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Wang F.,Tongji University | Wang F.,Shanghai Institute of Disaster Prevention and Relief | Huang H.W.,Tongji University | Zhang D.M.,Tongji University | And 2 more authors.
SHMII 2015 - 7th International Conference on Structural Health Monitoring of Intelligent Infrastructure | Year: 2015

To date, Shanghai has built an intensive network of metro tunnel system with the total mileage of 548 km and 337 stations. Shield tunnelling is being used as the main construction method in Shanghai metro tunnel. Because of extreme surcharge loading on the ground surface above the metro tunnel in some area, several kinds of diseases including large convergence, crack, seepage occurred in the shield tunnel structure are observed. These serious diseases will affact the metro opration significantlly. In order to ensure the safety of tunnel operation, the convergence performance is recovered by soil grouting at two sides of the tunnel lining. In this paper, Micro Electro Mechanical Systems (MEMS) and Wireless Sensor Network (WSN) are employed for the behavior study of shield tunnel structure during the soil grouting. Applications of convergence monitoring by MEMS inclinators is illustrated. The feasibility of WSN in metro shield tunnel is also discussed. According to the comparison to the convergence data by laser distance meter and total station, the result shows the successful application of MEMS and MSN. © 2015, International Society for Structural Health Monitoring of Intelligent Infrastructure, ISHMII. All rights reserved.


Zhang D.M.,Tongji University | Phoon K.K.,National University of Singapore | Huang H.W.,Tongji University | Hu Q.F.,Shanghai Institute of Disaster Prevention and Relief
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2015

This work presents a critical evaluation of the model factor for the mobilized strength design (MSD) method for cantilever deflection in undrained soft to medium-stiff clay. The model factor is characterized in two parts. A correction factor η is first defined as the ratio between the wall-top deflection computed from the FEM and its corresponding value computed from the MSD. The hardening soil with a small-strain model is used in FEM. The statistics of η are evaluated using 82 numerical simulations. Because η is not random, and therefore cannot be modeled directly as a random variable, it is decomposed as a product of a systematic part (f) and a random part (η*). The random part is modeled as a lognormal random variable with a mean of 1.01 and a coefficient of variation (COV) of 0.18. The model factor for FEM (e{open}FEM) is next defined as the ratio between the measured wall-top deflection and the corresponding FEM result. The statistics of e{open}FEM are evaluated using 45 field cases. The ratio e{open}FEM is random and can be modeled directly as a lognormal random variable with a mean of 1.01 and a COV of 0.21. The model factor for MSD (e{open}MSD) is finally derived from the product of η and e{open}FEM. This proposed approach is validated by 14 centrifuge tests. The importance of including the proposed model factor E{open}MSD in reliability analysis is illustrated using a field example. © 2014 American Society of Civil Engineers.


Zhang D.,Tongji University | Huang H.,Tongji University | Phoon K.K.,National University of Singapore | Hu Q.,Shanghai Institute of Disaster Prevention and Relief
Soils and Foundations | Year: 2014

In models based on Winkler springs for tunnel lining design, designers always face the difficulty of selecting appropriate values for the radial subgrade modulus (κr). The widely used solution κr for a circular tunnel in elastic ground proposed by Wood (1975) was found to be applicable only when the tunnel radial deformation is oval-shaped. On the basis of the Wood's solution, this note presents a general solution for κr when the radial deformation of the tunnel is described by a Fourier series. This modiied Wood's solution of κr using compatible stress functions is validated by a numerical example. The modiied solution for the example shows good consistency with the original Wood's solution when the tunnel becomes an oval shape with deformations. The example indicates that the magnitude of κr is signiicantly affected by the distribution shape of the tunnel radial deformation. The value of κr is no longer a constant value around the tunnel when the tunnel deforms into a general shape described by a Fourier series. It is quite different from the value of κr for a distribution shape described by a single Fourier term, i.e. one involving a single frequency. The application of a general solution for κr is illustrated by a design case using a bedded beam model. © 2014 The Japanese Geotechnical Society.


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


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.


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.


Zhang D.-M.,Tongji University | Huang H.-W.,Tongji University | Hu Q.-F.,Shanghai Institute of Disaster Prevention and Relief | Jiang F.,Shanghai Municipal Engineering Design Institute Group Co.
Tunnelling and Underground Space Technology | Year: 2015

The recent development of larger shield-driven tunnels has for consequence that the tunnel face consists more frequently of multi-layered formations. However, most tunnel designs are still currently conducted in the homogeneous soil condition. In this study, a series of 1-g plane model tests and FEM analyses were carried out to investigate the influence of the layered soils in terms of their relative stiffness and thickness on the lining behavior (i.e. inner force and convergence). The numerical results were found to agree reasonably well with the results obtained from the model tests. For multi-layered formation, a linear increase of the relative thickness of the sandy layer could reduce non-linearly the magnitude of both the moment and the convergence. The distributions of the bending moment and of the convergence along the tunnel perimeter were found to be strongly dependent on the relative stiffness of the layered formations. However, the multi-layered condition has little effect on the thrust force under the condition of this test. In view of these results, some discussions on the applicability of the widely used homogenized design model for the multi-layered soil condition are finally presented. © 2015 Elsevier Ltd.


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.


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.


He L.,Tongji University | He L.,University of North Carolina at Chapel Hill | He L.,Shanghai Institute of Disaster Prevention and Relief | Song Y.,University of North Carolina at Chapel Hill | And 2 more authors.
Tunnelling and Underground Space Technology | Year: 2012

This paper presents a case study on predicting demand for Urban Underground Space use (UUS) using recent data from Shanghai, China. Building on recent research that quantifies UUS, we analyze the relationship between the amount of UUS and other urbanization factors including population density, annual GDP per capita, and real estate price. Specifically, we utilize multivariate regression analysis with a Box-Cox transformation to construct a predictive model that assesses the demand for underground space in urban districts. The model indicates that population density and GDP per capita both have independent positive predictive power on the density of UUS use. The effect of real estate price is offset by these two factors. This model can serve as a foundation for developing urban master plans as well as conducting future comparative studies. © 2012 Elsevier Ltd.

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