İnşaat Mühendisliği Bölümü

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Citation Count: Dinçkal, Çiğdem. (2010). "Orthonormal decomposition of symmetric second rank tensors", International Journal of Pure and Applied Mathematics, Vol.65, No.2, pp.225-241.
Orthonormal decomposition of symmetric second rank tensors
(2010) Dinçkal, Çiğdem; 26773
In this paper, a new orthonormal decomposition method for symmetric second rank tensors namely as, orthonormal tensor basis is presented. Complex variable representation method is developed by using the existing theories in literature. For comparison purposes, a brief review of the spectral method is given. It is shown that stress tensor, as an example to symmetric second rank tensors, is decomposed into six orthonormal parts by orthonormal tensor basis and complex variable representation methods. The matrix forms of these decomposed parts are given. This is the first time in literature that physical meanings of each six decomposed parts which are obtained from the orthonormal decomposition of stress tensor by orthonormal tensor basis and complex variable representation methods, different from the traditionally form, are emphasized. Illustrative applications on orthonormal tensor basis and complex variable representation decomposition methods are given. Finally, it is proved that the spectral method is a non-linear decomposition method which yields three non-linear orthonormal decomposed parts. This case is a significant innovation in decomposition procedures for symmetric second rank tensors in literature.
Citation Count: Küçükali, S. (2011). Risk assessment of river-type hydropower plants using fuzzy logic approach. Energy Policy, 93(10), 6683-6688. http://dx.doi.org/10.1016/j.enpol.2011.06.067
Risk assessment of river-type hydropower plants using fuzzy logic approach
(Elsevier Science Ltd, 2011) Küçükali, Serhat; 20413
In this paper, a fuzzy rating tool was developed for river-type hydropower plant projects, and risk assessment and expert judgments were utilized instead of probabilistic reasoning. The methodology is a multi-criteria decision analysis, which provides a flexible and easily understood way to analyze project risks. The external risks, which are partly under the control of companies, were considered in the model. A total of eleven classes of risk factors were determined based on the expert interviews, field studies and literature review as follows: site geology, land use, environmental issues, grid connection, social acceptance, macroeconomic, natural hazards, change of laws and regulations, terrorism, access to infrastructure and revenue. The relative importance of risk factors was determined from the survey results. The survey was conducted with the experts that have experience in the construction of river-type hydropower schemes. The survey results revealed that the site geology and environmental issues were considered as the most important risks. The new risk assessment method enabled a Risk Index (R) value to be calculated, establishing a 4-grade evaluation system. The proposed risk analysis will give investors a more rational basis to make decisions and it can prevent cost and schedule overruns
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: Dinçkal, Ç. (2011). "Studies on the Optimum Mechanical Response of Anısotropıc Materials Related to Elastıc Constants", Journal of Innovative Research in Engineering and Science, Vol.2, No.3.
Studies on the Optimum Mechanical Response of Anısotropıc Materials Related to Elastıc Constants
(2011) Dinçkal, Çiğdem; 26773
In this paper, mechanical and elastic behaviour of anisotropic materials are investigated in order to understand the optimum mechanical behaviour of them in selected directions. For an anisotropic material with known elastic constants, it is possible to choose the best set of elastic constants (effective elastic constants) which determine the optimum mechanical and elastic properties of it. For this reason, bounds on the anisotropic elastic constants have been constructed symbollicaly for all anisotropic elastic symmetries. As illustrative examples, materials from different symmetries are selected and their elastic constants are used to compute bounds on the anisotropic elastic constants. Finally, by examining numerical results of bounds given in tables, it is seen that the materials selected from the same symmetry type which have larger interval between the bounds, are more anisotropic, whereas some materials which have smaller interval between the bounds, are closer to isotropy. The construction of bounds on anisotropic elastic constants is a significant and critical case in design of any engineering and structural materials.
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: Dinçkal, Ç. (2011). "Adaptation of generalized Hill inequalities to anisotropic elastic symmetries", International Journal of Engineering, Science and Technology, Vol.3, No.4.
