Sharif Digital Repository

In this thesis, a novel approach for assessment and rehabilitation of offshore platform structures will be introduced, which is based on the fatigue analysis. Although fatigue is not a limiting criteria for platforms having natural periods bigger than two seconds, some of this platforms may be susceptible to fatigue due to their specific design. In addition, fatigue analysis can be an effective solution in cases like assessing the efficiency of structural control instruments under platform’s operational loads, and in its life. The main merit of this approach is that it can model the exact behavior of various damper devices and show their influence on the fatigue life. In fact, control... 

The aim of this study is to evaluate the seismic performance of structures using a semi-active tuned mass damper minimizing the amount of structural damage caused by earthquakes. One of semi-active control mechanisms, which has been studied in recent years, is the damper with fluid controlled by a magnetic field (Magnetorehological Damper, MR). These type of dampers react to the magnetic fields that cause significant changes in the behavior of fluid flow. These dampers are acknowledged because of their simplicity, broad operating range as well as not requiring high-power energy sources. In this thesis, a MR damper is used instead of the existing viscous element of tuned mass damper. To... 

Wall systems are an essential part of the buildings and their capacity can be used in designing the structures. However, the seismic behavior of building systems with infilled walls has not been well understood. Implementation ofinfilled walls in the buildings without including them in the design process, changes the failure mechanism and the whole behavior of the structural system against earthquakes. On the other hand, there has been extensive research on rehabilitation of structures with infilled walls,or designing them as the main or one of the lateral load carrying systems against earthquake excitations. In this study, the existing 3-D Panel’s details as the infilled wall of a... 

Nonlinear dynamic procedure (NDP) can in general provide more realistic results than nonlinear static procedures (NSPs). That is due to consideration of higher modes effects and the shifts in inertia load patterns as the structural system experiences nonlinear behavior. Therefore, the simplified NSPs based on constant load patterns are inadequate to determine the inelastic seismic demands especially for top stories of tall buildings. The conventional procedures that have been implemented in design codes and guidelines such as ATC-40, FEMA356, FEMA440 and ASCE41-06, apply invariant load patterns such as inverse triangular, equal lateral force (ELF), first mode shape, uniform and SRSS modal... 

With the advent of virtual memory machines and parallel processing, there has been a considerable shift toward computer-aided design and nonlinear analysis of structures. But increasing the size of computer memory or increasing the number of processing units are not the only ways to achieve a satisfactory solution to a large, complex problem. Another useful method is to reduce the size of the problem so that the reduced model is small enough to be solved at an appropriate processing level, and yet the important engineering behavior of the model is preserved in the reduced problem.Reduced models as an alternative, have gained considerable attention throughout the years in order to meet the... 

The dynamic response of the structural systems are influenced by various parameters such as the effect of higher and torsional modes, the change in frequency or inertial loads caused by the structural softening, frequency content of earthquake records, etc.. Therefore, any method that is only based on static procedure without considering the dynamic characteristics of the structural system may lead to erroneous output. The enhanced pushover procedures have been developed to minimize the inaccuracies of the nonlinear static analyses in predicting the real nonlinear response of structures while maintaining their simplicity. In this research the innovative methods are proposed individually for... 

This study aims to develop machine learning models for predicting damage to steel frame structures equipped with viscous dampers under seismic effects. In this research, eight machine learning models including Linear Regression, Ridge Regression, Random Forest, Gradient Boosting, Natural Gradient Boosting, LightGBM, XGBoost, and CatBoost were employed for the analysis and prediction of structural damage. The structures analyzed were linear viscous damper-equipped steel frame structures with five and nine stories, featuring various characteristics such as the number of spans, dead loads applied to the floors, and different damping ratios, which formed the primary database for time history... 

In present thesis, experimental study of flow around a two-wing MAV using hot-wire anemometer will be performed which is divided to wake and boundary layer study. This leads to suitable understanding of various parameters affecting its wake and boundary layer. First, effects of upper wing, which has horizontal stabilizer's role, on the main wing's wake will be studied in which effects of angle of attack and distance between the two wings at its cruise velocity will be investigated. Then, effects of angle of attack, velocity and distance between wings on boundary layer of the MAV will be analyzed. Also, experiments are performed at three velocities as 10, 15 and 20 m/s, and three angles of... 

The objective of this study is to evaluate the seismic vulnerability of the existing buildings subjected to the near field earthquakes. The main applications of this research are loss estimation and performance evaluation of the existing buildings. That could provide a better solution and particularly more useful information to the owners, investors, and insurers about the expected performance of buildings under earthquake excitations. A number of 2, 5 and 8 story reinforced concrete buildings, designed according to the old Iranian seismic provisions of ISIRI-519 and ACI 318-83 codes for the ordinary moment resisting frames, are considered. By the use of a number of near field earthquake... 

Ever-increasing energy consumption and consequent extensive greenhouse gas (GHG) emissions are two major urgent problems faced by all human beings in the 21st century. As a major contributor, the energy production section appears to be the most suitable field where further improvements could be explored to tackle these problems. Multi carrier energy system is a typical type of next generation energy production technology with higher energy efficiency and lower/zero GHG emissions. The conversion of energy between different carriers establishes a coupling of the corresponding power flows resulting in system interactions. The investigation of such phenomena requires the development of tools for... 

