Geology topics

E. Kalkan

Publications and source records attributed to E. Kalkan.

9 recordsLinked to original sources

USGS2012

Evaluation of ground motion scaling methods for analysis of structural systems

Ground motion selection and scaling comprises undoubtedly the most important component of any seismic risk assessment study that involves time-history analysis. Ironically, this is also the single parameter with the least guidance provided in current building codes, resulting in the use of mostly subjective choices in design. The relevant research to date has been primarily on single-degree-of-freedom systems, with only a few studies using multi-degree-of-freedom systems. Furthermore, the previous research is based solely on numerical simulations with no experimental data available for the validation of the results. By contrast, the research effort described in this paper focuses on an experimental evaluation of selected ground motion scaling methods based on small-scale shake-table experiments of re-configurable linear-elastic and nonlinear multi-story building frame structure models. Ultimately, the experimental results will lead to the development of guidelines and procedures to achieve reliable demand estimates from nonlinear response history analysis in seismic design. In this paper, an overview of this research effort is discussed and preliminary results based on linear-elastic dynamic response are presented.

Conference Paper↗

USGS2010

Seismic hazard mapping of California considering site effects

In this paper, we have combined the U.S. Geological Survey's National Seismic Hazard Maps model with the California geologic map showing 17 generalized geologic units that can be defined by their VS30. We regrouped these units into seven VS30 values and calculated a probabilistic seismic hazard map for the entire state for each VS30 value. By merging seismic hazard maps based on the seven different V S30 values, a suite of seismic hazard maps was computed for 0.2 and 1.0 s spectral ordinates at 2% probability of exceedance (PE) in 50 years. The improved hazards maps explicitly incorporate the site effects and their spatial variability on ground motion estimates. The spectral acceleration (SA) at 1.0 s map of seismic shaking potential for California has now been published as California Geological Survey Map Sheet 48.

California↗

USGS2010

Recorded motions of the 6 April 2009 Mw 6.3 L'Aquila, Italy, earthquake and implications for building structural damage: Overview

The normal-faulting earthquake of 6 April 2009 in the Abruzzo Region of central Italy caused heavy losses of life and substantial damage to centuriesold buildings of significant cultural importance and to modern reinforcedconcrete- framed buildings with hollow masonry infill walls. Although structural deficiencies were significant and widespread, the study of the characteristics of strong motion data from the heavily affected area indicated that the short duration of strong shaking may have spared many more damaged buildings from collapsing. It is recognized that, with this caveat of shortduration shaking, the infill walls may have played a very important role in preventing further deterioration or collapse of many buildings. It is concluded that better new or retrofit construction practices that include reinforcedconcrete shear walls may prove helpful in reducing risks in such seismic areas of Italy, other Mediterranean countries, and even in United States, where there are large inventories of deficient structures. ?? 2010, Earthquake Engineering Research Institute.

Earthquake Spectra↗

USGS2010

İhtimaller Hesabına Dayalı İstanbul ve Çevresindeki Deprem Tehlikesi (Seismic hazard assessment of Istanbul and its surroundings)

Bu yazının amacı, İstanbul ve yakın çevresinin maruz olduğu deprem tehlikesine dair 1999 depremlerinden bu yana devam eden tartışmalara bilimsel verilere ve hesaplara dayanan ve mümkün olduğu ölçüde kolay anlaşılır bir açıklama getirmektir. Depremlerin bir bölgede yaratabileceği tehlike, yani yerin sarsılması yüzünden yapılar üzerinde doğacak deprem etkileri, bölgenin deprem riskine, yani o bölgede olabilecek en yüksek deprem büyüklüğüne ve bölgenin zemin durumuna bağlıdır. Bu çalışmada, deprem oluşturma potansiyeline sahip aktif faylar ve son 500 yılda meydana gelmiş depremler ihtimal hesapları kullanılarak ilişkilendirilmiş ve Marmara Bölgesi’nde deprem sonucu doğacak yer hareketi şiddetinin dağılımı haritalanmıştır. Sunulan yeni deprem tehlike haritaları önceki bölgesel tehlike haritaları ile karşılaştırıldığında, Marmara Bölgesi’nde hissedilebilecek yer hareketi şiddetinde, benzer çalışmalara oranla % 10 ila % 15 arası artış görülmektedir.

Bilim ve Teknik (Science and Technology Magazine)↗

USGS2008

Seismic hazard in the Istanbul metropolitan area: A preliminary re-evaluation

In 1999, two destructive earthquakes (M7.4 Kocaeli and M7.2 Duzce) occurred in the north west of Turkey and resulted in major stress-drops on the western segment of the North Anatolian Fault system where it continues under the Marmara Sea. These undersea fault segments were recently explored using bathymetric and reflection surveys. These recent findings helped to reshape the seismotectonic environment of the Marmara basin, which is a perplexing tectonic domain. Based on collected new information, seismic hazard of the Marmara region, particularly Istanbul Metropolitan Area and its vicinity, were re-examined using a probabilistic approach. Two seismic source and alternate recurrence models combined with various indigenous and foreign attenuation relationships were adapted within a logic tree formulation to quantify and project the regional exposure on a set of hazard maps. The hazard maps show the peak horizontal ground acceleration and spectral acceleration at 1.0 s. These acceleration levels were computed for 2 and 10 % probabilities of transcendence in 50 years.

