Sharif Digital Repository

Structures which are designed in accordance with previously used design codes are usually weak to sustain dynamic loading and therefore they shall be rehabilitated. One approach for rehabilitation is to use active control. In this study, active tendon is used as a structural device control. Various arrangements of controllers can be used to limit the response of the structure but it is desired to find an arrangement at which the cost of the placement will be minimized. The aim of this thesis is to find the best placement of active tendons on a frame such that the placement satisfies two general restrictions; namely structural response and control forces. Genetic algorithm is applied to the... 

This research work deals with application of poly-saccharide to improve coating process of bioactive ceramic composite on aNd-Fe-B magnetic alloy substrate. Bioactive glass particles were synthesized through a sol-gel process and coated in the form of composite with poly-saccharide onto a magnetic substrate by electrophoretic deposition technique. Stable suspensions of 0.5 gr/lit polysaccharide polymer-ceramic were prepared using bioactive glass particles (<1µm), acetic acid 1%. The influence of added water to ethanol, pH and tri-ethanol-amine (TEA) additive on suspension stability, deposition rate and coating’s structure was investigated. It was shown that by increasing the water to ethanol... 

This study aims to design and develop procedures, forms, and tools for post-earthquake reconnaissance. The current procedure for data collection is based on the sending of groups to identify the dimensions of the evidence and its consequences by the executive and responsible institutions. Studying and reviewing the reports that have been produced by this method shows that there is not any systematic mechanism for collecting data on a wide scale and from all aspects of the evidence. The limited data collected by the executive and responsible institutions are scattered in the reports and are less documented in the database. Therefore, it is necessary to collect big data on the severity and... 

In this thesis, by focusing on the hydraulics of three phase flow in vertical tubing to investigate asphaltene deposition problem, the solid particles behaviors in a turbulent flow is fully studied. Reasonable size distribution for particles (based on previous works and researches) was assumed and a model for 2 sections of a Marrat oil field well to evaluate their asphaltene deposition problem was developed. Three phase liquid-gas-solid flow in the well tubing was simulated. Asphaltene deposition profile on the well tubing, mean and maximum of the deposition rate and particle concentrations in the flow regime were calculated and compared with real field data. Better agreement with field data... 

This paper presents a new approach for developing multivariable fragility curves, which examines the effects of the variation of multiple design parameters on the probability of reaching different damage states. The database of this study comprises the results of 260 RC columns tested under the quasi-static cyclic loading. The push of the cyclic plots, technically named the backbone curve, is also extracted for the entire database by the authors. Accordingly, the RC columns are classified into four levels of damage based on the resisting lateral force observed throughout cyclic loading, derived from the backbone of the hysteresis curves. Considering the drift ratio as the primary variable... 

Large-size buried pipelines are an efficient way of transporting of water, waste water, sewage, gas, and oil resources in across the world. Since the buried pipe lines are exposed to many unexpected conditions, such as landslides, corrosion, fatigue, unexpected loading, earthquakes, material flaws or even intentional damaging, so the inspection requirements lead to adoption of new method of maintenance, protection and conserving of pipelines. This proposed project aims to improve the trustworthiness, reliable, yet economical technologies for monitoring of behavior of buried pipe lines during operation and assessing the risk of pipe lines failure. Piezoelectric sensor is bonded on the surface... 

Structures that change shapes are often called morphing structures. Smart morphing composites refer to the morphing structures that can detect the change in conditions and, through a control mechanism, command the actuators to maintain the stability and/or perform a new task. The present report provides a framework on the eld of smart morphing composite structures. The emphasis on this work is on, particularly, multi-stable composite structures with capability to detect the new conditions and adapt themselves to properly respond to them. Due to cycling nature of applied load on morphing, these structures are vulnerable to failure due to fatigue. A failure control mechanism utilizing a... 

Vibration is one of the major problems in gas and oil pipelines. Vibrations can cause damage to the pipes, supports, valves and other equipment installed in the system. These vibrations can be caused by equipment installed on pipelines like compressors and pumps or by fluid flow in pipes and fixed equipment like connections and valves. This research investigates the dynamic behavior of fluid flow in pipelines in Karanj and Parsi oil fields located in the southern part of Iran. The pipeline is responsible for injecting gas into the field. Excessive vibrations in the system cause repeatable damage which in turn increases the operating and maintenance cost. First, the vibration of pipelines has... 

During the past two decades, laminated composite structures have been used for many engineering applications, including aerospace, automotive, sport equipment and pressure vessels.
In spite of the excellent properties of strength to weight ratio, composite structures are vulnerable to failure when subjected to impact and vibration. It is well known that impact damage may severely degrade the strength and stability of laminated composite structures. For this reason the effect of impact on composites has been a subject of extensive research.
There are several ways of decreasing the vibration energy of structures, such as diminishing the source energy, designing structures... 

Minimally Invasive Surgery (MIS) is a modern surgical technique in which the operation is performed through small incisions in the body. Therefore, the surgeon looses his/her sense of touch which is of high importance in any medical operation. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum applied by surgeon and to measure the transmitted force/momentum to the tissue/organ. First, an accurate electro-mechanical model of the smart grasper is developed and the relations... 

Marine offshore structures are huge structures constructed in very harsh environments, like oceans and seas. These structures are highly exposed vibration due to ocean’s waves, wind, helicopter landing, etc. Preventing the damage to these structures due unpredicted vibration using a semi active vibration control is being considered. Magnetrorehological (MR) dampers have been used as active element to control the vibration and to provide the structural integrity of the structure. Providing high dynamic range, lower power requirements, large force capacity, robustness, and safe manner operation in case of fail made the MR dampers attractive devices to passive, semi-active and active control...