Change detection and deformation monitoring of concrete structures using terrestrial laser scanning

Concrete structures are routinely monitored to detect change and deformation in the field of engineering surveying and other overlapping disciplines such as civil and structural engineering. The monitoring of civil infrastructure is crucial to the safe operation and the longevity of the system. There is growing demand for the development of reliable non-destructive testing techniques for concrete structures in the assessment of the deteriorating condition of infrastructures or in an event of fire-damaged structures. This research investigated the use of terrestrial laser scanning (TLS) for structural health monitoring and the implemented workflow is designed for non full-waveform laser scanner data. Although the use of TLS is not new within the domain of structural health monitoring, the novelty of this research lies in the application of the technology in the specific area of assessing fire-damaged concrete on one hand and the assessment of robust point cloud processing algorithms for precise structural deformation analysis on the other hand. Laser intensity information has become an important object of study in recent years and several studies have shown the potential use of laser intensity data for a great variety of applications such as geomorphology, forestry and glaciology (Holfe and Pfeifer, 2007; Antilla et. al., 2011; Kaasalainen et al., 2011a). Laser intensity information can be used to aid segmentation and classification algorithms alongside geometrical information (Krooks et al., 2013). This evidence for detecting and classifying different materials using the laser intensity values necessitated an investigation into the idea of using the TLS intensity for post fire assessment of concrete. The use of TLS intensity to detect and assess fire-damaged concrete is a new area of research. In terms of the application of TLS for structural change detection and deformation monitoring, TLS is able to provide continuous spatial resolution and reliable 3D information with high redundancy. However, a recent review of studies that have applied TLS for change detection and deformation monitoring of structures has shown that the exploitation of the high data redundancy acquired by TLS is key to achieving good deformation measurement performance with TLS data and that this calls for the development and testing of robust tools. This being the case, several issues are still open to investigation such as rigorous methods of point cloud processing for change detection and deformation analysis. In view of this, the study also aimed at investigating and assessing algorithms for deformation analysis. This thesis presents the work undertaken during the entire period of the research project. The objectives of this research were twofold i.e. detecting and assessing fire-damaged concrete and well as structural deformation monitoring using laser scanning technique. In particular, the technique employed in detecting fire-damaged concrete involved modelling and analysing the laser intensity return. In the case of structural deformation monitoring, the study investigated robust techniques of processing laser scanner data for deformation analysis. This involved assessing the capability of using the multiscale model to model cloud comparison (M3C2) and the iterative similarity registration (ISR) algorithms for processing laser scanner data for deformation analysis. The achieved positive results relating intensity to exposure temperature of concrete demonstrate that laser scanning can be applied to detect and assess fire-damaged concrete and provide an understanding of the condition of concrete in relation to the strength changes of concrete when it is heated to elevated temperatures. In terms of structural monitoring, the study has ascertained that the M3C2 and the ISR algorithms are capable of resolving small scale displacements in the millimetre range which are needed in structural monitoring, due to their robustness

Change detection and assessment of fire-damaged concrete using terrestrial laser scanning

Fire is one of the serious potential hazards to most structures and damage assessment is the first and the most important job for structural safety evaluation of a structure subjected to fire. The extensive use of concrete as a structural material has neccessitated an investigation into more robust and cost-effective techniques for the assessment of fire-damaged concrete using terrestrial laser scanning. Although concrete is known to be a fire resistant structural material, it undergoes severe changes when exposed to elevated temperatures and this can affect the load bearing capacity of structural bearing elements in several ways. Apart from spalling, there can be a permanent loss of strength in the remaining material. In the aftermath of a fire on a structure, various workers get involved in a variety of response and recovery from disaster operations. Furthermore, following a catastrophic failure of a structure after a fire, rescue workers and emergency responders may be required to enter the fire-damaged structure which can be risky and so an assessment method which has the potential to improve safety was investigated. Within the field of structural and civil engineering, the methods employed in assessing fire-damaged concrete involve both field and laboratory investigations to determine the extent of fire damage in order to design appropriate and cost effective repairs or to decide whether to demolition the structure. Concrete structures show significant loss of strength when heated above 300ºC. This study aimed at investigating whether terrestrial laser scanning can be used to detect fire-damaged concrete using specimens heated up to 1000ºC as it is important to estimate the maximum temperature attained in a fire. The results obtained from the study clearly demonstrated the feasibility of using terrestrial laser scanning to detect fire-damaged concrete via modelling and analysis of laser returned intensity. Laser scanning has emerged as a complementary assessment method of fire-damaged concrete with a couple of advantages in that the whole concrete element can be scanned and an average intensity value over the area concerned can be determined which would represent the whole element overcoming the challenge of some traditional methods where cores are drilled in limited areas. Scanning is rapid with millions of points measured in a few seconds. Laser scanning of the fire-damaged structure can be done from a distance without having to enter the structure and this improves safety. Laser scanning is a non-destructive technique for detecting fire-damaged concrete