Natural disasters, such as earthquakes and hurricanes, can strike without warning, resulting in a range of destruction from structural damage to loss of life. For this reason, research on structural control, which provides a new basis for design of structural systems against winds, earthquakes, waves, and traffic loadings, become of interest in civil engineering. This thesis focuses on using fluid dampers as a passive energy dissipation device. Viscous Fluid Dampers (VFD) are the most commonly used passive energy dissipation devices that are manufactured in various forms. However, the orifice type of Viscous Fluid Damper (VFD) is considered for structural applications. In this thesis, the... 

Existing structural irregularities (in plan and elevation) has always been among the important causes of structural failures under strong earthquakes. The torsional related damages have especially been very important in multi-story buildings as the torsional behavior of structures changes their uniform translational vibration and causes concentration of demands in the elements at the perimeter of the buildings. On the other hand, the Tuned Mass Dampers (TMD) have in general been accepted as an effective passive structural control device to suppress the structural vibration. In this study, Three 3-D, irregular (in plan) steel structural models with 4, 8 and 15 number of floors are considered... 

In the last few decades, due to population growth and lack of habitable space, the need for construction of taller buildings with more stories has become an important topic. Design of these high-rise structures include different complex tasks in which the finance of the project is the most important parameter. In order to find an efficient and financially feasible design, engineers have always been looking for new approaches and materials. One of the structural systems to be used for tall buildings is the outrigger system. In this system, the surrounding columns are connected to the central core by deep beams or walls to reduce the core forces. In other words, in this method, a new load... 

The present work investigates two basic technologies to dissipate seismic energy and protect the buildings from damaging effects of earthquakes. Investigating the performance of a combination of the Base Isolation system and energy dissipating systems (Dampers) is the main objective of this research. A literature survey is first conducted on the development of each of these systems. In the next step, the design procedure for each of these elements wasreviewed. Finally the application of both elements in seismic mitigation of buildings was investigated. Various time history analyses were performed on a number of structural models with and without these elements to examine the efficiency of... 

The importance of the liquid storage tanks in this era is as much as their contained liquid that we use in our daily lives. Many studies have been carried out on these influential structures considering various aspects. The major damages inflicted to the liquid storage tanks in Loma Prieta, Lozan, Hokaido, Arzinkan, Northridge, Kobe, Izmit & Haiti Earthquakes, has led the researchers to perform various experimental and analytical studies on this regard in the last few decades. The most important part of a safe design of a storage tank is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Moreover,... 

In developing countries, one of the structural systems used for many buildings is the masonry system, and there are also many existing buildings worldwide with different uses constructed with this system, some of these buildings may have a major historical value and because of that, study of behavior of these buildings to find effective ways to improve their behavior is very important. In this study, the use of Textile Reinforced Concrete (TRC) for retrofit masonry walls is examined. For this purpose, seven scaled brick walls is used, including a test model, a model coated with plane concrete on one side of the wall, a model coated with plane concrete on both sides of the wall, a model... 

Processor cores in embedded applications is one the of important part of System-on-Chip designs. Among the most successful (Reduced Instruction Set Computer) RISC cores are the (Million Instruction Per Second) MIPS processors used in applications such as DVD, automotive, broadband access, networking, etc. In this work we have designed and verified Transaction Level Modeling (TLM) architecture of the MIPS in SystemC TLM2.0. The TLM in SystemC is adopted so that abstract data types can be used for higher (abstract) level modeling and faster simulation design. We implemented the processor such that the instruction and data caches contain all the necessary instructions and data to eliminate... 

Cracks are the earliest signs of damage in structures which are needed to get detected through structural inspection before causing failure. Regular inspection and post-disaster inspection of structures are usually conducted manually by engineers. These kinds of visual inspections could be expensive, subjective, not reliable, and most importantly inefficient. Computer vision developments help automate this process by analyzing digital images captured from the surface of structures. Despite the fact that masonry structures have more complex surfaces than other kinds of structures, limited studies have focused on presenting machine-vision-based techniques for crack detection in those... 

This research investigates the effect of soil-structure interaction on the buckling behavior of an above-ground storage tanks. For this purpose, a steel tank with a height-to-diameter ratio of 0.4 was selected. Four types of support conditions including a fixed-based condition and three soil islands with a depth of 30 meters, assuming a uniform stiff soil and a two-layered soil consisting of stiff and medium soil, and a three-layer soil with stiff, medium, and soft layers. The tank and soil were modeled using the finite element method, and absorbing boundaries were applied around the soil island to simulate the semi-infinite soil domain. After validating the modeling through parametric and... 

Nowadays, the design of new structures and the renovation of existing buildings against earthquakes using energy absorption systems are very common. On the other hand, the near-field earthquake are characterized by directivity related velocity pulses with large accelerations. Recent studies have shown that the performance of the passive energy dissipation mechanisms are significantly depended on the characteristics of the near field velocity pulses. The efficiency of various passive dampers in damage mitigation of different building structures have been carefully evaluated under near field and far field earthquake records. In this study, the ability of viscoelastic dampers in controlling the...