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Parameter effects on the dynamic characteristics of a super-long-span triple-tower suspension bridge
Hao Wang, Ke-guan Zou, Ai-qun Li, Chang-ke Jiao
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 305-316.
https://doi.org/10.1631/jzus.A0900496
A 3D finite element model for the Taizhou Yangtze River Bridge, the first triple-tower long-span suspension bridge in China, is established based on the nonlinear finite element software ABAQUS, and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method. The study focuses on the effects of the vertical, lateral and torsional stiffness of the steel box girder, the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. Our results show that, in general, the dynamic characteristics of the triple-tower suspension bridge are similar to those of two-tower suspension bridges. The vertical, lateral and torsional stiffness of the steel box girder have different effects on the dynamic characteristics of triple-tower suspension bridges. The elastic restraints have a more significant effect on the dynamic characteristics than the central buckle, and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. Also, rigid central buckles have a greater influence on the dynamic characteristics of triple-tower suspension bridges than on those of two-tower suspension bridges. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span triple-tower suspension bridges.
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Influence of baffle position on liquid sloshing during braking and turning of a tank truck
Ning Kang, Kui Liu
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 317-324.
https://doi.org/10.1631/jzus.A0900521
The influence of baffle position on liquid sloshing during the braking and turning of a tank truck was studied using a volume of fluid (VOF) model. The forces, their positions and weight distribution during braking and the forces and rolling moment during turning were calculated. The reliability of the calculation method was validated by comparisons with experimental results. The results showed that during braking, liquid splashes in the tank and the maximum forces and G (the ratio of weight acting on the front axle to the rear axle) are large when A (the ratio of the arch area above the baffle to the area of cross section)≤0.1. When A≥0.2, as the position of the baffle is lowered, the maximum of Fx (the force in direction x) first decreases then increases, and the maximum of Fy (the force in direction y) and G increase. During turning, liquid splashes in the tank and the maximum forces and M (the rolling moment) are large when D (the ratio of the arch area above the baffle to the area of cross section)≤0.2. When D≥0.3, as the position of the baffle is lowered, the maximums of Fy, Fz (the force in direction z) and M increase.
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Perturbation spectrum method for seismic analysis of non-classically damped systems
Wei Guo, Hong-nan Li, Zhen Guo
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 325-334.
https://doi.org/10.1631/jzus.A0900155
Fundamental principles from structural dynamics, random theory and perturbation methods are adopted to develop a new response spectrum combination rule for the seismic analysis of non-classically damped systems, such as structure-damper systems. The approach, which is named the perturbation spectrum method, can provide a more accurate evaluation of a non-classically damped system’s mean peak response in terms of the ground response spectrum. To account for the effect of non-classical damping, all elements are included in the proposed method for seismic analysis of structure, which is usually approximated by ignoring the off-diagonal elements of the modal damping matrix. Moreover, as has been adopted in the traditional Complete Quadratic Combination (CQC) method, the white noise model is also used to simplify the expressions of perturbation correlation coefficients. Finally, numerical work is performed to examine the accuracy of the proposed method by comparing the approximate results with exact ones and to demonstrate the importance of the neglected off-diagonal elements of the modal damping matrix. In the examined cases, the proposed method shows good agreement with direct time-history integration. Also, the perturbation spectrum method leads to a more efficient and economical calculation by avoiding the integral and complex operation.
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Optimized operation plan for sewer sediment control
Yong-chao Zhou, Tian Li
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 335-341.
https://doi.org/10.1631/jzus.A0900082
Severe operational problems of sediment deposition have frequently occurred in stormwater sewer systems in Shanghai city due to the flat topography of the area and serious illicit connections. To control sewer sediment and its subsequential problems, optimized operation plans were proposed and an innovative performance assessment method was developed. Simulation results demonstrated that, through changing the way of pump operation and installing necessary actuators in the system, the optimized operations, especially batch intermittent intercept plan, effectively improved the flow velocity in the entire system in dry-weather condition. In conclusion, the optimized operation is an innovative idea for improving the performance and solving the problem of sediment deposition in the sewer system in Shanghai, China.
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Evaluation of the performance of surface treatments on concrete durability
Yu-xi Zhao, Pan-feng Du, Wei-liang Jin
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 349-355.
https://doi.org/10.1631/jzus.A0900580
This paper reports on a laboratory-based study carried out to evaluate the effectiveness of surface treatments on the durability of concrete and suggests a number of different evaluation methodologies for assessing the performance of various surface treatments. Durability of untreated and treated concrete specimens was evaluated by measuring chloride diffusion, charge passing capacity, air permeability and water absorption. A total of six concrete surface treatments were selected to represent different generic types, including coating, penetrant and mixed-use treatments. Results show that the concrete specimens with a coating procedure have a better long-term performance and effectiveness than the specimens with the penetrant treatments. This work also indicates that the wetting and drying cycles test can be used to assess the weatherability of the surface treatments. The ASTM C 1202 and the Autoclam air permeability test can be used to evaluate the effectiveness of surface treatments quantitatively. Further work is needed, however, to assess the longevity of the various surface treatments.
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Catalytic dechlorination and detoxification of 1-(2-chlorophenyl) ethanol by Pd/Fe
Hong-yi Zhou, Shang-chen Wang, G. Daniel Sheng
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 356-362.
https://doi.org/10.1631/jzus.A0900469
1-(2-chlorophenyl) ethanol (CPE) is of health and environmental concern due to its toxicity and its use as an intermediate in pharmaceutical manufacturing. The current work deals with the catalytic reductive dechlorination and detoxification of CPE by Pd/Fe bimetal. CPE was effectively dechlorinated to 1-phenyl ethanol (PE) accompanied by the equivalent release of chloride. The extent of CPE dechlorination increased with temperature, Fe dosage and Pd loading. A decrease in solution pH increased CPE dechlorination, resulting presumably from an increase in hydrogen production. Under the specific conditions of 20 g/L Pd/Fe, 0.10% Pd (w/w) and initial pH 5–6, the CPE dechlorination was completed within 145 min. The dechlorination followed a pseudo-first-order kinetics with an activation energy of 56.7 kJ/mol. The results of toxicity testing showed that CPE was very toxic to Chlorella, whereas PE showed little toxicity. The toxicity of the reaction solution declined gradually and the promoting effects on Chlorella intensified consequently with the dechlorination process. Thus, the reductive dechlorination of CPE to PE by Pd/Fe was a detoxification process. It may be used to effectively reduce the toxicological effects of CPE-contaminated wastewater, thereby enhancing the performance of subsequent biological processes in wastewater treatment.
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Effects of SO2 and SO3 on the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans by de novo synthesis
Ke Shao, Jian-hua Yan, Xiao-dong Li, Sheng-yong Lu, Mu-xing Fu, Ying-lei Wei
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(5): 363-369.
https://doi.org/10.1631/jzus.A0900267
The effects of SO2, SO3 on de novo synthesis of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were studied using model fly ashes incorporating copper oxide and activated carbon. It was found that the inhibitive effect of SO2 on PCDD/Fs formation is similar to that of SO3. To investigate the inhibition mechanism, CuSO4 formations from both CuO and CuCl2 were examined. The ability of SO3 to convert CuCl2 and CuO on a silica support into sulfate is much stronger than that of SO2. However, replacing silica by activated carbon leads to a much high conversion of CuCl2 to CuSO4 in the presence of SO2. The promotion by activated carbon is explained by the reduction of CuCl2 to Cu2Cl2 and the eventual conversion of Cu2Cl2 into CuSO4 is the main inhibition mechanism of SO2 on de novo synthesis of PCDD/Fs.
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10 articles
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