Sharif Digital Repository

The main purpose of this study is to estimate the natural frequency and damping ratio for soil-structure systems with embedded foundation with sufficient accuracy. The results are then compared to guidelines in current seismic codes. This is done through an extensive parametric study using a set of non-dimensional parameters, which define the soil-structure systems. For this purpose a simplified soil-structure model is used. Although more rigorous models and numerical solutions are available, they are time consuming and not suitable for parametric study. Existing formula for seismic provisions for the equivalent period and damping ratio of soil-structure systems are based on studies on... 

The following dissertation examines the interaction between the free surface of a homogenous transversely isotropic half-space and a rigid circular foundation. The whole system is under a vertical and an inclined point loads applied simultaneously on the foundation and at the specified depth of the medium, respectively. Determination of the Green’s functions for the proposed mixed boundary value problem is of interest. By employment of the boundary conditions, the governing equations are represented in terms of a dual integral equation which are subsequently solved analytically. Furthermore, the exact closed-form expressions of the tilt (rotation and settlement) of the loaded rigid foundation... 

It has been realized that the raft (mat) foundations are capable of bearing very large loads when they are assisted with a pile group. The contribution of both raft and piles to carry the surcharge loads is taken into account, considering the stiffness and strength of involved elements in the system, i.e. piles, raft and surrounding soil. Piles are usually required to ensure the stability of the foundation and to act as settlement reducers especially for high rise buildings. The present study focuses on both kinematic and inertial effects of piled foundations and piled raft foundations under earthquake loading. The Finite Element Method (FEM) via ABAQUS will be used as an appropriate tool to... 

In this study, static and dynamic buckling of laminated composite beams resting on an elastic foundation under thermal and mechanical load is studied. Beam is resting on an elastic foundation with hardening/softening term. Nonlinear governing equations are obtained based on the energy method and are solved via the multi-term Galerkin method and the Newton-Raphson numerical method. Critical dynamic load is estimated by the Hoff Simitses criterion. The results are validated with the results of available articles in this field. In the following, the effects of different parameters of the problem on the results are examined. Results reveal that for a sufficiently stiff softening elastic... 

Nanotechnology with the tools, materials and their applications in areas such as engineering mechanics, materials, electronics, computers, and machines at the nanoscale is dealing. The Fnarvy, atoms and molecules as building materials, engineering bricks counts. In mechanical engineering branch, two aspects are discussed in view of nanotechnology, nano-scale structures and analyzing the behavior of phenomena that occur at the nanoscale. In this project, methods to analyze the behavior of nanoscale materials has been studied.
The present thesis examines the natural frequencies of nano graphene sheets on elastic foundation deals. The elastic foundation modeled with two springs.At first The... 

The present study investigates the vibrational behavior of a special type of nano-motor based on a thin cylindrical shell model and the nonlocal elasticity theory of Eringen. The presumed nano-motor is comprised of three single walled carbon nanotubes (CNT), where two of them are cantilevered and the third one is located in the middle. The CNT in the middle will suspend due to the Van-der-Waals forces generated from the interaction by the cantilevered CNT pair. Some proper chirality arrangements can conduct electricity and make the middle CNT rotate in extremely high speeds. In fact, the middle CNT rotates on a frictionless elastic foundation. In the present study, the nano-motor is modeled... 

Carbo nanocones are one of the nanostructures that are investigated and takes a large deal of attention in nanotechnology. In the present study the governing equilibrium equations of motion of carbon nanotubes under external pressure are derived using a nonlocal shell model and first order shear deformation theory. The natural frequency and buckling load are extracted using modal method along with Galerkin technique.Afterthis using both Winkler and Pasternak elastic foundation models, the governing equations of motion of nanocones embedded in the elastic medium extracted using a novel approach with the nonlocal shell model along with Hamilton’s principle. These equations solved using... 

The importance of the issue of laws of nature is obvious so that some say the purpose of science is discovering the laws of nature. In his “laws and symmetry” (1989) van Fraassen takes an antirealistic position toward the laws. His project is to clear science from metaphysics, and since the notion of laws of nature has heavy metaphysical presuppositions it should be eliminated from the literature of science. He tries to provide three kinds of arguments against the notion of laws: first, historical arguments, second, arguing in favor of insufficiency of all presented accounts of laws, and third, rejecting the tasks that accounts of laws should do. In van Frassen’s view, studies of science... 

Few years the traditional medicine in our society is considered: Traditional colleges have been established, Traditional medicine has been established and numerous media programs produced by experts in traditional medicine. All this indicates is that traditional medicine seek lost credibility and gain its rightful place in our society today. One of the most important aspects of the relationship between traditional medicine with modern medicine. On the one hand trying to make traditional medicine with modern medicine can be defined as complementary medicine. In this regard, first of all defined traditional medicine as a specialty, and efforts to rebuild the achievements of traditional... 

If we accept that there is a thing called “religious Science”, then we should accept that, all of its scientific elements should be based on, or be compatible with religion (in its general meaning). So, here is the question: Is there a particular “religious methodology” required for the “religious science”? Does “religious”, as an adjective also applies to methodology of science? Anyway, if we want to generate “religious science” based on religious foundations, we should characterize our position about “methodology of religious science”. Negligence of this important subject would cause a theoretical vacuum in discussions about religious science. In this thesis, after explaining some general... 

