Study On Damage Identification Of Steel Frame Structure Based On Wavelet Packet Energy Spectrum Under Ambient Excitation

Under the influences of disaster factors such as long-term loads, material aging and fatigue effect, the local damage accumulation of steel structure’s key components would be caused during use, and may lead to the sudden failure of structure eventually, which would bring huge economic losses and casualties. Study on the method of identifying damage and locating the parts, has important significance to avoid steel structure accidents.This paper put forward new structure damage identification indexes combining dynamic response of the structure and the wavelet packet energy spectrum, which were named by energy spectrum average(ESAD) and the variation rate of total energy difference for node storey drift(EDRV). On the premise of the excitation being same before and after damage, used ESAD to identify structure damage and locate the parts preliminary, and then EDRV to achieve precise positioning of structural damage.In the case of random white noise exciting at one single point on steel frame structure, the ability of eliminating the effects of random excitation was compared, with the correlation function and the virtual impulse response function between two points responses as structure’s dynamic characteristics parameters respectively. The result showed the robustness of the virtual impulse response function being better. Based on virtual impulse response function, the existing ERVD and ESAD presented in this paper was used to identify the damage. The result showed that the ESAD index was better than ERVD index in the aspect of the ability of damage identification and degree characterization.Establishing soil-superstructure model, the vertical random white noise excitation at three points on the surface of the soil was put forward to simulate the effect of complex environment incentive to the upper structure. The three key parameters(input data length, output data length and window function) of virtual impulse response function was determined by explaining and comparing. After achieving virtual impulse response function, combining wavelet packet energy spectrum, the damage identification effect of steel frame structure in the complex ambient excitation case was verified.