Applied Mechanics and Materials Vols. 166-169

Abstract: Aerodynamic characteristics of iced conductors were investigated by the wind tunnel test. Under the homogeneous turbulence of 5% intensity, aerodynamic force coefficients of single and bundled conductors were obtained at wind angles of 0°~180°. The variation patterns of aerodynamic forces on the iced conductors with respect to wind angels of attack were systematically studied for the ice thickness of 0.25, 0.5, 0.75 and 1 times of the conductor diameter. The difference of aerodynamic force characteristics for single and bundled conductors were identified and discussed. Based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed. The results show that lift and torsion force coefficients reach peak values at wind angles of 15°~20°. For bundled conductors, lift force curve is approximately agreed with the curve of single conductor. Drag force coefficients were smaller than these of single conductor at some wind angles. There are noticeably differences of torsion coefficients existed between bundled conductors and single conductor. According to two classical galloping mechanisms, wind angles of 15°~30°are critical for the galloping of iced conductors with crescent shapes.

Abstract: The double-shell structure under high temperature will lead to structural changes in material properties. Thermal expansion causes the production of thermal stress of the additional constraints bar, whose security research is the aim of this paper. The paper chooses Laoshan Velodrome Olympic venues as the research object, dividing the temperature zones of shell structure, and conducting the FDS simulation temperature field. The internal temperature of structural elements of computational shell in various zones will be in accordance with the first constant load and dead load after warming loading method to give a finite element analysis and give an evaluation of the safety of shell structure. The results show that: the temperature of the fire scenarioⅠis significantly higher than that of the fire scenario Ⅱ.We selecte the temperature of the fire scenario Ⅱ as the temperature load, and find that the local damage of six bars in the high-temperature zone occurs, which won’t cause structural damage to the whole structure. Therefore, these 6 bars need to be sprayed with fire retardant coating.

Abstract: Fire load exists in the building, and it is generally not the origin of fire occurred and spread, so attention has not been beloved paid although the fire size is closely related with it. It plays an important role in performance-based fireproof design, but the abroad data is used always, then which is not in accordance to the situation of our country. The article is based on national and international standards, and calculated the fire load theoretical maximum of the building to protect the building fire safety and can be referred by performance-based fireproof designer, so we can control the fire dangerous of the building, and then grasp the critical moment while the fire happened.

Abstract: The moment that isolation layer slider begins to slide has great effects on the whole system characteristics for sliding base-isolated system,and the moment plays a crucial role for the analysis of system energy and the confirmation of energy spectrum.Change rules of the moment that isolation layer slider begins to slide under the influence of the acting parameters and system’s design parameters,Taking two particle of plain sliding base-isolated system of building structure under harmonic excitation as the research object,are studied by using the numerical analysis method.The results show that the moment will be delayed if the friction coefficient of isolation layer or the natural vibration period of superstructure will be increased,and the moment will be advanced under the condition that the damping ratio of superstructure or external excitation which is exerted on structure being increased,while the mass ratio of isolation layer slider and superstructure has a very complex effect on the moment that isolation layer slider begins to slide,and the influence law relates to friction coefficient.

Abstract: Heavy rainfall has important implications to shallow landslide stability. In the paper, the relationship between the soil moisture content and soil shear strength and between surface displacements of landslide and rainfall were studied. Their statistical relationships were established. Relationship between soil moisture content and shear strength should be fitted using the logarithmic function. Relationship between soil slope and rainfall displacement should adopt the power function fit. Constitutive model of catastrophe theory of heavy rainfall landslides stability was known, which it is very important to provide a theoretical basis for prediction.

Abstract: Bedding rock slope stability is classic problem of its formation mechanism, and with mechanical means to study the breeding and instability model is one of the important means, Based on summarizing and inducting returns of former researcher, this paper stated that the mechanical model of two-dimensional space may be crossbar bend beam model and of three-dimensional space maybe plate or shell model. Crossbar bend beam catastrophe model of common and multi-load was built. The formulas of burst instable and limit length of bedding rock slope were gained. For example Bawangshan and a special slope near 318 national highway as typical burst slope, their burst and limit length were solved, and the result was proved to be correct and rationality by contrasting with calculation result of other researcher or the actual scene investigate.

Abstract: Subway plays an important role in urban transport system. Fire as the major risk of the subway, is gaining increasing concern. In this study, fire simulation is performed to estimate fire safety of different compartments of the subway train. Result shows that the two compartments in the middle become dangerous at 150s and the compartments in the two ends are not safe at 300s approximately. The other two compartments are always safe during the simulation time.

Abstract: Reducing the temperature is one of the key technologies in the metro fire emergency rescue, so it is the basic work to be done. Rapid and effective cooling can reduce the casualties caused by the metro fire. Water spray can quickly absorb a lot of heat for its large surface area. Water spray can quickly cool down the temperature of the metro fire and reduce the casualties caused by high temperature. Mobile water spray device is used in emergency rescue of the metro fire in this paper. Research on the mobile water spray device can do contribution to reduce casualties caused by metro fire.

Abstract: Debris landslide is a widely distributed and its hazard is huge and hard to forecast with traditional method. Instability drivers of the debris landslide and mechanism were systematically analyzed in this paper. And on that basis, the theory of unload-load response ratio was proposed to forecast the landslide's stability. In the view of system dynamics, the unload-load parameter and unload-load response parameter were singled out and the feasibility was able to build up analyzed, and then, the model of unload-load response ratio was built. As an example, the model was used to analyze and calculate the Xintan typical debris landslide. The results were showed. The steady state reflected by the timing curve of the unload-load response ratio was consistent with the landslide's actual status, when Y'→0, the overall unstability of landslide would appear. That showed it was available to use the unload-load response ratio to forecast landslide's deformation stage and as a criterion of landslide instability.

Abstract: Many sluices were damaged seriously after several decades’ use. In sluice safety level’s classification standard, there are quantitative indexes and qualitative indexes. Principal component analysis was used to evaluate the sluice. First the data were standardized, correlation matrix was got, and then confirmed principal components and weight, through this step principal components’ value and total value were received, finally sluice risk grades were determined and they could be ordered. The result is objective and reasonable, so we assess sluice easily.