Bridge Inspection Trucks: Types, Features, and Applications

II. Core Functions and Inspection Applications

The core value of bridge inspection vehicles lies in their dual capability of "close-range operation + professional equipment carrying," specifically manifested in defect diagnosis and maintenance construction scenarios.

1. Precise Defect Diagnosis

Visual Defect Identification: Through close-range platform contact (distance to bridge structure $\le$ 0.5m or 1.6 feet), combined with high-definition industrial cameras ($\ge$ 20 megapixels resolution) and crack width gauges (0.02mm or 0.0008 inches accuracy), it identifies surface defects such as concrete spalling, steel structure corrosion, and bearing deformation. Data is recorded in real-time into the bridge health monitoring system.

Structural Performance Evaluation:

• Material Property Testing: Equipped with rebound hammers (for concrete strength, error $\le \pm$1.5 MPa or $\pm 218$ psi) and ultrasonic detectors (for internal voids, detection depth $\ge$ 5m or 16 feet).
• Rebar Condition Analysis: Uses rebar corrosion detectors (for potential difference, 1mV resolution) to assess corrosion levels, combined with chloride content testers to determine durability.
• Load Test Support: Strain gauges (1με accuracy) and displacement sensors (0.01mm or 0.0004 inches accuracy) are deployed on the truss platform to simulate structural response under vehicle loads, evaluating the load-bearing potential of older bridges.

2. Maintenance and Construction Support

Large Equipment Carrying: Truss-type platforms can accommodate hydraulic breakers (weight $\le$ 300kg or 660 lbs), high-pressure sprayers (for anti-corrosion coatings), and other equipment, enabling tasks such as pier strengthening and beam repair.

Precision Maintenance Adaptation: Articulating arm platforms, through modular expansion (e.g., adding a rotating basket), can perform precise operations like bearing replacement (positioning accuracy $\pm 5$ mm or $\pm 0.2$ inches) and crack injection (pressure control 0.2–0.5 MPa or 29–73 psi). Single-sided inspection vehicles (e.g., certain XCMG models) specialize in drainpipe installation, achieving an average daily working length of 150–200 meters (approximately 490–650 feet), which is 3 times more efficient than manual scaffolding.

III. Scenario-Based Selection Strategy

The selection of bridge inspection vehicles should follow the principles of "scale matching, objective-oriented, and environment adaptation," specifically as follows:

1. Matching by Bridge Scale

Small and Medium-Sized Bridges (span $\le$ 50m or 164 feet, e.g., county road concrete T-beam bridges): Prioritize articulating arm inspection vehicles. Their 16-meter (approximately 52 feet) horizontal working range can cover a single bridge deck, and the equipment is lightweight (self-weight $\le$ 8 metric tons or 17,600 lbs), making it suitable for rural road access.

Large Bridges (span $\ge$ 100m or 328 feet, e.g., cross-river bridges, urban interchanges): Truss-type inspection vehicles are essential. For example, a bridge width of 4.75 meters (approximately 15.6 feet), requires a truss vehicle with an over 20 metersr (approximately 85 feet) span to cover the full cross-section, avoiding blind spots under the bridge deck caused by insufficient span of traditional equipment (previously, inspection omission rate reached 15%).

2. Selection by Inspection Objective

Full-Section Structural Evaluation (e.g., annual safety general inspection): Truss-type inspection vehicles, through continuous moving operations, can complete a full-element inspection of 3 km (approximately 1.86 miles) of bridge in one day, which is 4 times more efficient than articulating arm vehicles.

Local Key Maintenance (e.g., bearing defect treatment): Articulating arm vehicles, through precise positioning ($\pm 10$ cm or $\pm 4$ inches), can directly reach the work point, avoiding large-scale equipment deployment and traffic disruption.

3. Special Environment Handling

Railway Bridge Inspection: Rail-mounted inspection vehicles adapt to railway "maintenance window" (short duration, high precision) requirements, completing a single span (32m or 105 feet) inspection within 90 minutes. Their vibration-resistant design ensures data stability during train passage.

Busy Urban Sections: Articulating arm vehicles, through "over-barrier operation" (crossing railings to the outer side of the bridge), do not occupy traffic lanes and do not require traffic control, making them suitable for emergency inspections during morning rush hour (e.g., expressway crack detection).

IV. Frontier Developments and Challenges

Current bridge inspection vehicles are evolving towards "intelligence, specialization, and low-cost operation and maintenance":

1. Technological Upgrade Directions

Intelligent Integration: New models are equipped with IoT sensor networks that collect real-time data on the working environment (wind speed, temperature) and equipment status (hydraulic pressure, platform tilt). Data is transmitted via 5G to a GIS platform, supporting remote monitoring and intelligent early warning.

Lightweighting and Modularization: Carbon fiber composite materials (30% lighter than aluminum alloy) are used to reduce truss weight. However, a 26-meter (approximately 85 feet) span still requires a heavy-duty chassis (self-weight $\ge$ 20 metric tons or 44,000 lbs), limiting passability. Future breakthroughs are needed in "high-strength + low-self-weight" material bottlenecks.

Permanent Installation: For extra-large bridges, fixed inspection vehicles are pre-installed, with tracks laid along the bridge structure. The equipment is permanently stationed at the bridge, reducing single inspection costs by 60%, making it suitable for long-term maintenance of aging bridges.

2. Insights

In the future, bridge inspection vehicles will further integrate multi-modal technologies such as drone scanning (for large-scale preliminary surveys) and truck-mounted close-range re-inspection (for detailed inspection). Additionally, designs like adjustable basket lengths and modular truss combinations will adapt to the diverse needs of extra-large transportation hubs and aging bridges (over 30% of bridges in the US require key monitoring), transforming bridge maintenance from "passive repair" to "proactive early warning."