Load-deformation characteristics of multiple stump anchor systems Public Deposited

http://ir.library.oregonstate.edu/concern/defaults/bg257k89b

Graduation date: 1985

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  • This paper documents the development of a model which determines multiple stump anchor system displacement as a response to skyline load for four anchor rigging configurations: 1. Series multiple, 2. Tieback, 3. Elevated tieback, and 4. Equalizer block. It also documents the field testing of four two stump anchors rigged in the four rigging configurations. A comparison of the model and field results is presented, as well as discussion of load transfer from the skyline to the second stump. Diagrams are presented which illustrate the model loaddeformation curves for a variety of stump sizes and pretensions between the two stumps prior to skyline loading. Also presented on these diagrams re the loads at which system failure occurs. Load-deformation curves for all four rigging configurations are similar when the two stumps are the same strength. When one stump is weaker than the other, the equalizer block system load-deformation curve is different from the curves for the other three systems, and the system fails at a lower total load. Four sets of two stumps were field tested in the four rigging configurations. Within a load range common to all rigging configurations, the load-deformation curves for the four rigging configurations were similar. Load-deformation curves for the model and field test data were compared. Curves were most similar for the series multiple and high pretension tieback configurations. Since the load-deformation characteristics for the series multiple and the two tieback systems are similar, the preferable system is the one that is easiest to rig. The series multiple system requires less hardware to rig because the skyline is used as the link between the two stumps, rather than a twister. Consequently. the series multiple system appears to be the preferred system. The equalizer block system appears to be the least preferred system because it is likely to fail at a lower system load than the other systems. The results presented are of limited scope. The field data was collected during August 1984 when soil moisture conditions were relatively dry, and the model computations are restricted because the linkage between the stumps was assumed to be rigid. It is recognized that the capacity of a stump to resist applied loads might be influenced by varying soil moisture contents, particularly at a saturated level. However, the tests documented in this report were conducted when soil moisture was at a low level. The resulting load-deformation curves can be expected to change in magnitude as soil moisture content varies. The model load-deformation curves were developed with the assumption that the linkage between the two stumps was rigid. The linkage is not rigid in a real anchor system. The positions of the system load-deformation curves may change if the linkage length is affected by line stretch, line travel, or wood crushing. The ranking of the four systems from preferred to least preferred could change if these three factors were included in the multiple stump model.
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  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2009-05-04T23:00:00Z (GMT) No. of bitstreams: 1 Toupin, Richard MF.pdf: 645382 bytes, checksum: 7d28a89a86cc00a47d67f9bc1900b9cb (MD5)
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