What is Bridge and Metro Safety Assessment and Monitoring?

In the construction inspection industry, the safety assessment and monitoring of bridges and subways are critical aspects of ensuring the safe operation of public transportation infrastructure. This typically involves regular structural inspections, safety assessments, and long-term structural health monitoring, following a series of national and industry standards.

Bridge Safety Assessment and Monitoring

The safety assessment and monitoring of bridges (including urban elevated bridges) primarily focus on structural integrity and load-bearing capacity, specifically including the following aspects:

• Regular Inspections: Urban bridges usually require frequent inspections, routine periodic inspections, and special inspections. The first periodic structural inspection of extra-large bridges or special structures should be conducted approximately 1-2 years after completion, and subsequent inspections can be extended to 3 years; other bridges should be inspected every 6-10 years.

• Safety Assessment: When frequent inspections or periodic inspections reveal damage to major load-bearing components or structures that affect safety, bridge structure inspection and safety assessment should be carried out promptly. The assessment usually involves load-bearing capacity verification and structural resistance assessment.

• Structural Health Monitoring (SHM): For large or important bridges, long-term structural health monitoring systems are installed to collect data in real time, aiming to detect safety hazards in a timely manner. Monitoring content typically includes:

• Structural stress changes.

• Structural settlement and horizontal displacement.

• Vibration and modal parameters: Used to determine the overall working state and damage of the structure.

• Internal and external environmental monitoring: Such as temperature, humidity, and wind load.

• Damage quantification indicators: Developing universal indicators to classify and quantify the health status of the structure.

Subway Safety Assessment and Monitoring

• The focus of subway safety assessment and monitoring is to ensure the stability of underground structures, their deformation resistance, and the control of impacts from the surrounding environment, especially during external operations (such as nearby construction).

• Current Status Investigation: A current status investigation must be conducted before safety assessment, including data collection, inspection, and monitoring, to form the basis for evaluating the current condition of the structure.

• Impact Assessment: For the impact of new construction projects on existing subway structures, numerical simulation analysis is required (e.g., using the FLAC3D program to establish a three-dimensional stratum-structure model).

• Construction Period Monitoring: The monitoring unit needs to prepare a detailed monitoring implementation plan based on the safety assessment report, special design, and construction plan, and set monitoring warning values. Monitoring items are usually determined based on the expert review opinions on construction safety. • Technological Means: Utilizing modern information sensing technologies, including advanced technologies such as DAS (Distributed Acoustic Sensing), to enhance comprehensive sensing capabilities along the railway line.

Common Technologies and Equipment

The technologies and equipment widely used in this industry include:

• Sensors: Specialized sensors are used to measure physical parameters such as displacement, strain, vibration, tilt, and temperature.

• Data Acquisition and Transmission Systems: Including wired and wireless monitoring systems, enabling real-time data acquisition and remote transmission.

• Data Analysis Software and Models: Utilizing artificial intelligence, neural networks, and other technologies to analyze massive amounts of monitoring data and perform damage diagnosis.

• Non-destructive Testing Equipment: Used for detailed inspection of internal structural defects.

Main Standards and Specifications

China has a series of national, industry, and local standards for bridge and subway safety assessment and monitoring, such as:

• "Technical Specification for Monitoring of Building and Bridge Structures" (GB 50982)

• "Technical Specification for Monitoring of Highway Bridge Structures" (JT/T 1037)

• "Technical Regulations for Smart Monitoring Systems of Urban Bridges"

• "Technical Specifications for Detection, Assessment and Monitoring of Facilities Crossing Urban Rail Transit"

Relevant practitioners and responsible units can consult these standards and specifications to ensure the compliance and effectiveness of assessment and monitoring work.