Sharif Digital Repository

Concrete arch dams, because of their special shape as a 3-D huge shell which is fixed from three sides, are very sensitive to temperature and its variation. Therefore, it is required to include the temperature variations and their related thermal stresses and strains in the safety analysis of dams. In this research, the effect of applying the thermal gradients caused by the most critical thermal conditions, on dynamic behavior of concrete arch dams was studied. For this purpose, first a roughly exact 3-D finite element model of Karoon ІV arch dam was prepared by ANSYS program. Then, the temperature distribution through the dam thickness was determined by Stucky-Derron method and in a more... 

The behavior of pile foundations under earthquake loading is an important issue that affects the performance of structures. Design procedures have been developed for evaluating pile behavior under earthquake loading; however, the application of these procedures to cases involving liquefiable ground is uncertain. The performance of piles in liquefied soil layers is much more complex than that of non-liquefying soil layers because not only the superstructure and the surrounding soil exert different dynamic loads on pile, but also the stiffness and shear strength of surrounding soil diminishes over time due to both non-linear behavior of soil and pore water pressure generation. In this... 

Reciprocating Machinery are one of the key components of chemical and petrochemical plants and their down time cause loss of production. Therefore condition monitoring in these machinery is of special interest and high value. In this thesis first, different methods of condition monitoring for reciprocating compressors are introduced then the main cause of high vibrations of three compressors in a refinery is investigated. Finally by using the foundation model prepared, it would be shown that insufficient strength of foundation block has lead cracks initiation and development in these foundations. Therefore high vibration is consequence of weak design  

The most important step in current dynamic analysis of machine foundations is determining dynamic impedance functions. Impedance functions are defined as ratios of applied force or moment to induced displacement or rotation angle of foundation. In this research, horizontal dynamic response of foundation on homogeneous halfspace was investigated using physical modeling. Soil medium was built in a 1mx1mx0.8m steel box whose interior walls were covered by 0.1m of sawdust (a material with high damping). In order to prevent possible reflection of waves, this cover was extended to the box bottom with 0.2 m thickness. Sand raining method was used to build soil medium. In this method, with... 

One of the most efficient methods in stiffening tall buildings to withstand lateral loads such as wind loading is to link the shear resisting core to the exterior columns using outrigger trusses. Many tall buildings such as Taipei 101 have benefited from outriggers. In this system, the outriggers force the perimeter frame to take part in resisting the bending moment of the lateral load acting on the structure by developing axial restraining forces in the windward and the leeward columns of the perimeter frame and forming a resisting moment.Most of the present analytical methods have studied the performance of outrigger braced structures neglecting shear deformation of the shear wall core and... 

Base plates as the connecting components of steel structures to their foundations, have a crucial role in the behavior of these structures. In order to limit the thickness of base plates hence their cost within reasonable values, various types of attachments (stiffeners) are normally added to them. In this project 6 different configurations, Models, for the base plate and its attachments were considered and studied through finite element analysis. Each Model was studied under the combination of biaxial moments and a range of compressive loads including 0, 0.05 P/Py, 0.10 P/Py and 0.15 P/Py, where Py is the plastic load of the column. The moment-rotation curves of all models under various... 

Non rigidity of the soil beneath the structure, alters elastic and inelastic response of it. This effect is caused by the soil-structure interaction. The effect of soil-structure interaction is studied in two parts, Kinematic interaction and inertial interaction. Among these, kinematic interaction effects are often assumed to be negligible so that even in existing regulations it has been ignored. While the kinematic part of soil-structure interaction effect could produce a rocking input motion that might be important. In recent years, according to expanding usage of performance based design philosophy, researches on inelastic behavior of the soil-structure systems has been done which is... 

Foundation is the lowest load-bearing part of a structure and a part of underneath soil that is affected by the structure load. In fact, foundation transfers the loads from the superstructure to the substructure, preventing excessive settlement of soil or stresses exceeding soil bearing capacity. Indeed, almost all structures are placed on the ground, therefore the effects of soil and structure on each other, which is known as Soil Structure Interaction (SSI), is considered as a key factor in many important and engineered structures. In contrast to structures on a rigid footing, a flexible foundation may show stiffness degradation along with an increase of damping and natural period of the... 

The dynamic behavior of beams and rectangular plates on elastic foundation under the effect of deterministic and random excitations is investigated in the cases of controlled and uncontrolled systems. The equations of motion are developed in each case in both deterministic and stochastic states. In all cases, the eigenfunction expansion method is used to solve the obtained equations.Moreover, the classical linear optimal control algorithm with displacement-velocity is considered to achieve the required control efforts. The applied dynamic excitations are supposed as moving loads, moving masses accompanied with random lateral excitations of supports and the uniform distributed linear loading... 

