<![CDATA[Rotation measurement is a key parameter in evaluating the mechanical behavior of steel connections under moment loading. Direct measurement of rotation using conventional sensors such as Linear Variable Differential Transformers (LVDTs) is challenging, as LVDTs are primarily designed to measure translational displacement rather than angular deformation. This study presents the development and calibration of an indirect rotation measurement device based on LVDT displacement conversion using a mechanical wire–roller system. The proposed device converts rotational motion of a horizontal steel member into linear displacement through a steel wire wound around a roller, which is subsequently measured by an LVDT. The calibration was performed within a rotation range of 0°–30° using a 14 mm roller diameter under laboratory-controlled conditions. Calibration was conducted using two approaches: manual rotation measurement with a protractor and controlled loading using a Universal Testing Machine (UTM) equipped with an anglemeter. The results show that calibration performed using UTM loading provides closer agreement with theoretical arc-length calculations, particularly for small rotation angles. The average deviation of the UTM-based calibration relative to theoretical arc-length calculation was ±0.94%, with a maximum deviation of 5.8% at small rotations. The regression model yielded R² = 0.99, indicating excellent linearity. A linear correlation between LVDT displacement and rotation angle was established and adopted as the calibration equation. The proposed measurement system demonstrates adequate accuracy and reliability for experimental investigation of rotational behavior in steel connections.]]>
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