Scientia Iranica
Volume:18 Issue: 1, 2011

The nonlinear finite element method and serendipity eight nodes element are used for determining ground surface settlement due to excavation of a tunnel. A modified generalized plasticity model with a non-associated flow rule was applied for analysis of a tunnel in Sao Paulo, Brazil. A linear element with elastic behavior was used for modeling the lining. A two story building with hinged connections and X braces, on Tehran and Houston sand, was also studied for the process, with each tunnel at different depths. Results showed an interaction between the tunnel and the building, which was evaluated in the tunnel at a 2D depth. However, there is no interaction between the tunnel and the super structure when it is at 3D depth. Also, the super structure increases the settlement due for excavation. The predicted results showed good agreement with field data from the Sao Paulo tunnel. The predicted plastic strain below the structure increases when the overburden is decreased. The settlement was almost zero at the distance of 5D from the center of the tunnel. When the super structure is on the ground surface, the settlement is induced between the center of the tunnel and 2.5D from the center of the tunnel; not beyond this distance.

The system of a steel plate bolted to a Reinforced Concrete (RC) shear wall goes by the name of a ‘Composite Steel Plate Shear Wall’ (CSPSW), which is used as the lateral resisting system in tall buildings. In this system, the steel plate buckles under medium-strong earthquakes, which may lead to instability. However, the buckling load of steel plates is usually a limited criterion for the design of CSPSW. This paper reports a series of experiments on CSPSW. The experiments were used to investigate the buckling load of a steel plate bolted to one side of a high strength reinforced concrete panel. Furthermore, theoretical modeling, based on energy methods, was used to obtain the elastic buckling coefficients of steel plates with various aspect ratios under shear loading. The results were presented in graphical and tabular forms showing good agreement of theoretical modeling with experimental results. The elastic buckling coefficients can be used for determination of the number of bolts or the spacing between the bolts.

The theory of Zero Extension Lines (ZEL), based on the solution of soil plasticity equations along ZEL directions, has wide applications in determination of the bearing capacity and load–displacement behavior of foundations and retaining walls. It is known that soil behavior and shear strength parameters are stress level dependent. In fact, a dense soil presenting a dilative behavior under low stress levels may show a contractive behavior under higher levels of stress. On the other hand, foundation size has a significant effect on the level of imposed stress on subsoil elements. In this work, the ZEL method is employed to consider the stress level dependency of soil strength in the bearing capacity computation and load–displacement behavior of foundations. A computer code is developed to solve ZEL equations in MATLAB. The results obtained by this numerical model have been then compared with experimental tests and those obtained by other methods.

The infiltration problem is one of the most interesting issues considered by geotechnical and water engineers. Many researchers have studied the infiltration problem and have developed models that can be categorized by analytical and numerical concepts. For nonlinear infiltration simulation, however, analytical solutions are few due to the difficulties and complexities involved. The Richards equation is one of the most well-known equations to describe the behavior of unsaturated infiltration zones in soil; many other relations have been introduced based on this equation. The exp-function method is one of the most recent analytical approaches used for the solution of nonlinear Partial Differential (or algebraic) Equations (PDE). In this paper, the exp-function method, with the aid of symbolic computation systems, in particular Maple, has been applied to the Richards equation to evaluate its effectiveness and reliability, and to reach a more generalized solution of the problem. Free parameters can be determined using initial or boundary conditions and the soil water content at any given time and depth is determined in a semi-infinite and unsaturated porous medium. It is shown that the exp-function method applied here results in a more realistic solution and that the concept is very effective and convenient.

Although many in-situ Reinforced Concrete (RC) beams are of continuous constructions, there has been very little research on the behavior of such beams strengthened with Fiber Reinforced Polymer (FRP) laminate. Ductility is even more important for statically indeterminate structures, such as strengthened continuous beams, as it allows for moment redistribution through the rotations of plastic hinges. In addition, some aspects of the flexural condition of strengthened RC beams still need experimental and analytical investigation; furthermore, especially for serviceability checks, code provisions are lacking. This paper presents an experimental and analytical program conducted to investigate the serviceability and ultimate behavior of RC continuous beams strengthened with carbon FRP (CFRP) sheets. The program consists of four continuous (two-span) beams with overall dimensions equal to 250×150×6000 mm. Beams were strengthened by CFRP in flexure along their sagging and hogging regions. The results show that by strengthening beams, a lower rate of transition of flexural rigidity from the uncracked to the fully cracked section occurs. The crack width and deflection are acceptably predicted by an analytical model. Also the acceptable lower bound of ductility for ensuring minimum moment redistribution is 3.

This study investigates the acoustic radiation of rectangular Mindlin plates in different combinations of classical boundary condition. A set of exact close-form sound pressure equations is given for the first time, using the so-called Mindlin plate theory (a first-order shear deformation theory), for plates having two opposite edges that are simply supported. The other two edges may be given any possible combination of free, simply-supported and clamped boundary condition. It is assumed that mechanical in-plane loading occurs on the plate structure. In order to study the transverse vibration of moderately thick rectangular plates, the dimensionless equations of motion are derived, based on the Mindlin plate theory. Structural-acoustic coupling is implemented for vibrating plate models. The radiation field of a vibrating plate with a specified distribution of velocity on the surface can be computed using the Rayleigh integral approach. The acoustic pressure distribution of the radiator is analytically obtained in its far field. Additionally, the influence of six possible combinations of boundary condition, foundation parameter, loading case, aspect ratio and thickness ratio, on the sound pressure is examined and discussed in detail.

This paper examines the capability of a least square support vector machine (LSSVM) model for slope stability analysis. LSSVM is firmly based on the theory of statistical learning, using regression and classification techniques. The Factor of Safety (FS) of the slope has been modelled as a regression problem, whereas the stability status (s) of the slope has been modelled as a classification problem. Input parameters of LSSSVM are: unit weight (γ), cohesion (c), angle of internal friction (ϕ), slope angle (β), height (H) and pore water pressure coefficient (ru). The developed LSSVM also gives a probabilistic output. Equations have also been developed for the slope stability analysis. A comparative study has been carried out between the developed LSSVM and an artificial neural network (ANN). This study shows that the developed LSSVM is a robust model for slope stability analysis.