Finite element model updating of a stone masonry tower using 3D laser scanner and accelerometers

Abstract

This study’s main objective was to investigate the dynamic response of the ancient masonry stone tower Slottsfjelltårnet located in the oldest city of Norway, Tønsberg. The study takes in use several fields in the process for the extraction of the dynamic response of the tower and the calibration of it in a finite element software.

The emphasis on finding the dynamic response of heritage structures using nondestructive tests and without hindering the daily operations paved the way to use operational modal analysis, which allows for attaining the dynamic characteristics without interfering with the daily activities of the structure.

The study was carried out with the initial scanning and mapping on the inside and outside of the tower with the use of 3d laser scanners. This data was used to model the structure in the building information modeling software, Autodesk Revit. The model was in turn imported into the finite element software Diana FEA, which was used for analysis and later calibration.

Secondly, the core part of the study took in use ambient vibration testing and operational modal analysis to extract the dynamic characteristics of the tower in operational conditions. Accelerometers were placed on the structure which gave readings that were then processed, which sequentially gave the dynamic behavior of the tower.

The third and final part of the study included both the modeling of the structure and the results from the operational modal analysis and ambient vibration testing in order to calibrate the finite element model, according to the extracted data. The process was performed on two different models with the use of soil-structure interaction and without it, where the different methods were modeled and evaluated. Results were then compared, where the material properties and other aspects were presented for comparison.

The procedure of operational modal analysis, with ambient vibration testing and modeling of the structure using 3d laser scanners is assessed towards available literature. Furthermore, previous studies and theory concerning the main aspects of the study are also presented.