Adaptation of generalized Hill inequalities to anisotropic elastic symmetries
(2011) Dinçkal, Çiğdem; 26773
Mechanical and elastic behaviors of anisotropic materials are investigated in an innovative way. This is based on generalized Hill inequalities. From different type of anisotropic elastic symmetries, numerical examples are given. Constructing bounds on effective eigenvalues provides a deeper understanding about mechanical behavior of anisotropic materials. Generalized Hill inequalities are adapted to all anisotropic elastic symmetries. The materials selected from the same symmetry type which have larger interval between the bounds, are more anisotropic whereas smaller interval between the bounds, are closer to isotropy. Besides it is proved that there are relations between bulk and shear modulus and eigenvalues of cubic and isotropic symmetry and by these relations, two linear invariants are found out.
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
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: Dinçkal, Çiğdem. (2011). "Norm, norm ratio calculations and anisotropy degree", International Journal of Pure and Applied Mathematics, Vol.69, No.2, pp.125-136.
Norm, norm ratio calculations and anisotropy degree
(2011) Dinçkal, Çiğdem; 26773
In this paper, for elastic constant tensor, the norm concept, norm ratio and anisotropy degree are described. The norm of a tensor is used as a criterion for comparing the overall effect of the properties of anisotropic materials and norm ratios are used as a criterion to represent the anisotropy degree of the properties of these materials. Norm and norm ratios as well as the measure of "nearness" to the nearest isotropic tensor are computed for several examples from various anisotropic materials possessing elastic symmetries such as cubic, transversely isotropic, tetragonal, trigonal and orthorhombic. These computations are used to compare and assess the anisotropy in various anisotropic materials by means of strength or magnitude and also determine the "nearness" of the nearest isotropic tensor for the materials with lower symmetry types.
Citation Count: Gülkan, Polat...et al. "The Fatih Project: A pilot seismic assessment of the architectural heritage in the Historic Peninsula of Istanbul", WCCE-ECCE-TCCE Joint Conference on Seismic Protection of Cultural Heritage, October 31-November 1, 2011, Antalya.
The Fatih Project: A Pilot Seismic Assessment of the Architectural Heritage in the Historic Peninsula of Istanbul
(2011) Gülkan, Polat; Sozen, M.A.; Yakut, A.; Celep, Z.; Güler, K.; Kubin, J.; Kubin, D.; Eroğlu, E.; İrfanoğlu, A.; Ahunbay, Z.; 5743
Citation Count: Dinçkal, Ç. (2011). "Analysis of Elastic Anisotropy of Wood Material for Engineering Applications", Journal of Innovative Research in Engineering and Science, Vol.2, No.2.
Analysis of Elastic Anisotropy of Wood Material for Engineering Applications
(2011) Dinçkal, Çiğdem; 26773
This paper presents a convenient method to describe the degree of the elastic anisotropy in a given type of wood and then discusses its practical values. Besides mechanical and elastic behaviour of wood are investigated in order to understand the optimum mechanical behaviour of it in selected directions. Bounds on the wood elastic constants have been constructed in terms of elasticity and compliance tensors for any type of woods by developing Hill (1952) approach. So for any type of wood with known elastic constants, it is possible to choose the best set of elastic constants (effective elastic constants) which determine the optimum mechanical and elastic properties of it. Bounds on the wood elastic constants as well as the degree of elastic anisotropy are significant and critical cases in design of any engineering and structural materials made up of wood.
Citation Count: Gunes, Oguz...et al. "Use of UHPC in Bridge Structures: Material Modeling and Design", Advances In Materials Science and Engineering, (2012)
Use of Uhpc In Bridge Structures: Material Modeling and Design
(Hindawi Publishing Corporation, 2012) Güneş, Oğuz; Yeşilmen, Seda; Ulm, Franz-Joseph; Güneş, Burcu; 160252
Ultra-high-performance concrete (UHPC) is a promising new class of concrete material that is likely to make a significant contribution to addressing the challenges associated with the load capacity, durability, sustainability, economy, and environmental impact of concrete bridge infrastructures. This paper focuses on the material modeling of UHPC and design of bridge girders made of UHPC. A two-phase model used for modeling the behavior of UHPC was briefly discussed, and the model was implemented in a preliminary design case study. Based on the implemented design and the reported use of UHPC in bridge applications, the advantages, limitations, and future prospects of UHPC bridges were discussed, highlighting the need for innovative research and design to make optimum use of the favorable properties of the material in bridge structures.
