A New Approach for Health Monitoring of Structures: Terrestrial Laser Scanning

TLDR

Three‑dimensional coordinates from terrestrial laser scanning can have errors up to about 10 mm, which is too large for structural health monitoring, whereas GPS can only measure displacements at the antenna, so TLS offers a realistic solution for monitoring entire buildings or bridges at both structure and member levels. The study proposes a new terrestrial laser scanning approach and a displacement measurement model to improve accuracy for structural health monitoring. The displacement model was experimentally validated on a simply supported steel beam using LVDTs, strain gages, and a fiber‑optic sensor, and it enables continuous health monitoring through periodic deformation measurements and inverse structural analysis. The TLS model estimates maximum deflections within 1 mm and 1.6 % of LVDT measurements, and it can automatically generate 3D finite element models of structural members or entire structures at any time.

Abstract

Abstract: A new approach is presented for health monitoring of structures using terrestrial laser scanning (TLS). Three‐dimensional (3D) coordinates of a target structure acquired using TLS can have maximum errors of about 10 mm, which is insufficient for the purpose of health monitoring of structures. A displacement measurement model is presented to improve the accuracy of the measurement. The model is tested experimentally on a simply supported steel beam. Measurements were made using three different techniques: (1) linear variable displacement transducers (LVDTs), (2) electric strain gages, and (3) a long gage fiber optic sensor. The maximum deflections estimated by the TLS model are less than 1 mm and within 1.6% of those measured directly by LVDT. Although GPS methods allow measurement of displacements only at the GPS receiver antenna location, the proposed TLS method allows measurement of the entire building's or bridge's deformed shape, and thus a realistic solution for monitoring structures at both structure and member level. Furthermore, it can be used to create a 3D finite element model of a structural member or the entire structure at any instance of time automatically. Through periodic measurements of deformations of a structure or a structural member and performing inverse structural analyses with the measured 3D displacements, the health of the structure can be monitored continuously.