APPLICATION OF LEAST ABSOLUTE SUM (LAS) TECHNIQUE FOR DETECTING DEFORMATION OF STRUCTURES
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Date
2016-03
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Publisher
NIGERIAN INSTITUTION OF SURVEYORS
Abstract
This study focuses on the deformation analysis using a geodetic method known as the Least Absolute Sum. The method consist mainly of independent adjustment of each epoch data, Compatibility test on their a-posteriori variances, followed by determination of trends of movement for all the common points in the network. A triangulation network was designed consisting of 45 YTT series second order control points within the study area resulting in a total of 63 triangles, 189 observations and 90 unknown parameters with 90% degrees of freedom. The network adjustment was done using the method of least squares observation equation. The estimated variance factors for the 2D (Horizontal) network were 7.82989325645394e-08 and 7.7207636996395e-08 while 0.03944 and 0.052339 represent the estimated variance factors for the 1D (height) for the first and second epochs respectively. The compatibility of the two epoch data was tested with the variance ratio and the compatibility test passed. Actual displacement vectors were computed and transformed into the same computational base using S-transformation by Least Absolute Sum (LAS), stable and unstable points were determined using single point displacement test. The displacement vector magnitude was computed, represented graphically to indicate possible trends of movement that might have occurred. This study finds Least Absolute Sum (LAS) technique useful in studying the deformation of large engineering structures such as high rise buildings, bridges, dams, oil exploration zones, mining sites and land slide monitoring.
Description
Quality Research
Keywords
Epoch, Coordinates, Least Square Adjustment, Compatibility Test, Deformation Analysis, Least Absolute Sum (LAS )