Sharif Digital Repository

The common approach toward soil-pile-structure interaction phenomenon is that it will cause an increase in both effective natural period and damping ratio. Therefore, considering such a phenomenon in design and analysis of piled structures, will lead to smaller displacements. This attitude has gone far in a way that in different suggestions in various practices, this subject is neglected in a conservative manner. In this study, by investigating the response of a single degree of freedom structure founded on a pile group as the first vibrational mode of a structure, by the means of calculating several displacement ratios, has been proved that soil-pile-structure interaction can cause an... 

Continuous synthesis of different kinds of industrial copolymers plays an important role in economics of the polymer industry. But copolymerization reactions are complex and with a high degree of nonlinearity so the control problem in this case needs a detailed study on system dynamic behavior. One of the solutions is using a optimal control method in the shape of predictive controllers. The main goal in this thesis is to design a generalized multi-varriable predictive controller for a solution copolymerization of methyl methacrylate and vinyl acetate in a continuous stirred tank reactor with separator and recycle stream. In this study, after simulating the nonlinear model of the process... 

The ever-increasing growth of Nanotechnology has elevated the necessity for the development of new numerical and computational methods that are better capable of evaluating systems at this scale. The existing techniques, such as Molecular Dynamics Methods, in spite of being fully capable of evaluating nanostructures, lack the ability to simulate large systems of practical size and time scales. Therefore, in order to be able to provide a realistic simulation of a large model, simulation of which is limited by the computational cost of the current molecular dynamics methods at hand, Coarse-Graining technique has recently become a very effective and beneficial method which refers to the... 

Nowadays high temperature superconductors (HTS) are very efficient and useful materials for microwave devices such as planar filters, resonators, hybrids, antennas and delay lines. The advantages of these devices are high quality factor, low insertion loss and reduced size. However the nonlinear effects of superconductors in high incident powers has limited usage of HTS in some applications and causes disadvantages such as reducing quality factor, intermodulation distortion and third harmonic generation of signal. The nonlinear effects of superconductor are due to the dependency of penetration depth and normal conducting coefficient to the current density of superconductor. Nonlinr effect... 

A special steel beam-to-column connection, named Khor-jini, is commonly used for steel framing system in Iran. In this system, two continuous beams are passed next to the columns and are connected to the column side using seated brackets.This type of connection has been common in Iran from the late past. Unfortunately, the seismic behavior of Khorjini frames had not been sufficiently studied prior to Manjil Earthquake of 1990. Due to very large damages which occurred in steel structures especially in connections during the said earthquake, the seismic behavior of this type of connection was studied and some of its weak points were recognized.In this study non-linear... 

The purpose of this research is to study the behavior of conventional and retrofitted Khorjini connections. Thus the software ABAQUS 6.11 was used to fabricate the FEM models of the connections with experimental prototypes. In analytical studies, 21 specimens with different size of the connection components were analyzed. True stress–strain curves for steel and weld materials were used and damage initiation and revolution were considered in the weld material. Also cracking of the welds were considered by a micromechanical method. Behavioral characteristics of the conventional connections are specified and appropriate relations are suggested, using Stability equations of the connection... 

Nowadays, the usage of beam-shaped structures has widely spread in micro- and nano-electromechanical systems; consequently, scholars are extremely interested in precise modeling of static and dynamic behaviors of them. As the beams utilized in MEMS and NEMS structures have thicknesses in the order of microns and sub-microns, the experimentally validated small scale effects would be considerable in their behavior. In fact, experiments manifest that the size-dependent behavior is an intrinsic feature of materials when they are used in small-scale structures. In the classical continuum mechanics, there exists no material length scale parameter. Thus, the classical theory is unable to capture... 

Nowadays, according to increasing development of construction industry in the world especially in the building area, the need to use technology and innovation for fabrication and maintenance of this industry has increased. And this fact becomes apparent that the use of traditional systems of construction isn’t tailored the countries’ requirements anymore. One of the construction industry’s limitations is the restrictions on architectural designs reys. The columns are among the most important components of structure and have a major role in bearing all gravity and lateral loads and transferring them to the foundation. The failure or destruction of the components in the structure under applied... 

This thesis reveals the influence of soil-structure interaction (SSI) on the collapse potential of structures and also investigates the change in collapse margin ratio (CMR) of structures for which the design base shear has been reduced based on the soil-structure interaction provisions. According to the properties of structures and seismic excitations, SSI can increase, decrease or make no change in the response of structures. Based on seismic design codes for fixed-base structures, SSI causes reduction in design base shear of buildings. These provisions are based on linear behavior of structures. But under strong ground motions, specially at collapse level, structures can experience strong... 

The process of implementing a damage detection strategy for aerospace, civil and mechanical engineering infrastructure is referred to as Structural Health Monitoring (SHM). Many portions of our technical infrastructure are approaching or exceeding their initial design life. As a result of economic issues, these civil, mechanical and aerospace structures are being used in spite of aging and the associated damage accumulation. Therefore, the ability to monitor the health of these structures is becoming increasingly important. In many cases, damage causes a structure that initially behaves in a predominantly linear manner to exhibit nonlinear response when subject to its operating environment.... 

Tapering the beam along its length may lead to an increase in the voltage density of piezoelectric energy harvester. In this study, the energy harvester voltage with linear variable cross section is studied by developing an analytical method in both linear and nonlinear states. In linear mode, the results are compared with the experimental results. For the development of linear and nonlinear analytic relations, the Euler–Bernoulli beam and linear voltage variations in the thickness direction are used, and for the separation of variables, the mass normalized mode shapes has been used. The results of the linear analytical method are compared with the results of past research and experimental... 

The reconnaissance reports of past earthquakes indicate that the damages induced by the destruction of secondary systems under earthquakes have a significant share of the total estimated destruction. In many cases, destruction of these non-structural components leads to complete stop of normal operation of sensitive centers such as hospitals and reduces the performance of these centers after the earthquake. Therefore, noticing the important parameters in the design load of these components is of great importance and must be taken into account. In this study, the effect of increasing the mass of secondary systems on the accelerations and displacements response and the effect of considering...