Structural Health Monitoring of Civil Infrastructure †Free Samples

Question: Discuss about the Structural Health Monitoring of Civil Infrastructure. Answer: Introduction Civil infrastructure is very fundamental area when it comes to addressing the prosperity of any society. To keep track of the structural integrity of civil infrastructure, and monitor their overall performance, SHM systems are put into use. Structural Health monitoring involves the use of intelligent sensors and related technologies to collect a wide array of data and giving an output that will be used to rate the condition of a structure or structural element. SHM systems help in the detection of possible damage on civil infrastructure due to natural hazards, aging, and/ or deterioration1. This study aims at investigating the overall use of sensors for SHM in of asset management, assessment of structural integrity, risk assessment and scrutinizing of civil infrastructure in New Zealand. Several studies in the field of damage detection in civil infrastructure have shown a rising need for the monitoring of structures such as bridges, dams, tunnels, buildings and other civil infrastructure. According to Chang, many SHM systems depend on changes in the shape modes and/or the changes in the resonant frequencies of a structure. This method works by the principle of sensing the slight variations in a structure. Hence, the variations in a structure due to environmental factors such as vibration, temperature variations, or even humidity changes are considered as noise in SHM systems. There is a need to make systems that would take measurements other than those considered as noise to the SHM system. Rytter suggests that in New Zealand, SHM is mainly use for damage detection in road bridges, especially along major highways 4 The main areas of application for bridges are: in short span and medium span bridges, for performance checking, operational health and security monitoring, and overall implementation in New Bridges. Further suggests that the level of damage detection and condition rating relies on the systems ability to predict damage and classify it into four general levels: Level 1: ability to sense the occurrence of damage; Level 2: detection of a likely location of destruction; Level 3: sensing of the likely degree of destruction; and Level 4: forecast the safety and level of service of the structure. The following are the objectives of the research: To understand the significance of sensors in SHM systems; To establish the challenges faced in the implementation of SHM in New Zealand; To appreciate the existing measures put in place by Statutory bodies in New Zealand for monitoring the structural integrity of civil infrastructure; and To highlight opportunities to be explored in SHM. When monitoring the condition and performance of non-homogeneous material like concretes, the systems used for sensing should be able to collect and record data in small increments with an allowance for local effects and discontinuities. Therefore, a number of sensing technologies have been developed. They main ones used in New Zealand include: Wireless sensors: These are sensors with an autonomous platform for collection of data. They are fitted with strain gauges that are sensitive to inertial forces induced into the structures. The inertial sensors have a gyroscope and accelerometer. Studies are being done in New Zealand to develop embedded wireless sensors to be integrated into concrete elements for purposes of monitoring the concrete in structures from the initial curing phase and subsequent strength gain of the concrete. Fiber optic sensors: The commonly used type of fiber optic sensor is the discrete point sensors which works by detecting the strains along localized areas of the construction material. They are ideal for homogeneous material. While there are a variety of benefits offered by the Structural Health Monitoring Systems, there are also major challenges associated with structural health monitoring systems. These include: Buying a structural health monitoring system is not the same as purchasing a commodity. Design work is needed for each system whether the structural monitoring system is going to be used on an existing structure or a new one. Due to high costs involved and inadequate resources required to incorporate a structural health monitoring system in a structure, many organizations find it difficult to implement one. Also, many structural health monitoring systems depend on sensors that acquire data about only one point to monitor properties i.e. point sensors. This limitation is not about efficiency or reliability; rather, it is about insight. Therefore, events that occur between critical points will not be captured hence important structural response will be lost. Finally, employment of point sensors in structural health monitoring involves interpolation to simulate additional measurement locations. This practice leads to biased damage indices since true local information is lost. Another major challenge faced by many existing structural health-monitoring systems is data normalization. This is the procedure of separating changes in sensor output caused by damage and changes brought about by varying environmental conditions. Since most structural health monitoring systems do not monitor continuously, data normalization becomes a big challenge. This becomes even harder when point sensors are used to collect the data. SHM is used in the process of damage detection and condition characterization of civil infrastructure. SHM is used to keep track of the structural integrity of buildings, dams, tunnels, levees, bridges, wind turbines, and other civil infrastructure. The following are the opportunities in the SHM technology: Control of material properties, process of construction and geometry more so in segmental construction with a complicated posttensioning and/or erection process; SHM may help in the safety management of infrastructure under construction as incomplete structures are at risk due to accidents and environmental hazards; SHM offers the chance for the validation of assumptions made during design with regards to forces, deflection, displacements, drifts, and reactions during construction. Avenues for further work In this paper, the focus has been the various ways in which Structural health monitoring can be applied in civil infrastructure damage detection. However, there are a numbers of avenues to be pursued in research to ensure that SHM gains maximum potential in New Zealand. This includes: As the sensors used in SHM are likely to be influenced by the environmental changes such as temperature variations and random vibrations during the design period of the civil infrastructure, a study of the impacts of environmental changes on the performance of SHM systems. As sensors will be collecting a vast amount of data, a data collection framework and inventory needs to be developed. Therefore, further work needs to be done focusing on developing software functionalities and algorithms to aid in civil infrastructure database and repositories management. To incorporate SHM in the monitoring of infrastructure in adverse environments, studies need to be conducted towards the development of chemical sensors for corrosion, humidity, and corrosion especially for marine structures and civil infrastructure built in areas with high Sulphur content. Conclusion Well-managed structures are the safest and durable. The ability to measure flows of information throughout the building is vital in ensuring digital future buildings that utilize innovation and next generation monitoring systems. Structural health monitoring is currently an area of interest as it presents a potential solution for future examination of structures. With the size, cost and ability of sensors becoming cheaper, the more it is becoming financially viable and feasible to install sensors all over the world. Currently, there is a gap between advanced sensing technologies that are being developed and their applicability to monitor structural performance of buildings. The ability to sense the presence of defects in concrete structures has a vital role in the damage assessment of the structures. Therefore, further research and experimental validation tests are needed to evaluate the limitations and practicality of installing the latest sensor technology to monitor the structural health of structures. References BROWNJOHN, J. M. W. 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