Sharif Digital Repository

During times, reinforced concrete sturctures might need to be strengthened due to environmental factors, material properties, design errors or changes indesign guidelines.Fibre-reinforced-polymer (FRP)composites are prominentmaterialsfor this purpose. Externally full bonding systemhas been widely used for flexural strengthening of reinforced concrete sturctures with FRP. However, the drawback of using this strengthening system is the high reduction of structure's deformability.In this research, partially bonding system used in finite element modeling of a bridge’s deck to increase deformability compared to full bonding system. Results showed that not only deformability but also load... 

Through the recent years application of FRP material in structural engineering has been developed significantly. According to possible changes of a building function during its lifetime or alteration of the building codes, building structures usually need to be strengthened. Referring to merits of FRP material, its application seems to be a convenient idea toward the cited requirement. Curved beam and slab are known as highly used elements in building structures. Bridges composed of horizontal or vertical arches could be noted as common examples which need to be reinforced by FRP. However curved concrete surfaces, reinforced by FRP plates, seem to be studied than it is really required; For,... 

In this study the dynamic responses of finite Euler-Bernoulli beams and homogeneous isotropic 2D half-spaces, as one and two dimensional structures, under a moving object are investigated. First, the dynamic responses of finite beams with various boundary conditions were investigated. The results illustrated that the speed of a moving mass has direct influence on the entire structural dynamic response, depending on its boundary conditions. Critical influential speeds in the moving mass problems were introduced and obtained in numerical examples for various BC’s. Dynamic response of a half-space under an inertial foundation subjected to a time-harmonic loading was investigated in the next... 

Finding suitable locations for installing conventional concentric bracings such as X and V, without interfering with building architecture and its openings, is a routine challenge in building design. One of the less known forms of concentric bracings which can be used to solve this issue, is the y-shaped bracing composed of three braces. In the current thesis, results of analytical studies, computer modeling and experimental tests are presented to extend the knowledge of structural behavior of y-bracings. As the first step, effective buckling lengths of braces with rigid connections were found from equilibrium equations incorporating the effect of axial force on rotational stiffness of... 

Steel shear wall system has been used in recent years as the lateral-load resisting system in the design and retrofit of high-rise buildings. This system consists of infill shear panel is framed by surrounding steel frames. Infill shear panel can be applied in two types: stiffened or unstiffened. Considering to the previous studies, the stiffened type is more convenient in the seismic performance and utility condition. However, in the stiffened system, the construction cost is considerably higher because of the complicated construction details. This dissertation concentrates on the experimental and analytical studies of trapezoidally corrugated steel shear walls as an option for removing the... 

Solid foams are novel materials with outstanding characteristics that have found numerous applications in the construction of light, stiff structures during the past two decades. At the micro-level, solid foams benefit from a cellular structure, which is composed of either closed or open cells. Open-cell foams, which were the concern of this study, are described as a network of inter-connected struts (or ligaments) with beam-like action. The mechanical design of foams requires their mechanical properties to meet certain criteria. These criteria can be satisfied by careful selection of the base material and the microstructural morphology (geometry). However, the selected material has to be... 

Reinforced concrete shells are widely used to cover the small to large area with more aesthetics at minimum cost. Shell structures carries load through their shape rather than material strength. Funicular shells are special type of shells that their shape is obtained so that stresses be compressive under a special load (for shell, this load is its dead weight). This study deals with forced vibration of funicular shells on a rectangular ground plan under impulse loads using shallow shells theory. Two boundary conditions, simply supported and clamped, are considered. Displacement components are product of position and time functions. The analysis is based on the expansion of displacement... 

In recent decades, most of the codes have placed a high value on Performance Based Design of structures; however, these methods are computationally complex and time-consuming, and caused researchers to seek new and efficient methods to investigate performance of structures under different intensities of seismic loading. The Usage of Endurance Time method (ET) and thus reducing the size of analysis can be a useful tool for excuting Performance Based Design of structures. Endurance Time analysis is based on time history analysis, but in this method structure subjected to an intensifying acceleration function and different damage indices of the structure are evaluated through analysis time. The... 

With the transportation progress and appearance of transit industry, necessity of modern vehicles redounded to appearance of heavier trucks with higher speeds, moving on the roads. In addition, with the progress in mechanical engineering and automobile industry, appearance of such trucks is growing increasingly. So, bridges as one of the structures that civil engineers design and construct, nowadays are subjected to higher moving dynamic loads in comparison with the past. As a result, lots of investigation and researches in the universities and institutions all over the world are being conducting on the effects of the vehicle speeds on the dynamic stresses of the bridges. Bridge codes... 

In this research the critical speed of a moving oscillator on a single-span bridge with different support (boundary) conditions and by considering the presence of road surface roughness surface with finite element perspective is studied. Due to the fact that passing a moving load on top of the beam causes increased maximum stress and deformations in beam compared to static situation, therefore in reputable codes for bridge design such as AASHTO a dynamic amplification factor is used for designing bridge components. Moving oscillator is a more precise model compared to moving mass for modeling vehicles and the suspension system is modeled as a spring and damper and the moving mass is... 

