Person: LİVAOĞLU, RAMAZAN
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LİVAOĞLU
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RAMAZAN
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Publication Degradation of the first frequency of an rc frame with damage levels(Gruppo Italiano Frattura, 2023-04-01) Nguyen, Quy Thue; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; 0000-0003-3436-8551; 0000-0001-8484-6027; M-6474-2014; AAW-6878-2021Damage in RC structures causes the degradation of stiffness and frequency. In this study, the relationship between the two coefficients and damage severities is numerically investigated considering a three-dimensional (3D) RC frame in which the concrete damage plasticity model (CDPM) and the elastoplastic model are selected for concrete and reinforcements, respectively. Crack propagation is obtained utilizing a nonlinear static pushover analysis (NSPA). After pushing, according to the base shear force versus top displacement curve, the bending stiffness of the structure is determined rapidly based on the first derivative of the relationship. Thereafter, the degradation of the first frequency is obtained based on the derivative of the nonlinear curve of stiffness, the second derivative of the force -displacement curve viz. As a result, it is observed that the degradation of the first frequency of the RC frame is proportional to the severity of damage but not linearly. More significant damage, a more profound decrease in the frequency. Particularly, the frequency of the frame reduces gradually until the base shear force reaches 70% of the ultimate value at which the parameter is 60% of the healthy counterpart. After that, the reduction gets more significant when the bending capacity approaches the ultimate value.Publication Dynamic characteristics of minarets of hoca tabip mosque(Ediciones Univ Oviedo, 2015-01-01) Livaoğlu, Ramazan; Baştürk, Mehmet Hudai; Serhatoğlu, Cavit; Doğangün, Adem; Aenlle, ML; Pelayo, F; Canas, FJC; Prieto, MG; Hermanns, L; Rey, MJL; FraileDeLerma, A; Canteli, AF; LİVAOĞLU, RAMAZAN; SERHATOĞLU, CAVİT; DOĞANGÜN, ADEM; Uludağ Üniversitesi; Aenlle, ML; Pelayo, F; Canas, FJC; Prieto, MG; Hermanns, L; Rey, MJL; FraileDeLerma, A; Canteli, AF; 0000-0001-8484-6027; 0000-0002-1867-7103; AAH-4411-2021; AAR-6126-2020; M-6474-2014; S-4676-2019With its thousands of years of history and traces from the past, Bursa is an open-air living history museum. Unfortunately Bursa is located in the earthquake zone and many catastrophic earthquakes occurred in the past. From inscriptions, it is learned that great majority of historical buildings like mosques, madrasahs, inns were damaged by the latest earthquake occurred in 1855. Because of their slender form, minarets were influenced much more than the other structures.Because one of the most important component of liabilities of our society is to preserve and transfer this historical heritage to our posterity, another problematic issue arise on this subject is the lack of literature about minarets. This is because that minarets were built in only Islamic regions. Furthermore, literature review shows that there are only a few scientific studies about seismic behavior of this type of structures. For the mentioned reasons, in this study, dynamic characteristics of Hoca Tabip Mosque which was built in 15th century, were evaluated. One of the in situ tests, modal analysis technique was carried out and the dynamic characteristics of the minaret were captured. At the same time the construction techniques were investigated. These results were compared with those obtained from the numerical model of minaret which was constituted using in situ size measuring. Finally, it was seen that the results from two approaches correspond to each other. In conclusion, it is shown that the numerical model which was carried out in this study represent actual structure with high accuracy.Publication Structural damage identification of high-rise buildings: An artificial neural network based hybrid procedure(Pergamon-elsevier Science Ltd, 2023-06-06) Nguyen, Quy Thue; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0001-8484-6027; M-6474-2014Structural damage detection of high-rise buildings is by far not reached because of their complexity. In this study, an artificial neural network (ANN) method-based two-step approach is suggested to detect damage at element levels of a 3D 30-storey 90 m high RC building containing 2880 degrees of freedom (DOFs). One biaxial accelerometer per floor is erected, making the number of measured DOFs equal to about 2% of the full system. Only the first three bending modes in the orthogonal axes are accounted for. A network is constructed in Step 1 to detect damaged storeys based on the similarities between tall buildings and beam-like systems. All components' stiffness parameters of each storey are assigned to one variable. In Step 2, another network is built focusing only on the detected storeys to localize ruined elements. Furthermore, aiming at detecting damage considering modal data generated under ambient conditions, inevitable measurement noise effects are also considered to challenge the proposed ANN technique. As a result, the light and robust networks lead to precise storey- and element-level detection promptly as long as the desired vibration-based properties are free of noise as well as noise-corrupted.Publication The effect of the ratio of ?-shaped shear connectors on the flexural behavior of a reinforced concrete frame(Sage Publications, 2020-05-27) Quy Thue Nguyen; Livaoğlu, Ramazan; Quy Thue Nguyen; LİVAOĞLU, RAMAZAN; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-3436-8551; 0000-0001-8484-6027; IUQ-1185-2023; M-6474-2014; AAW-6878-2021Failure in a structural system can appear because of different types of pathologies and can cause a large number of problems during seismic action. Among these pathologies are design and execution flaws, underestimation of the required capacity of cross-section or seismic demand, and use of low quality of materials. The jacketing technique for a frame element is the most common use strengthening method in the practice to remove such disadvantages in a structural system. Then, the shear stress transferability at the concrete-to-concrete interface surface is the main objective. Shear connectors application is a solution for that consideration, but the investigation in the literature focusing this point is not adequate. The effect of the ratio of steel shear connectors on the interfaces of a reinforced concrete frame constructed using reinforced concrete formworks on its flexural behavior is numerically evaluated. Initially, the same ratio of pi-shaped and ?-shaped shear connectors, 0.312%, is applied to determine the more effective shape. It should be clear that the ratio of shear connectors on any separate surface is calculated as the fraction of the total area of the cross-section of shear connectors placed perpendicularly (pi-shaped) at the surface and the area of that surface. The same ratio is understood as after evaluating the pi-shaped shear links, each of them is replaced by a ?-shaped link at the same location. As a result, compared to the bending capacity of the frame whose surfaces are smooth, ?-shaped connectors enhance the bending capacity of the frame up to 9.67% while the amount of improvement brought by pi-shaped ones is modest, about 2.172%. After that, a wide variety of the ratio of ?-shaped connectors, 9 values, are placed on concrete-to-concrete interfaces. Tremendously, due to clamping stress brought by ?-shaped shear connectors at the concrete substrates, the nonlinear behavior is improved and the amount of enhancement rises as the number of applied connectors is augmented but not linearly. The most important observation is that the amount of improvement is insignificant after the ratio of shear connectors reaches the percentage of between 0.3% and 0.4%. On the other hand, compared with the frame whose interfaces are smooth, the displacement ductility factor of the frame strengthened using 0.4% decreases an amount of about 30%.Publication Dynamic identification of monumental and historical minaret of the sehadet(Ediciones Univ Oviedo, 2015-01-01) Serhatoğlu, Cavit; Livaoğlu, Ramazan; Bağbancı, Bilal; Aenlle, ML; Pelayo, F; Canas, FJC; Prieto, MG; Hermanns, L; Rey, MJL; FraileDeLerma, A; Canteli, AF; SERHATOĞLU, CAVİT; LİVAOĞLU, RAMAZAN; Uludağ Üniversitesi; Aenlle, ML; Pelayo, F; Canas, FJC; Prieto, MG; Hermanns, L; Rey, MJL; FraileDeLerma, A; Canteli, AF; 0000-0001-8484-6027; AAH-4411-2021; S-4676-2019; M-6474-2014Modal analysis has been used in three decades in the civil engineering disciplines in order to solve complex structural dynamic problems. In this study, dynamic parameter such as fundamental frequency, mode shapes and damping ratios of minaret of Sehadet mosque, historical masonry minaret, was investigated using operational modal analysis