ABSTRACT Determination of the axial load acting on steel reinforcement tie-rods is of crucial importance for ensuring the effectiveness and safety of structures, especially in the case of ancient masonry buildings. Many non-destructive dynamic techniques have been proposed and successfully tested over recent decades; however, ancient tie-rods can be affected not only by excessive loads but also by cracks, flaws and localized damage due to ageing and environmental effects, resulting in hidden dangers. This work introduces an operative, simple technique for the detection of cracks in structural tie-rods based on analysis of the dynamic behaviour of the rod itself and estimation of the flexural compliance. The method, refined and validated with extensive laboratory tests, shows how the presence of a crack changes the natural frequencies, damping and compliance of the rod in a way that can be quantified and recognized in unknown situations. On the basis of these results, a novel quantitative damage index is defined for practical use.

中文翻译：

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通过振动分析检测轴向载荷拉杆中的裂纹

摘要 确定作用在钢筋拉杆上的轴向载荷对于确保结构的有效性和安全性至关重要，尤其是在古老的砖石建筑中。近几十年来，人们提出并成功测试了许多非破坏性动态技术；然而，古老的拉杆不仅会受到过大载荷的影响，还会因老化和环境影响而出现裂纹、缺陷和局部损坏，从而产生隐患。这项工作介绍了一种可操作的简单技术，用于检测结构拉杆中的裂纹，该技术基于对拉杆本身的动态行为的分析和对弯曲柔量的估计。该方法经过广泛的实验室测试改进和验证，显示了裂纹的存在如何改变固有频率，杆的阻尼和顺应性以一种可以在未知情况下量化和识别的方式。在这些结果的基础上，定义了一种新的定量损伤指数以供实际使用。