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A numerical study on fire endurance of wood beams exposed to three-side fire
Jin Zhang, Qing-feng Xu, Yi-xiang Xu, Bin Wang, Jing-xiang Shang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(7): 491-505.
https://doi.org/10.1631/jzus.A1200022
To investigate the fire endurance of wood beams exposed to three-side fire, we conducted bearing capacity tests of two wood beams and experiments of five wood beams exposed to three-side fire. The finite element software ANSYS was also used to predict the fire endurance of those beams with the indirect order coupling method. It was found that the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. In the case of a certain load level, the fire endurance is improved if the section size is increased or covered by the fire protection coating. The central deformation increases as the fire duration increases, and the ratio of increase tends to rise. On another note, an increase in the density of wood leads to a rise in the fire endurance of a given beam. From the finite element method (FEM) calculation results, the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. When the load level is greater than 0.5, the fire endurance is significantly reduced, and it does not change significantly when the load level changes. Lastly, for a load level magnitude below 0.5, the fire endurance and load level are proportional to one another.
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Theoretical elastoplastic analysis for foundations with geosynthetic-encased columns
Yuan-yu Duan, Yi-ping Zhang, Dave Chan, Ya-nan Yu
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(7): 506-518.
https://doi.org/10.1631/jzus.A1100334
As a new technique in ground improvement, geosynthetic-encased columns (GECs) have promising applications in soft soil foundation. By assuming yielding occurs in the columns while the surrounding soil and the geosynthetic remain elastic, an elastoplastic analytical procedure for foundations improved by GECs is proposed. The radial stresses that the geosynthetic provides and the elastoplastic deformations of the foundation resting on a rigid base are derived. A comparison with finite element analysis shows that the proposed method is effective and can provide a reasonable prediction of a GEC’s deformation. Subsequent parametric analysis indicates that higher geosynthetic stiffness leads to better performance of the composite foundation. The optimum length of encasement is related to the load acting on the foundation and the permissible vertical and radial displacements of the column. Moreover, as the dilation angle of the column increases, the settlement decreases, especially under high loading. The influence of the encasement is more significant in soils with smaller elastic modulus.
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Strain transfer of surface-bonded fiber Bragg grating sensors for airship envelope structural health monitoring
Hai-tao Zhao, Quan-bao Wang, Ye Qiu, Ji-an Chen, Yue-ying Wang, Zhen-min Fan
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(7): 538-545.
https://doi.org/10.1631/jzus.A1100336
This paper deals with an improved bonding approach of surface-bonded fiber Bragg grating (FBG) sensors for airship envelope structural health monitoring (SHM) under the strain transfer theory. A theoretical formula is derived from the proposed model to predict the strain transfer relationship between the airship envelope and fiber core. Then theoretical predictions are validated by numerical analysis using the finite element method (FEM). Finally, on the basis of the theoretical approach and numerical validation, parameters that influence the strain transfer rate from the airship envelope to fiber core and the ratio of effective sensing length are analyzed, and some meaningful conclusions are provided.
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Enhancement of ion transport in porous media by the use of a continuously reoriented electric field
Juan Almeira, Chang-sheng Peng, Ahmed Abou-Shady
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(7): 546-558.
https://doi.org/10.1631/jzus.A1200017
Electromigration in porous media is enhanced by a new type of electrokinetic processing. Compared with a single -oriented electric field, a continuously reoriented electric field was proven to sharply enhance mass transport of several heavy metals in kaolin. The initial concentration of the metals was: Cd: 250 mg/kg; Cu: 250 mg/kg; Ni: 250 mg/kg; Zn: 900 mg/kg. Electric field reorientation was obtained by the use of a fixed anode and a cathode that rotated at different frequencies (0, 0.25, 1.00, 1.25, 2.00, 5.00 and 10.00 r/m). Mass transport evidently increased from 0 r/m to 1.25 r/m, and then decreased as the rotation speed reached 10 r/m. From 0 r/m to 1.25 r/m, mass transport increased 2.87 times for Cd, 3.17 times for Cu, 2.11 times for Ni, and 4.13 times for Zn. We suggest that continuous reorientation of the electric field facilitates the advance of ions through kaolin pores, minimizing the retardation effect caused by media tortuosity.
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Identification of sources of pollution and contamination in water distribution networks based on pattern recognition
Tao Tao, Ying-jun Lu, Xiang Fu, Kun-lun Xin
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(7): 559-570.
https://doi.org/10.1631/jzus.A1100286
An intrusion of contaminants into the water distribution network (WDN) can occur through storage tanks (via animals, dust-carrying bacteria, and infiltration) and pipes. A sensor network could yield useful observations that help identify the location of the source, the strength, the time of occurrence, and the duration of contamination. This paper proposes a methodology for identifying the contamination sources in a water distribution system, which identifies the key characteristics of contamination, such as location, starting time, and injection rates at different time intervals. Based on simplified hypotheses and associated with a high computational efficiency, the methodology is designed to be a simple and easy-to-use tool for water companies to ensure rapid identification of the contamination sources, The proposed methodology identifies the characteristics of pollution sources by matching the dynamic patterns of the simulated and measured concentrations. The application of this methodology to a literature network and a real WDN are illustrated with the aid of an example. The results showed that if contaminants are transported from the sources to the sensors at intervals, then this method can identify the most possible ones from candidate pollution sources. However, if the contamination data is minimal, a greater number of redundant contamination source nodes will be present. Consequently, more data from different sensors obtained through network monitoring are required to effectively use this method for locating multi-sources of contamination in the WDN.
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7 articles
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