Hu X.,Tongji University |
Xie L.,Tongji University |
Shim H.,University of Macau |
Zhang S.,Shanghai Urban Construction Design and Research Institute |
Yang D.,Tongji University
Chinese Journal of Chemical Engineering | Year: 2014
A novel full scale modified A2O (anoxic/anaerobic/aerobic/pre- anoxic)-membrane bioreactor (MBR) plant combined with the step feed strategy was operated to improve the biological nutrient removal (BNR) from low C/N ratio municipal wastewater in Southern China. Transformation of organic carbon, nitrogen and phosphorus, and membrane fouling were investigated. Experimental results for over four months demonstrated good efficiencies for chemical oxygen demand (COD) and NH+ 4-N removal, with average values higher than 84.5% and 98.1%, respectively. A relatively higher total nitrogen (TN) removal efficiency (52.1%) was also obtained at low C/N ratio of 3.82, contributed by the configuration modification (anoxic zone before anaerobic zone) and the step feed with a distribution ratio of 1: 1. Addition of sodium acetate into the anoxic zone as the external carbon source, with a theoretical amount of 31.3 mg COD per liter in influent, enhanced denitrification and the TN removal efficiency increased to 74.9%. Moreover, the total phosphate (TP) removal efficiency increased by 18.0%. It is suggested that the external carbon source is needed to improve the BNR performance in treating low C/N ratio municipal wastewater in the modified A2O-MBR process. © 2014 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP).
Sun Y.,Shanghai JiaoTong University |
Shen S.-L.,Shanghai JiaoTong University |
Xia X.-H.,Shanghai JiaoTong University |
Xu Z.-L.,Shanghai Urban Construction Design and Research Institute
Materials and Design | Year: 2013
Studying the ratcheting and shakedown behavior of materials under cyclic loading is significant for controlling structural deformation and improving the service lifetime of materials. In this study, cyclic loading tests were performed on DH36 steel at room temperature under various conditions while evaluating the effects of the loading waveform, the loading rate and the stress ratio to reveal the material characteristics of ratcheting and shakedown behavior and to provide an experimental basis for proposing and implementing a numerical method that predicts the shakedown limit in this type of cyclic plastic behavior. A numerical analysis method using the plastic deformation energy as a shakedown criterion was proposed based on the energy dissipation phenomena observed in the tests. The method was then applied to two classic examples of shakedown analysis by computation and was compared with related results from the literature to evaluate its effectiveness and reliability. This method provides a new approach for the numerical analysis of the material shakedown limit. © 2012 Elsevier Ltd.
Huang A.,Shanghai Urban Construction Design and Research Institute |
Zhang X.,Shanghai Urban Construction Design and Research Institute
Modern Tunnelling Technology | Year: 2015
Based on the situation of Beijing metro line 14, where the construction of the receiving station for the shield machine lagged behind the construction of the shield-bored tunnel, a new construction method is proposed in which the shield machine is placed before the construction of the retaining structure and is later hoisted out during construction of the station's retaining structure. With a focus on the stress mechanism of the shield machine and its segments as well as the soil stability theory, a method of soil-mass grouting reinforcement and temporary support inside the segments was adopted, and the surrounding environment was monitored. The results show that when the conditions of the receiving station cannot satisfy the requirements for hoisting out the shield machine, this method can mitigate the constraints of lagged station construction and has significant social and economic benefits, thereby providing a broad basis for future application. © 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.
Peng F.-L.,Tongji University |
Wang H.-L.,Tongji University |
Tan Y.,Tongji University |
Xu Z.-L.,Shanghai Urban Construction Design and Research Institute |
Li Y.-L.,Shanghai Foundation Engineering Co.
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2011
Characterized by unmanned excavation and remote controlling, the new pneumatic caisson (NPC) method has advantages in deep excavation such as deep shield tunnel shafts and some underground construction close to the existing structures or facilities. When adopted in urban areas, it is very important to control the ground deformation during a caisson construction. For this purpose, field measurements of ground deformation were conducted during a tunnel shaft construction in Shanghai soft ground, in which the NPC method was used. On the basis of the particular construction procedure of a pneumatic caisson, one kinematic mechanical model was proposed for evaluating the influence of NPC construction on the surrounding strata. This model was incorporated into a finite-element (FE) program. By comparing the FE-predicted results of the proposed model and the field measurements, the accuracy and reliability of this model were verified. © 2011 American Society of Civil Engineers.
Bao L.,Shanghai Urban Construction Design and Research Institute
IET Conference Publications | Year: 2011
A knowledge-based prediction and evaluation system (KBPEs) for highway networks development planning is put forward, which is a decision support for transportation government. Firstly, the architecture of KBPEs is presented, and then with an example of Weihai city, the paper goes into more detail about how the system works. After analyzing current highway networks of Weihai city and concluding some factors that hold back transportation development, social and economic indexes (population, GDP) are predicted according to the statistics with the historical data. The regression formula among highway networks, national economy and population is presented. Furthermore, future highway networks are reasonably predicted quantitatively and qualitatively so as to meet the requirement of local social and economic development. According to the highway networks development planning of Weihai city, the total highway scale will reach to 2600 km in 2015, 3000 km in 2020 and about 3500 km in 2030. Finally, from the point of technical performance, besides macro-economy and social benefit, the paper gives evaluation of the adaptability of predicted highway networks in Weihai City.