method. However; dynamic character identification of historical masonry minarets are considerably difficult for Structural Health Monitoring. The historical masonry minarets have complicated stiffness, heterogenic element material and direct indeterminable boundary conditions. Thus, scope of this study, ambient vibration test which is measure in-situ tests were carried out for determination of dynamic characteristics with the aid of accelerometers and appropriate analysis programs. In order to achieve the modal analysis- frequency domain, Peak-picking method was employed in derivation of modal data from frequency response function data. In addition ultrasound test was performed to the material taken from minaret elements, which is coarse (kufeki) stone and laboratory test was made to the stone sample for the characteristic properties of material. Thereby, only few criteria such as boundary conditions and mesh control calibration was made for the correct model of the minaret. Three dimensional finite element model was designed for the minaret using finite elements analysis program, ABAQUS. The results obtained from a finite element analyses of the minaret were compared with results of experimental approach. Finally, it can be easily stated that the proposed finite element models themselves are the meritorious approximations to the real problem, and this makes the model appealing for use in comprehensive investigations.Publication Comparison and assessment of material models for simulation of infilled rc frames under lateral loads(Croatian Soc Civil Engineers-hsgi, 2019-01-01) Doğangün, Adem; TİMURAĞAOĞLU, MEHMET ÖMER; DOĞANGÜN, ADEM; Timurağaoğlu, Mehmet Ömer; LİVAOĞLU, RAMAZAN; Livaoğlu, Ramazan; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-6329-905X; 0000-0002-1867-7103; 0000-0001-8484-6027; M-6474-2014; ABF-2355-2020; AAR-6126-2020; S-4676-2019In the present study, the behaviour of infilled RC frames under earthquake loading is investigated numerically, and the influence of three different concrete material models on the in-plane behaviour of infilled RC frames is evaluated using the finite element analysis (FEA). For this reason, the efficiency of infilled walls is examined on full scale models. Finite element analysis results show that mathematical model of concrete may change behaviour of infilled RC frames. The post-peak behaviour is especially influenced.Publication Investigation of the infill wall effect on the dynamic behaviour of RC frames(Ediciones Univ Oviedo, 2015-01-01) Timurağaoğlu, M. Ömer; Livaoğlu, Ramazan; Doğangün, Adem; Aenlle, M. L.; Pelayo, F.; Canas, F. J. C.; Prieto, M. G.; Hermanns, L.; Rey, M. J. L.; FraileDeLerma, A.; Canteli, A. F.; TİMURAĞAOĞLU, MEHMET ÖMER; LİVAOĞLU, RAMAZAN; DOĞANGÜN, ADEM; Fen Bilimleri Enstitüsü; Aenlle, M. L.; Pelayo, F.; Canas, F. J. C.; Prieto, M. G.; Hermanns, L.; Rey, M. J. L.; FraileDeLerma, A.; Canteli, A. F.; 0000-0002-6329-905X; 0000-0001-8484-6027; 0000-0002-1867-7103; AAR-6126-2020; S-4676-2019; M-6474-2014; ABF-2355-2020The simplicity of construction and economic reasons have made the infilled frame one of the most preferred structural form for reinforced concrete (RC) frame buildings around the world. For these reasons, the usage of infill walls with reinforced concrete frames increased rapidly over the past decades. On the other hand, although the reinforced concrete frame-infill systems are commonly used throughout the world, the infill is rarely included in the numerical analysis of the structures. For this reason the main goal of this study is to investigate, obtain and compare the dynamic characteristics such as natural frequencies, mode shapes and damping ratios of RC frames with and without infill wall by using classic vibration test results within elastic limit. In addition, the contribution of infill wall to the RC frame behavior for the small strain level is also the target of this paper. For this purpose, full scaled, one bay and one storey RC frames with and without infill wall are constructed and tested.Enhanced Frequency Domain Decomposition technique is used in order to attain the experimental dynamic characteristics of the frames. The results from tests showed that the forced vibration test measurements are sufficient and satisfying to identify the dynamic properties of the RC frames for both with and without infill walls. Furthermore, addition of infill wall to the bare frame does not have an important effect on the dynamic characteristics of