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Öğe A practical methodology to estimate site fundamental periods based on the KİK-net borehole velocity profiles and its application to Istanbul(Seismological Society of America, 2022) Güllü, Ahmet; Hasanoğlu, Serkan; Yüksel, ErcanDetermination of site fundamental periods is remarkably important to classify soil deposits and to identify the resonant probability of any structures during an earthquake. Recent developments in the literature exposed that the fundamental period is a better proxy than time-averaged velocity to 30 m (VS30) or the best complementary parameter to VS30 to evaluate the soil characteristics. Because great efforts have been paid to achieve VS30 maps of many regions and countries, an approximate methodology based on this parameter and engineering bedrock depth (Zbr), in which the shear-wave velocity reaches 760 m/s (Z0.76) or 1000 m/s (Z1.0), is presented here to find out the site fundamental periods. The meth-odology is developed and verified using the Kiban Kyoshin network database. Outcomes of the proposed methodology are also compared with some of the literature equations and methods. The comparative studies resulted in a great correlation with a relatively low standard deviation. Therefore, it is conceivable to apply the proposed methodology easily to the regions where VS30 and engineering bedrock depth are already known.Öğe Characterization of energy dissipative cushions made of Ni-Ti shape memory alloy(IOP Publishing Ltd , 2022) Güllü, Ahmet; Danquah, Josiah Owusu; Dilibal, SavaşEarthquake-resistant design of structures requires dissipating seismic energy by deformations of structural members or additional fuse elements. Owing to its easy-to-produce, plug-and-play, high equivalent damping ratio, and large displacement capacity characteristics, energy dissipative steel cushions (SCs) were found to be an efficient candidate for this purpose. However, similar to other conventional metallic dampers, residual displacement after a strong shaking is the most notable drawback of the SCs. In this work, cushions produced from Ni-Ti shape memory alloy (SMA) are evaluated numerically by experimentally verified finite element models to assess their impact on the performance of earthquake-resistant structures. Furthermore, a reinforced concrete testing frame is retrofitted with energy dissipative steel and Ni-Ti cushions. Performance of the frames (e.g. dissipated energy by the cushions, hysteretic energy to input energy ratio, maximum drift, and residual drift) with different types of cushions are evaluated by nonlinear response history analyses. The numerical results showed that the SCs are effective to reduce peak responses, while Ni-Ti cushions are more favorable to reduce residual drifts and deformations. Hence, a hybrid system, employing the steel and SMA cushions together, is proposed to reach optimal seismic performance.Öğe Closed-form demonstration and shake table verification of damping effect on the seismic energy(World Scientific, 2022) Güllü, Ahmet; Yüksel, Ercan; Altinta, ElifThis paper discusses closed-form demonstrations of the damping effect for a basic mass, spring, and damper (MSD) and a single degree of freedom (SDOF) system that are exposed to harmonic loading. Initially, the energy balance equations of the systems were solved in closed form by considering the damping ratio and loading frequency. Verification of the solutions obtained for SDOF systems is achieved by shake table tests. Based on the analytical and experimental results, it was found that the damping effect is highly related to the ratio of loading frequency to the natural vibrational frequency of the system. For the lower and higher values of the ratio, damping is found to be almost ineffective. However, the effect becomes substantial when the ratio reaches unity i.e. at the resonant frequency. Damping has a reverse relation with seismic energy at the dominant frequency. In contrast, the relation is proportional in the vicinity of resonance frequencies. Hence, considering the damping as a parameter for the energy-based design of structures is suggested.Öğe Cyclic behavior of reinforced concrete cladding panels connected with energy dissipative steel cushions(Elsevier Sci Ltd, 2019) Karadoğan, Faruk; Yüksel, Ercan; Khajehdehi, Arastoo; Özkaynak, Hasan; Güllü, Ahmet; Şenol, ErkanPrecast concrete structures show damage after the destructive earthquakes and indicate that the connections of reinforced concrete (RC) cladding panels might be inadequate. RC cladding panels greatly increase the lateral stiffness and strength of the building when they are rigidly connected to the structural system. However, this also increases the seismic requirements. Consequently, a robust mechanical connection device with energy-dissipating capability was produced for RC cladding panels. Extensive experimental and numerical studies on an energy-dissipative steel cushion (SC) connection device were carried out in the framework of the SAFECLADDING project. Cladding panel tests were conducted with various connection configurations. The fundamental variables are the location, quantity, and thickness of SCs used in the cladding systems. The test results demonstrate that the SCs used in panel-to-panel and panel-to-support connections made large contributions to the total energy dissipation capacity. The parameters of a numerical model were also evaluated to reproduce the experimental results.