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Ding H.,Tianjin University | Zhang Y.,Tianjin Municipal Engineering Design and Research Institute | Sun H.,Tianjin University | Feng L.,Tianjin University
Energy and Buildings | Year: 2016

To investigate the transfer characteristics of PM2.5 in a car cabin, several experiments were performed featuring real-time online monitoring of the concentration of PM2.5 and CO2 in the cabin under different ventilation modes (circulation with outdoor air and recirculation without outdoor air), at a minimum of mechanical ventilation and matching experimental route conditions. We analyzed the PM2.5 concentration distribution characteristics and the ratio of inside-to-outside PM2.5 concentration (I/O). The ventilation rate was determined by the CO2 concentration change during the experiments, and it was used to analyze the transfer characteristics of PM2.5. The results showed that under the "circulation with outdoor air" condition, the average I/O was 0.6, while it was 0.25 under the "recirculation" condition. I/O value decreased with acceleration of driving speed. It could be concluded that the ventilation mode has a significant impact on the concentration of PM2.5 in the cabin, and plays a decisive role in PM2.5 levels. The quantitative evaluation of PM2.5 transfer characteristics under the "circulation with outdoor air" condition showed that the contributions of ventilation, penetration, and deposition to the cabin PM2.5 concentration accounted for 69.3%, 22.8%, and 7.9%, respectively; while under the "recirculation" condition, penetration accounted for 72.0% and deposition accounted for 28.0%. © 2016 Elsevier B.V. All rights reserved. Source

Ji X.-B.,Northeastern University China | Zhao W.,Northeastern University China | Li S.-G.,Northeastern University China | Zhou Z.-S.,Tianjin Municipal Engineering Design and Research Institute
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2013

The mechanical behavior and deformation of a metro tunnel using isolation piles adjacent to existing buildings with shallow foundation were studied with orthogonal finite element analysis method. Comparative analysis was implemented to examine: the settlement at the surface of existing building, the isolating effect of isolation piles and effectiveness of grouting on tunnel stability. Orthogonal finite element analysis was adopted to optimize three main parameters of isolation piles. The present results indicated that the existing building changes the shape of settlement trough and increases the inter-force and deformation. Isolation piles and grouting have some control on the deformation and inter-force of supporting structures. The optimal parameters of isolation piles are 33 m in length, 0.5 m in longitudinal spacing, and the distance between piles and tunnel is 1.5 m. This kind of optimization may provide references for the similar construction design. Source

Gao Q.,Harbin Institute of Technology | Wang Z.,Harbin Institute of Technology | Guo B.,Zhejiang Institute of Communications | Bu H.,Tianjin Municipal Engineering Design and Research Institute | Xiong W.,Shenzhen China Overseas Construction Ltd
Key Engineering Materials | Year: 2014

Based on the survey of existing highway bridges, there are a large number of flaws induced by moving vehicles. The most important cause of this phenomenon is the lack of design codes on dynamic performance of highway bridges to moving vehicular loads. The existing theory of vehicle-bridge interaction is reviewed. Then the home-code program VBCVA combined with finite element program ANSYS is introduced to analyze the problem of vehicle-bridge interaction. Also, the existing design indexes of dynamic performance are discussed, such as dynamic impact factor, deflection limit, and acceleration. On the basis of above theory and program, the framework of design on dynamic performance of highway bridges to moving vehicular loads is proposed. © (2014) Trans Tech Publications. Source

Yang H.,Tsinghua University | Xu W.,Tsinghua University | Zhang Q.,Tianjin Municipal Engineering Design and Research Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015

The strain localization in granular material due to its internal fabric under external load is a popular topic in the field of geotechnical engineering. However, current studies have focused on the analysis of statistical parameters, while the intrinsic link between the macroscopic phenomena and the mesoscopic mechanism has been ignored. The macroscopic and mesoscopic mechanical characteristics and the mechanism of deformation failure in the direct shear tests were systematically analyzed with the discrete element method(DEM). According to the development of shear stress ratio under the different normal stresses during the shearing process, anti-friction properties of granular material were discussed from the perspective of particle movement. A synchronic development between the anisotropic parameters of fabric and the macro-scale stress ratio was found. Through the statistical analysis of particle rotation, the friction between particles was revealed to be an important factor to maintain the relative stability of the mesoscopic structure. The morphological analysis of the networks of force chains revealed an agreement between the direction of principle stress and the principle direction of anisotropy. The decrease of the force chain intensity and the increase of porosity during the shearing tests were discovered. Two main mechanical models of force chain structures under different normal stresses were proposed. The fluctuation of macro-scale mechanical parameters was explained with the stability of system and the cumulative release of energy, showing the microscopic mechanism of deformation localization and dilatancy. ©, 2015, Academia Sinica. All right reserved. Source

Sun Y.,Tianjin University | Sun Y.,Pennsylvania State University | Wang Z.,Tianjin Municipal Engineering Design and Research Institute | Zhang Y.,Tianjin University | And 2 more authors.
PLoS ONE | Year: 2011

Objective: To test whether the incidence of common colds among college students in China is associated with ventilation rates and crowdedness in dormitories. Methods: In Phase I of the study, a cross-sectional study, 3712 students living in 1569 dorm rooms in 13 buildings responded to a questionnaire about incidence and duration of common colds in the previous 12 months. In Phase II, air temperature, relative humidity and CO 2 concentration were measured for 24 hours in 238 dorm rooms in 13 buildings, during both summer and winter. Out-to indoor air flow rates at night were calculated based on measured CO 2 concentrations. Results: In Phase I, 10% of college students reported an incidence of more than 6 common colds in the previous 12 months, and 15% reported that each infection usually lasted for more than 2 weeks. Students in 6-person dorm rooms were about 2 times as likely to have an incidence of common colds ≥6 times per year and a duration ≥2 weeks, compared to students in 3-person rooms. In Phase II, 90% of the measured dorm rooms had an out-to indoor air flow rate less than the Chinese standard of 8.3 L/s per person during the heating season. There was a dose-response relationship between out-to indoor air flow rate per person in dorm rooms and the proportion of occupants with annual common cold infections ≥6 times. A mean ventilation rate of 5 L/(s•person) in dorm buildings was associated with 5% of self reported common cold ≥6 times, compared to 35% at 1 L/(s•person). Conclusion: Crowded dormitories with low out-to indoor airflow rates are associated with more respiratory infections among college students. © 2011 Sun et al. Source

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