Bridge Axle Load Estimation Using Multi-Point Strain Gauge Deflection
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Solution Overview
Problem
Existing bridge weigh-in-motion systems struggle to accurately measure axle loads when strain gauges cannot be placed at the central position of a bridge's superstructure, leading to incomplete or inaccurate measurements.
Innovation Solution
A measurement method that uses multiple observation points along a bridge to calculate deflection waveforms at central and non-central positions, employing a structural model and amplitude coefficients to estimate physical quantities like load and displacement, even without direct measurement at the central position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauge is arranged at central position of bridge superstructure, then measurement accuracy of axle load is improved, but installation difficulty and structural interference increase
Solution Approach 1:
The patent uses an intermediary approach by placing strain gauges at accessible non-central positions (first, second, and third observation points) rather than directly at the central position. A calculation unit then acts as a mediator to compute the central position deflection waveform from these intermediary measurements using beam theory and superposition principles, thereby achieving central position measurement accuracy without the installation difficulties.
Solution Approach 2:
The patent creates a copied representation of the central position deflection waveform by calculating it from measurements at other positions. The calculation unit generates a virtual central position deflection waveform that replicates what would be measured at the central position, allowing accurate axle load measurement without physically placing strain gauges at the difficult-to-access central location.
2Ease of manufacture
If strain gauge is arranged at non-central position of bridge superstructure, then installation ease is improved, but measurement accuracy of axle load deteriorates
Solution Approach 1:
The patent transitions from a single-point measurement approach to a multi-dimensional approach by placing strain gauges at multiple non-central positions (first, second, and third observation points) along the bridge superstructure. By measuring deflection waveforms at these multiple positions and combining them through calculation, the system achieves accurate central position measurement without requiring direct central placement, effectively adding spatial dimensions to the measurement system.
Solution Approach 2:
The patent segments the measurement task by dividing the single central position measurement into multiple non-central position measurements. Instead of one strain gauge at the central position, the system uses multiple strain gauges at different accessible positions, with each measuring a portion of the overall deflection pattern. The calculation unit then integrates these segmented measurements to reconstruct the central position deflection waveform.
3Measurement precision
If multiple observation points are used to calculate central position deflection, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The calculation unit serves multiple functions: it calculates deflection waveforms at multiple observation points, applies superposition to combine these waveforms, computes the central position deflection waveform, and determines axle load from the result. This multi-functional approach consolidates what could be separate complex subsystems into a single integrated unit, reducing overall system complexity while maintaining high measurement accuracy.
Data Source
AI summary
A measurement method includes: a step of acquiring first observation point information; a step of acquiring second observation point information; a step of calculating a path deflection waveform at a third observation point; a step of calculating a path deflection waveform at a central position between the first observation point and the second observation point; a step of calculating a measurement waveform as a physical quantity at the third observation point; a step of calculating an amplitude coefficient at which a difference is minimized between the measurement waveform and a waveform obtained by multiplying the path deflection waveform at the third observation point by the amplitude coefficient; and a step of calculating, based on the path deflection waveform at the central position and the amplitude coefficient, an estimation waveform as a physical quantity at the central position.