The unique characteristics of solid foams make them ideal for both natural and man-made structures. The cellular structure of these materials allows for the construction of natural structures such as bone and wood that have high strength and use minimal primary materials. Their unique structure has inspired studies in the automotive and aerospace industries, leading to a new generation of lightweight materials. The focus of this study was the effects of the microstructure of foams on the macro mechanical response of specific structures. Homogenization methods are well suited for the study of these effects due to the random nature of the microstructures. One major problem in using numerical... 

Various theoretical studies have been developed to obtain a deeper understanding of concrete behavior lead to the concrete constitutive models in the macroscale. In these models, however, the microstructure of the concrete and its effects on the concrete behavior has not been taken into account.Several numerical approaches have been incorporated to determine the effects of concrete mesostructure on the overall behavior of concrete. They may be classified at least in three main groups. In the first group, Continuum finite element methods (FEM) equipped with interface elements is incorporated. Second group is to incorporate more efficient elements, such as lattice or truss elements, instead of... 

Endurance Time (ET) method is a dynamic analysis in which structures are subjected to intensifying acceleration time histories. These excitations are also called Endurance Time Excitation Functions (ETEF). The reliability and accuracy of the ET method heavily depends on the accuracy of ETEFs. ETEFs are generated so that ETEFs dynamic characteristics must be consistent with dynamic characteristics of real ground motions. Since the number of ETEFs equations are considerably more than variables noninear optimization is used to generate ETEFs. In order to improve the accuracy of ETEFs two approaches can be used. First, modifying the objective function equations by considering more dynamic... 

Performance based design was first introduced in order to evaluate seismic vulnerability of structures in retrofitting topic and was rapidly implemented in new design codes. The main cause conducting widely developing of performance based design methods, has been accurate estimation of seismic demand parameters. Since seismic structural members displacement during earthquake has a direct effect on the amount of sustained damages, displacement index has always been a key concept in performance based design. The main goal followed by this research is comparing the results obtained from the standard pushover method (with two theorems of distributed plasticity and plastic hinges) and the... 

Vibration of a stationary structure excited by another structure moving on the surface of the stationary Structure is very common in engineering, such as vibration of bridges or railway track under travelling vehicles. In the simplest case, the moving structure maybe modeled as a constant load or a mass or an oscillator, in this case the moving mass is attached to the structure either by a spring or by a mass-spring assembly.The model of a moving mass brings some improvements to the model of the moving load where there is no inertia effect. However, the relative displacement between the moving structures and the beam cannot be considered in the moving mass model. A more appropriate model in... 

The Hubbard model is one of the simplest interacting models in theoretical physics, especially condensed matter physics which despite its simplicity, its solutions are highly nontrivial and intractable. After 5 decades since its introduction, its phase diagram is not fully understood and whether or not, it has a high-temperature superconducting phase. In this thesis, we aim to employ the recent advances in machine learning and GPU programming to accelerate the QMC method. By accelerated QMC methods, we can explore the Hubbard model's phase diagram more efficiently. Using massive parallelization of the GPUs can speed up the measuring process by several times. The self-learning quantum... 

The Hamiltonian of the Hubbard model was introduced by Hubbard in 1963 to model electron correlations in narrow energy bands and it provided an approximate description of electrons in solids.This model provides a simple description of materials, but its exact solution is possible only in one dimension.In the physical examining of this model in quasi two-dimensional systems, the Density Matrix Renormalization Group(DMRG) is used, which is one of the most powerful numerical methods in studying quantum systems. The quantity that is important to solve the systems is the density matrix, which by knowing, many of the observable quantities of the systems can be obtained. Calculating the density... 

Recent advances in numerical computations in the field of strongly correlated systems have provided us to calculate the entanglement spectrum and the entanglement entropy for interacting systems. Calculating the explicit form of the entanglement Hamiltonian (a.k.a. the modular Hamiltonian) is considered as a difficult problem.In this dissertation, we intend to introduce a method and by means of the d ensity-matrix-renormalization-group algorithm to obtain for the first time the second quantization form of the entanglement Hamiltonian of interacting systems at zero temperature. We implement our method for one-dimensional Heisenberg spin chain and also Heisenberg model on a square lattice... 

After the introduction of the framework of quantum mechanics and its experimental success, it was assumed that any physical phenomenon could be analyzed and understood accurately using quantum mechanics. But very soon we found out that in most cases, it is too hard or sometimes impossible to solve the Schrödinger equation exactly even for few-body systems. The reason is that the dimension of the Hilbert space increases exponentially with the number of particles, in a way that for a spin chain(spin-1/2), which has only two single-particle states, even using modern classical computers we are barely able to find an exact solution of a 30-40 particles system which is far smaller than the... 

Base plate is one of the crucial elements in steel structures which transfer force from column to foundation and also prevent stress concentration in jointing area between them. For investigating the behavior of base plate under different caseloads such as axial, transverse and earthquake loads, it is necessary to consider all the involved elements including column, base plate, foundation, anchor rods and also interaction between these elements. In this study the connection between column and base plate, base plate and foundation are analyzed thoroughly. The behavior of base plate with a box type column with and without stiffener under the static loads is analyzed using finite element...