İnşaat Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/395

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Citation Count: Gülkan, Polat (2013). "A dispassionate view of seismic-hazard assessment", Seismological Research Letters, Vol. 84, No. 3, pp. 413-416.
A dispassionate view of seismic-hazard assessment
(2013) Gülkan, Polat; 5743
Citation Count: Karasin, Halim; Gulkan, Polat; Aktas, Gultekin, "A finite grid solution for circular plates on elastic foundations" KSCE Journal Of Civil Engineering, Vol.19, No.4, pp.1157-1163, (2015).
A finite grid solution for circular plates on elastic foundations
(Korean Society of Civil Engineers-KSCE, 2015) Karasın, Halim; Gülkan, Polat; Aktaş, Gültekin; 5743
The transmission of vertical or horizontal structural forces to the supporting soil is a challenge to analyze for structures on elastic foundation which represent a complex medium. The two-parameter elastic foundation model that provides a mechanical interaction between the individual spring elements shows a more realistic behavior of the soil reaction than does the single parameter Winkler model. Since the structural behavior of a beam resembles that of a strip in a plate, in this study, the exact stiffness and mass matrices of the beam element on two-parameter elastic foundation is extended to plates. The framework method that replaces a continuous surface by an idealized discrete system can represent a two-dimensional plate. In the light of this situation, circular plates are modeled as an assemblage of individual beam elements interconnected at their neighboring joints in radial and tangential direction. So, a useful tool called finite grid solution as a numerical method developed in this study lead to solve circular plates resting on two parameter elastic foundation problems. Examples for bending of ring, circular and annual plates on elastic foundation are solved to compare with known analytical solutions and other numerical solutions. The comparisons show that the literature and the computed results are compatible.
Citation Count: Cağnan, Zehra; Akkar, Sinan; Gülkan, Polat (2011). "A Predictive Ground-Motion Model for Turkey and Its Comparison with Recent Local and Global GMPEs", in Earthquake Data in Engineering Seismology, pp. 39-52.
A Predictive Ground-Motion Model for Turkey and Its Comparison with Recent Local and Global GMPEs
(2011) Cağnan, Zehra; Akkar, Sinan; Gülkan, Polat; 5743
We present a local ground motion prediction equation (GMPE ) for estimating the peak ground-motion values that was derived using the recently compiled Turkish strong motion database . The new GMPE is comparable with the recent global GMPEs in terms of model sophistication and quality of underlying database. Using this equation, we explore the inter-event , inter-station ground motion variability of the recent Turkish strong motion database as well as suitability of some local and global GMPEs for regional seismic hazard assessment analyses. The inter-event error underlines the distinguishing characteristics of few earthquakes, suggesting that the use of local GMPEs can be important especially when specific scenario studies are to be carried out. The inter-station variability allowed us to detect stations with outlier site response and to investigate the goodness of the employed site effect s model. Results also indicate suitability of some global and local GMPEs for use in regional seismic hazard assessments together with the model presented in this study. These should be combined through a logic tree scheme to reduce both aleatory and epistemic uncertainty in local hazard assessments.
Citation Count: Bayhan, B.; Polat, G. (2011). "Buildings Subjected to Recurring Earthquakes: A Tale of Three Cities", Earthquake Spectra, Vol.27, No.3.
Buildings Subjected to Recurring Earthquakes: A Tale of Three Cities
(2011) Bayhan, Beyhan; Polat, Gülkan; 5743
Three different buildings built according to the same design have experienced three different near-field strong ground motions over a period of 11 years in three different cities in Turkey. The input motion was known for each because strong-motion sensors were located adjacent or close to the buildings. We examine the performance of the five-story, reinforced concrete-frame buildings. Bidirectional nonlinear time history and nonlinear static analyses on 3-D analytical models are performed. The principal focus is to assess whether the analytical model of the buildings could indicate column-beam damage consistent with that observed at the sites after the earthquakes. Results illustrate that nonlinear time history analyses are capable of indicating the occurrence of shear failure in captive columns; however, they overestimate the global damage. The overestimation is greater where the building sustained a pulse-type motion without significant distress. It appears that difference between visual observations and analytical results persists.
