Sharif Digital Repository

The lateral movement of a liquefiable layer on gently slopes is the most visible and devastating type of liquefaction-induced ground failure. Occurrence of liquefaction in sloping ground causes large deformations on ground surface, which may lead to several meters in some cases. Recent earthquakes have shown that this phenomenon causes severe damages to coastal structures, piers of bridges and life-lines, by exerting large lateral forces. In this research, a fully coupled two-dimensional dynamic analysis has been used to simulate the lateral spreading phenomenon and to evaluate the magnitude of deformations occurred in liquefiable soils. The critical state bounding surface elastic-plastic... 

Complex networks serve as generic models for many social, technological and biological systems that have been shown to share a number of common structural properties such as power-law degree distribution and small-worldness. These networks determine interactions and influence the spread of diseases, behaviours and ideas. Epidemics and failures like new behaviours ideas and innovations can spread throughout a network and prevent it from doing its functionalities. In this work, we investigate error and attack tolerance of epidemic spreading in complex networks. The main content of this thesis is arranged in three sections as follows: Firstly, the effect of random and systematic failures is... 

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... 

Lateral spreading is a common mode of earthquake-induced failure that usually occurs as a result of liquefaction in gently sloped sandy layers. Numerical simulation of this phenomenon requires fully coupled analysis of displacement of solid sand particles and pore water pressure under seismic loading. Predicting occurrence of initial liquefaction and sub-sequent ground movement requires employing an efficient and robust constitutive model that can predict the undrained behavior of saturated sand under different conditions. In this study, a fully coupled finite element code “PISA” utilizing a critical state two-surface plasticity constitutive model, proposed by Manzari and Dafalias (1997),... 

Lateral Spreading, which usually occurs as a consequence of liquefaction in gently sloped loose saturated sand layers, is known to be a major source of earthquake-induced damages to structures such as bridge piers, quay walls, pipelines and highway/railway. Therefore, evaluation of liquefaction potential and using appropriate methods for prediction of the adverse events of lateral spreading is of great importance. In this study, numerical modeling has been used to study of lateral spreading phenomenon behind rigid waterfront structures. In order to perform a numerical modeling of lateral spreading and also designing the structures exposed to its effects, the interaction of the soil solid... 

In this research, a study on Mirror Neuron and Active learning method was done based on the human capability of using their past knowledge in order to understand new systems faster and with more accuracy. Mirror ALM, A new modeling technique based on ALM was proposed that is capable of merging the IDS planes of an old system in order to improve the output of the modeling for a new system. This new technique was tested on a 3D function, state estimation of an inverted pendulum and finally in control procedure of an inverted pendulum. The results of the tests were compared with the classic ALM method to recognize the advantages and disadvantages of the introduced method. The results showed... 

Pile foundations suffered severe damages during the past earthquakes in all around the world. These damages were more severe in laterally spreading grounds and they mostly have been observed in gently sloping grounds and coastal areas. In these cases, Pile foundations not only are subjected to structures inertial loads and kinematic loads of liquefied soil but also lateral spreading intensifies damages. Thus, in the recent decade, several researches have been conducted to investigate the behavior of pile foundations in liquefiable and laterally spreading grounds, however, some uncertainties still remain in modeling of soil-pile interaction. In this study, the effects of liquefaction- induced... 

In recent earthquakes piles have been severely damaged due to liquefaction-induced lateral spreading. Liquefaction causes lateral spreading in gently sloped saturated soft granular soils, leading to significant damage in structures and deep foundations. Although in recent years many studies have focused on different aspects of this phenomenon, the complex nature of the dynamic interaction between piles and liquefied soil is not yet fully understood. This potential damages are of high degree of importance in southern and northern coastal areas of Iran where several ports and critical facilities are located. The present study focuses on the behavior of a 2x2 pile group against lateral loads... 

