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Strain Energy as a Basis for Optimizing Roof Truss Installations in Bedded Roof.

Authors
Mangelsdorf-CP
Source
MISSING :24 pages
Link
NIOSHTIC No.
10006155
Abstract
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.
Publication Date
19880101
Document Type
IH; Report of Investigations;
Fiscal Year
1988
NTIS Accession No.
NTIS Price
Identifying No.
RI 9182
NIOSH Division
PRC;
Source Name
MISSING
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