To enhance the monitoring of construction conditions during the building process, it is essential to implement a wireless network perception system based on BIM technology. This system relies on BIM models to set up and install sensors within subway stations, establishing communication channels under varying conditions. The system primarily consists of two components: a BIM-based subway station model and router nodes. Utilizing this model, different elements within the subway stations can be displayed at multiple levels and specific spaces. These spaces serve as constraints to organize and store data collected by wireless sensors within the BIM model.
The comfort monitoring system in a subway station tracks parameters such as indoor and outdoor temperature, humidity, comfort temperature, and date. The temperature values vary depending on the outdoor location of the humidity and heat comfort monitor, reflecting the atmospheric temperature most passengers find comfortable. The comfort temperature is calculated based on the average neutral temperature (Tn.0) indoors and outdoors, alongside the atmospheric temperature (T0), using the formula: Tn.0 = 17.6 + 0.31T0. When this information is integrated into the BIM model, parameters are updated dynamically according to the current date and other relevant data.
The wireless sensor system includes two types of deployment points: router nodes and receiver nodes. The microcontroller embedded in these devices has storage capacity to hold code, monitor router node activity, and track sensor statuses connected to the routers. For instance, temperature and humidity can be measured using the DHT11 digital sensor module, which offers a temperature accuracy of ±2 ℃ and humidity accuracy of ±5%. Data flows from the router nodes to the receiver nodes and then onward to the computer for processing.
Given that subway stations are excavated more than 10 meters below platform level, the temperature on the platforms is often higher than the outdoor temperature. Additionally, the large number of passengers generates body heat, which contributes to the overall temperature rise inside the station. Train operations also add significant heat. Therefore, it is crucial to strengthen environmental monitoring of subway stations using BIM systems and sensors, allowing for timely adjustments to temperature and humidity to ensure passenger comfort.
Source: Science and Technology Innovation and Application, Issue 35, 2021
Author: Guo Jie (China Railway Fifth Survey and Design Institute Group Co., Ltd.)
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