Structural Health Monitoring of Civil Infrastructure Systems

Vistasp M. Karbhari, F Ansari, Farhad Ansari

• Publisher: Woodhead Publishing
• Year: 2009
• ISBN:
  9781845696825
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Structural health monitoring is an extremely important methodology in evaluating the 'health' of a structure by assessing the level of deterioration and remaining service life of civil infrastructure systems. This book reviews key developments in research, technologies and applications in this area of civil engineering. It discusses ways of obtaining and analysing data, sensor technologies and methods of sensing changes in structural performance characteristics. It also discusses data transmission and the application of both individual technologies and entire systems to bridges and buildings.With its distinguished editors and international team of contributors, Structural health monitoring of civil infrastructure systems is a valuable reference for students in civil and structural engineering programs as well as those studying sensors, data analysis and transmission at universities. It will also be an important source for practicing civil engineers and designers, engineers and researchers developing sensors, network systems and methods of data transmission and analysis, policy makers, inspectors and those responsible for the safety and service life of civil infrastructure.

• Reviews key developments in research, technologies and applications
• Discusses systems used to obtain and analyse data and sensor technologies
• Assesses methods of sensing changes in structural performance

1

Structural health monitoring: applications and data analysis

F.N. Catbas University of Central Florida, USA

Abstract

This chapter first provides an overview of structural health monitoring (SHM) along with components of a complete monitoring design. These components are associated with fundamental knowledge needs, technology needs and also socio-organizational challenges for applications especially in the area of civil infrastructure systems. A successful SHM design requires addressing each of these considerations with an integrated approach offering various types of application scenarios for decision making. In this chapter, particular emphasis is given to data analysis and interpretation as a very critical aspect of SHM implementation. Some of the data analysis methods are presented with the goal of illustrating particular engineering applications and needs. Critical considerations for SHM data analysis and interpretations are discussed in terms of system characterization, sensing, data quality, presentation and decision making.

Key words

monitoring

sensing

computer vision

analysis

interpretations

prediction

decision making

bridges

1.1 Structural health monitoring (SHM) approach

SHM has matured as a routine practice in aerospace structures for many years. The approach is still being considered for routine applications for civil infrastructure systems. In developing an SHM design, the first step is to define the objectives of monitoring. At this point, it is important to discuss health and performance as these have major impact on successful SHM system development. While it is somewhat difficult to find commonly accepted terminology for health and performance in the literature, one recommended reference is an article that summarizes the activities of the ASCE SEI Technical Committee on Performance-Based Design and Evaluation of Civil Engineering Facilities by Aktan et al. (2007).

It would be proper to define the health of a structure as deviation from ‘a sound condition’ as a result of damage and deterioration that would warrant repair, retrofit or strengthening of the structure. For large civil structures, it may be difficult to set thresholds for health and health indices which can be monitored using a number of different methods and technologies. In bridge engineering practice in the US, the condition index (Federal Highway Administration (FHWA) 2005) is the most fundamental index related to health. There are other indices or metrics that are based on SHM data such as frequency change, flexibility, curvature, and displacement-based indices. The health can be continuously monitored by means of various tests and using various experimental measurements (Aktan et al. 2002a).

In order to discuss performance, formulation of objective and quantitative criteria for a limit-event (or a limit-state) need to be defined first. The desired performance is achieved by not exceeding in the limit states during the life-cycle of a structure. The most common limit-states that can be considered are safety, serviceability and durability of a structure or a structural component. Component or system reliability index can be considered as a performance index and has been utilized by engineers especially for the design of new structures or the evaluation of existing structures. The health monitoring data can be used along with various simulations and probabilistic methods to determine the performance indices (Catbas et al. 2008).

SHM is therefore typically employed to track health and evaluate performance, symptoms of operational incidents, anomalies due to deterioration and damage during regular operation and/or after an extreme event. A complete and successful SHM system can be achieved by means of the continuous measurement of the loading environment and the critical responses of a system or its components to provide necessary data for health and performance about the structural system (Aktan et al. 2000).

1.2 Components for a complete SHM

Although SHM is a maturing concept in the manufacturing, automotive and aerospace industries, there are a number of challenges for effective applications on civil infrastructure systems. There are many real-life SHM studies in the USA, Japan, Hong Kong and Europe, especially applications on highway and long span bridges. New advances in sensor and information technologies and the wide use of the Internet make SHM a promising technology for better management of such civil infrastructure. Large-scale, real-life studies have been presented at a number of specialty conferences and workshops. In spite of the recent advances in sensing, communication and information technologies, there are still challenges facing structural engineers for successful health monitoring applications. Fundamental knowledge needs, technology needs and socio-organizational challenges for routine applications are interrelated and have to be carefully addressed (Catbas et al. 2004). These challenges linked with the main components of a complete structural health monitor system are summarized in Fig. 1.1.

1.1 Main components of a complete health monitoring design and challenges.

A successful health monitor design requires the recognition and integration of these different components. Identification of health and performance metric is the first component which is a fundamental knowledge need and should dictate the technology needs and requirements. Current status and future trends to determine health and performance in the context of damage prognosis are reported by Farrar et al. (2003), Catbas et al. (2004) and Aktan et al. (2002b).

New advances in wireless communications, data acquisition systems and sensor technologies offer possibilities for SHM design and implementations (Lynch et al. 2001; Spencer 2003). Development, evaluation and use of the new technologies are important but they have to be considered along with our ‘health’ and ‘performance’ expectations of the structure. Socio-organizational challenges are important and often overlooked. Routine applications on reallife structures can be achieved if the value of the SHM can successfully be demonstrated to industry, government engineers and infrastructure owners when SHM can be utilized for better decision making. The ‘end-users’ would like to take advantage of SHM for efficient operation, timely maintenance, reduced costs, and improved safety. In that respect, the success metrics for the stakeholders (researchers, practicing engineers, infrastructure owners, decision makers, etc.) need to intersect to have broader acceptance and utilization of SHM especially for civil infrastructure applications.

1.3 Application scenarios for decision making

While the fundamental concepts and components of a complete SHM should be considered for applications, the needs and requirements may be different and may dictate the final design, application and data interpretation strategies. In this section, the application scenarios are discussed in relation to bridges, which are key civil infrastructure components. SHM may include the geometry for deformations, material properties for deterioration, mechanical properties such as flexibility, frequency and damping coefficients, intrinsic forces and stresses at the critical locations and regions of structures. By measuring and tracking the critical loads and responses of the structures together with any structural modifications and maintenance, the complete history throughout the life-cycle can be generated, and the data can be used to predict the f...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Contributor contact details
• Introduction: structural health monitoring – a means to optimal design in the future
• 1: Structural health monitoring: applications and data analysis
• Part I: Structural health monitoring technologies
• Part II: Applications of structural health monitoring in civil infrastructure systems
• Index