Ph.D. Theses
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Browsing Ph.D. Theses by Subject "Buildings -- Earthquake effects."
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Item Earthquake behavior of geosynthetic-reinforced retaining structures(Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2011., 2011.) Selek, Öznur.; Güler, Erol.Geosynthetic-reinforced soil walls have so far shown a very good performance during earthquakes. Nevertheless, additional tests like reduced-scale shaking table testing can be useful in understanding the effects of various parameters. Eight different reduced-scale models were tested using the shaking table facility at the Kandilli Observatory and Earthquake Research Institute (KOERI) of Boğaziçi University in the scope of this study. A woven geotextile was used as reinforcement and concrete blocks were used as wall facing. Four tests were conducted using 1:2 scale models of two meters height, one test involved a 1:4 scale model with 1 meter height, and the remaining three models were 1:4 scale two meters high walls. The models were instrumented with eight optical laser distance sensors to measure face displacement, ten accelerometers to measure accelerations on face and top of wall, and eight special transducers to measure the strain in geotextiles. The effects of peak ground acceleration, reinforcement length and spacing, model scale, and treatment of top two rows of facing blocks on amplification of acceleration, maximum displacements during shaking, permanent displacements and geotextile stresses were investigated. Maximum accelerations observed during shaking on the wall face increased from bottom to top and increased linearly with increasing table acceleration. Geotextile length and spacing did not affect the amplification factors for acceleration and affected maximum face displacements during shaking only slightly as long as the geotextile length was meeting the minimum requirements of FHWA design procedure for seismic loading. No noteworthy permanent displacements were observed. Measured geotextile stresses were higher than the design values calculated and the difference was more pronounced in walls with short reinforcements. It is concluded that for the tested type of geosynthetic reinforced soil wall with purely frictional reinforcement-block connection, determining the length and spacing of reinforcement using the pseudo-static design approach suggested by FHWA provides satisfactory performance during seismic loading, but geotextile stresses higher than those calculated in design may be encountered.Item Earthquake protection of Beylerbeyi Palace by reversible mixed technologies(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2007., 2007.) Aras, Fuat.; Aşkar Altay, Gülay.The historical building stock and seismic risk of Anatolia draws considerable attention of the engineers for studying the earthquake performance of these structures and investigating appropriate protection techniques. In this respect, this study aims to examine the earthquake performance of the historic Beylerbeyi Palace which is a representative of the great buildings in the late of 19th century in Istanbul and elsewhere in the Ottoman Empire and search the possible retrofit techniques by means of reversible mixed technologies within the framework of FP6-Earthquake Protection of Historical Structures by Reversible Mixed Technologies (PROHITECH). Starting with the mineralogical structure of the mortar and ending with mechanical properties of masonry, material identification process has been carried out. Later on Ambient Vibration Survey, (AVS) was conducted in the structure with the University of "St. Cyril and Methodius", Institute of Earthquake Engineering and Engineering Seismology. Numerical model of the palace has been constructed and calibrated according to results of AVS. Response spectrum analyses have been carried out by using three different earthquake cases, defined by accounting the site specific soil and seismic characteristics of the site. The performance of the structure was assessed as weak. Furthermore the vulnerable parts of the structure were revealed by nonlinear analyses. Finally according to results of the analyses and considering the historical and architectural perspective of Beylerbeyi Palace three different retrofit strategies have been proposed and discussed in details. According to order of presentation, the first proposed strategy is the use of fiber reinforced polymers. The second strategy is the installation of the base isolation and the last one is the consolidation of the roof level to have the rigid diaphragm behavior with the application of fiber reinforced polymers to the required walls.Item Investigation of dynamic behavior of geosynthetic reinforced soil retaining structures under earthquake loads(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2007., 2007.) Enünlü, Ali Kasay.; Güler, Erol.Due to their advantageous engineering properties and cost effectiveness large numbers of Geosynthetic-Reinforced Soil Retaining Walls (GRS-RWs) are being designed and constructed throughout the world and also in our country. In this thesis, in order to gain better insight into dynamic behavior of a GRS-RW under earthquake loads, two 1/2 reduced-scale shaking table tests were carried out using the shaking table facility at the Kandilli Observatory and Earthquake Research Institute (KOERI) of Boğaziçi University. The walls were 1.9 m tall, making them one of the tallest reduced-scale walls of its kind. By installing 8 linear displacement transducers to measure the strains of the geotextile members, 8 laser displacement sensors to measure the displacements of the facing blocks, an LVDT to measure the displacement of the shaking table and 11 accelerometers on several locations of the soil structure and onto the shaking table to evaluate the acceleration amplifications occurred, detailed displacement-time, average strain-time and acceleration-time histories of the components of the GRS-RW were obtained. In addition to the experimental tests, numerical analyses with the finite element (FEM) program Plaxis v 8.4 and the Newmark’s displacement method were utilized. The experimental test results showed that both experimental walls behaved rigidly and almost no residual displacements were observed on the front wall. While Newmark’s analysis confirmed this phenomenon, Plaxis v8.4 simulated the dynamic behavior of the wall reasonably by demonstrating minor residual displacements at the top of the wall attaining to 5 mm and 6 mm for 1st and 2nd experiments, respectively. The general conclusion is that GRS-RWs designed according to the current specifications behave very successfully under earthquake loading conditions.