Long-term geodetic displacements. Evaluating the quality of measured displacements

Abstract

The displacements measured by geodetic methods have long been used by civil engineers to the structural safety control. For a normal structural behaviour it is possible to establish a simple model for describing the relations between the loads (gravity, temperature, hydrostatic pressure, etc.) and the structural response (e.g. displacements). Using data from many geodetic campaigns – displacements, campaigns dates, age of the structure, water level (in the case of dams), etc. – it is possible to create simple statistical/empirical models (linear regression models for effects separation) for supporting the analysis of the observed behaviour. Once the model is established it can be used to predict the displacements. The quality control of the displacements measured by geodetic methods should be based on the analysis of the compatibility of observations. Under some conditions the quality control cannot be performed due to the lack of redundancy of observations. In this case information about the expected displacements can help us to decide about the quality of the measurements. This paper presents the regression models usually considered in common structures (dams, buildings) to analyze the observed behaviour. A simple method using Excel functions to perform the regression and to build the functions for displacements prediction is presented. Some results from the application of this method on some large structures, two dams and a pavilion with a glulam structure, will be also presented.