Citation Count: Kazaz, Ilker; Gulkan, Polat, "Damage Limits for Ductile Reinforced Concrete Shear Walls" Teknik Dergi, Vol. 23, No. 4, pp. 6113-6140, (2012)
Damage Limits for Ductile Reinforced Concrete Shear Walls
(Turkish Chamber Civil Engineers, 2012) Kazaz, İlker; Gülkan, Polat; 5743
Although the strain based damage limits proposed in the existing Turkish Earthquake Code were adopted from reported studies of leading researchers, the appropriateness of these limit state definitions and corresponding values to evaluate the performance with the analytical tools and methods used in the displacement based design and assessment procedures has not been verified properly. The moment-curvature analysis based on the plane section hypothesis is severely violated especially for reinforced concrete walls. This indicates that a comprehensive investigation is required to investigate the validity of proposed damage limits for structural walls. This study is based on advanced and computationally rigorous numerical procedures to investigate the relation between drift ratio, plastic rotation and curvature, compressive strain in concrete and tensile strain in steel for rectangular reinforced concrete structural walls. Validity of the requirements related to deformation limits in the Turkish Seismic Code and other design guidelines is then evaluated. Modeling and acceptance criteria that are more accurate than the existing ones have been proposed for structural walls.
Citation Count: Kazaz, Ilker; Gulkan, Polat; Yakut, Ahmet, "Deformation Limits for Structural Walls with Confined Boundaries", Earthquake Spectra, Vol. 28, No. 3, pp. 1019-1046, (2012)
Deformation Limits for Structural Walls With Confined Boundaries
(Earthquake Engineering Research INST., 2012) Kazaz, İlker; Yakut, Ahmet; Gülkan, Polat; 5743
For accurate analytical assessment of performance and damage in reinforced concrete members, well-defined deformation limits at particular damage states are required. With advanced and computationally intensive finite element analyses, we establish deformation limits at yield and ultimate limit states for adequately confined rectangular reinforced concrete structural walls in terms of drift ratio, plastic rotation, and curvature. To investigate the deformation limits of structural walls, a parametric study on isolated cantilever wall models is performed. The primary variables of the parametric study are the shear-span-to-wall-length ratio, wall length, axial load ratio, normalized shear stress, the amount of horizontal web reinforcement, and the amount of longitudinal reinforcement at the confined boundary of structural wall models. Expressions and limit values are proposed for yield and ultimate deformation capacity of structural walls, based on the most influential parameters. The proposed equations are found to be promising when compared to results of experiments.
Citation Count: Masoudi, M.; P. Gülkan; A. Dazio. "Displacement Induced Torsion in Structures."
Displacement Induced Torsion in Structures
(2012) Masoudi, M.; Gülkan, Polat; Dazio, A.; 5743
Satisfying the equations of motion in the deformed configuration leads to actions that inherently contain secondary effects. Similar to the product of vertical loads and lateral displacements which leads to the PΔ effect in structures, lateral displacements may cause significant secondary torsion due to the presence of lateral loads. A simple finite-element formulation is presented in the paper to capture this effect. This formulation is verified by means of the Corotational approach and the updated Lagrangian formulation for acceptable drift limits in structural engineering practice. A simple single-story structure and a 7-story RC and steel structures with no predefined mass eccentricity are subjected to an ensemble of bi-axial ground motions recorded on different soil conditions to demonstrate secondary effects. The paper shows that when the period of the structure is not identical in the two horizontal directions secondary torsion is important and may result in significant torsional amplification.
Citation Count: Kazaz, Ilker; Gulkan, Polat, "Dynamic shear force amplification in regular frame-wall systems", Structural Design of Tall and Special Buildings, Vol. 25, No. 2, pp. 112-135, (2016).
