王利恒¹，  周锡元²，  阎维明²，  涂  鸣²
（1 北京长城计量测试技术研究所重点实验室，北京 100095； 2 北京工业大学工程抗震与结构诊治北京市重点实验室，北京100124）

[摘要] 对无粘结预应力钢筋混凝土简支梁，分11级损伤加载直到结构达到极限承载能力状态。在每一级损伤状态下，对结构进行了锤击试验与共振试验。对锤击试验结构跨巾位移响应进行时频分析以及就共振试验通过找共振峰的方法都可以得到结构的振幅与频率关系。进一步将二者结合起来，通过分析得到了合适的时频分析所用窗口宽度。再结合时频分析方法，分析得到各级加载后无粘结预应力钢筋混凝土梁振幅与频率关系曲线族。通过分析结构振幅与频率关系曲线族的特点，总结了各级损伤状态下结构的非线性动力特性并分析了用无粘结预应力钢筋混凝土梁的非线性动力特性做损伤检测的可行性。
[关键词] 无粘结预应力；时频分析；非线性动力特性；损伤检测；试验

Study on nonlinear dynamic characteristics of unbonded prestressed reinforced concrete beam
Wang Liheng1， Zhou Xiyuan2， Yan Weiming2， Tu Ming2
(1 Changcheng Institute of Metrology & Measurement, State Key Lab for Metrology and Catibration, Beijing 100095,C hina; 2 Municipal Key Lab. of Earthquake Engin. and Stru. Retrofit, Beijing Univ. of Tech.，Beijing 100124,China)

Abstract: For an unbonded prestressed reinfcrced concrete simply suppcrted beam, eleven load levels are designed until it reaches ultimate bearingcapabilities. At each damage level, impact excitation vibration tests and harmonic excitation vibration tests are conducted. The time-frequency analysis of structural midspan displacement responses of impact excitation vibration tests is carried out, as well as the relationship of structural displacement amplitude and its fundamental frequency is obtained. By combining the results of the time-frequency analysis with the results of the hannonic excitation vibration tests, reasonable window width for time-frequency analysis can he obtained. Using time-frequency analysis, the group of curves of structural displacement amplitude and its fundamental frequency at each impairing level can he obtained. By analyzhg the characteristics of the group of curves of the stuctural displacement amplitude and its funclamental frequency, the nonlinear dynamic characteristics of the impairing unbonded prestressed reinforcd concrete beam are drawn. Then the possibilities of using nonlinear dynamic characteristics to detect the damage levels of the unbonded prastressed reinforced concrete beam are discussed.
Keywords: unbonded torestressed; time-frequency analysis; nonlinear dynamic characteristic; damage detection; test