|
Environmental problems of vibrations induced by railway traffic
XIA He, CAO Yanmei, De Roeck Guido, Degrande Geert
Front. Struct. Civ. Eng.. 2007, 1 (2): 142-152.
https://doi.org/10.1007/s11709-007-0015-1
In this paper, a general review is made on the problems of vibrations of the ground and nearby buildings induced by railway traffic, and on the researches on this subject in theoretical analyses, numerical simulations, and field experiments. The characteristics of ground vibrations induced by railway traffic and their propagation, from the aspects of duration, intensity distribution, vehicle load and speed, are summarized. The vibration influences on the daily life of people, the operation of high-tech devices and the safety of buildings, and the vibration properties of subsoil and buildings adjacent to the underground, ground and elevated railway systems are introduced.
Related Articles |
Metrics
|
|
Investigation of the structural form optimization methods of high-rise buildings
ZHANG Shihai, WANG Li, OU Jinping, WANG Guangyuan
Front. Struct. Civ. Eng.. 2007, 1 (2): 182-187.
https://doi.org/10.1007/s11709-007-0020-4
In this paper, the structural form optimization methods of high-rise buildings based on the expert system (ES), case-based reasoning (CBR), and knowledge discovery in database (KDD) are evaluated systematically. The characteristics and shortcomings of each method are pointed out. It is predicted that the incorporation of these three techniques into an intelligent form optimization method will be an important development direction in the future. Finally, the unified intelligent form selection model combined with concepts of ES, CBR, KDD and artificially intelligent beautification is proposed. In consideration of the needs of human beings, machinery and computation, the model has been used for structural design combined with relevant knowledge, means, maneuver and strategy. The model plays an important role and has practical value in the process of artificially intelligent form optimization. It effectively reduces the blindness and failure of computer-aided structural design.
Related Articles |
Metrics
|
|
Soil-water interaction in unsaturated expansive soil slopes
ZHAN Liangtong
Front. Struct. Civ. Eng.. 2007, 1 (2): 198-204.
https://doi.org/10.1007/s11709-007-0023-1
The intensive soil-water interaction in unsaturated expansive soil is one of the major reasons for slope failures. In this paper, the soil-water interaction is investigated with the full-scale field inspection of rainwater infiltration and comprehensive experiments, including wetting-induced softening tests, swelling, and shrinkage tests. It is demonstrated that the soil-water interaction induced by seasonal wetting-drying cycles is very complex, and it involves coupled effects among the changes in water content, suction, stress, deformation and shear strength. In addition, the abundant cracks in the expansive soil play an important role in the soil-water interaction. The cracks disintegrate the soil mass, and more importantly, provide easy pathways for rainfall infiltration. Infiltration of rainwater not only results in wetting-induced softening of the shallow unsaturated soil layers, but also leads to the increase of horizontal stress. The increase of horizontal stress may lead to a local passive failure. The seasonal wetting-drying cycles tend to result in a down-slope creeping of the shallow soil layer, which leads to progressive slope failure.
Related Articles |
Metrics
|
|
Experimental study on flow behavior at open channel confluences
WANG Xiekang, WANG Xianye, LU Weizhen, LIU Tonghuan
Front. Struct. Civ. Eng.. 2007, 1 (2): 211-216.
https://doi.org/10.1007/s11709-007-0025-z
Channel confluences are common in natural rivers and hydraulic engineering, and the flow behavior at confluences becomes very complex because of the interaction between the tributary and the main river. In this study, the experiments were performed in a combined flume with a 30º angle between the main and tributary flume located at Sichuan University. The velocity was measured by using a three-component acoustic Doppler velocimeter (ADV) over a grid defined throughout the junction region. Based on the analysis of the velocity at the confluence, the distinctive characteristics of a channel confluence flow may be divided into several zones including a zone of separation immediately downstream of the junction branch channel, the maximum and minimum velocity regions at the upstream and downstream in the confluent channel, and a shear plane developed between the two combining flows downstream of the confluent channel. In addition, secondary circulations in different directions at the higher and lower velocity zones are observed as well.
Related Articles |
Metrics
|
|
Experimental research on the mechanical property of prestressing steel wire during and after heating
ZHENG Wenzhong, HU Qiong, ZHANG Haoyu
Front. Struct. Civ. Eng.. 2007, 1 (2): 247-254.
https://doi.org/10.1007/s11709-007-0031-1
The mechanical property of prestressing steel wire during and after heating is the key factor in the design of fire resistance and after-fire damage evaluation of prestressed structures. Tensile experiment of 16 prestressing steel wires ( fptk = 1770 N/mm2, d = 5 mm, low relaxation of stress) at high temperature and tensile experiment of 14 prestressed steel wires after heating are carried out. According to the experiment, the shapes of stress-strain curves of steel wire at high temperature go smooth and the mechanical property indexes of the steel wire such as strength, modulus of elasticity, etc., degenerate continuously as temperature increased. According to the experiment after heating, the mechanical property of steel wire varies little when the highest temperature that the steel wire has ever been heated to is lower than 300vH; while the stress-strain curves of steel wire become more ductile and the mechanical property indexes of the steel wire degenerate gradually when the highest temperature is higher than 300vH. By applying the theory of viscoelastic mechanics, stress-strain curves of steel wire at high temperatures without loading rate influence are obtained. The law of mechanical property indexes of the wire is presented. The mathematical models of the stress-strain relationship of the pre-stressed steel wire are established. All can serve as basic data for the analysis of fire resistance and after-fire damage evaluation of pre-stressed structures.
Related Articles |
Metrics
|
19 articles
|