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ÖgeThe fragility curves for lowrise reinforced concrete buildings in Libya(Graduate School, 20230619)In the last century with the huge development in building materials, people used reinforced concrete to provide strong buildings for themselves. These buildings can stand against nature phenomena such as winds, rain, snow, etc. For the effect of earthquakes, these buildings must be considered during design to tolerate collapse and avoid damage and lives. This study uses a new technique to develop a method that can measure the percentage of damage under earthquake motion. Using nonlinear analysis for target buildings and generating pushover curves for these houses to generate earthquake_based fragility curve. Moreover, the calculated fragility curve can help to evaluate these buildings by estimating the percentage of damage caused by a certain level of the earthquake, which leads also to help the designers to review the way to enhance the seismic performance of these buildings, as well as adding new parameters in future building code for design taking into consideration earthquake affect. The first chapter discusses the background and scope of the earthquake history in Libya over the years. This chapter define the region of Libya seismically and describe its activity regarding earthquakes. In addition to that, some of these earthquakes caused damage to the region through loss of lives or properties. This information represents the importance of this study. In the second chapter, the style of the buildings in Libya is shown including materials that have been developed over the years. In this chapter, it is necessary to know the type of structures that will be exposed to the effects of earthquakes when they occur. In the third chapter, the methodology of measuring the fragility curve and estimating damage is described. Definition of FEMA HAZUS loss estimation methodology for calculating the fragility curve, and the different levels of damage. The calculation of the fragility curve depends on pushover analysis results which are calculated using software SAP2000. In the fourth chapter, the description of this study case's building is given. The dimensions and properties, as well as the number of stories and the definition of loads. In this study, two types of buildings are primarily used by locals in Libya for residential buildings. To determine a push over or capacity curve for the case study building, we model the two buildings and define loads, hinges, and materials' details. After calculating the capacity curve, using FEMA HAZUS loss estimationmethodology to generate the estimated fragility curve based on the damage percentage of the building related to corresponding drifts. The performance point can be calculated at the intersection of capacity curve and demand curve for the common maximum earthquake in the region given by the spectral acceleration. Using the calculated spectral displacement at the performance point caused by the maximum earthquake in a region, we can estimate the percentage of damage to the building.

ÖgeEffect of coarse aggregate concentration on bond strength and bondslip behavior between reinforcing steel and low and midstrength concrete(Graduate School, 20230616)Concrete is currently the most consumed building material in the world. The 20 th century saw a significant increase in the use of concrete in construction due to its high quality, speed, and ease of implementation. Reinforced concrete is one of the most commonly used loadbearing systems in buildings. However, despite the development of highperformance concrete, medium, and lowstrength concrete is still widely used in ordinary residential buildings due to various factors. These factors include the use of substandard materials, insufficient details, lack of implementation based on clear scientific bases, and bad construction practices, such as pouring concrete on site without giving importance to increasing the water/cement (W/C) ratio or using aggregates with an inappropriate gradation. Such practices are responsible for most failures in reinforced concrete structures. While most modern buildings use deformed rods to improve the bonding between the rod and concrete, many older structures still rely on smooth rods.The increasing need to evaluate existing construction means that there is a constant need for information about its performance. The research on plain rebars was discontinued because they were not used in the first place when producing ribbed rebars, and ordinary bars have been surpassed in progress in understanding and behavior since the 1960s with the advent of ribbed rebars. The bond between concrete and reinforcement is an important factor in the evaluation of reinforced concrete structures. With the widespread use of reinforced concrete structures, it has become essential to understand the bonding properties between concrete and steel. For a structural element consisting of concrete and reinforcement to act as reinforced concrete, the bars must be clamped to the concrete.This interlocking is affected by many variables, such as the tensile strength of the concrete, the bond strength between reinforcement and concrete, and the concrete compressive strength. Other factors include the concrete reinforcement interface