Dynamic shear force amplification in regular frame-wall systems
(Wiley, 2016) Kazaz, İlker; Gülkan, Polat; 5743
A parametric study is conducted to investigate the dynamic shear amplification factor (DAF) in low-to-mid-rise frame-wall systems in which the reinforcement curtailment along the height matches the required code strength. The level of frame-wall interaction is varied by changing the wall index, defined as the ratio of the total wall area to the floor plan area, in a generic frame-wall system, and its correlation with the DAF is investigated. Wall index values ranging in the 0.2% to 2% interval are selected. Walls with lengths of 3m, 5m and 8m are used in the design of model buildings of 4, 8 and 12 stories. Shear-flexure beam continuum formulation is used in design and modeling. The global behavior is analyzed using nonlinear response history procedure using spectrum compatible ground motions. It is found that the primary source of amplification is the level of inelastic demand on the system. Walls designed for code-specified force reduction factor R=6 experienced an average base shear force amplification in the order of 1.64 with standard deviation of 0.19 with respect to design shear force. Amplification diminishes with decreasing R. An expression for the dynamic amplification factor as a function of the number of stories and force reduction factor R is proposed. Copyright (C) 2015 John Wiley & Sons, Ltd.
Citation Count: Dinckal, Cigdem; Alemdar, Bulent N.; Gulkan, Polat H., "Dynamics of a beam-column element on an elastic foundation", Canadian Journal of Civil Engineering, Vol. 43, No. 8, pp. 685-701, (2016).
Dynamics of a beam-column element on an elastic foundation
(Canadian Science Publishing, 2016) Dinçkal, Çiğdem; Alemdar, Bülent N.; Gülkan, Polat H.; 26773; 5743
An exact analytical solution of a harmonically vibrating beam-column element resting on an elastic Winkler foundation is derived. The solution covers four cases comprised of constant compressive or tensile axial force with the restrictions k(s) - m omega(2) < 0 and k(s) - m omega(2) > 0. The proposed solution is not restricted to a particular range of magnitudes of the foundation parameter. Closed form solutions of dynamic shape functions are explicitly derived for each sub-case to obtain frequency-dependent dynamic stiffness terms that constitute the exact dynamic stiffness matrices. Four numerical examples are provided to demonstrate the merits of the present study.
Citation Count: Sıkan, F...et al (2020). "Effect of Sm on Crystallization Kinetics of Cu-Zr-Al Metallic Glasses", Thermochimica Acta, Vol. 683.
Effect of Sm on Crystallization Kinetics of Cu-Zr-Al Metallic Glasses
(2020) Sıkan, F.; Polat, Gülkan; Kalay, I.; Kalay, Y. E.; 5743
The effect of Sm micro-alloying on non-isothermal and isothermal crystallization kinetics of (Zr50Cu40Al10)(100-x)Sm-x (x = 0, 2, 4 at. % Sm) alloys were investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Crystallization activation energies for each composition were calculated in non-isothermal conditions using Kissinger and Ozawa methods and in isothermal conditions using Johnson-Mehl-Avrami model. XRD analysis showed that crystallization product Cu10Zr7 changes to Cu2Sm with Sm presence in isothermal conditions. Both isothermal and isochronal calculations yield that the energy barrier for crystallization has increased with Sm addition. On the other hand, crystallization point drops to lower temperature at the expense of an increase in the pre-exponential factor. The Avrami exponents for all compositions were found to be below 2.5, indicating that crystallization was governed by a diffusion-controlled three-dimensional growth with a decreasing nucleation rate. The apparent increase in crystallization activation energies with increasing Sm content can be one of the affecting factors for commonly held idea of increased glass forming ability for rare-earth containing Zr-based metallic glasses.
