OasisLMS

Abstract: A valuable objective of statically load testing deep foundations is to determine load-transfer response. Integral to this objective is determining internal forces at various elevations within the deep-foundation element. These internal forces are often calculated from strain measurements (strain measurements do not determine internal forces directly). Strain measurements can sometimes yield atypical results, with multiple strain gauges at given strain-gauge level (i.e., the same depth/elevation) providing significantly different individual readings, or the deep-foundation element changing effective rigidity (composite-section elastic modulus times total cross-section area, EA) during the test. A case history will be presented in which both: a) atypical results occurred simultaneously at multiple strain-gauge levels, and b) effective rigidity changed during the test. The strain data were evaluated using the Incremental Rigidity (“ I.R.” ) method. At each strain-gauge level which provided atypical strain readings, the differing readings from multiple individual gauges, as well as the gauges’ average, were evaluated using I.R. In addition, I.R. was employed to interpret the change in effective rigidity at the individual strain-gauge levels during the test. The resulting load-transfer responses are reasonable, and so demonstrate the usefulness of applying I.R. to atypical strain data, thus providing a means of interpreting internal forces at strain-gauge levels which might otherwise have to be disregarded (i.e., “ salvaging” a strain-gauge level). A brief overview of the Incremental Rigidity method is provided, and conclusions are presented regarding its usefulness in interpreting individual atypical strain data (differing individual readings at a strain-gauge level) and the average of those differing data, as well as modelling change in effective rigidity at individual strain-gauge levels during the test.

Mr. VAN E. KOMURKA; Mr. SETH ROBERTSON

Annual Conference Proceedings