RFID Sensor-Driven Structural Condition Monitoring in Integrated Building Information Modeling Environment
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Steel structures are very popular structural forms for both buildings and bridges. Under extreme loading such as strong earthquakes or winds, structural members in steel structures could fail in buckling or yielding. In buildings, structural members are often hidden behind fire-proof coating and drywall, and thus buckling or yielding in steel members are very difficult to detect, often requiring removal of coverings and thus time consuming and costly. Fast and accurate assessment of damage conditions is important to the occupant safety and uninterrupted use. This research presents a method for integrating Building Information Modeling (BIM) and Radio Frequency Identification (RFID) based wireless strain sensor technologies to enable automated structural condition assessment. BIM can serve as an ideal 4-dimensional graphical computing environment for integrating structural health monitoring (SHM) with management practice, which often involves considerable amounts of sensor data of different modalities and changes of structural condition over time. To detect the exceedence of preset threshold strain levels, this research custom designed a novel breakage-triggered (BT) strain sensor for detection of threshold strain levels. This BT strain sensor uses RFID tag for wireless communication with RFID reader. With a special design, the sensor breaks at pre-set strain level and the connected RFID tag is activated. By altering its configuration to include multiple threshold strain levels, actual strain at the monitored location can be estimated after hazardous events. This system can rapidly identify and locate the spot where pre-set strain or crack has happened and the corresponding structure element of the BIM model is automatically highlighted to provide alert signal. Such damage spots require immediate action after hazardous events such as earthquake or extreme wind. The RFID tag can be scanned from a distance up to several meters by using an RFID reader. This system is highly automated, low power consumption, and low cost. A custom developed middleware was developed to enable automated sensor data entry into BIM environment and thus avoid possible human related errors. The BIM environment allows for capturing, organizing, processing (cleansing, fusion, mining, etc.), visualizing the sensor data from the monitoring system, updating relevant models and running finite element analysis for structural response and reliability computation as well as structural health prognosis. Process (inspection scheme) and work-flow automation can be realized. Therefore, the proposed method would lead to more user-friendly, highly automated and more economical way for structural condition assessment and SHM information management.