Dynamic assessment of structural building components.

Abstract

The development of methods that correlate the measure of dynamic parameters with the condition of the structure has received a considerable attention from the engineering community in the last few years. In the field of structural assessment of buildings, dynamic testing can be used to extend the inspection to every structural component, covering the gaps left by other more complex techniques (such as core extraction or load testing). The information obtained by the dynamic means is not restricted only (as traditional methods are) to the location in which the tests is developed while the use of a low number of sensors and simple excitation devices helps to reduce dramatically the cost of implementation.<br/>The general objective of the thesis consists on the demonstration of the usefulness of dynamic assessment on building components (such as masonry walls, stone piers or RC beams and slabs) using a simple-layout experiment but based intensively in numerical simulation.<br/>The methodology to achieve the objective include tasks such as:<br/>- The study the influence of different parameters on dynamic behavior of structures. This process -also known as parametrical study- recognizes the influence of the variables when performing a model updating. <br/>- A series of laboratory campaigns to identify the influence of different structural damages on dynamic parameters. Studied damage-influence include: Stiffness deterioration by cracking on supported or suspended beams, carbonation of concrete, sulfate attack on concrete and rebars, chloride attack on concrete and axial load on masonry walls and piers. <br/>- The application of a simple-layout method of dynamic assessment in real-life buildings. In some of those cases, static load test (direct identification method) is also developed to compare the reliability of the dynamic approach. <br/>Experimental works and field studies carried out in this investigation have permitted to conclude that a combined implementation of a simple dynamic testing and numerical modeling is able to characterize the current structural conditions of a building component. The proposed dynamic assessment layout has conduced to the identification of characteristics such as boundary conditions, cracking levels, geometry properties or levels of axial loading. By comparing systematically the experimental and the numerical frequencies, it can also be concluded that a detailed model is able to predict the dynamic behavior of a building component. This prediction was accurate not only for undamaged conditions, but also for different damage scenarios. The present research has contributed to ascertain that dynamic testing is a valuable tool to assess the structural conditions of single concrete or masonry building elements such as concrete beams, RC or prestressed slabs, masonry walls or stone piers.