Cenk Alhan | Istanbul University (original) (raw)

Papers by Cenk Alhan

Research paper thumbnail of Necessity and adequacy of near-source factors for not-so-tall fixed-base buildings

Earthquake Engineering and Engineering Vibration, 2015

Nonlinear response history analyses and use of strong ground motion data including near-fi eld ef... more Nonlinear response history analyses and use of strong ground motion data including near-fi eld effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildings. On the other hand, ordinary buildings are commonly analysed via response spectrum analysis following the rules of conventional seismic codes, most of which do not take near-fi eld effects into account. This study evaluates the necessity and the adequacy of near-source factors for ordinary fi xed-base buildings that are not specifi cally classifi ed as tall, by comparing dynamic responses of 3, 8, and 15-story benchmark buildings obtained via (1) linear time history analyses using 220 record components from 13 historical earthquakes and 45 synthetic earthquake records of different magnitudes and fault distances and (2) response spectrum analyses in accordance with the Turkish Earthquake Code 2007-representing seismic codes not taking near-fi eld effects into account-and the Uniform Building Code 1997 which takes near-fi eld effects into account via near-source factors that amplify design response spectrum. It is shown that near-source factors are crucial for the safe design of not-so-tall ordinary fi xed-base buildings but those defi ned in UBC97 may still not be adequate for those located in the vicinity of the fault.

Research paper thumbnail of Parametric Analysis of Passive Damping in Base Isolation

Structures 2004, 2004

This study examines the sensitivity of structural response statistics to the characteristics of b... more This study examines the sensitivity of structural response statistics to the characteristics of both the ground motion and the passive damping components for seismic isolation systems. Conclusions regarding appropriate levels of passive damping to protect an isolated building from ground motions representative of both near-field and far-field motions are based on time domain analysis of a large proto-typical seismically isolated building structure, as described in the Benchmark Problem statement (Narasimhan et al. 2003). Results indicate that there are ranges of passive damping for linear isolation systems for which superstructure responses such as floor accelerations and inter-story drifts are minimized and in some cases, these minima are within code requirements.

Research paper thumbnail of Control of torsionally asymmetric structures

Proceedings of the 2002 American Control Conference (IEEE Cat. No.CH37301), 2002

The effects of near-field earthquakes with large ve-locity pulses has motivated passive damping r... more The effects of near-field earthquakes with large ve-locity pulses has motivated passive damping require-ments for the protection of seismically isolated struc-tures. Structures in which the first mode damping ex-ceeds twenty or thirty percent typically do not exhibit classical modes ...

Research paper thumbnail of Fault Tolerance of Semiactive Seismic Isolation

Journal of Structural Engineering, 2003

A six story seismically isolated structure fitted with semi-active hydraulic devices is analyzed ... more A six story seismically isolated structure fitted with semi-active hydraulic devices is analyzed in order to study the effect of time delay in the devices and mass eccentricity in the superstructure on the lateral-torsional behavior. The computer program 3DBASIS, which allows the non linear dynamic analysis of three dimensional structures, is used in this work. Appropriate modifications were made to this program to incorporate the behavior of semi-active hydraulic devices. Three different types of base isolation systems were considered: (1) lead rubber bearings; (2) lead rubber bearings with supplemental viscous damping, and (3) lead rubber bearings with semi-active viscous damping. A comparison of these three base isolation systems, considering both the effects of eccentricity in the structure and differential time lags in semi-active hydraulic devices are studied. The peak isolator shear, isolation drift, rotation and torsional moment are reported. Three major earthquake motion records, namely the El-Centro record of the 1940 Imperial Valley Earthquake, the Meloland record of the 1979 Imperial Valley Earthquake, and the Sylmar free field record of the 1994 Northridge Earthquake were used as inputs in the analyses.

Research paper thumbnail of Optimal Control: Basis for Performance Comparison of Passive and Semiactive Isolation Systems

Journal of Engineering Mechanics, 2006

Passive damping in shock and vibration isolation systems reduces the deformation of the isolation... more Passive damping in shock and vibration isolation systems reduces the deformation of the isolation system but can increase the acceleration sustained by the isolated object. Semiactive(ie, controllable) damping systems offer a solution to the problem of increased ...

Research paper thumbnail of A parametric study of linear and non-linear passively damped seismic isolation systems for buildings

Engineering Structures, 2004

The effects of near-field ground motions with large velocity pulses have motivated passive dampin... more The effects of near-field ground motions with large velocity pulses have motivated passive damping requirements for the protection of seismically isolated structures. Structures in which the first mode damping exceeds 20% or 30% typically do not exhibit classical modes, and simulation via a simple superposition of uncoupled second order equations is not possible. When the damping is produced by viscous or linear visco-elastic devices, we can, however, gain insight into the dynamic behavior of these structures using a convenient first-order formulation and frequency domain methods. When the damping effects are created by nonlinear mechanisms such as yielding or friction, the behavior of the structure is amplitude dependent and analyses are commonly carried out in the time domain. In this paper, frequency domain analysis and earthquake time history analysis are applied to study the influence of isolation damping on higher-mode effects and inter-story drift ratios. Because higher mode effects, plan irregularities, and bi-directional ground motions are all important attributes of the dynamic behavior of these structural systems, a simple comparison of isolation damping mechanisms can not be carried out via simple single or two degree of freedom realizations. In order to incorporate these important details in the study of the dynamic behavior of these structures, a set of 8-story prototype building models with L-shaped floor plans, different isolation periods, isolation damping characteristics, and levels of isolation stiffnesses are examined.

