# Investigating the Mechanical Properties and Temperature Compensation of a Spot-Welded Strain Sensor within an Intelligent Steel Strand Cable

## TL;DR

This paper introduces a new strain sensor for steel cables that can be spot-welded without damaging the structure and works well for long-term tension monitoring.

## Contribution

A novel chip-based spot-welded strain sensor for intelligent steel strand cables with high strain transfer efficiency and low temperature sensitivity.

## Key findings

- The strain transfer efficiency of the sensor exceeded 96% in simulations.
- Experimental load-strain fitting reached a degree of 0.999 with tension errors under 1.26%.
- Temperature-induced tension errors were within 1.0%, and sensor accuracy improved after relaxation.

## Abstract

According to current regulations, welding is strictly prohibited for prestressed and tension cables. In response, this article proposes the use of a portable spot-welding machine to spot weld steel strands. This method generates a small current during spot welding, with a voltage of only 3 V to 5 V, and does not damage the internal structure of the steel strand. To effectively monitor cable tension in cable-supported structures, a novel approach utilizing a chip-based, encapsulated spot-welded strain sensor was investigated. The strain sensing capability, temperature sensitivity, stress relaxation, and static load responses were investigated on the proposed smart steel strand cables with spot-welded strain sensors. The theoretical analyses and finite element simulations revealed that the strain transfer efficiency of the spot-welded strain sensor exceeded 96%. The experimental results demonstrated that the load-strain relationship of the smart steel strand cable had a fitting degree greater than 0.999, and the tension errors obtained under different loads were within 1.26%. The tension full capacity errors measured at different temperatures were generally within 1.0%. The relaxation rate of the smart steel strand cable after 120 h was 3.78% and reduced the sensor accuracy error by 3.97%. Thus, the proposed strain sensor equipped with a smart steel strand cable is suitable for use in long-term tension monitoring.