Graduate Thesis Or Dissertation

Critical conditions for carriage passage at the support jack for uphill yarding

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  • Critical skyline and mainline tensions were identified as the conditions necessary for successful carriage passage uphill over an intermediate support jack. These critical tensions were measured during field tests and compared with predicted values from weightless line, rigid link, and catenary analyses. All three analyses predicted critical skyline tensions within the range of field measured values while critical mainline tensions were consistently overestimated. An existing computer multispan skyline analysis program (MSAP) was modified using the rigid link analysis to check for critical tensions at the support jack. A.comparison of MSAP results with measured field values showed good agreement for skyline tension and conservative estimates for mainline tension. As an alternative to the computer program, a graphical method for determining the critical midspan deflection was developed, patterned after the chain and board method. The analysis and test results indicated that present multispan design criteria for uphill yarding were overly conservative in many instances. To evaluate the economic effects of designing below system potential, yarding costs/mbf were compared, on a typical setting, based on predicted payloads using present and new design methods. Results of this comparison, based on payload effects only, showed that a considerable economic advantage existed when the new design procedure was used.
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