Selective laser sintering is an additive manufacturing technique based on fusion of powder bed, wherein after spreading a powder layer, a focused laser beam directs onto selected points of powder bed to fuse powder particles together. This process is repeated layer by layer until the final part is created. Although utilization of blade as a conventional powder spreading (CPS) mechanism has a good compression ability, the fixed contact line between blade and powder bed surface results in improper powder flowability and increasing shear forces applied on underneath layer. In this study, in order to obtain the basis for conducting practical experiments, discrete element simulation of powder... 

Lateral spreading is defined as finite lateral displacement of mildly sloping grounds or those ending in free faces induced by liquefaction. Severe damages of pile groups due to lateral spreading in past earthquakes has been reported. Since earthquake is unavoidable, it is necessary to study the response of piles, especially pile groups, to liquefaction induced lateral spreading. Until now, a number of methods have been developed by researchers for design of deep foundations against lateral spreading, but reported failure of piles in last earthquakes indicates that these methods are associated with high uncertainties. This is due to the lack of laboratory and experimental data to evaluate... 

Fire spread in a road tunnel and its transmission from one vehicle to another was investigated numerically in this study. FDS was used as an open-source, free CFD software. Two boxes close to the car’s dimensions were modeled in a 40m long tunnel and fire transmission from one to another was considered. Ignition temperature was assigned to the second box’s surface as the condition for its ignition start and longitudinal ventilation was applied to the tunnel. At each case, ignition time of the second box was captured. Effects of ventilation velocity, HRR, distance, tunnel height and slope of the tunnel parameters were considered on the ignition time of the second box. Moreoveras a case study,... 

Multiuser detection provides the first comprehensive of the subject of multiuser digital communication, dealing with demodulation of mutually interfering digital information streams. Multiple access spread time codes which are more resistant to various channel impairments, is a motivation to design a multiple access system using spread time systems via circulant codes, to detect users bit stream without multiuser interference. So first of all we introduce multiple access systems and spread time codes. To have an overview of desired system we present a matrix representation of OFDM system. With allocating multiuser circulant coded to users in spread time system, in AWGN channel , users’ bit... 

Active Learning Method (ALM) is a soft computing methodology which has been used for modeling and control. Unlike the good results of ALM’s ability, there is not any analytic expression to prove its power, because ALM’s main operators don’t satisfy fuzzy S-norm & T-norm properties. This problem considered from three viewpoints: Mathematics, Geometry and fuzzy sets. In this paper, we try to introduce two new operators based on morphology to satisfy three conditions: at first, they must be fuzzy S-norm and T-norm to confirm the committal of fuzzy set theory. Secondly, they must satisfy Demorgans law, because they are complement of each other. And finally, they resemble the main operators of... 

In recent earthquakes piles have been severely damaged due to liquefaction-induced lateral spreading. Liquefaction causes lateral spreading in gently sloped saturated soft granular soils, leading to significant damage in structures and deep foundations. Although in recent years many studies have focused on different aspects of this phenomenon, the complex nature of the dynamic interaction between piles and liquefied soil is not yet fully understood. Thus more studies in this regard is inevitable. The present research focuses on the discussion and analysis of two large scale shaking table tests of 2x2 and 3x3 group piles. A three layer soil profile was used for the model, consisting of one... 

Research on how the human brain processes information leading to the creation of two major groups in the field of soft computing. The first group believes that information is being processed based on linguistic concepts and if-Then rules. Fuzzy logic is based on this idea and tries to avoid exact calculations in information processing tasks. Second group believes that the power of human brain in processing is because of a large network of neurons with small abilities. These studies led to the presentation of artificial neural networks algorithms. Spiking neural network is known as third generation of artificial neural networks and tries for processing information using a real model of brain... 

Using appropriate box as an artificial boundary condition is one of the critical tasks in geotechnical physical modeling of the soil mass especially under cyclic loading such as earthquakes. In general there are two types of boxes which can simulate boundary conditions of scaled models as rigid or flexible conditions. Main purpose of this study is design and construction of a flexible box in a way that effects of boundary condition have been minimized during tests. Construction of this box is the first step of an investigation project which concern to evaluate the effect of lateral spreading as a result of liquefaction on deep foundations of bridges, piers, harbors by using shake table test...