Journal of Earthquake Engineering↗

USGS2008

Response of pendulums to complex input ground motion

Dynamic response of most seismological instruments and many engineering structures to ground shaking can be represented via response of a pendulum (single-degree-of-freedom oscillator). In most studies, pendulum response is simplified by considering the input from uni-axial translational motion alone. Complete ground motion however, includes not only translational components but also rotations (tilt and torsion). In this paper, complete equations of motion for three following types of pendulum are described: (i) conventional (mass-on-rod), (ii) mass-on-spring type, and (iii) inverted (astatic), then their response sensitivities to each component of complex ground motion are examined. The results of this study show that a horizontal pendulum similar to an accelerometer used in strong motion measurements is practically sensitive to translational motion and tilt only, while inverted pendulum commonly utilized to idealize multi-degree-of-freedom systems is sensitive not only to translational components, but also to angular accelerations and tilt. For better understanding of the inverted pendulum's dynamic behavior under complex ground excitation, relative contribution of each component of motion on response variants is carefully isolated. The systematically applied loading protocols indicate that vertical component of motion may create time-dependent variations on pendulum's oscillation period; yet most dramatic impact on response is produced by the tilting (rocking) component. ?? 2007 Elsevier Ltd. All rights reserved.

Soil Dynamics and Earthquake Engineering↗

USGS2007

Pros and cons of multistory RC tunnel-form (box-type) buildings

Tunnel-form structural systems (i.e., box systems), having a load-carrying mechanism composed of reinforced concrete (RC) shear walls and slabs only, have been prevailingly utilized in the construction of multistory residential units. The superiority of tunnel-form buildings over their conventional counterparts stems from the enhanced earthquake resistance they provide, and the considerable speed and economy of their construction. During recent earthquakes in Turkey, they exhibited better seismic performance in contrast to the damaged condition of a number of RC frames and dual systems (i.e., RC frames with shear wall configurations). Thus the tunnel-form system has become a primary construction technique in many seismically active regions. In this paper, the strengths and weaknesses of tunnel-form buildings are addressed in terms of design considerations and construction applications. The impacts of shear wall reinforcement ratio and its detailing on system ductility, loadcarrying capacity and failure mechanism under seismic forces are evaluated at section and global system levels. Influences of tension/compression coupling and wall openings on the response are also discussed. Three-dimensional nonlinear finite element models, verified through comparisons with experimental results, were used for numerical assessments. Findings from this projection provide useful information on adequate vertical reinforcement ratio and boundary reinforcement to achieve enhanced performance of tunnel-form buildings under seismic actions. Copyright ?? 2007 John Wiley & Sons, Ltd.

Structural Design of Tall and Special Buildings↗

USGS2007

Behavior of tunnel form buildings under quasi-static cyclic lateral loading

In this paper, experimental investigations on the inelastic seismic behavior of tunnel form buildings (i.e., box-type or panel systems) are presented. Two four-story scaled building specimens were tested under quasi-static cyclic lateral loading in longitudinal and transverse directions. The experimental results and supplemental finite element simulations collectively indicate that lightly reinforced structural walls of tunnel form buildings may exhibit brittle flexural failure under seismic action. The global tension/compression couple triggers this failure mechanism by creating pure axial tension in outermost shear-walls. This type of failure takes place due to rupturing of longitudinal reinforcement without crushing of concrete, therefore is of particular interest in emphasizing the mode of failure that is not routinely considered during seismic design of shear-wall dominant structural systems.

Structural Engineering and Mechanics↗

USGS2007

Multi-component ground motion response spectra for coupled horizontal, vertical, angular accelerations, and tilt

Rotational and vertical components of ground motion are almost always ignored in design or in the assessment of structures despite the fact that vertical motion can be twice as much as the horizontal motion and may exceed 2g level, and rotational excitation may reach few degrees in the proximity of fault rupture. Coupling of different components of ground excitation may significantly amplify the seismic demand by introducing additional lateral forces and enhanced P-?? effects. In this paper, a governing equation of motion is postulated to compute the response of a SDOF oscillator under a multi-component excitation. The expanded equation includes secondary P-?? components associated with the combined impacts of tilt and vertical excitations in addition to the inertial forcing terms due to the angular and translational accelerations. The elastic and inelastic spectral ordinates traditionally generated considering the uniaxial input motion are compared at the end with the multi-component response spectra of coupled horizontal, vertical and tilting motions. The proposed multi-component response spectrum reflects kinematic characteristics of the ground motion that are not identifiable by the conventional spectrum itself, at least for the near-fault region where high intensity vertical shaking and rotational excitation are likely to occur.

ISET Journal of Earthquake Technology↗