properties, geometric properties of the reinforcement, reinforcement production technique, reinforcement diameter, corrosion, embedment length, concrete confinement, concrete cover thickness, and the type and size of aggregate used. Therefore, the characteristic properties of concrete have a great effect on the bond between concrete and reinforcement. In areas that are located on the active seismic belt, in order to understand the behavior and performance of existing buildings, The worst implementation scenarios in addition to using two types of rebars that resemble the existing case were simulated. In the presented work, investigating the stressstrain properties and bond behavior of reinforced concrete with low and medium strength at different coarse aggregate concentrations was aimed. To achieve this, concrete mixtures with 3 different W/C ratios (0.6, 0.9, and 1.2) and 4 different coarse aggregate concentrations (0%, 20%, 40%, and 60%) were produced. The volume of aggregate and cement paste was kept constant in all mixtures. Pullout tests were carried out to examine the bond properties between concrete and reinforcement. For this purpose, 12mm nominal diameter ribbed and plain steel rebar were used. The results showed that the compressive strength increased up to a certain coarse aggregate concentration and then decreased, particularly in lowstrength classes, with this trend decreasing as the W/C ratio decreased. The contribution of coarse aggregate concentration to compressive strength became more evident with a decrease in the W/C ratio. For instance, in concrete groups with W/C ratios of 1.2, 0.9, and 0.6, the strength increases percentages of concrete with a 40% coarse aggregate ratio compared to a 0% coarse aggregate ratio were 13.8%, 28.8%, and 70.2%, respectively. The study also found that the modulus of elasticity values increased with the increasing coarse aggregate ratio, and the slope of the postpeak region of the stressstrain curves became steeper. The bond strength of the concretereinforcement interface is affected by the W/C ratio. A decrease in the W/C ratio results in a denser concrete structure with reduced porosity, which positively affects the adherence between concrete and reinforcement. The bond strength values of mixtures with a W/C ratio of 0.60 were found to be higher than those with other dosages for both types of rebars. In summary, the type of rebar, watercement ratio, and concentration of coarse aggregate affected the bond strength and bondslip behavior between the concrete and reinforcement. Understanding these factors is crucial in designing and constructing safe and durable concrete structures.

ÖgeEvaluation of seismic response of topside equipment at fixed offshore platforms(Graduate School, 20220202)Nowadays, oil and gas have an enormous role in the global economy, being the most common energy source. Considering the more significant oil and gas reserves are located in subsea, particular offshore structures assist the oil and gas extraction process. Besides operational and dead loads, these structures take the risk of being subjected to high rates of seismic, wind, and wave loads. Considering the heavilyweighted vessels containing flammable materials on offshore topside structures, any damage to these vessels during a seismic event can lead to a collapse of a part, leading to a fire or blast concluding with a disaster. Hence, a study on the response of topside equipment and their connections to seismic actions is a worth approach of disaster management to be looked into. This study aims to study the response of typical topside equipment subjected to seismic events. Hence, a model of a fixed offshore structure and several types of equipment widely used in upstream operations with reallife physical parameters have been developed in finite element analysis software. In the finite element analysis, 22 historical ground motion records have been utilized. These records have been chosen based on several parameters as earthquake magnitude, peak ground acceleration, peak ground velocity, frequency content parameters, and et cetera. Firstly, the response of the fixed offshore platform has been analyzed and the topside acceleration time histories have been found. Then, these topside acceleration time histories have been applied to the bases of the equipment to capture the response of these vessels to seismic events. The probability of failure occurring at the vessels has been observed to have a direct relationship with several ground motion parameters and the seismic response of the platform structure. Damage levels on the equipment have been represented by effective plastic strain values. The ground motion parameters like the peak ground acceleration and duration have been observed to have a significant impact on the plastic strain formation at the vessels. Moreover, nearfault ground motions containing displacement and velocity pulses have been noted to form significant damages at the vessels according to the displacement and velocity pulses. Furthermore, the results show that the damage probability of the vessels demonstrated diversity according to the geometrical shape and natural period. The results obtained from the study provide a basis for several seismic design recommendations for topside equipment at fixed offshore structures.

