Sharif Digital Repository

Carbon dioxide emissions account for 80% of current greenhouse gas emissions that contribute to global warming; this majority stake held by carbon dioxide indicates that reduction in its release to the atmosphere and capturing emissions accomplished is imperative in conservation of human life in earth. The aim of this project is CO2 capturing from ambient air to decrease air pollution with uses building surface that is wide available surface, as basis of adsorbent. In this research, we select CaO as absorbent that it is proven good absorbent in high temperature for CO2. We studied this absorbent in low temperature and pressure. We experimented different weight amount of sorbent 2,3,4,5,6.5... 

Structures face various loadings and confront different circumstances as they are built and used. This situation causes the aging structures to deteriorate, which would lead to a decrease in reliability and safety. In the recent decades, the need for systems to assure the integrity of structures in terms of their age, usage and level of safety when experiencing infrequent and extreme forces such as earthquakes, tornados, hurricanes, large waves has deeply been recognized. These systems are often referred to as structural health monitoring (SHM) in the literature. The main objective of such system is to increase reliable operating lifetime. In the case of offshore structures, utilizing... 

Jacket type offshore platforms are classified as expensive and also strategic structures, and the cost of their maintanace is considerable. Therefore, any inspection and retrofit plans for life extension of the existing structures is economically and logically preferable rather than making decision for design and construction of new structures. The first stage of assessment plan is monitoring the performance of structure during critical loadings for which the structure is designed. One of the critical loads that should be considered in assessment of jacket structures is seismic loading. Due to dynamic nature of the applied loads in seismic assessment of jacket structures the accuracy of... 

A structural system will normally fail as a result of a chain of failures of different components. In this thesis, fatigue reliability of fixed offshore platforms is investigated through analyzing different failure scenarios. In order to evaluate the occurrence probability of a special scenario, each failure scenario is divided into a finite number of sub-scenarios. To do this, all combinations of time sequences are generated for a given sequence of failures, using a specially developed program.
In order to calculate the occurrence probability of each scenario, a massive reliability analysis should be done for each of corresponding sub-scenarios. Knowing that there are a large number of... 

packed columns are important in liquid-liquid extraction processes. In most studies, at first, drops are broken to small drops as much as possible and then they contact with packings. But, because of different reasons drops during their moving up coalescence together. So far, there is not serious investigation about hydrodynamics of these large drops and their breakage in packed columns. Thus, breakage of two different sizes of drops while collision to 3 different height of 4 different type of packings with two volumetric flow rates and in 2 cases of straight collision of drops to bed and collision to support plate has been investigated. Then size distribution of produced drops throughout... 

Nanostructure matrials have reached a special place to be used in wide applications in recent decades. Among those carbon nanotubes have got much attention due to their excellent mechanical and electrical properties and their ability of developing new nanocomposites, though the issues of perfect dispersion and interaction with polymeric matrix hinders their development. In this work, recent advances on carbon nanotubes (CNTs) and rubbers nanocomposites have been reviewed and the intrinsic potential of carbon nanotubes as reinforcing filler in elastomeric materials has been demonstrated. In experimental section in addition to CNTs, two different grades of CBs, i.e. N330 and super conductive... 

In this thesis, a novel probabilistic framework named Probabilistic Spectral Fatigue Analysis (PSFA) will be introduced for the purpose of assessing the performance of jacket offshore platforms under high-cyclic short-waves fatigue degradation. This method can take into account the uncertainties in three main elements consisting of material properties, sea state parameters and collapse capacity of structure. The main advantage of PSFA approach is the ability to recognize the fatigue failure scenarios and specifies the limit state function of critical members as a super-branch or sub-branch of those scenarios. Therefore, a new and accurate method is proposed for combination of scenarios’... 

One of the most important elements of performance-based seismic engineering elements is precision in determination of seismic displacement demand evaluation. Although seismic demands which are estimated by utilizing non-linear dynamic analysis are most effective, but with regards to inherent complexities of these methods and demands for time-consuming calculations , non-¬linear static methods seems to be an appropriate representative and is recently considered by engineers. In countries with oil resources including Iran, offshore jacket platforms are among outstanding structures being considered. Inasmuch as high design and execution expenses of these structures and also important role of... 

Employing dampers to control wave-induced and seismic vibrations of offshore jacket platforms is an attractive method in order to mitigate fatigue and seismic damage. However, adjustable parameters of a damper are designed by considering only one type of environmental loads; either normal-condition load or extreme-condition load. So, it is important to investigate effectiveness of damping system, for both of two main categories of environmental loads. Also it is ideal for the system to have an acceptable performance in both normal and extreme conditions. The idea investigated in the current study is to use a friction damper device (FDD) and a tuned mass damper (TMD) simultaneously in... 

Extracting modal parameters is necessary for future vibration-based health monitoring studies of the structures. Due to the reason that it is difficult to measure the input excitation forces acting on a real large structure in its operational condition, it is preferable to use the output-only methods which estimate the modal model by using responses data only. Also, the output-only dynamic testing has advantages of being inexpensive since no equipment is needed to excite the structure and the service condition does not have to be interrupted.This paper presents the results of modal identification of an offshore jacket platform using output-only methods with the assumption of ambient... 