Due to the importance of concrete gravity dams, safety issues are of great importance in these structures. On the other hand, because of the uncertainty in the geotechnical characteristics of the rock foundation in the design phase, and also consider the significant affects of these parameters on seismic response of concrete gravity dams, it’s not possible to determine safety factor accurately. Since the Sliding control in the base of the dam can protect the stability of concrete gravity dams in the operation phase, this study concentrate in this subject and intends to calculate the Sliding between the dam base and the foundation with finite element analysis, considering the rock foundation... 

Although the issue of separation is studied frequently in the last few decades, in presence of numerous parameters and unknown effects of earthquakes and soil condition, scientists confront with remarkable difficulties. It was supposed that performance of structures which are secluded from soil remains in the elastic region and doesn’t bear nonlinearity. But according to recent studies, scientist assert that nonlinear performance might be possible as a result of various soil condition and ingredients of earthquake(magnitude and frequency). General procedure for seismic improvements of structures includes increasing the strength and resistance, capability of structure to absorb energy and... 

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... 

In this study, the linear dynamic response of an inclined FGM Timoshenko beam on linear viscoelastic foundation subjected to a traveling mass with constant and variable velocity is investigated. Timoshenko beam theory and von-karman strain-displacement relations are utilized to model the problem. the FGM beam is made of metal and ceramic and it is assumed that material properties of the beam vary continuously in the thickness direction according to the exponential law and the power-law form. The kelvin-voigt damping model is applied to model the internal damping of the FGM beam. The partial differential equations of motion for the bending rotation of cross-section, longitudinal and... 

Dynamic impedance functions method is most recent approach in the analysis of soil-foundation dynamic interaction, and presented for massless rigid foundations. Impedance functions are frequency dependent functions, and used to obtain dynamic response of foundation with arbitrary mass subjected to dynamic loading of any frequency and magnitude. The important assumptions for appropriate useof mentioned method are rigidity of foundation and visco-elastic behavior of the soil beneath the foundation. In this study, experimental vertical impedance functions of square and circular foundations have been investigated,using physical modeling tests. A granular soil layer with finite thickness... 

Thread the bearing capacity of soil beneath the foundations of the main topics in Engineering is considered that main reason it is the more contact structures. if all the factors that are likely to impact on bearing capacity is more useful to consider more accurate results are obtained. This thesis has tried using FLAC software is a comprehensive review on the soil bearing capacity of foundations under certain conditions of Geotechnical and foundation strip, can be done .The modeling of soil layers and soil bearing capacity based on changes in properties (clay and sandy soils) and changes in depth are examined. The changes in the deep layer of soil and properties of soil, bearing capacity is... 

Pile is used to transfer high loads from the structure by bearing on the hard soil layers or through the friction between the soil and the pile. Axial loads and transversal or lateral loads are the main loads apply on the piles. There are several different methods to investigate the pile behavior under lateral load: (1) Limit State method (2) Subgrade Reaction method (3) Elastic method (4) P-Y method (5) Evans and Duncan method (6) Numerical methods. Blum, Brinch Hansen and Broms methods are based on the Limit State method to determine the lateral capacity of pile. Although these methods are simple and the results can find quickly, they failed to calculate the soil resistance under lateral... 

In this study, the performance of different boundary conditions in dynamic analysis of embankment dams, with consideration of dam-foundation interaction, is compared. All of models are in 2D space. The behavior of dam and the foundation are assumed to be linear elastic. Dam is built of compacted clay, whereas three types of soil are considered for foundation: loose, Medium and dense sand. Direct method is used for dam-foundation interaction analysis. We used Finite Element Method (FEM) using 8-node, quadrilateral and isoparametric elements to analyse the models. The incitement is horizontal displacement with different frequencies that is applied to lower boundary of foundation. In addition,... 

MAPNA is a leading project oriented company in the field of power, water, oil and transportation in Iran. MAPNA has the policy of using quality management principles and tools to improve the company and in this regard has chosen EFQM excellence model as a tool to move towards excellence. EFQM requires a set of indicators to measure performances of the processes and their results. These indicators should be tailor made for the company.
The subject of this thesis is to evaluate the present indicators used in implementing EFQM in MAPNA and considering MAPNA’s characteristics propose any changes required. The study is limited to indicators for key results and customer results for certain... 

Productivity is the effective usage of input or resources for production or output. Input (including Energy, raw materials, capital and work force), which is being used for output (including final products or services performed by an organization). Productivity, increases gross domestic product and competitiveness, and improves level of living. Firms and related management levels play the main role in improving productivity. Using productivity cycle management brings the productivity to improve as a permanent process, specifies the rout for productivity and prepares the ground. The most important step in productivity cycle (PDCA) is the measurement of productivity. In this research several... 

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...