A non-destructive technique for health assessment of fire-damaged concrete elements using terrestrial laser scanning

Concrete structures are routinely monitored to detect changes in their characteristics in the field of engineering surveying and other disciplines such as structural and civil engineering. There is growing demand for the development of reliable Non-Destructive Testing (NDT) techniques for concrete structures in the assessment of the deteriorating condition of infrastructures or in an event of fire-damaged structures. In this paper, the feasibility of using Terrestrial Laser Scanning (TLS) technology for change detection and assessment of fire-damaged concrete has been investigated through measurements and analysis of laboratory size concrete specimens that underwent heating up to 1000°C. The TLS technique employed in detecting fire-damaged concrete involved modelling and analysis of the TLS intensity returns as well as RGB image analysis. The results obtained clearly demonstrate the feasibility of using TLS to detect fire-damaged concrete. Although the laser scanners used in the study have different wavelengths, the results obtained in both cases are promising for a detection technique of fire-damaged concrete structures

Change detection and deformation monitoring of concrete structures using terrestrial laser scanning

Concrete structures are routinely monitored to detect change and deformation in the field of engineering surveying and other overlapping disciplines such as civil and structural engineering. The monitoring of civil infrastructure is crucial to the safe operation and the longevity of the system. There is growing demand for the development of reliable non-destructive testing techniques for concrete structures in the assessment of the deteriorating condition of infrastructures or in an event of fire-damaged structures. This research investigated the use of terrestrial laser scanning (TLS) for structural health monitoring and the implemented workflow is designed for non full-waveform laser scanner data. Although the use of TLS is not new within the domain of structural health monitoring, the novelty of this research lies in the application of the technology in the specific area of assessing fire-damaged concrete on one hand and the assessment of robust point cloud processing algorithms for precise structural deformation analysis on the other hand. Laser intensity information has become an important object of study in recent years and several studies have shown the potential use of laser intensity data for a great variety of applications such as geomorphology, forestry and glaciology (Holfe and Pfeifer, 2007; Antilla et. al., 2011; Kaasalainen et al., 2011a). Laser intensity information can be used to aid segmentation and classification algorithms alongside geometrical information (Krooks et al., 2013). This evidence for detecting and classifying different materials using the laser intensity values necessitated an investigation into the idea of using the TLS intensity for post fire assessment of concrete. The use of TLS intensity to detect and assess fire-damaged concrete is a new area of research. In terms of the application of TLS for structural change detection and deformation monitoring, TLS is able to provide continuous spatial resolution and reliable 3D information with high redundancy. However, a recent review of studies that have applied TLS for change detection and deformation monitoring of structures has shown that the exploitation of the high data redundancy acquired by TLS is key to achieving good deformation measurement performance with TLS data and that this calls for the development and testing of robust tools. This being the case, several issues are still open to investigation such as rigorous methods of point cloud processing for change detection and deformation analysis. In view of this, the study also aimed at investigating and assessing algorithms for deformation analysis. This thesis presents the work undertaken during the entire period of the research project. The objectives of this research were twofold i.e. detecting and assessing fire-damaged concrete and well as structural deformation monitoring using laser scanning technique. In particular, the technique employed in detecting fire-damaged concrete involved modelling and analysing the laser intensity return. In the case of structural deformation monitoring, the study investigated robust techniques of processing laser scanner data for deformation analysis. This involved assessing the capability of using the multiscale model to model cloud comparison (M3C2) and the iterative similarity registration (ISR) algorithms for processing laser scanner data for deformation analysis. The achieved positive results relating intensity to exposure temperature of concrete demonstrate that laser scanning can be applied to detect and assess fire-damaged concrete and provide an understanding of the condition of concrete in relation to the strength changes of concrete when it is heated to elevated temperatures. In terms of structural monitoring, the study has ascertained that the M3C2 and the ISR algorithms are capable of resolving small scale displacements in the millimetre range which are needed in structural monitoring, due to their robustness