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, 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: Büyüköztürk, Oral...et al (2012). "Nondestructive Testing of Materials and Structures: Proceedings of NDTMS-2011, Istanbul, Turkey, May 15-18, 2011", RILEM Bookseries, Vol. 6.
Nondestructive Testing of Materials and Structures: Proceedings of NDTMS-2011, Istanbul, Turkey, May 15-18, 2011
(2012) Büyüköztürk, Oral; Taşdemir, Mehmet Ali; Güneş, Oǧuz; Akkaya, Yılmaz; 160252
Citation Count: Gunes, Burcu; Gunes, O. (2012). "Structural health monitoring and damage assessment Part II: Application of the damage locating vector (DLV) method to the ASCE benchmark structure experimental data", International Journal of Physical Sciences, Vol.7, No.9, pp. 1509-1515.
Structural health monitoring and damage assessment Part II: Application of the damage locating vector (DLV) method to the ASCE benchmark structure experimental data
(2012) Gunes, Burcu; Gunes, Oguz; 160252
This paper builds on the review of structural health monitoring (SHM) and damage assessment approaches provided in a companion paper by presenting an application of the damage locating vector (DLV) approach to the experimental (Phase II) data obtained from the experimental benchmark structure of the IASC-ASCE task group on SHM, which is a laboratory (scaled) size steel frame. Different damage conditions were simulated in the frame for braced and unbraced configurations, and the DLV technique was used to detect and localize damage. The damage identification results were presented and the successes and limitations of the DLV method in detecting and locating the simulated damages were discussed.
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: Kazaz, İlker; Gülkan, P. (2012). "Süneklik Düzeyi Yüksek Betonarme Perdelerdeki Hasar Sınırları", Teknik Dergi, Vol.23, No.114, pp.6113-6140.
Süneklik Düzeyi Yüksek Betonarme Perdelerdeki Hasar Sınırları
(2012) Kazaz, İlker; Gülkan, Polat; 5743
Halen geçerli olan Deprem Yönetmeliğinde önerilen birim şekil değiştirme hasar sınır değerleri, teknik literatürde mevcut önde gelen çalışmalardan alınmakla birlikte, bu değerlerin yer değiştirmeye dayalı tasarım ve değerlendirme yöntemlerinde kullanılan analitik araç ve yöntemlerle performans düzeyini tanımlamak için uygun olup olmadığı tam olarak sınanmamıştır. Düzlem kesitlerin deformasyondan sonra da düzlem kaldığına dayanan moment-eğrilik hesaplamaları, özellikle betonarme perdeler için sorun teşkil etmektedir. Dolayısıyla önerilen hasar sınır değerlerinin betonarme perdeler için geçerliliğinin araştırılması için kapsamlı bir çalışmaya ihtiyaç duyulduğu görülmektedir. Bu çalışma iyi kalibre edilmiş bir sonlu eleman modelleme yaklaşımı kullanarak dikdörtgen kesitli betonarme perdelerin ötelenme, kesit dönmesi ve eğriliği, perde uçlarındaki beton ve donatı birim şekil değiştirmeleri arasındaki ilişkiyi incelemektedir. Deprem Yönetmeliğinde ve bazı diğer hesap kılavuzlarında verilen şekil değiştirme ile ilgili hükümlerin geçerliği irdelenmektedir. Perde elemanları için mevcut değerlerden daha doğru olduğuna inanılan modelleme parametreleri ve kabul kıstasları teklif edilmektedir
Citation Count: Baris, Kemal; Kucukali, Serhat, "Availibility of renewable energy sources in Turkey: Current situation, potential, government policies and the EU perspective", Energy Policy, Vol. 42, pp. 377-391, (2012)
Availibility of Renewable Energy Sources in Turkey: Current Situation, Potential, Government Policies and the Eu Perspective
(Elsevier SCI LTD, 2012) Barış, Kemal; Küçükali, Serhat; 20413

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