Cemented material dam(CMD) are a type of dams constructed using cement-based materials. They are situated between earth dams and roller-compacted concrete (RCC) dams and are used in irrigation and hydropower projects. These dams are known for their high strength and stability and can be easily built on various foundations, including weak foundations. One of the significant advantages of cemented material dams is their reduced environmental impact, leading to less damage to surrounding lands and improved environmental sustainability. Considering the mentioned advantages and appropriate locations and foundations for dam construction are used, building cementitious material dams on soft... 

The purpose of designing the foundation is to transfer the load of the structure to the subsoil without creating shear failure and additional settlement in the soil. Therefore, choosing the appropriate bearing capacity is an important point that should be considered in any project. Determining the bearing capacity of foundations is one of the topics that has long been considered by researchers and geotechnical engineering designers. For this reason, its design is not considered a new issue, but the application of new methods and the development of computers, raises new perspectives on this issue that justifies new studies.Most of the recent study, which have done so far on bearing capacity,... 

Nowadays, due to advancements in technology and processing power, earthquake engineering is moving toward more realistic modeling of actual problems in different fronts. In the case of considering seismic waves for design and analysis of concrete dams, numerous challenges exists due to complex nature of the problem which have absorbed abundant attention from a number of researchers around the world. In recent studies about earthquake input mechanisms, accounting for true nature of the foundation and applied earthquake have been hot topics. Therefore, in this thesis, thorough investigation on these effective factors in dynamic analysis of concrete dams is performed.In the first part of this... 

This thesis aims to study the dynamic behavior of circular and annular plates. First, free vibration of the plate, resting on a Pasternak foundation with a variable subgrade modulus, by using the infinite power series method is presented. The proposed method applies to various boundary conditions with no restriction. A comprehensive study is carried out to investigate the effects of the different parameters on the behavior of the plate. The obtained results demonstrate that the Pasternak foundation has a significant influence on the natural frequencies and greatly increases them. Secondly, the dynamic response of thin and moderately thick plates subjected to a moving load is considered. In... 

Foundation which is lowest load-bearing part of structure, transfers load of superstructure to substructure. Because structures are usually placed on soils, the response of the soils influences the motion of the structures and the motion of structures affects the response of the soils. This phenomenon is termed Soil Structure Interaction (SSI). One of these mutual effects is the rocking of shallow foundations in which the base of the foundation under dynamic loading may separate from the underlying ground, by rotating about the longitudinal axis. This rotational mode elongates natural period of the soil-structure system and decreases the base shear demands of the superstructure. Indeed... 

Mount Polley Tailings Storage Facility (MP-TSF) failed on its perimeter embankment on August 4, 2014, when its 9th construction stage has just been completed. The failure releasedmillions of m3 of toxic tailings, supernatant water and construction materials todownstream. Up to this point, some research studies have been conducted into the causes of the failure. These studies have considered the stability of the TSF in different stages of its construction as well as in the last stage. The aim of the present study is to investigate the causes of the very failure, using numerical methods by the aid of the finite element based software, PLAXIS 2D. In the present study, the results of the... 

Investigating the behavior of piled-raft foundations is a three-dimensional problem. The shape and location of the piles in the raft as well as the complex interaction of the soil-structure in these foundations should be analyzed in a three-dimensional fashion to indicate the real behavior of this type of foundations. The soil must also be analyzed in a nonlinear state to achieve the correct bearing capacity of these foundations. In this research, a nonlinear 3D analysis was performed using FLAC3D to investigate the behavior of piled-raft foundations, and the effect of various factors such as the length, arrangement and number of the piles, the loading level and the thickness of the raft, on... 

Safety assessment of existing dams and analysis and design of new dams as an important part of infrastructures of any country, hinges on proper and precise modeling of coupled system of dam-foundation-reservoir under appropriate seismic excitation. In this dissertation, effective methodology for seismic analysis of concrete dam, using finite element method, is presented which takes account for numerical modeling of wave propagation from excitation source to site and interactions between dam, foundation and reservoir. To model the effects of mass, wave propagation and radiotional damping in unbounded foundation as well as modeling the fault itself, two boundary conditions namely, free-field... 

This thesis investigates the dynamic response of a viscoelastic plate resting on a viscoelastic Winkler foundation subjected to the excitation of a moving mass. Through application of the Laplace transform, the governing equation of the problem is derived for a general viscoelastic material. Thereafter, an analytical-numerical method is proposed in order to determine the dynamic response of the viscoelastic plate. The method is based on transforming the governing partial differential equation into a new solvable system of linear ordinary differential equations. To that extent, the proposed solution proves to be applicable to plates made of any viscoelastic material and with various boundary... 

Up till now, various contributions of research to soil-structure-interaction context have been primarily focused on structural systems exhibiting elastic-perfectly plastic material behavior. In this paper, combined effects of material degradation, p-delta, and soil-structure-interaction considering foundation uplift have been deemed to determine seismic response of a single degree of freedom system. The system is composed of a column with a lumped mass on top that is placed on a rigid foundation. The foundation is mounted on Winkler springs and dashpots to account for soil-foundation compliance and material/radiational damping. The springs are tensionless to guarantee that uplift phenomenon...