Abstract: By exploring the nature of the analogy between optimum trusses and optimum layouts of discontinuities, a novel numerical analysis method for rock/soil masses is proposed in this paper. The procedure is used to determine the critical layout of discontinuities and associated upper bound limit analysis for stability problems. The alternative approximation procedure to the traditional finite element method might involve discretization of a given body using a suitably large number of nodes laid out on a grid, with the failure mechanism comprising the most critical subset of potential discontinuities interconnecting these nodes. Potential discontinuities which interlink nodes laid out across the problem domain are permitted to crossover one another, giving a much wider search space than when such discontinuities are located only at the edges of finite elements of fixed topology. Highly efficient SOCP (second-order cone programming) solvers can be employed when certain popular failure criteria are specified (e.g. Hoek-Brown and Mohr-Coulomb). Stress/velocity singularities are automatically identified and visual interpretation of the output is straightforward. Several numerical examples including rock slope are studied by the new method, and the results are very close to those calculated by using analytical method and FEM.
Abstract: A hydropower station is located in the middle reach of the Dadu River in southwest China. The natural slope angles at the project site are generally 40~65 and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the project. According to the statistical distribution of joints at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model are established by the Monte-Carlo method. The mechanical characters of fractured rock with different sizes are studied using FLAC3D. The REV characteristic scale is identified for rock masses. Numerical simulation is performed to obtain the mechanical parameters and the strength of the jointed rock. With the numerical model and the site monitoring data, a self-developed stochastic mechanical analysis software is applied for back analysis and stability assessment.
Abstract: A yielding inverted arch of composite structures is designed to control serious floor heave of tunnel. Constitution of the inverted arch is studied to present mechanism of the composite structure to restrain floor heave. By field trial of the yielding inverted arch with composite structures, it is an effective method to control floor heave, and its important function is to absorb main elastic deformation coming from bottom strata.
Abstract: For the irregular rotational displacement of curved girder bridge under seismic action there are some limits to calculate collision effect with pounding element approach. In order to analyze the inhomogeneous distributing rule of seismic collision effect for curved girder bridge, the new approach of explicit dynamic contact algorithm is presented. Seismic impactive response characteristic of girder, pier and block is analyzed. The results indicated that pounding action between girder and abutment limits longitudinal displacement of girder and makes bending moment of fixed pier less than that with collision effect unconsidered. After pounding the radial stress of block inside and outside the curve distribute severely inhomogeneously. The radial stress of block outside the curve is more than that inside the curve distinctly. This can provide theoretical guide for interpretation of the seismic damage of pounding for curved girder bridge.
Abstract: Based on the impact phenomenon between the end of the beam and the bridge abutment of the curved continuous bridge during earthquakes, a spatial finite element calculating model with collision element is presented. The law of collision is studied by the nonlinear contact time history analysis method under two three-dimensional ground motions. The variation laws of relative displacement and the internal force at the bottoms of piers are researched. In addition the changing of displacement and internal force at the end diaphragm are studied. The results show that the pounding action can easily lead to significant collision forces between the end beam and the abutment of the curved bridge which increases the axial force of girder evidently. The collision forces and longitudinal displacements from the inner to outer of the diaphragm generally are showed by an increasing trend, and the pounding action is more fierce under Elcentro ground motion than that under Tianjin ground motion.There is no relative displacement of consolided pier, bending moment and shear force of the consolided pier are greater than that of the mobile pier.The conclusions from the present study may serve as a reference base for seismic design of continuous curved bridges.
Abstract: Based on the method of separation of wind speed and direction variable, considering the wind direction frequency function, ascending order to calculate the probability of the actual distribution of the sample, extreme type Ⅰ (Gumbel) and three parameters of extreme type Ⅱ (Frechet) and extreme type Ⅲ (Weibull) probability distribution to fit the sample, this paper has analyzed the weather station observations of 34 consecutive years of the joint distribution of wind speed and direction near to a huge bridge, gained the basic design wind speed in different directions, comparatively analyzed the impact of the sampling interval of change on the basic wind speed as well. The results shows: wind speed in different directions at the same location or different sampling intervals samples of the wind speed sample may be subject to different types of extreme value distribution, should separately fitting; different wind direction frequency of extreme wind speed occurrence and the basic wind speed there are certain differences, taking into account the joint distribution of wind speed and direction is necessary to determine the design basic wind speed of the bridge, and will be conservative without considering the joint distribution; for the same sample wind speed matrix, the shorter the sampling intervals, the optimal distribution of the higher probability model fitting precision, the smaller the basic wind speed, the more economic and reasonable the results.
Abstract: The stability study is one of the hot spots of the urban transport design for the subway through the existing structure. The maximum settlement of the structure is regarded as the index of underneath the subway construction and design in this article, the mechanical parameters for pipe shed reinforcement layer on a subway station passing through the existing structure is back analyzed by utilizing the orthogonal experiment design methods, and the mechanical integration properties parameters which is close to engineering practice including elastic modulus, Poisson ratio, cohesion and internal friction angle for the material in the pipe shed reinforcement area are got. The steel pipe reasonable spacing range of advanced pipe shed support is got mainly on the basis of flexural rigidity. The stability analysis and evaluation for the construction of the new subway through the existing subway structure are carried out by utilizing the obtained optimum parameters.
Abstract: Abstract .Transportations one of the important indexes of air pollution in cities has always occurred in the form of a big Unavoidable problem. Lack of comprehensive approach and enough (Sufficient) attention toward transportation and traffic issues have unsparing social, economical and environmental costs and damages in the country which the most important of them are: high fuel consumption and growth of the fatal and injury crashes, air pollution and environmental damages. Among the public transportation networks, railway public transit is known as the healthiest, fastest, safest and generally the most efficient transportation network which is proved the undeniable role in solving economic, social and environmental problems caused by public transport and traffic problems. Considering the political and economic centrality of Tehran as capital of Islamic Republic of Iran with an increasing population of over 10 million people, and the construction of satellite cities, and conducting population to these cities, it is important to construct several connecting subway lines for these satellite cities. This paper focuses on economic problems via comparing underground subway as public vehicle with motor vehicle.
Abstract: The responses of the buried pipeline due to reverse fault dislocating are studied by a 3-dimension shell finite element model with equivalent boundary spring in ANSYS program. The calculating length of the model is determined by dip angle of the reverse fault: The length is 150 times pipe diameter when the angle is equal to or bigger than 45°; but the length is 240 times pipe diameter when the angle is less than 45°. The finite element model is fit for computing that dip angle is less than 80°. Results show: Failure modes of the pipes are determined by dip angle and dislocation value of the fault. When the angle is gentle and the dislocation is small, either local buckling(wrinkling) or beam buckling can be happened. The angle is equal to or bigger than 75°, local buckling and beam buckling can be happened at same time.
Abstract: This paper mainly aims to investigate and analyze seismic fortification standards, the actual earthquake intensity and damages of the existing bridges in the 51 hard-hit areas in Wenchuan Earthquake. Based on the investigation and studies on the relationship among highway bridge damages, building year, bridge type and seismic protection classification, the assessment of seismic fortification standards is also presented.