2 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 2 / 2
Yayın Seismic behavior of an ordinary RC structure exposed to corrosion(Işık Üniversitesi, 2019-01-18) Türkmen, Gizem Ceren; Karadoğan, Hüseyin Faruk; Işık Üniversitesi, Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıWithin the scope of this thesis, seismic behavior of a 15 years old, approximately ½ scale, one storey, one bay frame which has concrete made of sea sand, mild reinforcing steel, and which was exposed to outdoor conditions for 15 years that resulted in a certain amount of corrosion of reinforcement, subjected to constant axial load and displacement reversals was examined analytically and experimentally. This frame represents the building stock with insu?cient seismic details in Turkey which is built without conforming the existing design codes. Analytical part of the study consists of two approaches; distributed plasticity approach and concentrated plasticity approach. Parameters such as unit deformation and strength of materials were obtained by the axial tension and compression tests for the steel and concrete, respectively. A reference frame having same dimensions and characteristics with the corroded frame except for compressive strength of concrete, was tested 9 years ago with the same experimental procedure also takes a part of this study for comparisons. Experimental results of corroded frame were compared with analytical results which are obtained by nonlinear static time history analysis and pushover analysis. Besides, a retro?tting technique that is RC jacketing is assumed to be applied on the columns of the frame and in?uence of this technique on the seismic behavior of the frame was examined for several assumptions with static pushover analysis and the obtaining the capacity curves for each assumption, comparisons were done. Moreover, a parametric study which involves the increase in the amount of corrosion of the specimen tested, was performed to have the insight about the effect of diameter loss of reinforcement due to corrosion on the lateral load carrying capacity and deformation capacity of the structure. The experiment was ended at %3 drift ratio and bending and shear cracks were observed at the ends of columns. Structure elements underwent excessive loading which is beyond their load carrying capacity and had plastic deformation at the column ends which refers to strong beam weak column analogy. Furthermore, implementation of RC jacketing as a retro?tting technique analytically, led the plastic deformation to occur at the beam ends instead of column top end which complies with the proposal of TEC known as strong column-weak beam situation. According to the experimental and analytical studies, seismic behavior of the frame which is presented by capacity curve is modeled better with concentrated plasticity approach. Secondly, load carrying capacity, energy dissipation, cumulative energy dissipation of recently tested frame is higher than the reference frame which has lower compressive strength of concrete. Also, when comparing capacity curves,the frame has quite similar behavior when the concrete is 32 days old. Furthermore increasing corrosion rates of column reinforcements leads lower lateral load carrying capacity and ductility under lateral loading. As it is expected, it was observed that retro?tting of the columns by RC thin jacketing like 4-6 cm thickness is an e?ective and useful method to increase sectional and hence the displacement ductility and the lateral strength of the frame. Self-leveling and self-compact special concrete can be used for those thin jackets.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.
