根据有限观测的结构动力响应，实时对结构发生损伤的时间、位置与损伤程度进行诊断，是目前土木工程健康监测的一个重要的任务。本文提出一种在对结构加速度部分观测的情况下，对结构刚度发生突变的结构损伤形式进行实时的追踪和诊断的算法。该算法的主要思想是首先基于扩展卡尔曼滤波识别结构刚度参数，然后通过观测加速度和计算预测的加速度误差平方和，对结构刚度发生突变时刻进行判断，再通过优化突变时的结构的刚度参数变化，对损伤位置与损伤程度进行识别。数值模拟和实验的结果都表明了，该方法能够有效地追踪时变参数，并实时诊断出损伤发生的时间、位置和程度。

In health monitoring of civil structures, it is an important task to on-line detect the instant, location and degree of structural damage based on limited structure dynamic responses when disaster occurs. In this paper, a damage detection approach is proposed for on-line tracking and detecting the abrupt degradations of structural stiffness using partial measurements of structural acceleration responses. The main idea of the proposed approach is to identify structural stiffness parameters based on Extended Kalman Filter first, and detect the time instant of abrupt change of structural stiffness parameters based on deviation of the quadratic sum of observed and predicted acceleration responses. The exact locations and extents of structural damages are determined by optimizing the change of structural stiffness parameters. Both a numerical example and an experimental verification demonstrate that the proposed approach is able to on-line detect the time instant, location and degree of structural damage due to the abrupt degradation of structural stiffness.