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Yang F.,Tongji University | Luo Q.-F.,Shanghai Institute of Disaster Prevention and Relief
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2010

At present, an equal-distance circle model is generally used for directly fitting acceleration peak attenuation curve, epicentral distance or focal distance is only the coordinate statistical parameter for a seismic observation station. For large earthquake with a long fault, the isoseismic curves of the equal-distance circle model exist serious deviation from realistic isoseismic curves. There is enormous differences between the acceleration peak attenuation curve along the long axis and that along the short axis. An four-area elliptical model was proposed here dividing seismic observation stations into four areas according to the long axis and the short axis. Every elliptical acceleration isoseismic curve in four areas was respectively figured out using interpolation in relation to seismic intensity isoseismic curves. On this basis, Wenchuan earthquake acceleration peak attenuation curve was derived along two long semiaxes and two short semiaxes. Comparing Wenchuan 8.0 rank earthquake acceleration peak attenuation curve using the four-area elliptical model with that using the circle model, the former was more close to the real situation and it could reflect the hanging and foot wall effect of fault and the direction effect of earthquake. Source


Zhao X.,Shanghai Institute of Disaster Prevention and Relief | Zhao X.,Tongji Architectural Design Group Co. | Yang W.,Tongji University
Proceedings of the 12th International Symposium on Structural Engineering, ISSE 2012 | Year: 2012

There are several objectives in damage identification, such as damage time, damage position and damage severity etc. The exact results would be achieved only if the full details about structures were available. However, it is almost impossible to grasp the details of the dynamic characteristics of super high-rise buildings. In view of the disadvantage, a new method was proposed in this paper that wavelet transform was combined with modal updating to identify damages. Damage information would be achieved without too much information about structural properties if the new method was employed. The damage time would be obtained through discrete wavelet transform, and the damage position would be obtained through the distribution of wavelet spikes. And the change of stiffness would be reflected through continuous wavelet transform, which is helpful to observe the time-varying property of the structure. Finally, damage severity would be determined by importing mode information of the structure after damaged into the procedure of modal updating. Source


Zhao X.,Shanghai Institute of Disaster Prevention and Relief | Zhao X.,Tongji Architectural Design Group Co. | Lin Z.,Tongji University
Proceedings of the 12th International Symposium on Structural Engineering, ISSE 2012 | Year: 2012

This article focuses on the analysis of wind-induced vibration response of high-rise buildings and the damage identification through the response. The spectral representation method was used to simulate fluctuating wind speed time series with venue wind loads on statistical properties. Wavelet transform analysis and modal updating methods were introduced to determine damage time, damage location and damage severity of the structure. The research shows that damage information would be achieved with only acceleration time series of structure under wind load. The damage time would be obtained through discrete wavelet transform, and the damage location could be approximately found the distribution of wavelet spikes. And the change of stiffness would be reflected through continuous wavelet transform, which is helpful to observe the time-varying property of the structure. Finally, damage severity would be determined by importing mode information of the structure after damaged into the procedure of modal updating. Source


Liu J.-H.,Shanghai Maritime University | Cong B.-H.,Shanghai Institute of Disaster Prevention and Relief
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology | Year: 2011

Water mist for fire suppression and control has received considerable attention as one of the potential methods for halon replacement. The effectiveness of water mist fire suppression systems (WMFSS) can also be further enhanced by additives. A series of experimental study has been conducted to explore the critical fire suppression concentration of water mist with metal chloride additives. The results show that the metal chloride can obviously improve fire suppression efficacy of water mist which can be affected by the type and concentration of metal chloride. With respect to their fire suppression effectiveness, there has the relationship of CaCl2, NaCl, KCl, FeCl2. Because of three co-existing effects, there must be an optimal concentration of metal chloride match to fire suppression effectiveness of water mist. Source


Liu J.,Shanghai Maritime University | Cong B.,Shanghai Institute of Disaster Prevention and Relief
Journal of Thermal Science | Year: 2013

In order to investigate the fire suppression effectiveness of water mist with metal chloride additives, ultrafine water mists of these salts with diameters about 10μm were introduced into CH4/air non-premixed flame in the cup burner. Results showed that these droplets hard to make itself to the flame front under the cup burner flow conditions functioned as a carrier of the vaporized solid particles or its decomposed materials. The metal chloride improved fire suppression efficacy of water mist which were affected by the type and concentration of metal chloride. On a mass basis, there is a fire suppression effectiveness relationship of MgCl2 Source

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