Evaluation of Tsunami Scenarios For Western Peloponnese, Greece
(Ist Nazionale Di Oceanografia E Di Geofisica, 2014) Yalçıner, Ahmet Cevdet; Gülkan, Polat; Dilmen, Derya; Aytore, Betül; Ayça, Aykut; İnsel, I.; Zaytsev, A.; 5743
Tsunami hazard assessment of the eastern part of the Mediterranean Sea is the current interest of the countries having, a coastline in this region. Considering today's increasing population on the coasts and historical tsunamis, it is essential to estimate the probable tsunami risk, which might occur, to be able to mitigate the risk before the actual tsunami event happens. For this purpose, European Union funded project., SEAHELLARC is formed to develop a methodology and tools for seismic and tsunami safety and enhance the protection of coastal areas in the western part of Peloponnese in Greece by simultaneous observations and evaluation of onshore and offshore data. In this paper, we present the tsunami simulations of characteristics of possible tsunami source scenarios for the Pylos-Zakynthos-Filiatra and Kyparissia regions, located at western part of Greece. We use NAMIDANCE tsunami simulation and visualization tool to estimate extreme but possible tsunami wave effects in these regions. In the simulations the tsunami arrival times, maximum positive and negative amplitudes are computed, plotted, compared and discussed for the coastal areas of Zakynthos, Filiatra, Kyparissia and Pylos. Furthermore, a detailed mapping of the bathymetric features is performed to define possible landslides and lithological variations at the marine bottom. The uppermost sediments are mapped by sub-bottom profiling, while possible faults are identified by multi-channel reflection mapping at the western Peloponnese. This paper also builds upon the background of a seismic hazard assessment for the region to draw several credible tsunami occurrence scenarios that have been numerically simulated.
Citation Count: Kazaz, İ.; Gülkan, Polat; Yakut, A. "Examination of code performance limits for shear walls", 15 WCEE, 2012.
Examination of code performance limits for shear walls
(2012) Kazaz, İ.; Gülkan, Polat; Yakut, A.; 5743
Recently proposed changes to modeling and acceptance criteria in seismic regulations for both flexure and shear dominated reinforced concrete structural walls suggest that a comprehensive examination is required for improved limit state definitions and their corresponding values. This study utilizes a well calibrated modeling tool to investigate the deformation measures defined in terms of plastic rotations and local concrete and steel strains at the extreme fiber of rectangular structural walls. We compare requirements in ASCE/SEI 41, Eurocode 8 and the Turkish Seismic Code. This way, a critical evaluation of the requirements embedded in these documents becomes possible. It is concluded that the performance limits must be refined by introducing additional parameters. Significant recommendations are provided for Eurocode 8 and the Turkish Seismic Code.
Citation Count: Akansel, Vesile Hatun; Yakut, Ahmet; Gülkan, Polat. "Fragility of Shear Wall Buildings with Torsional Irregularity", 15 WCEE, 2012.
Fragility of Shear Wall Buildings with Torsional Irregularity
(2012) Akansel, Vesile Hatun; Yakut, Ahmet; Gülkan, Polat; 5743
Fragility curves are useful for damage assessment of structures. There are many criteria that affect the reliability of fragility curves such as transitional damage states, plan irregularity and different measures of seismic intensity. Determination of fragility of a shear wall structure is important, especially for installations that have torsional irregularity. In this study fragility curves of a shear wall building with torsional irregularity have been obtained. This building was subjected to synthetic earthquake motions on the AZALEE shaking table under the coordination of CEA (Commissariat à l’Energie Atomique) and Electricité de France (EDF) in Saclay, Paris under the scope of the SMART program. Maximum inter-story drift values have been used as the damage indicator to obtain the fragility curves and different seismic intensity measures such as PGA, PGV, PGD and CAV have been used. Thirty bi-directional horizontal ground motions have been applied for the time history analyses. These synthetic acceleration sets applied to the structure have different amplitudes in the range of 0.1 to 1 g. Micro modeling approach has been used to obtain reasonably accurate and consistent results with experiments. ANSYS finite element software has been used for the response history analyses. Fragility curves of shear wall building have been calculated according to pre-established damage indicators. The limits are light, controlled and extended damage indicators. These curves are compared with those of the HAZUS damage states for correlation.
Citation Count: Karancı, Ayşe Nuray; Gülkan, Polat. "Grassroots participation vs. dictated partnership: Anatomy of the Turkish risk management reality," in Disaster Risk and Vulnerability Mitigation through Mobilizing Communities and Partnerships , McGill –Queen’s University Press, 2012, pp.137-153.
