Browsing by Author "Yakut, Ahmet"

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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: 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: 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.