Based on a sample of some real earthquakes,we have suggested in previous papers that there is a density-tectonic stress wave with ultra-low frequency which is emitted from the epicenter region for months before earthq...Based on a sample of some real earthquakes,we have suggested in previous papers that there is a density-tectonic stress wave with ultra-low frequency which is emitted from the epicenter region for months before earthquakes,and a micro-fracture wave 1 ～ 10 days before earthquakes. The former has been observed by different kinds of measurements and the latter has been observed by a few chance observations which consists of electromagnetic,gravitational and sonic fluctuations. We show real observational results that depict the two waves and they have very different frequencies,which are not difficult to discriminate. The classical elastic-rebound model is one of the most influential theories on earthquakes,and the thermodynamic elastic-rebound model has amended the classical framework. Considering the two waves above,we attempt to further modify the elasticrebound model,and the new framework could be called the "micro-fracture elasticrebound model". We infer that tectonic earthquakes could have three special phases: the accumulation of tectonic stress,micro-fracture,and main-fracture. Accordingly,there would be three waves which come from the epicenter of a tectonic earthquake,i. e. ,the tectonic stress wave with ultra-low frequency a few months before the earthquake,the micro-fracture wave about 1 ～ 10 days before the earthquake and the main-fracture wave (common earthquake wave).展开更多
A timely and accurate damage identification for bridge structures is essential to prevent sudden failures/collapses and other catastrophic accidents.Based on response surface model(RSM)updating and element modal strai...A timely and accurate damage identification for bridge structures is essential to prevent sudden failures/collapses and other catastrophic accidents.Based on response surface model(RSM)updating and element modal strain energy(EMSE)damage index,this paper proposes a novel damage identification method for girder bridge structures.The effectiveness of the proposed damage identification method is investigated using experiments on four simply supported steel beams.With Xiabaishi Bridge,a prestressed continuous rigid frame bridge with large span,as the engineering background,the proposed damage identification method is validated by using numerical simulation to generate different bearing damage scenarios.Finally,the efficiency of the method is justified by considering its application to identifying cracking damage for a real continuous beam bridge called Xinyihe Bridge.It is concluded that the EMSE damage index is sensitive to the cracking damage and the bearing damage.The locations and levels of multiple cracking damages and bearing damages can be also identified.The results illuminate a great potential of the proposed method in identifying damages of real bridge structures.展开更多
文摘Based on a sample of some real earthquakes,we have suggested in previous papers that there is a density-tectonic stress wave with ultra-low frequency which is emitted from the epicenter region for months before earthquakes,and a micro-fracture wave 1 ～ 10 days before earthquakes. The former has been observed by different kinds of measurements and the latter has been observed by a few chance observations which consists of electromagnetic,gravitational and sonic fluctuations. We show real observational results that depict the two waves and they have very different frequencies,which are not difficult to discriminate. The classical elastic-rebound model is one of the most influential theories on earthquakes,and the thermodynamic elastic-rebound model has amended the classical framework. Considering the two waves above,we attempt to further modify the elasticrebound model,and the new framework could be called the "micro-fracture elasticrebound model". We infer that tectonic earthquakes could have three special phases: the accumulation of tectonic stress,micro-fracture,and main-fracture. Accordingly,there would be three waves which come from the epicenter of a tectonic earthquake,i. e. ,the tectonic stress wave with ultra-low frequency a few months before the earthquake,the micro-fracture wave about 1 ～ 10 days before the earthquake and the main-fracture wave (common earthquake wave).
基金The National Natural Science Foundation of China(Grant Nos.51178101 and 51378112)The University Graduate Student Scientific Research Innovation Plan of Jiangsu Province(Grant No.CXZZ13_0109)China Scholarship Council under Program for Graduate Student Overseas Study Scholarship
文摘A timely and accurate damage identification for bridge structures is essential to prevent sudden failures/collapses and other catastrophic accidents.Based on response surface model(RSM)updating and element modal strain energy(EMSE)damage index,this paper proposes a novel damage identification method for girder bridge structures.The effectiveness of the proposed damage identification method is investigated using experiments on four simply supported steel beams.With Xiabaishi Bridge,a prestressed continuous rigid frame bridge with large span,as the engineering background,the proposed damage identification method is validated by using numerical simulation to generate different bearing damage scenarios.Finally,the efficiency of the method is justified by considering its application to identifying cracking damage for a real continuous beam bridge called Xinyihe Bridge.It is concluded that the EMSE damage index is sensitive to the cracking damage and the bearing damage.The locations and levels of multiple cracking damages and bearing damages can be also identified.The results illuminate a great potential of the proposed method in identifying damages of real bridge structures.