Öğe Damping effect on seismic input energy and its verification by shake table tests(Sage Publications Inc, 2021) Güllü, Ahmet; Yüksel, Ercan; Yalçın, Cem; Büyüköztürk, OralSeismic input energy per unit mass (E-I/m) imparted into a structure is a function of earthquake (duration, frequency content, amplitude etc.), soil (shear velocity, dominant period etc.) and the structural (vibrational periods etc.) characteristics. Generally, the damping properties of the structure is assumed negligible for seismic input energy. Most of the existing spectral equations derived for SDOF systems generally use a constant damping ratio of 5%. In this study, the damping effect on E-I/m is investigated experimentally and numerically on SDOF systems with distinct damping ratios. Experimental investigation and numerical computations proved that seismic input energy is very sensitive to variation of damping within the vicinity of fundamental frequencies. Specifically, up to 50% increment was observed in the plateau region of the input energy spectrum, where maximum E-I/m values occur, by variation of damping from 2% to 10%. Hence, a novel damping modification factor (DMF), which could be utilized for existing energy spectra, is proposed in this paper. Validation studies of the proposed DMF are achieved through the various energy spectra found in the literature.Öğe Development of Finite Element Model for a Special Lead Extrusion Damper(2021) Güllü, Ahmet; Çalım, Furkan; Yüksel, Ercan; Soydan, CihanA significant amount of seismic energy is imparted to the structures during earthquakes. Theenergy spreads within the structure and transforms in various energy forms as dissipatedthrough the structure. The conventional seismic design provides specific ductile regions,namely plastic hinges, on structural elements. Therefore, the energy dissipation capacities ofthe structural elements and the structure enhance. However, this approach accepts that thedeformations will concentrate on the plastic hinge zones and severe damage may occur onstructural elements within deformation limits that are defined by the seismic codes. The modernseismic design aims to dissipate a large portion of the seismic input energy by installing energydissipating devices (EDDs) to the structure. Thus, deformation concentrates on EDDs whichcan be replaced after an earthquake, and energy demand for structural elements is decreased.Lead extrusion damper (LED) is a passive EDD that utilizes the hysteretic behavior of lead. Inthis paper, the preliminary results of the developed three-dimensional finite element model(FEM) for a LED is presented. The results obtained from the finite element analysis (FEA) werecompared with the experimental ones in which LEDs were exposed to sinusoidal displacements.Also, the applicability of the developed FEM was checked for different component dimensionsgiven in the literature. The comparison study yielded a satisfactory consistency. Additionally,the maximum relative difference obtained for the literature devices was reduced to 12% from39% by the developed FEM.Öğe Effect of building importance factor on seismic performance of rc frame type shopping malls subjected to pulse-like records(Elsevier Science Inc, 2021) Güllü, Ahmet; Karameşe, GencoSince they offer many alternatives for shopping, eating, resting, etc. many people spend a considerable time in shopping mall buildings. Therefore, this type of building is increasing rapidly. The increment rate was almost three in Turkey for the last decade. The recently released seismic code of the country has some serious alterations such as increased seismicity of some regions and reduced performance level limits of structural members. Besides, the building importance factor (I) of the shopping malls was defined clearly to be 1.2 whereas some shopping malls were designed considering I = 1.0 and constructed before 2018. Therefore, seismic performances of the shopping malls became questionable according to the code. In this study, seismic performances of two existing shopping mall buildings, which were designed and constructed by considering I = 1.0, are investigated based on the recently released seismic code and nonlinear analyses in which the utilized records were scaled considering I = 1.2. The results showed that the increased seismicity and reduced performance level limits may lead to excessive story drifts and plastic rotations for some records. However, the mean value of the analysis results satisfies the life safety (LS) performance level. Therefore, the importance factor might be suggested to be 1.0 for shopping malls close to the faults to avoid an unnecessary increment of the initial cost.