Study On Intelligent Selection Method For Time-domain Signals Of Long-span Continuous Rigid Frame Bridge Model Under Working Conditions

At present, domestic and foreign long-span continuous rigid-framed bridges areapllied extensively and the frequent injury desease arouses the attention in the field ofengineering. The paper takes long-span continuous rigid-framed bridge as the mainresearch object. On the theoretical basis of existing structural dynamics, signal analysis,voiceprint recognition, structure pattern recognition, probabilistic statistics andstructural damage identification, the scaled model of bridge is made and research ondynamic damage detection of bridge structure is done according to subsection analysisof acceleration response signal and voiceprint spectrum under many types of incentivefunction. The main achievements are follows:â‘ According to principle of similarity-ratio, the scaled model of HeichonggouBridge (left part) is designed and made; through artificial static loading of concentratedforce, transverse natural cracking appears in base plate of the middle part of the mainspan and the structural damage state are simulated.â‘¡Collection and dealing analysis of acceleration signal of model bridge aredone in every types of structural state under ambient excitation and hammeringexcitation. Finite element simulated model of prototype and model bridge structure arebuilt. The measured data of actual bridge, measured data of scaled model andcalculated data getting from finite element calculation are compared and the efficiencyof scaled model of bridge and finite element numerical model are verified.â‘¢Aiming at initial intact status, cracked damage condition and fracturepropagation status of scaled model of brodge, many working condition experiment ofdriving excitation are done in condition of different mass and different driving speedand acceleration time history response signal of key part are gotten. Using signalPiecewise spectrum method, voiceprint spectrum of structural dynamic response isbuilt on the basis of acceleration and characteristic frequency of model structure inevery working condition are gottten by weghting of probability of frequency point byuse of subsection spectral analysis.â‘£On the basis of probability meaning that structural damage causes reductionof natural frequency of structure, by use of statistical characteristics of characteristicfrequency in every working condition in the condition of intact status and damage state of model bridge, performance function of structural damage identification is built andprobability distribution of performance function is used to do identification ofstructural damage.