Plastic bending of reinforcement bars against mandrels is the usual procedure to provide bends and hooks for steel reinforcement bars. Minimum mandrel diameters are usually given in to codes of practice, depending on the type of detail and diameter of the bar. These recommendations for the bend diameter ensure a safe transfer of forces, avoiding splitting failures that may potentially limit the resistance of the detail. In most cases, these recommendations are largely based on a number of experimental works performed several decades ago. At that time, these investigations were performed on reinforcement and concrete with lower strengths than currently used. This paper presents the results of a comprehensive research programme on bend detailing and required mandrel diameter to avoid local concrete failures leading to spalling of the concrete cover. The results of an experimental programme are presented, showing the influence of different parameters such as the mandrel diameter, the bending angle and the concrete cover. The tests were instrumented with advanced measurement techniques (fibre-optic measurements and digital image correlation), showing that consistent modelling of the transfer of forces can be performed on the basis of the geometrical and mechanical parameters of the details.

钢筋在心轴上的塑性弯曲是为钢筋提供弯曲和钩子的常用程序。最小心轴直径通常在实践规范中给出，具体取决于钢筋的细部类型和直径。这些关于弯曲直径的建议可确保力的安全传递，避免可能会限制细节阻力的分裂失败。在大多数情况下，这些建议主要基于几十年前进行的一些实验工作。当时，这些调查是对强度低于目前使用的钢筋和混凝土进行的。本文介绍了一项关于弯曲细节和所需心轴直径的综合研究计划的结果，以避免局部混凝土破坏导致混凝土保护层剥落。给出了一个实验程序的结果，显示了不同参数的影响，如心轴直径、弯曲角度和混凝土保护层。这些测试采用了先进的测量技术（光纤测量和数字图像相关），表明可以根据细节的几何和机械参数对力的传递进行一致的建模。