In 19th Century: rail road wheel tappers - used the sound of a hammer when striked against the wheel of train to detect the damage. In rotating machinery, vibration monitoring is used as performance evaluation technique.
Then, these techniques are utilized to detect the damages in the structure, and then a new field emerged namely Structural Health Monitoring.
What is Structural HealthMonitoring? The process of implementing a damage detection and characterization strategy for engineering structures is referred as Structural Health Monitoring. (in short…)
Pattern of SHM: Operational Evaluation, Data Acquisition and Cleansing, Feature Extraction & Data Compression, and Statistical Model Development for Feature Discrimination
Operational Evaluation: Under which operations, the structure services and damage. Life safety and economic justification for performing SHM. Limitations of acquiring data in SHM.
Data Acquisition: This parts deals with: number of sensors, types of sensors, selecting their excitation methods & data storage techniques.
Data Normalization: separating changes in sensor readings from damage to those caused by varying operational & environmental conditions.
Feature Extraction: Feature extraction gives the technical literature to distinguish between damaged and non damaged items of buildings.
Statistical ModelDevelopment: Statistical Model Development is used for determining damaged and undamaged structures.
Importance of SHM: SHM improves - safety & functionality of structures. Monitoring - develop innovative design methodologies - timely warning of impending failures. Structural condition monitoring and assessment are required for timely and cost-effective maintenance.
Embedment of sensors during construction and measurement of structural responses during service will enable condition assessment and remaining life estimation easy and convenient Monitoring scheme helps to gather data on the realistic performance of the structures, which in turn will help to design better structures for the future.
Saptha Suthras: All materials have inherent laws or defects The assessment of damage requires a comparison between two system states Identifying the damage differs than the type and vulnerability of the damage, which requires skill.
Sensors cannot measure damage. Feature extraction and statistical classification is required to convert sensor data to damage information. Damage information depends upon the intelligence of sensor’s feature extraction.
There is a trade-off between the sensitivity to damage of an algorithm and its noise rejection capability. DS α 1/RE (damage size) α (1/ frequency range of excitation)
Components: Structure Sensors Data acquisition systems Data management Data transfer Data interpretation and diagnosis
Sensors: Sensors measure the physical quantity of damage and sends it to computer. Good Sensor : Is sensitive to the measured property Isinsensitive to any other property likely to be encountered in its application Does not influence the measured property.
DA systems: Data acquisition is the process of sampling signals that converts the resulting samples into digital numeric values. Sensors Signal conditioning circuitry Analog-to-digital converters
Data management system manipulates the management of data obtained from sensors. Data transfer systems are used to transfer the data to systems which help in predicting the failures of structures.
Conclusion: There is always no particular conclusion for any technology related concept. But, this concept ends with conclusion with that even structures have life and we (civil engineers) are here to protect it from various diseases.