Research paper thumbnail of Reliability of base isolation for the protection of critical equipment from earthquake hazards

Engineering Structures, 2005

... They examined the evolution of the structural response variance and the degree of dependency ... more ... They examined the evolution of the structural response variance and the degree of dependency of this response on the mean ... We investigate the level of this sensitivity with increasing distances of the location of the critical facility to the hypocenter of the earthquake excitation. ...

Research paper thumbnail of Shear building representations of seismically isolated buildings

Bulletin of Earthquake Engineering, 2011

Abstract Seismic isolation, with its capability of reducing floor accelerations and interstory dr... more Abstract Seismic isolation, with its capability of reducing floor accelerations and interstory drifts simultaneously, is recognized as an earthquake resistant design method that protects contents of a building along with the building itself. In research studies, superstructures of ...

Research paper thumbnail of Parametric analysis of irregular structures under seismic loading according to the new Turkish Earthquake Code

Engineering Structures, 2001

In order to investigate the effects of torsion on moment and shear values of vertical structural ... more In order to investigate the effects of torsion on moment and shear values of vertical structural elements, a typical model building has been selected. Torsional irregularity has been created in the building by changing the location of the shear walls. Three cases of different centers of rigidity for 1, 5, and 10-story buildings have been considered. Each case has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis, and the results compared. In order to investigate the effects of nonorthogonality on the distribution of moments and shears of the vertical structural elements, a 5-story building has been studied with one nonorthogonal and two orthogonal shear walls. Three cases of different orientations of the nonorthogonal wall have been considered. Each case has been analyzed for five different directions of earthquake.

Research paper thumbnail of Guidelines for low-transmissibility semi-active vibration isolation

Smart Materials and Structures, 2005

Page 1. Guidelines for low-transmissibility semi-active vibration isolation This article has been... more Page 1. Guidelines for low-transmissibility semi-active vibration isolation This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2005 Smart Mater. Struct. 14 297 (http://iopscience.iop.org/0964-1726/14/2/001) ...

Research paper thumbnail of Necessity and adequacy of near-source factors for not-so-tall fixed-base buildings

Earthquake Engineering and Engineering Vibration, 2015

Nonlinear response history analyses and use of strong ground motion data including near-fi eld ef... more Nonlinear response history analyses and use of strong ground motion data including near-fi eld effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildings. On the other hand, ordinary buildings are commonly analysed via response spectrum analysis following the rules of conventional seismic codes, most of which do not take near-fi eld effects into account. This study evaluates the necessity and the adequacy of near-source factors for ordinary fi xed-base buildings that are not specifi cally classifi ed as tall, by comparing dynamic responses of 3, 8, and 15-story benchmark buildings obtained via (1) linear time history analyses using 220 record components from 13 historical earthquakes and 45 synthetic earthquake records of different magnitudes and fault distances and (2) response spectrum analyses in accordance with the Turkish Earthquake Code 2007-representing seismic codes not taking near-fi eld effects into account-and the Uniform Building Code 1997 which takes near-fi eld effects into account via near-source factors that amplify design response spectrum. It is shown that near-source factors are crucial for the safe design of not-so-tall ordinary fi xed-base buildings but those defi ned in UBC97 may still not be adequate for those located in the vicinity of the fault.

Research paper thumbnail of Parametric Analysis of Passive Damping in Base Isolation

Structures 2004, 2004

This study examines the sensitivity of structural response statistics to the characteristics of b... more This study examines the sensitivity of structural response statistics to the characteristics of both the ground motion and the passive damping components for seismic isolation systems. Conclusions regarding appropriate levels of passive damping to protect an isolated building from ground motions representative of both near-field and far-field motions are based on time domain analysis of a large proto-typical seismically isolated building structure, as described in the Benchmark Problem statement (Narasimhan et al. 2003). Results indicate that there are ranges of passive damping for linear isolation systems for which superstructure responses such as floor accelerations and inter-story drifts are minimized and in some cases, these minima are within code requirements.

Research paper thumbnail of Control of torsionally asymmetric structures

Proceedings of the 2002 American Control Conference (IEEE Cat. No.CH37301), 2002

The effects of near-field earthquakes with large ve-locity pulses has motivated passive damping r... more The effects of near-field earthquakes with large ve-locity pulses has motivated passive damping require-ments for the protection of seismically isolated struc-tures. Structures in which the first mode damping ex-ceeds twenty or thirty percent typically do not exhibit classical modes ...