ÖgeSeismic risk of substandard RC frames with foundation settlement(Graduate School, 20220201)Foundation settlement is one of the most common problems in buildings. Situations such as poorly administered deep excavations and soil liquefaction cause ground deformation and thus trigger the settlement of nearby buildings. Substandard RC buildings may suffer substantial damage from foundation settlements, and seismic effects exacerbate the problem. Although the seismic risk of buildings exposed to settlement has been studied by some researchers, in the majority of them, interstory drift ratios (IDRs) have been used as the key response parameter. However, because settlement causes considerable strain on structural elements, the stresses in critical regions of structural elements may approach their flexural capacity even when lateral deformations are very low. Therefore, the strainbased approach was employed in the study. As the case study building, a substandard RC frame with poor concrete quality and inadequate transverse reinforcement is studied. It is numerically modelled using OpenSees software framework, and the simulated response is validated using data from an earlier experiment. Elements are defined using a forcebased approach, and fibersections are used in the section definitions to capture the axial forcemoment interaction. A number of settlement profiles are applied to the frame, each with a specific range of settlement amounts. First, the redistribution of internal forces following settlement is examined. The findings of the static analysis show that the internal force distributions change substantially following the settlement. Members near the settled area experience a significant increase in axial, shear, and bending moment demands. In some cases, flexural and shear demands exceed capacity. The results of the pushover analysis lead to some remarkable observations as well. The direction of pushover loading has been demonstrated to have a considerable effect. The type of failure and the collapse mechanism are demonstrated to be dependent on the settlement profile. It is shown that the maximum base shear and drift ratio at ultimate displacement capacity decrease significantly as the settlement amount increases. Incremental dynamic analyzes (IDA) are performed using a ground motion set scaled to a specific intensity range. To construct seismic fragility curves, the amount of settlement is added as a new independent parameter to the conventional functional form. A set of damage states are defined based on resultant strains. Two sites with different seismic activity rates are chosen as the case study sites, and the seismic hazard associated with each is identified. Seismic fragility analysis data and seismic hazard information are combined to calculate the annual probability of collapse. The presence of a vertical excitation component as well as consideration of shear failure are found to have a significant influence on the seismic fragility analysis results. The median collapse capacity decreases by up to 26% due to foundation settlement. The annual probability of collapse increases by 0.5% as an outcome of this reduction in the median capacity.

ÖgeThe analysis of unanchored brms considering a velocitydependent friction model and soilstructure interaction effects(Graduate School, 20220201)Blastresistant Modular Buildings (BRMB) are multiplepurpose structures that are used in many different areas including in petrochemical facilities, in blast zones near mining fields, in military industries to shelter personnel, etc. Since these modular buildings are prefabricated and are manufactured offsite, they are costeffective, have better quality compared to onsite manufactured structures, and are built within the construction schedule. Due to the mentioned reasons, they have become more popular, recently. Although extensive studies regarding the dynamic behavior of these buildings have been done over time, there are still gaps that need to be filled. Especially, regarding the unanchored modular buildings since they are relatively a recent trend. The modular buildings which are not anchored to the foundation are more costeffective in comparison to the typically anchored modular buildings because the anchorage to the foundation requires costly installation of anchorages and building of larger foundations. Additionally, the maximum deflection demands for the structural members of the unanchored buildings are significantly smaller. In this study, the behavior of an unanchored blastresistant modular building under blast loads has been studied for two different cases: In the first case, the blastresistant modular building is placed on a reinforced concrete foundation, unanchored and freely sliding. In this case, the response of the building is calculated using a relativevelocitydependent friction model which is based on the Stribeck curve. For a realistically representative friction model to be used in this case, a review of the existing static and dynamic friction models is carried out. In the second case, the behavior of a blastresistant modular building is studied with the effects of the soilstructure interaction being included. In this case, the building is placed directly on siltysand soil. The soilstructure interaction effects are calculated in the time domain using dynamic impedance functions which were proposed by Pais and Kausel (1988). Additionally, the accelerations and forces impacting the inhabitants of the BRMB have been calculated for a test dummy assumed to be positioned in the building using the provisions in the literature regarding human injury criteria. In this part, a brief description of the head injury criteria, the neck injury criteria, the chest, and femur injury criteria is provided according to the existent literature on the topic and later the calculations are carried out. The results of the first and second cases and the human response are later validated against the results of a series of blast tests. The comparisons of the test results and the calculated results seem to be approximate enough, in order for the methods which are used in this study to be verified.