Railway Bridge Dynamic Response Measurement Using Frequency Domain Filtering
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Solution Overview
Problem
Existing dynamic response evaluation methods for railway bridges struggle to accurately separate static and dynamic responses due to errors in measurement positions and vehicle vibration, leading to insufficient accuracy in calculating the attenuation rate of dynamic responses.
Innovation Solution
A measurement method that generates first and second measurement data by observing the response of a structure to a moving object, reduces vibration components through filter processing, and calculates an attenuation rate based on envelope amplitude analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the acceleration amplification coefficient is calculated by dividing the feature amount of vertical acceleration measured by the rearmost vehicle accelerometer by the feature amount measured by the leading vehicle accelerometer, then the static response and dynamic response can be separated, but the accuracy is insufficient due to measurement position errors and vehicle vibration
Solution Approach 1:
The patent introduces a transfer function H(f) as an intermediary to relate the acceleration measurements from different vehicle positions to the bridge response. This transfer function accounts for the spatial relationship between measurement points and the bridge's dynamic characteristics, enabling accurate separation of static and dynamic responses while compensating for measurement position errors and vehicle vibration effects.
Solution Approach 2:
The patent transforms the acceleration data from the time domain to the frequency domain using Fast Fourier Transform (FFT), changing the parameter representation from temporal acceleration values to spectral components. This parameter transformation enables the application of frequency-dependent transfer functions to accurately separate static and dynamic responses, overcoming the limitations of time-domain division methods.
2Measurement precision
If filter processing is applied to reduce vibration components in measurement data, then the vibration component can be reduced, but the necessary signals may be attenuated
Solution Approach 1:
The patent applies filter processing in the frequency domain after transforming the acceleration data via FFT. The filters are designed to target specific frequency ranges corresponding to vehicle vibration and train passage effects, allowing preliminary removal of these components while preserving the bridge's natural vibration frequencies and other necessary signal information through careful frequency band selection.
Solution Approach 2:
The patent uses the transfer function H(f) as a feedback mechanism that continuously adjusts the filtering process. The transfer function incorporates information about the bridge's dynamic characteristics and the measurement system's response, enabling adaptive filtering that maintains signal integrity while removing unwanted vibration components.
Data Source
AI summary
A measurement method includes: generating second measurement data by performing filter processing on first measurement data; calculating a first deflection amount based on an approximate equation of deflection of a structure; calculating a second deflection amount by performing filter processing on the first deflection amount; calculating a third deflection amount based on the second deflection amount and a first-order coefficient and a zero-order coefficient which are calculated based on the second measurement data and the second deflection amount; calculating an offset based on the zero-order coefficient, the second deflection amount, and the third deflection amount; calculating a static response by adding the offset and a product of the first-order coefficient and the first deflection amount; calculating a first dynamic response by subtracting the static response from the first measurement data; calculating a second dynamic response by attenuating an unnecessary signal from the first dynamic response; and calculating an attenuation rate of the second dynamic response based on an envelope amplitude of the second dynamic response.