Research paper thumbnail of Fault Tolerance of Semiactive Seismic Isolation

Journal of Structural Engineering, 2003

A six story seismically isolated structure fitted with semi-active hydraulic devices is analyzed ... more A six story seismically isolated structure fitted with semi-active hydraulic devices is analyzed in order to study the effect of time delay in the devices and mass eccentricity in the superstructure on the lateral-torsional behavior. The computer program 3DBASIS, which allows the non linear dynamic analysis of three dimensional structures, is used in this work. Appropriate modifications were made to this program to incorporate the behavior of semi-active hydraulic devices. Three different types of base isolation systems were considered: (1) lead rubber bearings; (2) lead rubber bearings with supplemental viscous damping, and (3) lead rubber bearings with semi-active viscous damping. A comparison of these three base isolation systems, considering both the effects of eccentricity in the structure and differential time lags in semi-active hydraulic devices are studied. The peak isolator shear, isolation drift, rotation and torsional moment are reported. Three major earthquake motion records, namely the El-Centro record of the 1940 Imperial Valley Earthquake, the Meloland record of the 1979 Imperial Valley Earthquake, and the Sylmar free field record of the 1994 Northridge Earthquake were used as inputs in the analyses.

Research paper thumbnail of Optimal Control: Basis for Performance Comparison of Passive and Semiactive Isolation Systems

Journal of Engineering Mechanics, 2006

Passive damping in shock and vibration isolation systems reduces the deformation of the isolation... more Passive damping in shock and vibration isolation systems reduces the deformation of the isolation system but can increase the acceleration sustained by the isolated object. Semiactive(ie, controllable) damping systems offer a solution to the problem of increased ...

Research paper thumbnail of A parametric study of linear and non-linear passively damped seismic isolation systems for buildings

Engineering Structures, 2004

The effects of near-field ground motions with large velocity pulses have motivated passive dampin... more The effects of near-field ground motions with large velocity pulses have motivated passive damping requirements for the protection of seismically isolated structures. Structures in which the first mode damping exceeds 20% or 30% typically do not exhibit classical modes, and simulation via a simple superposition of uncoupled second order equations is not possible. When the damping is produced by viscous or linear visco-elastic devices, we can, however, gain insight into the dynamic behavior of these structures using a convenient first-order formulation and frequency domain methods. When the damping effects are created by nonlinear mechanisms such as yielding or friction, the behavior of the structure is amplitude dependent and analyses are commonly carried out in the time domain. In this paper, frequency domain analysis and earthquake time history analysis are applied to study the influence of isolation damping on higher-mode effects and inter-story drift ratios. Because higher mode effects, plan irregularities, and bi-directional ground motions are all important attributes of the dynamic behavior of these structural systems, a simple comparison of isolation damping mechanisms can not be carried out via simple single or two degree of freedom realizations. In order to incorporate these important details in the study of the dynamic behavior of these structures, a set of 8-story prototype building models with L-shaped floor plans, different isolation periods, isolation damping characteristics, and levels of isolation stiffnesses are examined.

Research paper thumbnail of Reliability of base isolation for the protection of critical equipment from earthquake hazards

Engineering Structures, 2005

... They examined the evolution of the structural response variance and the degree of dependency ... more ... They examined the evolution of the structural response variance and the degree of dependency of this response on the mean ... We investigate the level of this sensitivity with increasing distances of the location of the critical facility to the hypocenter of the earthquake excitation. ...

Research paper thumbnail of Shear building representations of seismically isolated buildings

Bulletin of Earthquake Engineering, 2011

Abstract Seismic isolation, with its capability of reducing floor accelerations and interstory dr... more Abstract Seismic isolation, with its capability of reducing floor accelerations and interstory drifts simultaneously, is recognized as an earthquake resistant design method that protects contents of a building along with the building itself. In research studies, superstructures of ...

Research paper thumbnail of Parametric analysis of irregular structures under seismic loading according to the new Turkish Earthquake Code

Engineering Structures, 2001

In order to investigate the effects of torsion on moment and shear values of vertical structural ... more In order to investigate the effects of torsion on moment and shear values of vertical structural elements, a typical model building has been selected. Torsional irregularity has been created in the building by changing the location of the shear walls. Three cases of different centers of rigidity for 1, 5, and 10-story buildings have been considered. Each case has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis, and the results compared. In order to investigate the effects of nonorthogonality on the distribution of moments and shears of the vertical structural elements, a 5-story building has been studied with one nonorthogonal and two orthogonal shear walls. Three cases of different orientations of the nonorthogonal wall have been considered. Each case has been analyzed for five different directions of earthquake.

Research paper thumbnail of Guidelines for low-transmissibility semi-active vibration isolation

Smart Materials and Structures, 2005

Page 1. Guidelines for low-transmissibility semi-active vibration isolation This article has been... more Page 1. Guidelines for low-transmissibility semi-active vibration isolation This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2005 Smart Mater. Struct. 14 297 (http://iopscience.iop.org/0964-1726/14/2/001) ...