the system for small strain level. On the other hand, it is shown that the application of plaster to the infill wall changes the dynamic behavior of the system significantly even for such a so small forces used in this study.Publication A health monitoring solution on damage detection of minarets(Pergamon-Elsevier Science Ltd, 2022-02-12) Nguyen, Quy Thue; Livaoğlu, Ramazan; Nguyen, Quy Thue; LİVAOĞLU, RAMAZAN; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-3436-8551; 0000-0001-8484-6027; AAW-6878-2021; M-6474-2014Historical buildings play a monumental role in religious communities around the world. Masonry structures such as minarets built in areas prone to dynamic effects such as earthquakes are vulnerable as a consequence of their brittle materials and slenderness. Structural health monitoring (SHM) has not been carried out in the regular control of minarets' health for early warning of collapse. Meanwhile, the protection and preservation of such a cultural heritage are urgent. Effective techniques to recognize damage occurrence and location in minarets are vital. In this study, a health monitoring solution on damage detection of minarets is presented. In particular, damage detection of the minaret (24.25 m high) of Hacilar mosque that was built using stone and brick in 1467 in Bursa city (Turkey) is aimed. Only four accelerometers are erected along with the height of the minaret to collecte lateral displacements, making an incomplete number of measured degrees of freedom (DOFs). To circumvent the complicated problem, the minaret is transferred into a lumped mass system correspondingly to the erected sensor network considering the similarities in terms of bending behavior at low modes between slender minarets and beamlike structures. Due to the changes in modal data at two bending modes, an eigenvalue problembased inverse solution is employed to localize damage in the minaret based on the reduction in terms of stiffness of the simplified system. As a result, reliable damage detection is achieved as long as the modal data is noise-free or low-level noise-contaminated (about 0.5%-1% random noise level).Publication Simplified seismic response model for a bulk solid- silo-embedded foundation/soil system(Elsevier Sci Ltd, 2022-11-24) Demir, Ayşegül Durmuş; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0001-8484-6027; M-6474-2014A new analytical procedure encompassing a finite element model approach to perform seismic analysis of a bulk solid-silo-embedded foundation/soil system, as presented here, not only allows for more efficiency in terms of practical design but also successfully accounts for a more thorough evaluation of the behavioral aspects of system. A parametric study was performed on both slender and squat silos with embedded foundations for four different soil types. The research presented here confirms both the efficiency and realiabilty of this new ana-lystical procedure in determining the seismic behavior of silos with embedded foundations.Publication Investigation of wall flexibility effects on seismic behavior of cylindrical silos(Techno, 2015-01-10) Livaoğlu, Ramazan; Durmuş, Ayşegül; LİVAOĞLU, RAMAZAN; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0001-8484-6027; M-6474-2014; S-4676-2019This paper is concerned with effects of the wall flexibility on the seismic behavior of ground-supported cylindrical silos. It is a well-known fact that almost all analytical approximations in the literature to determine the dynamic pressure stemming from the bulk material assume silo structure as rigid. However, it is expected that the horizontal dynamic material pressures can be modified due to varying horizontal extensional stiffness of the bulk material which depends on the wall stiffness. In this study, finite element analyses were performed for six different slenderness ratios according to both rigid and flexible wall approximations. A three dimensional numerical model, taking into account bulk material-silo wall interaction, constituted by ANSYS commercial program was used. The findings obtained from the numerical analyses were discussed comparatively for rigid and flexible wall approximations in terms of the dynamic material pressure, equivalent base shear and bending moment. The numerical results clearly show that the wall flexibility may significantly affects the characteristics behavior of the reinforced concrete (RC) cylindrical silos and magnitudes of the responses under strong ground motions.