Grassroots participation vs. dictated partnership: Anatomy of the Turkish risk management reality
(2012) Karancı, Ayşe Nuray; Gülkan, Polat; 5743
Citation Count: Korucu, H., Gülkan, P. (2011). High-velocity impact of large caliber tungsten projectiles on ordinary Portland and calcium aluminate cement based HPSFRC and SIFCON slabs. Part I: experimental investigations. Structural Engineering And Mechanics , 40(5), 595-616.
High-velocity impact of large caliber tungsten projectiles on ordinary Portland and calcium aluminate cement based HPSFRC and SIFCON slabs. Part I: experimental investigations
(Techno-Press, 2011) Polat, Gülkan; Korucu, Hasan; 5743
Impact experiments have been carried out on concrete slabs. The first group was traditionally manufactured, densely reinforced concrete targets, and the next were ordinary Portland and calcium aluminate cement based HPSFRC (High performance steel fiber reinforced concrete) and SIFCON (Slurry infiltrated concrete) targets. All specimens were hit by anti-armor tungsten projectiles at a muzzle velocity of over 4 Mach causing destructive perforation. In Part I of this article, production and experimental procedures are described. The first group of specimens were ordinary CEM I 42.5 R cement based targets including only dense reinforcement. In the second and third groups, specimens were produced using CEM I 42.5 R cement and Calcium Aluminate Cement (CAC40) with ordinary reinforcement and steel fibers 2 percent in volume. In the fourth group, SIFCON specimens including 12 percent of steel fibers without reinforcement were tested. A high-speed camera was used to capture impact and residual velocities of the projectile. Sample tests were performed to obtain mechanical properties of the materials. In the companion Part II of this study, numerical investigations and simulations performed will be presented. Few studies exist that examine high-velocity impact effects on CAC40 based HPSFRC targets, so this investigation gives an insight for comparison of their behavior with Portland cement based and SIFCON specimens
Citation Count: Gülkan, P., Korucu, H. (2011). High-velocity impact of large caliber tungsten projectiles on ordinary Portland and calcium aluminate cement based HPSFRC and SIFCON slabs. Part II: numerical simulation and validation. Structural Engineering And Mechanics, 40(5), 617-636.
High-velocity impact of large caliber tungsten projectiles on ordinary Portland and calcium aluminate cement based HPSFRC and SIFCON slabs. Part II: numerical simulation and validation
(Techno-Press, 2011) Korucu, Hasan; Gülkan, Polat; 5743
We present the numerical implementation, simulation, and validation of the high-velocity impact experiments that have been described in the companion article. In this part, numerical investigations and simulations performed to mimic the tests are presented. The experiments were analyzed by the explicit integration-based software ABAQUS for improved simulations. Targets were modeled with a damaged plasticity model for concrete. Computational results of residual velocity and crater dimensions yielded acceptable results
Citation Count: Kazaz, Ilker; Gulkan, Polat; Yakut, Ahmet, "Performance limits for structural walls: An analytical perspective", Engineering Structures, Vol. 43, pp. 105-119, (2012)
Performance Limits for Structural Walls: An Analytical Perspective
(Elsevier SCI LTD, 2012) Kazaz, İlker; Gülkan, Polat; Yakut, Ahmet; 5743
Recently proposed changes to modeling and acceptance criteria in seismic regulations for both flexure and shear dominated reinforced concrete structural walls suggest that a comprehensive examination is required for improved limit state definitions and their corresponding values. This study utilizes nonlinear finite element analysis to investigate the deformation measures defined in terms of plastic rotations and local concrete and steel strains at the extreme fiber of rectangular structural walls. Response of finite elements models were calculated by pushover analysis. We compare requirements in ASCE/SEI 41, Eurocode 8 (EC8-3) and the Turkish Seismic Code (TSC-07). It is concluded that the performance limits must be refined by introducing additional parameters. ASCE/SEI 41 limits are observed to be the most accurate yielding conservative results at all levels except low axial load levels. It is shown that neither EC8-3 nor TSC-07 specifies consistent deformation limits. TSC-07 suggests unconservative limits at all performance levels, and it appears to fall short of capturing the variation reflected in the calculated values. Likewise EC8-3 seems to fail to represent the variation in plastic rotation in contrast to several parameters employed in the calculation. More accurate plastic rotation limits are proposed. (c) 2012 Elsevier Ltd. All rights reserved.