Öğe Evaluation of the Relation between Seismic Input Energy and Spectral Velocity(2020) Güllü, AhmetEnergy based seismic design concept is getting attention owing to its advantages over theconventional methodologies. Particularly, the consideration of duration and frequency content ofthe earthquake record are chief superiority of the concept. For this original design procedure,accurate determination of seismic input energy is crucially important. Because of solving energybalance equation is a tedious job, the seismic input energy is determined in terms of equivalentvelocity in the literature mostly. However, it was also shown that this relation is valid for onlyundamped systems. Therefore, this study aims to provide the nonsteady relation between seismicinput energy and equivalent velocity for damped systems. Intensive response history analyseswere performed by using plenty of earthquake records those were selected by considering theimpulsive characteristics (ordinary and pulse-like) and shear wave velocity. It was found that therelation given in the literature for seismic input energy and spectral velocity relation is not true fordamped systems. Dependently, it is proposed a set of coefficients considering structural dampingproperties to modify the existing relation.Öğe Experimental investigation and pseudoelastic truss model for in-plane behavior of corrugated sandwich panels with polyurethane foam core(Elsevier Science Inc, 2021) Yüksel, Ercan; Güllü, Ahmet; Özkaynak, Hasan; Soydan, Cihan; Khajehdehi, Arastoo; Şenol, Erkan; Saghayesh, Amir Mahdi; Saruhan, HakanSandwich panels are commonly used in facades and the roofs of industrial buildings due to their well-known advantages. However, there is limited data about the in-plane behavior of the panels. Hence, this paper aimed to propose a pseudoelastic truss model to represent the effective in-plane stiffness and strength properties of the corrugated sandwich panels with a polyurethane foam core. Two separate sets of experiments (mock-up and system test) were conducted in the laboratory. The variables were the number of fasteners, sheet thickness, loading direction, and number of ribs. The number of fasteners, sheet thickness, and loading direction are the most effective parameters for the in-plane behavior. A formula was proposed to compute axial stiffness of the truss members by considering the effective parameters. Experimental results showed that the proposed robust truss model could give a good estimate of the pseudoelastic stiffness and maximum load bearing capacity of the sandwich panels.Öğe Multi-objective optimal sizing of energy dissipative steel cushions for longitudinal loading(Springer, 2021) Güllü, Ahmet; Göktepe Körpeoğlu, Seda; Selek Kılıçarslan, Elif SılaContemporary approach in earthquake engineering tends to dissipate some part of seismic energy by additional fuses. Owing to its easy-to-produce and plug-and-play characteristics, energy dissipative steel cushion (SC) can be a prominent candidate to serve this purpose. Since its closed form design equations are already available in the literature, seismic performance and energy dissipative characteristics of SC might be improved by optimal sizing. Hence, distinct mathematical optimization techniques, namely sequential quadratic programming, gradient-based method, and Lagrange multiplier method, are employed. Results of the optimization techniques are evaluated through experimentally verified finite element analyses. Consequently, some geometric dimension ratios are provided for the optimal sizing of SCs. Comparisons between the optimization studies yielded that the gradient-based method requires fewer function evaluations to converge while the Lagrange multiplier method with a Hessian produces more accurate results.Öğe Piecewise exact solution of the seismic energy balance equation and its verification by shake table tests(Springernature, 2022) Güllü, Ahmet; Yüksel, ErcanThe seismic energy-based design concept is attracting increasing attention due to its known advantages such as counting for frequency content of earthquake and duration-related cumulative damage. The concept requires the solution of a relatively complex integration namely the energy balance equation. Thus, some researchers have preferred to use equivalent parameters (e.g. spectral velocity) and prediction equations for the determination of seismic energy. In this study, a piecewise integration technique is proposed to achieve the exact solution of the energy balance equation. The proposed algorithm was validated through shake table tests conducted on the single degree of freedom (SDOF) and multi-degree of freedom (MDOF) systems in elastic and inelastic ranges, as well as analyses of the nonlinear response history of a benchmark frame. To evaluate the efficiency of the proposed solution technique, two MDOF specimens were supplemented by metallic dampers to have discrete damping properties. The seismic energy responses of all specimens with and without metallic dampers were determined satisfactorily. A maximum relative difference of 15% was obtained between the algorithm and the results of the experimental and numerical examples used for the validation.