Improving LUR testing accuracy and practicability for prestressed concrete sleepers through bending stiffness and visco-plastic deflection-based analysis techniques

Prestressed concrete railway sleepers are critical components of the railway track superstructure, designed to support the rails and maintain the gauge under various load conditions. Their performance is typically evaluated according to EN 13230 standards, which mandate Loading-Unloading-Reloading (LUR) tests for assessing design and quality. However, these standards present significant limitations, particularly in evaluating decompression capacity and detecting micro-crack formations, which are difficult to observe through traditional methods. This study introduces an innovative approach based on progressive bending stiffness and visco-plastic deflection analysis to overcome these challenges. Key modifications, such as standardized waiting times and enhanced measurement techniques, were incorporated to improve accuracy and consistency. The proposed method allows for precise estimation of critical capacity values, including decompression load and first crack formation, without the need for visual inspection, making it more reliable than current standards. Our results show that this new method not only aligns with, but also refines the load estimations of EN 13230, yielding more accurate and reproducible outcomes. For the analyzed B70-type prestressed concrete sleepers, the decompression load was found to occur between 65 and 75 kN, a range not detected by standard testing methods. Furthermore, this approach significantly reduces the potential for human error and holds promise for future automation. These advancements make the proposed method highly applicable for both quality control and design of prestressed concrete railway sleepers, warranting further validation across different sleeper types and prestressed concrete structures.