Lu J.-S.,Shanghai Urban Construction Design and Research Institute |
Zhang Q.-L.,Tongji University
Gongcheng Lixue/Engineering Mechanics | Year: 2013
An efficient approach that employs a convex model to deal with the most unfavorable initial geometrical imperfection of spherical latticed shells is proposed. Initial geometric imperfection, as one of random variables, is a linear combination of N eigenmodes based on linear buckling analysis. The deviation of N dominant mode shapes is assumed to vary on an ellipsoidal set in the N-dimensional Euclidean space. The limit load of nonlinear buckling will be determined as a function of the N linear buckling mode amplitudes. This approach can replace the computationally expensive probabilistic approach, typically used in the study of imperfection sensitive structures. A Monte Carlo simulation has been performed to validate the results obtained by the convex model. ANSYS Parametric Design Language secondary development is used to carry out the finite element analysis.
Jia R.Y.,Shanghai Urban Construction Design and Research Institute
Applied Mechanics and Materials | Year: 2013
Drop shafts, especially the vortex drop structure, are vertical conveyance conduits used in hydraulic engineering, water supply and drainage engineering, and so on. Because of complex flow properties and safety requirement, the system running security and reinforcement measure should be verified before it was built. In this paper, numerical and physical simulation methods were employed to verify mutually and analyze the hydraulic characteristics in a tangential vortex dropshaft. It is shown that the water carrying capacity of the dropshaft could be increased suitably and the safety freeboard of the conduit is the limiting factor. The air-water mixing at the junction may reduce the energy dissipation and reinforcement measure for the whole wall is necessary. © (2013) Trans Tech Pudlications, Switzerland.
Huang H.,Tongji University |
Sun L.,Tongji University |
Jiang X.,Shanghai Urban Construction Design and Research Institute
Smart Structures and Systems | Year: 2012
Mechanical dampers have been proved to be one of the most effective countermeasures for vibration mitigation of stay cables in various cable-stayed bridges over the world. However, for long stay cables, as the installation height of the damper is restricted due to the aesthetic concern, using passive dampers alone may not satisfy the control requirement of the stay cables. In this connection, semi-active MR dampers have been proposed for the vibration mitigation of long stay cables. Although various studies have been carried out on the implementation of MR dampers on stay cables, the optimal damping performance of the cable-MR damper system has yet to be evaluated. Therefore, this paper aims to investigate the effectiveness of MR damper as a semi-active control device for the vibration mitigation of stay cable. The mathematical model of the MR damper will first be established through a performance test. Then, an efficient semi-active control strategy will be derived, where the damping of MR damper will be tuned according to the dynamic characteristics of stay cable, in order to achieve optimal damping of cable-damper system. Simulation study will be carried out to verify the proposed semi-active control algorithm for suppressing the cable vibrations induced by different loading patterns using optimally tuned MR damper. Finally, the effectiveness of MR damper in mitigating multi modes of cable vibration will be examined theoretically.
Xia S.,Tongji University |
Jia R.,Tongji University |
Jia R.,Shanghai Urban Construction Design and Research Institute |
Feng F.,AECOM Technology Corporation |
And 4 more authors.
Bioresource Technology | Year: 2012
The effect of solids retention time on reactor performance and microbial community composition in anoxic/aerobic membrane bioreactors (A/O-MBR) were investigated in this study. Experimental results showed high removal efficiencies of conventional pollutants. Antibiotics removal efficiencies were obviously affected by SRT changes. Longer SRT (above 30. days) was proved to be suitable operational condition for antibiotics removal. Denaturing gradient gel electrophoresis (DGGE) and clone library analysis revealed that bacteria belong to Betaproteobacteria and Gammaproteobacteria were the dominant species during wastewater treatment and antibiotics removal. SRT significantly influenced the relative numbers of nitrifying bacteria. Removal efficiency of total nitrogen (TN) decreased when SRT was 3. days, because nitrogen loading exceeded the denitrification ability of the reactors. Unlike tet C and tet E genes, sulfa antibiotics resistance gene presented a decreasing tendency with the decrease of SRT, and finally affected sulfa antibiotics removal efficiencies. © 2011 Elsevier Ltd.
Lu X.,Tongji University |
Wang H.,Shanghai Urban Construction Design and Research Institute |
Huang M.,Tongji University
Mathematical Problems in Engineering | Year: 2014
By FE simulation with Mohr-Coulomb perfect elastoplasticity model, the relationship between the support pressure and displacement of the shield tunnel face was obtained. According to the plastic strain distribution at collapse state, an appropriate failure mechanism was proposed for upper bound limit analysis, and the formula to calculate the limit support pressure was deduced. The limit support pressure was rearranged to be the summation of soil cohesion c, surcharge load q, and soil gravity γ multiplied by their corresponding coefficients Nc, Nq, and Nγ, and parametric studies were carried out on these coefficients. In order to consider the influence of seepage on the face stability, the pore water pressure distribution and the seepage force on the tunnel face were obtained by FE simulation. After adding the power of seepage force into the equation of the upper bound limit analysis, the total limit support pressure for stabilizing the tunnel face under seepage condition was obtained. The total limit support pressure was shown to increase almost linearly with the water table. © 2014 Xilin Lu et al.