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Yayın Progressive damage analyses of masonry buildings by dynamic analyses(Springer International Publishing AG, 2020-08) Aras, Fuat; Akbaş, Tolga; Ekşi, Hızır; Çeribaşı, SeyitThis study investigates the effects of prescribed damage on the walls of masonry buildings by experimental and numerical methods. Ambient vibration survey method was applied to an existing, two-story, unreinforced masonry building to determine its dynamic characteristics, such as mode shapes and natural frequencies. Then, the walls on two exterior sides of the building were demolished, and dynamic testing was repeated for the damaged building. As the next step, the amount of damage on the building was increased by more impacts, and the dynamic characteristics of the heavily damaged building were identified. The results obtained from the undamaged, damaged and heavily damaged building were compared, and the damage effect on the natural frequencies of the building was noted. Besides, finite element analyses of the undamaged, damaged and heavily damaged buildings were performed. It was found that, the numerical models, constructed with code-based material properties, do not sufficiently represent the dynamic behavior of masonry buildings. Secondly, as the result of the sustained damage, while the experimental and the numerical modal analyses revealed the decrease in the dominant frequencies of the building, the difference between them increases with the severity of the damage. With the framework presented in this study, the behavior of masonry buildings can better be determined and used for analysis purposes.Yayın Seismic behavior of fifteen years old RC frame(Işık Üniversitesi, 2019-01-18) Ekşi, Hızır; Karadoğan, Hüseyin Faruk; Işık Üniversitesi, Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıIt is known that during the construction process of signi?cant part of RC structure stock, mild steel and aggregates coming from sea bed used before the existing code proposals and standards in Turkey. Low concrete quality, mild-nonribbed reinforcement and sea type of aggregates are some of the under design features of those structures. This study mainly focused on seismic behaviour of this type of RC frame as experimentally and analytically. Especially in humid environments, reinforcement corrosion probably occurs when the concrete quality is low and it includes aggregates coming from sea bed. The reinforcement corrosion can cause a lot of structural problems such as cracking of concrete, bond lost and decreasing of e?ective cross sectional area of rebar during the service life of RC structure. These destructive corrosion results limit the service life of existing structure stock. Depending on the degree of natural corrosion attack, the adherence between the reinforcement and concrete is adversely a?ected, the e?ective reinforcement cross section is reduced as a function of time and the cracking of the concrete cover can be seen as the main structural damages. Within the scope of this study, the ?fteen years old RC frames were tested to represent the structures which are naturally corroded and constructed before recent earthquake codes and standards. Nearly 1/3 scale one RC frames and one reference frame (15 years ago) were tested under the cyclic horizontal loads and constant axial forces in the ?Istanbul Technical University Building and Earthquake Engineering Laboratory. The seismic behavior of reinforced concrete frames has been tried to be explained by analysing the strength development, displacement capacity, ductility, lost of e?ective cross sectional area of reinforcement, sti?ness, moment-curvature relations and displacement components obtained under cyclic load procedures. The poisson ratio of ?fteen years old con?ned and uncon?ned concrete in descending branch of stress-strain diagrams was another topic for which only limited amount of literature is available. In the theoretical part of this study; non-linear pushover analysis of the structural frame was investigated using by DC2B-v2 which include distributed plasticity theory, Sap2000 and SeismoStruct that are based on concentrated plasticity theory computer programs. The outputs obtained from these programs by using theoretical models and the results of the experimental behavior are compared. There is a special purpose computer program has been developed for ?nding the buckling load parameters of a frame with and without plastic hinges. According to the experimental and analytical results; strength development, lateral and vertical displacement capacity, ductility and moment curvature relationships have been measured, evaluated and compared. The tested frame specimen did not reach its theoretical load capacity and drift level due to decrement of e?ective cross sectional area of reinforcement and decrement of adherence between the concrete and rebar. Displacement capacity of tested corroded frame was reduced visibly when compared with uncorroded reference frame. Some of the reinforcing bars of stirrups which are closer to the outer joints were ruptured at 4% story drift that indicate a loss in displacement capacity and shear capacity due to high corrosion attack on those outer stirrups reinforcements.
