. ;
Corporate Authors:
United States. Bureau of Mines. ;
Description:
"When the finely bedded shale frequently encountered over coal seams experiences a separation, the material below the separation must behave like a beam or plate in that it must resist both bending and shear. Because of the weakness in interlaminar shear inherent in such strata, shear deflections that are usually ignored in isotropic beam theory may account for a significant part of the total roof sag. Similarly, when a roof truss is installed in such a roof the upward displacement reducing the sag will have components due to shear as well as bending. Questions asked by mine operators about the installation of roof trusses frequently deal with optimum position, slope, and initial tension of the inclined chords. This Bureau of Mines report examines the effects of those chord parameters on the strain energy of both shear and bending and offers optimum values that will minimize the total strain energy of the immediate roof. Design charts are provided, several design examples are included, and the results are compared with current practice. The effects of in situ stresses are investigated and are shown to be equivalent to an additional load on the beam." - NIOSHTIC-2 NIOSH no. 10006155
Subject:
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Mine Roof Control.
Roof Trusses.

Document Type:
Report ;
Collection(s):
National Institute for Occupational Safety and Health
Main Document Checksum:
[+]
urn:sha256:c1d1a67b1dce0a6c32fa3c3b2312afe2cf69a0254e803cad8bb819e8a8cdfda6
File Type:

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