Browsing by Author "Gulkan, Polat"

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Citation - WoS: 8
Citation - Scopus: 8
Damage Limits for Ductile Reinforced Concrete Shear Walls
(Turkish Chamber Civil Engineers, 2012) Gülkan, Hakkı Polat; Kazaz, Ilker; Gulkan, Polat; 5743; İnşaat Mühendisliği; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 - WoS: 23
Citation - Scopus: 30
Deformation Limits for Structural Walls With Confined Boundaries
(Earthquake Engineering Research inst, 2012) Kazaz, Ilker; Gulkan, Polat; Yakut, Ahmet; 5743; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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. [DOI: 10.1193/1.4000059]
Citation - WoS: 22
Citation - Scopus: 26
A Dispassionate View of Seismic-Hazard Assessment
(Seismological Soc Amer, 2013) Gulkan, Polat; 5743; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - WoS: 8
Citation - Scopus: 8
Dynamic Shear Force Amplification in Regular Frame-Wall Systems
(Wiley-blackwell, 2016) Kazaz, Ilker; Gulkan, Polat; 5743; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 - WoS: 6
Citation - Scopus: 9
A Finite Grid Solution for Circular Plates on Elastic Foundations
(Korean Society of Civil Engineers-ksce, 2015) Karasin, Halim; Gulkan, Polat; Aktas, Gultekin; 5743; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 - WoS: 22
Citation - Scopus: 27
Performance Limits for Structural Walls: an Analytical Perspective
(Elsevier Sci Ltd, 2012) Kazaz, Ilker; Gulkan, Polat; Yakut, Ahmet; 5743; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 - WoS: 17
Citation - Scopus: 22
Seismic Risk Assessment and Mitigation in the Antakya-Maras Region (Seramar): Empirical Studies on the Basis of Ems-98
(Earthquake Engineering Research inst, 2013) Abrahamczyk, Lars; Schwarz, Jochen; Langhammer, Tobias; Genes, M. Cemal; Bikce, Murat; Kacin, Selcuk; Gulkan, Polat; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The main objective of the SERAMAR project has been to utilize current tools for earthquake risk assessment and to establish a unique partnership between universities, professional associations, and local governments, which might serve as a model for similar future activities in Turkey and adjacent areas. In order to reach this goal, a thorough microzonation survey program combined with vulnerability and social preparedness studies in anticipation of a damaging seismic event were conducted. The paper is focused on activities related to surveying building stock and classifying and evaluating through the use of different levels of consideration. Empirical risk scenarios and casualty estimations are carried out for different levels of consideration under scenario earthquakes similar in size to historic events. Preliminary findings of the pilot phase are reported in terms of credible building performance and casualty estimates. For empirical studies, the building vulnerabilities are expressed in terms of vulnerability classes of EMS-98.
Citation - WoS: 1
Citation - Scopus: 1
Site-Structure Resonance as a Proxy for Structural Damage
(Earthquake Engineering Research inst, 2011) Lang, Dominik H.; Schwarz, Jochen; Gulkan, Polat; 5743; 06.05. İnşaat Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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. [DOI: 10.1193/1.3651403]