As per the low quality of structural health inspection of buildings, predominant issues in the structure of buildings may be unnoticed. This can lead to potential damages to the buildings. Therefore, monitoring the structural health of a building is vital. Monitoring the structural health of a building helps to get an understanding of the status of the building which can benefit in corrective maintenance and preventing potential damages that could occur ensuring the building’s safety.
Monitoring the critical structural health regularly is vital as all manmade structures hold a limited lifespan as they degrade over time.
Even though other structural analysis systems such as Non-Destructive Testing (NDT) and Non-Destructive Evaluation (NDE) are simply one-time analysis systems, SMH is a continual structural analysis system. Moreover, while some infrastructure owners tend to avoid using SMH due to high costs, SMH systems have proven to optimize the lifespan of a building by reducing the cost of frequent maintenance and inspection cost.
Elements of SHM
To be well managed, any system must accumulate elements. However, elements of SHM include hardware such as sensor systems and instrumentations (wiring, junction boxes, conduits) and software elements such as data acquisition, damage detection and modeling algorithms and data analyzing and interpreting software. Sensors in terms of receiving and conveying data are of two types such as passive and active sensors.
While passive sensors such as conventional straining devices only receive signals, active sensors such as piezoceramic (PZT) and fiber optic sensors (FOS) have the capability to both receive and transmit signals.
Technical advancements have replaced wireless sensors, minimizing the usage of lengthy lead cables that used to cause mistakes due to electromagnetic interference. However, some small structural owners still use the old methods. Although, the purpose of any system used is to collect valuable data to organize, monitor, process into information and make better decisions. At the stage of data collection, sensors will gather primarily variables such as temperature, motion, pressure. Then, a transducer will convert the variables to electrical signals. Next, processes including filtering, implicating, signal sealing, and calibrating transpires to increase the quality of these signals. Finally, since the signal is in its analog form, it must be converted into a digital form so that the computers can store data and transfer and store the data for damage detection. Moreover, the importance of data management arises when we consider that a single vibration measurement contains hundreds of samples from each sensor.
System design of SHM
A well-designed system will guarantee increased performance and efficiency. However, it is important to understand how to make relations between elements such as physical constraints, sensing ability, economic and human interference and its optimal results. Tasks such as follows benefit in understanding if the engineers can meet their expectations.
Aesthetics – Bondable sensors might cause aesthetic issues (If the building uses sensors, they will have a minimal visual impact)
Calibration – used to determine a device’s readings.
Cost – costs such as installation, operation, maintenance.
Serviceability – the choice of the sensor varies as per aspects such as test time, environment, loading conditions and more.
Installation and maintenance – All systems require maintenance as the structure uses numerous types of sensors. However, depending on the sensitivity and other factors such as environmental changes, the methods for sustaining these systems may differ.
Some other tasks identified are measured, the purpose of the SHM, security and energy consumption.
Placing the sensors
Moisture and air conditions may penetrate the soil through concrete and cracks. An SHM may include thermocouples, strain gauges and accelerometers. As a huge difference in the temperatures of the interior and exterior may cause cracks, the thermocouple can monitor the differences in the temperatures.
The number of thermocouples per beam may be larger than two due to the possibility of damage during concrete placement. Furthermore, they should be located closer to the beam surface since the structure’s changing rates of temperature are higher near the surface and lower towards the core. Thermal contraction on the surface might cause cracking.
In the symmetrical part, installing thermocouples symmetrically will boost effectiveness. It also is a good idea to put them close to the joints, as joints minimize cracking.
Accelerometers are important in delivering data as signals to the data gathering system because they assess acceleration from structure vibration. To record vibrations, one precise accelerometer installed at the middle of the beam will be enough. This is important for capturing any fault, such as beam failure caused by timbre frequency.
Benefits of SHM
An SHM is a custom-built system that allows the user to precisely suit their demands. This system also allows easy integration at any level, including connection, device, cloud, and more. It has a stronger ability to satisfy standards for potential extensions and is extremely dependable. This approach also allows for flexibility depending on variances in buildings and environments, which has a favorable impact on the outcomes of the monitoring and controlling process for making future judgments.