Öğe Rapid and easily applicable procedure for full-scale laboratory tests of ballastless slab tracks(ASCE-American Society of Civil Engineers, 2021) Güllü, Ahmet; Özden, Bayezid; Ölçer, Beyazıt; Özcan, Ali İhsan; Binbir, Ergün; Durgun, Yavuz; Saruhan, Hakan; Şahin, Fatih; Şenol, Erkan; Khajehdehi, Arastoo; Noobakhtjoo, Amir; Yüksel, ErcanIncreasing demand for high speed railway lines necessitates reducing construction and maintenance costs. Accordingly, RC slab tracks are preferred due to their advantages such as being almost maintenance free and supplying uniform support conditions. However, new testing procedures are required for the performance evaluation of the slab tracks to identify possible failure modes which may not be observed in numerical analyses. Although there are some procedures in the literature, there still is no consensus on loading intensity, shape, frequency, or number of cycles. A testing procedure that greatly decreases experimental costs was adopted for the design approval tests of precast RC slab tracks. The procedure was evaluated experimentally through full-scale laboratory tests of intact and intentionally damaged specimens. The study demonstrated that the proposed testing procedure reduces experimental costs and identifies the mechanical properties of slab tracks.Öğe Simultaneous multi-objective optimal sizing of energy dissipative steel cushions for transversal loading(World Scientific Publishing Co Pte Ltd, 2022) Güllü, Ahmet; Göktepe Körpeoğlu, SedaCurrent practice in structural engineering requires dissipating some part of seismic energy by sacrificial elements rather than structural members and/or joints. As an easy-to-produce and plug-and-play damper with stable hysteretic loops and large displacement capacity, steel cushion (SC) is a significant device to improve the seismic performance of the structures. It was stated in the previous studies that SC is less effective in the transversal direction. Hence, the efficiency of the damper is improved by optimal sizing through intelligent optimization techniques in this study. The complex optimization problem could be converted to a relatively simple mathematical problem since closed-form equations of the damper are exist in the literature. The optimal sizing problem was solved using two distinct methods namely the 6-constraint method and the elitist non-dominated sorting genetic algorithm (NSGA-II). The employed optimization methods were verified by each other as almost similar geometric ratios were obtained. The efficiency of the optimization is evaluated through finite element analysis (PEA). It is shown that the optimally sized SC is superior in terms of energy dissipation.Öğe The efficiency of photovoltaic panels to meet energy demand of a school building in the Mesopotamia region(2022) Al-Rubaii, Shaimaa; Köse, Ali; Kazar, Gökhan; Güllü, AhmetAll kinds of energy are one of the basic requirements in life to sustain it. Therefore, the majority of research and applications have been mostly focused on self-sufficient energy or zero-energy buildings in developed countries. Most of these countries encounter energy demand and suffer from carbon dioxide emissions from existing buildings. Energy-efficient applications must be also spread across developing and undeveloped countries especially in the Mesopotamia region due to the hot climate. Hence, the efficiency of a common practice, implementation of photovoltaic panels (PVs), in Iraq is investigated in this study. PVs were designed and empirically implemented in an existing conventional primary school building in Baghdad, Iraq as a case study for the Mesopotamia region. The sustainability and energy analysis of a school building was conducted in diverse scenarios to explore the potential of energy-saving and payback period of the PVs. The slope and number of PV panels located on the school building are the parameters of the current study. Results showed that PV panels with a 30° inclination angle reduced the energy cost of the building by 50%. The payback for the implementation of PVs can be obtained approximately in 8 years. Consequently, the PVs have major potential in energy efficiency and can be implemented in governmental buildings such as public-school buildings in the Mesopotamia region. Besides, society and private institutions may become aware of the importance of sustainable energy with this study. With this case study, the importance of taking advantage of solar energy has been emphasized for undeveloped countries.Öğe Z-type shear connector for interface of hollow-core slab and cast-in-place topping concrete(Elsevier Science Ltd, 2020) Yüksel, Ercan; Güllü, Ahmet; Durgun, Yavuz; Binbir, Ergün; Şenol, Erkan; Khajehdehi, Arastoo; Saruhan, HakanPrecast hollow-core slabs (PHSs) are widely used in precast construction due to their relatively low dead weight and easy assemblage. Cast-in-place topping concrete (TC) is utilized to obtain composite sections and to enhance in-plane stiffness of the slab system. Shear transfer between the layers of a composite slab can be provided by the upper face roughness of PHS. However, the roughening process may not be preferred in some plants. This paper evaluates the efficiency of Z-type shear connectors applied in the interface between PHS and TC. Three dissimilar interface conditions (i.e., Z-reinforced, smooth and rough) were studied experimentally in full-scale specimens. Push-off loading was applied to evaluate the interface shear transfer capability of the specimens, and Z-type shear connectors were found to be the most effective when they are applied at each joint between PHSs. The achievements of some code equations to assess interface shear strength were also investigated, and an alteration for the interface shear capacity equation of ACI 318M is proposed.
