## 3 Results and Discussion
### Practical Guidelines for Implementation  
Based on the findings from the laboratory experiments and the field demonstration, the following practical guidelines are provided for the implementation of the collaborative sensing approach in precast concrete construction projects:  
1. Pre-installation of embedded sensors: During the prefabrication stage, install the damped vibration sensors at the grout outlets of the sleeve connections, ensuring that the sensors are properly sealed and integrated into the sleeve assembly.  
Ensure the proper functioning of the pre-embedded sensors and the compatibility with the grout filling degree testing instrument. The grouting fullness detector is required to meet an amplitude linearity specification of within \(\pm\)1.0 dB for every 10.0 dB, with a frequency bandwidth between 10 kHz and 100 kHz. A damping vibration sensor should be utilized, ensuring that the diameter of the core component at the end does not exceed 10.0 mm, and the diameter of the steel wire connected to the core component is maintained between 2.0 mm and 3.0 mm. Additionally, the sensor and rubber plug should be designed as an integrated unit, with the diameter of the hole through which the steel wire passes matching the diameter of the steel wire, and the diameter of the exhaust hole being no less than 3.0 mm;
2. Grout filling and testing procedure: Flush the sleeves with high-pressure water to remove any residual debris before grouting. Prepare the grout and bedding mortar, and use the bedding mortar to seal the bottom of the sleeves. Connect the pre-embedded sensor signal cables to the grout filling degree testing instrument, and initiate the continuous monitoring of the vibration energy values during the grouting process. After the grouting is completed, record the final vibration energy values for each sleeve connection;
3. Collaborative data analysis: Use the function relationship in Equation (1) to convert the vibration energy values from the pre-embedded sensor method into the corresponding grout filling degree values. If access to the exposed reinforcement ends is available, conduct the impact-echo technique testing to obtain the density information and cross-validate the grout filling degree results. Integrate the vibration energy-based grout filling degree and the impact-echo-based density information to establish the collaborative assessment of the grout filling quality;
4. Quality assurance and decision-making: Compare the collaborative assessment results with the specified grout filling degree requirements, as per the relevant technical specifications. Identify any sleeve connections with inadequate grout filling and prioritize them for remedial actions, such as additional grouting or replacement. Implement the collaborative sensing approach as a standard quality control procedure for precast concrete sleeve connections, ensuring consistent and reliable grout filling quality. By following these practical guidelines, construction teams can effectively implement the collaborative sensing approach to enhance the assessment of grout filling quality in precast concrete sleeve connections, leading to improved structural integrity and long-term performance of the precast concrete structures.