Characterization of Railway Traffic and its Effect on Structures

As part of joint research work between FiberSensing and the Faculty of Engineering of the University of Porto, several experimental campaigns were conducted with tests being performed at a railway line in Canelas, Northern Portugal.

Fiber Bragg Grating strain measure- ments on railway tracks.

Wheel Defect Detection

To study the impact of damaged wheels on the rails, an experimental campaign took place using a temporary FBG measurement system.


Measurements were performed automatically without interrupting the traffic using eight FBG polyimide strain sensors, glued onto the rails and interrogated by a high speed BraggSCOPE measurement unit.


The test proved the feasibility of a system, based on a frequency selective algorithm, that automatically detects wheel defects, train length and speed and axle counting by simply measuring the strain caused by moving loads on rails.


Such a method, applied as a long-term monitoring system, will allow significant prevention of rails degradation, as well as reduction of replacement costs, while operation safety is increased.

Train Weight-in-Motion

Tests for the characterization of traffic effects on a short span railway bridge served as the starting point for the development and testing of a bridge weight-in-motion algorithm (SISPEFE) based entirely on an FBG sensing system.

The main items that integrate the developed SISPEFE system are:

  • Three FBG weldable strain sensors installed on the rail track and one strain sensor on the bridge structure;
  • Remote BraggSCOPE measurement unit for dynamic acquisition of the FBG sensors;
  • Software application with the WIM algorithm;
  • Fiber optic cables;
  • Video recording cameras with wireless and solar power.

The system allows the determination of the weight per axle of a train passing over a bridge using the dynamic measurements performed on the rails and bridge structure. Speed and acceleration are also characterized.

Train passing over a bridge
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  • 10 k Samples/second
  • 0,1μ Strain Measurement Resolution
  • 49 Recorded Train Passages
  • +6 Measured Parameters

Due to Fiber Bragg Grating (FBG) sensors immunity to EMI and RFI, low noise was observed in the attained measurements.

The testing campaigns demonstrate the applicability of a FiberSensing Fiber Bragg Grating (FBG) technology system for railways instrumentation.

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