In 1933, Gödel’s paper “An interpretation of the intuitionistic propositional calculus”[12] introduced a proof interpretation of the intuitionistic propositional logic to the modal system, S4, which interprets the logical constant as a provability predicate. Fortunately, this interpretation has the soundness-completeness property and therefore we can prove the constructivist’s viewpoint which states that the intuitionistic truth and provability are identical. However, there is a mathematical trick in his work. In fact, Gödel used a proof theory of the concept of proof instead of an explicit interpretation. Furtheremore, he proved the failure of any interpretation of this implicit proof as a... 

Offshore platforms are the most important and enormous wealth of each country that these structures are in situation thatthelikelihoodof damageinhigh. With considering this pointthatplatformsaresubjected to oscillatinglateralloads, so the occurrenceand growth offatigue crack sinthe misvery common. These cracks are always seen in jacket connections, cause these connections are bearing large forces and have massive welding and the presence ofresidualstresses. The fatigue crack caused negligible change in stiffness of connections and in consequence insignificant change in stiffness of structure; So for this reason, they are difficult to detect in global methods. Fiber optic sensors and... 

structures during their service life continually accumulate damage as a result of the action of various environmental forces. Clearly the development of robust techniques for early damage detection is crucial to avoid the possible occurrence of catastrophic structural failure. In a big picture we can divide process into two subcategories: first – we need modal properties of structure. In this case we install several motion sensors on structure and collect their data. Then use a group of methods named as System Identification Process to discover dynamic properties of structure as natural frequencies and mode shapes. Three famous system identification method have been used in this thesis and... 

Nowadays, many offshore jacket platforms have been built in all over the world for excavating oil and gas. Due to cost of construction and maintenance, they are considered as national assets. Jacket platforms are always under various types of loads in their time life, so they cause some damages to them. Hence, on time damage detection can prevent possible extravagant costs of repair and reconstruction. Because many jacket platforms are in Iran, this issue can be very important.Structural health monitoring (SHM) improvised to ensure safety and detect damages of structures uses sensors. They transfer data received from structures to the computers in order that after interpretation of data,... 

In this study, low carbon plain steels joined with TLP bonding method using Fe-44Ni-7B-4Mo interlayer, The bonding parameters (holding time, temperature) have been changed to find optimum conditions of TLP bonding. Microstructure and properties of joints have also been investigated. Dual phase processing of the used steel has been carried out during joints homogenization. Microstructural studies with scanning electron microscope and optical microscope showed that isothermal solidification completed at holding for 50 minutes at the bonding temperature of 1180℃. These parameters are taken as optimum conditions of TLP bonding. Microstructure of the isothermally solidified zone (joint region)... 

In this research, absorption and oxidation catalytic scenarios were examined using previous studies in the field of SO2 removal. Nanostructures zeolite 13X, 5A zeolite, gamma alumina and activated carbon were purchased, then structure, function and adsorption isotherm of each adsorbent were evaluated in 5 concentrations of 250, 500, 750, 1000 and 1250 ppm of contaminants. Final results showed that zeolite 13X compared to other Nano-adsorbents has higher ability to SO2 absorption, and thus the final tests such as temperature and pressure evaluation were performed on the selected sorbent. To further evaluation, the absorbent curves based on two models of BDST (Bed depth service time) and... 

Marine risers are tubular components, which are used to transfer fluids between seabed and floating platform. They may have a great share in cost of oil and gas production systems. One of the risers used in deep-water, is Steel Catenary Riser which is an economic alternative. However, amongst issues in designing this type of risers, high stress level in floating platform connection point and seabed touch- down zone is notable which is created due to platform movements, currents and wave loading and finally, leads to fatigue life reduction. Using buoyancy modules which are attached to risers is one of stress levels reduction solutions in hotspot points. In this study, considering the Caspian... 

High construction and installation costs of offshore platforms, and also harsh environments in which they operate, make health monitoring of these structures more important. Conventional methods to solve the health monitoring problem are deterministic, whereas much uncertainties are imposed to the problem. In most methods of health monitoring methods we try to identify natural frequencies and mode shapes of structures by using its dynamic response. This set of data is then compared to results of modal analysis performed on a finite element model of structure in order to detect any possible damage. In deterministic methods each response of structure is pertained to one damage state, in a... 

Offshore platforms are one of the most important structures in oil-rich countries, so that their economic benefit makes it very expensive to stop their usage. Therefore, it is essential that their performance is not disrupted by earthquake or the tidal waves made by severe storms. According to statistics many of the offshore platforms of their design life pass and need an important loss inspection. The assessment of existing platforms is a relatively new process. The lack of comprehensive standard creates some difficulty in establishing performance requirements, on a case by case basis depending upon the risks associated with the future operations of the platform. In this study the criteria... 

Standard model of cosmology successfully describes the properties of the universe on large scales. General relativistic perturbation theory accurately describes how the initial fluctuations created in the inflation era grew larger and became the seeds of structure formation later in the radiation and matter dominated era. However, linear perturbation theory breaks at the scales of approximately 10Mpc. In such scales, the gravitational effects are non-linear and we should use standard pertubation theory to find the corrections to the linear power spectrum. In this thesis, I calculated these non-linear contributions analytically and proved the stability of the linear point which is believed to...