Structural Deformation Monitoring Survey Of Nnamdi Azikiwe University Main Library, Awka, Anambra State

Abstract

Deformation refers to the changes a deformable body undergoes in its shape, dimension and position. Deformation monitoring surveys constitute a systematic high-precision process of measuring and analyzing changes in position of natural or man-made features over a period of time to detect movement or displacement. Deformation monitoring surveys utilizes high-precision instrumentation such as geodetic GNSS receivers, total stations, laser scanners, digital micrometers, extensometers, and tilt sensors to observe, record, and interpret spatial changes to the millimeter. This enables the assessment of structural integrity and associated construction risks, and provide data for engineering analysis, construction management or early-warning systems. Nnamdi Azikiwe University main library is multi-story building whose foundation was designed to support very heavy gravity loads and to withstand the lateral forces imposed by winds and potential ground movements. But in view of the fact that a structural failure can lead to potential loss of life and property, it is very important to initiate and maintain a continuous deformation monitoring of this structure in order to ensure that it is exhibiting safe deformation behavior. Such monitoring provides us with the opportunity to identify anomalies that may signal unusual loading conditions or modified structural behavior, which can in the extreme case cause damage or catastrophic structural failure. To monitor this structure, second order geodetic reference stations were established on stable areas surrounding the building using GNSS receivers running on static mode. Deformation stations established on load bearing columns on the building were observed from the geodetic reference stations using static GNSS observation campaign in three epoch schemes spanning a period of 30months. After processing the field obtained data using post-processing software and precise orbit parameters, an analysis of the position coordinates across the baseline epoch and the final (third) epoch shows a minimum position difference of 0.0014m at DFN 2 and a maximum position difference of 0.0024 at DFN 4. Analysis of height difference across the same epoch shows a minimum height difference of 0.0016m at DFN 2 and 0.0032m at DFN4, which imply that the building was structurally stable within the observation session. Conclusively, it was recommended that although, the building under study lacked a monitoring scheme ab initio, since this research has developed a schema, it is necessary that this monitoring be maintained so as to enable continuous modeling of its structural integrity.

Keywords: GNSS; GNSS Receivers; Deformation; Structural Integrity; Static GNSS Observation.