Applied Mechanics and Materials Vols. 204-208

Abstract: Steel–concrete composite columns are used extensively in modern buildings in recent decades due to the benefits of combining two construction materials: reinforced concrete is inexpensive, massive, and stiff, while steel members are strong, lightweight, and easy to assemble. For concrete-encased composite structural members, an additional advantage is that the concrete used for encasing a structural steel not only increases its stiffness, but also protects it from fire damage and local buckling failure. Traditionally, the fire resistance of composite structural members has been determined in standard fire tests, with the temperature-time curves representing more severe heating conditions compared to that which occurs in many typical natural fire compartments. To design a concrete encased H-section steel structure safely and economically, it is necessary to calculate temperature distribution in composite steel-concrete columns under natural fire. In this paper, the program TFIELD written by first author is used to calculate the temperature distribution in a concrete encased H-section steel column under natural fire and ISO 834 fire. The calculating results under the standard ISO 834 fire and a natural fire have been compared which exhibit obvious differences.

Abstract: The method, using slope buckling safety factor to measure the degree of dam-break hazard, results in the unscientific conclusions of identical dam-break risk with respect to the desolate & uninhabited gobi desert and densely populated & highly economic-developed city. On the basis of vulnerability theory, a dam-break hazard vulnerability assessment index system, which comprehensively considering the inherent risks of dam-break and the intrinsic vulnerability of hazard-affected bodies, was established. The production of dam-break hazard-causing factor intensity, including the current dam height, reservoir capacity & downstream main ditch longitudinal, and accident probability by the Monte Carlo method is the inherent risk level of dam-break. The result by the multiplying physical exposure and the intrinsic vulnerability, including household fitness index & the emergency self-help index, as well as the disaster relief capacity is the hazard-affected body vulnerability. Results are contributable to further consummate the vulnerability risk assessment technology and the reliability of dam-break hazard.

Abstract: In order to study the probability of occurrence of secondary fire after the earthquake in urban areas, the probability model of the hazard analysis that the fire occurred and the spread is established and applied. Probability models need to consider the destruction level of buildings under earthquake excitation as well as the probability of the leakage and diffusion of combustible material in the buildings in the corresponding destruction level, combination of weather, season, housing density and other factors to determine the probability of the single building earthquake secondary fire. On this basis , the natural administrative areas in the city as a unit , considering the factors of regional hazard analysis such as population density , property distribution and density within a region , to calculate the hazard indicator and determine the high hazard areas of secondary fire in the city. The Geographic Information System was used as the platform, to division of urban earthquake secondary fire high-hazard areas.

Abstract: China is suffering from severe environmental accidents that many have catastrophic impacts on public health and the environment. It is urgent to update the standards for environmental accidents prevention in China. This paper analyses the causes of fifty-three major accidents that happened in 2008 to obtain insight to help prevent similar events in the future. The results show that production accidents, which were mainly triggered by process analysis, training and human error, were the dominant causes of environmental accidents in China. In addition, current regulations on the control of environmental accident hazards and their implementation are also presented in this paper, which comprise legal requirements centering on hazardous chemicals, industrial safety evaluation, risk analysis and preparation of emergency plans. Based on our analysis, some key points that should be developed in future environmental accident hazard control measures are put forward with the aim of shedding light on decision making and risk management in China.

Abstract: In order to improve the gas drainage effect of "three soft" coal seam with low-permeability and eliminate the gas overrun in the upper corner and return air during the production process, this paper did an exploration on the comprehensive gas management on the fully mechanized caving face of gassy mines in Xuangang mine area and its application achieved a good result.

Abstract: Cases of pipeline damage caused by landslide are common in coastal or mountainous regions, where the design of buried pipelines should be improved in order to reduce the risk of damage or failure. Dynamic responses of large diameter thin wall steel pipes under impact loading were analyzed using a nonlinear contact model of pipe-soil coupling in this paper. Several influence factors were studied, such as the impact velocity of rockfall, buried depth of pipeline, ratio of diameter to thickness and style of soil. The results show that an ellipsoid induces much more impact force than a sphere which has the same volume, and the larger one in volume have greater impact force for two spheres. Dangerous compressive areas of pipeline occupy 1/6 of the whole area, so the pipelines subject to landslide occur local failure. Based on results, some useful suggestions for the design of pipelines in landslide region are given

Abstract: Through improving the real-coded genetic algorithms and embedding the algorithm of accelerating the local search in the Powell direction and the operation of accelerating cycle, thereby it is constructed the New blend Accelerating Genetic Algorithm (hereinafter referred to as NBAGA). The applied examples of the calibration on nonlinear single return period storm intensity model parameters show that this method takes into account of the advantages of both the advantages of the improved real-coded genetic algorithms and the Powell Algorithm, therefore this method is an excellent nonlinear optimization method which can search the global optimal exact solutions quickly and in greater probability, as well as doing subtle search locally.

Abstract: The paper has analyzed the mechanical mechanism of movement and deformation of overlying strata and surface on stope, defined the moving structures of the overlying strata of three strata space forms, explored the mechanism of surface subsidence caused by loose layers’ pressure consolidation , and pointed out that when the loose layers are much thicker, what is indispensable is that, the pressure consolidation of loose layers loosed water, or soil body’s deformation leading to additional stress in the mining soil body, and the dissipation of excess pore water pressure resulting in the consolidation. And according to the surface subsiding features of thick loose layers in mining area, the paper has applied the correction model by probability integral method to predict subsidence with a rather satisfying prediction result.

Abstract: Surface subsidence caused by mining operation can amount to several meters, which is far above the standard value in design code. Once mining collapse occurs, bridges’ large deformation can result in bridge disasters. In order to prevent bridge disasters in mining area, bridge disaster characteristics in different districts in working face of mining are analyzed on the base of large deformation regularity of ground. A method of avoiding location of piers at inferior fovea and superior fovea in the migrated basins is presented to reduce the deformation of bridges on condition that subsidence area can’t be bypassed. And smooth joints between road and bridge are also advised to be designed to reduce staggering of joint and cracking. Moreover, applicability of several prevention methods for bridge disasters is demonstrated based on different bridge design and foundation treatments in mining area. The results show that geological disasters of bridges can be prevented by choosing reasonable foundation and structure type, which provides reliable basis for bridge construction in mining area.

Abstract: The paper has systematically studied stability, deformation property and early warning of high engineering slope in depth, and established the early-warning monitoring system of slope. The results show that: ① The time of displacement deformation is more consistent with the slope treatment, as well as the position of dislocation more consistent with geological conditions, and displacement deformation is less below the position and basically unchanged below a certain depth. ② Lateral deformation increases with increasing reduction factor. Lateral deformation has smaller increment with smaller strength reduction factor, and has a larger increment with larger strength reduction factor. ③ The early-warning monitoring system of slope safety based on deformation amount and safety factor is established.