Citation Count: Ozdemir, Gokhan; Gulkan, H. Polat, "Scaling Legitimacy for Design of Lead Rubber Bearing Isolated Structures Using a Bounding Analysis", Earthquake Spectra, Vol. 32, No. 1, pp. 345-366, (2016).
Scaling Legitimacy for Design of Lead Rubber Bearing Isolated Structures Using a Bounding Analysis
(Arthquake Engineering Research Inst, 2016) Özdemir, Gökhan; Gülkan, Polat; 5743
In dynamic analyses, although there is no limitation for scale factors, the customary values vary from 0.25 to 4. However, these values are based on subjective judgments rather than a quantitative evaluation. This study focused on scaling legitimacy of acceleration time series to be used in dynamic analyses performed during the design of lead rubber bearing (LRB) isolated structures, to obtain a limit for scale factors. For this purpose, several dynamic analyses are performed with the parameters, namely, isolation period, peak ground velocity, and site class. In the analyses, a recently proposed deteriorating hysteretic bilinear representation is used to model the behavior of LRBs. Limitation for scale factors is discussed through the concept of bounding analysis that intends to provide design envelopes for response quantities of isolated structures. As a result, limits for scale factors, providing that the bounding analysis fulfills its intended purpose in design of LRBs, are proposed.
Citation Count: Kazaz, İ...et al. "Seismic behavior of a four-legged masonry minaret", 15WCEE, Lisboa, 2012.
Seismic behavior of a four-legged masonry minaret
(2012) Kazaz, İ.; Akansel, V.; Gülkan, Polat; Kazaz, E.; 5743
The four-legged Minaret of Sheikh Mutahhar Mosque has been constructed in the early 16th century during the Aq Qoyunlu Period in Diyarbakır, Turkey, which is located in the second most hazardous zone of the Turkish Seismic Zones Map. This is a special structure, because the minaret body has been placed on four cylindrical stone columns. Therefore, this minaret is seemingly vulnerable though it has survived for five centuries. We use the square cross sectioned minaret as a possible large-scale seismograph to examine the possible limits of ground motion that must have affected it without causing its collapse. In order to investigate the likely seismic performance and strength of the four-legged minaret, a model, which is very close to real structure, was generated with explicit dynamic code LS-DYNA. The developed model takes into account the material nonlinearities and the interface friction and contact behavior between the masonry units. It was displayed that the amplitude of the ground motion in Diyarbakır could not be 0.15g.
Citation Count: Lang, D.H., Schwarz, J., Gülkan, P. (2011). Site-structure resonance as a proxy for structural damage. Earthquake Spectra, 27(4), 1105-1125. http://dx.doi.org/10.1193/1.3651403
Site-structure resonance as a proxy for structural damage
(Earthquake Engineering Research Inst., 2011) Lang, Dominik H.; Schwarz, Jochen; Gülkan, Polat; 5743
Since 1992, the reconnaissance teams of the German Task Force for Earthquakes have undertaken numerous field missions to disaster areas after strong earthquakes worldwide. During these missions, a unique database of damage cases has been collected, which serves as the basis for examining whether site-structure resonance effects contribute to building damage. The selected buildings that partly experienced slight to moderate damage during a recent major event have been experimentally tested in order to identify their structural parameters and to allow a calibration of the structural building models. In addition, instrumental noise recordings were made directly at the building sites to derive the ranges of predominant site periods. By correlating the ranges of predominant site periods with the building's capacity curves, representing the inelastic displacement behavior under lateral effects, a quick survey procedure has been developed to estimate the impact of agreements between periods of the site and the structure contributing to structural earthquake damage

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