Evaluation of the Ground Motion Scaling Procedures for Concrete Gravity Dams

The seismic safety of dam structures is often evaluated using time history analyses conducted with a limited number of ground motions. The selection and scaling of the ground motions is usually the most effective factor determining the results of the safety assessment. The inherent variability in the ground motion as well as the difficulty of conducting the analyses for a large number of ground motions renders the selection as the most important factor in the analysis results. The guidelines for the nonlinear transient analyses of buildings, such as the one presented in ASCE/SEI-7-10, are well studied. For dams, however, it is not clear how the selection and scaling of the accelerograms should be conducted with the goals of a) consistency b) reliability and the c) practicality of the analyses. In this context, consistency implies obtaining consistent results for the same problem, reliability implies a reduction in the variability in the results while practicality implies the completion of the process with lesser effort. The selection and scaling of the ground motions for use in the nonlinear seismic analysis of the concrete gravity dams was investigated in this study with the aforementioned goals focused on the efficient prediction of the seismic demands on these structures. Three different concrete gravity dam monoliths were selected for this purpose, using 15 selected ground motions for the appropriate local site conditions. The material nonlinearity, dam-reservoir interaction and vertical component of ground motions were considered in the analyses. The engineering demand parameters were selected as the crest displacement, the maximum crest acceleration and the crack extent, a direct indicator of the damage on the monoliths. Nine different scaling methods were investigated. The effectiveness in the prediction of the mean demand and the corresponding dispersion levels were compared. The required number of motions to conduct effective analyses was determined. (c) 2017 The Authors. Published by Elsevier Ltd

Yapısal sistemler için yer hareketi kaydı seçme ve ölçeklendirme yöntemi.

This study presents a ground-motion selection and scaling procedure that preserves the inherent uncertainty in the modified recordings. The proposed procedure provides a set of scaled ground-motion records to be used in the response estimation of structural systems for a pre-defined earthquake hazard level. Given a relatively larger ground-motion dataset, the methodology constrains the selection and scaling of the accelerograms to the differences between individual records and corresponding estimations from a representative ground-motion predictive model. The procedure precisely calculates the distribution parameters of linear structural systems whereas it provides estimations of these parameters for nonlinear structural response. Thus this method is not only useful for ground-motion selection and scaling but also for probability based performance assessment studies. The proposed procedure is also capable of matching with a pre-defined target elastic response spectrum and corresponding variance over a period range. Case studies that compare the performance of the proposed procedure with some other record selection and scaling methods suggest its usefulness for the accurate verification of structural systems and rapid loss estimation studies.Ph.D. - Doctoral Progra

Türkiye'deki az ve orta katlı betonarme çerçeveli binaların hasargörebilirliğinin incelenmesi.

In this study, structural vulnerability of reinforced concrete frame structures by considering the countryspecific characteristics is investigated to manage the earthquake risk and to develop strategies for disaster mitigation. Lowrise and midrise reinforced concrete structures, which constitute approximately 75% of the total building stock in Turkey, are focused in this fragilitybased assessment. The seismic design of 3, 5, 7 and 9story reinforced concrete frame structures are carried out according to the current earthquake codes and two dimensional analytical models are formed accordingly. The uncertainty in material variability is taken into account in the formation of structural simulations. Frame structures are categorized as poor, typical or superior according to the specific characteristics of construction practice and the observed seismic performance after major earthquakes in Turkey. The demand statistics in terms of maximum interstory drift ratio are obtained for different sets of ground motion records. The capacity is determined in terms of limit states and the corresponding fragility curves are obtained from the probability of exceeding each limit state for different levels of ground shaking. The results are promising in the sense that the inherent structural deficiencies are reflected in the final fragility functions. Consequently, this study provides a reliable fragilitybased database for earthquake damage and loss estimation of reinforced concrete building stock in urban areas of Turkey.M.S. - Master of Scienc

A Proposed Criteria Matrix for Decision Analysis of Post Disaster Temporary Accommodation Units

Disasters caused by natural hazards or socio-political crises pose widespread damage on built environment resulted with loss of housing. To meet accommodation needs of disaster victims, temporary accommodation units are a common solution not only to bridge the gap until permanent housing are ready to use but also to provide physical and psychological rehabilitation. As post-disaster accommodation units are absolutely diversified from the housing production in usual conditions with respect to necessity of prompt readiness and instant as well as extensive response, the management of provision, design and construction of them require rapid and organizational evaluation. In an ideal disaster management process, it is critical to define decision criteria of temporary accommodation units in ‘preparedness’ period to achieve a rational decision-making process in limited time of ‘reconstruction’ and ‘recovery’ phase. In literature, there are several studies on decision criteria of temporary accommodation units, yet they generally concentrate on a particular feature. The aim of this study is to generate an extensive and holistic decision criteria matrix to guide decision makers in evaluation of post-disaster temporary accommodation units

Yatay Perdeli Narin Yüksek Yapılarda Rüzgâr Kaçış Katlarının Optimizasyonu

Narin yüksek binalarda cephe ve kütlenin aerodinamik tasarımına ek olarak yapı cephesinde oluşturulan açıklıklar (rüzgâr kaçış katları) ile binadaki yatay ötelenme kontrol edilebilir. Ancak bu durum yapıdaki kullanılabilir alanı azaltmaktadır. Benzer şekilde yüksek yapılarda rijitliğin arttırılması (örn. yapının taşıyıcı elemanlarının boyutunun büyümesi) kullanılabilir alanların veya panoramik görüşün azalması gibi tasarımcılar tarafından arzu edilmeyen sonuçlar ortaya çıkarabilir. Bu çalışmada, rüzgar kaçış katları ve yatay perde duvarların (sanal yatay perdeler de dâhil) bir arada kullanılması ile yapıdaki kullanılabilir katların sayısının ve binanın rüzgar performansının (maksimum tepe ötelenmesi ve taban moment değerleri) optimizasyonu hedeflenmektedir. Bu çalışma kapsamında rüzgar açıklıklarının sayısı ve konumu, narin yüksek bir yapıda kullanılamayan kat sayısını düşürmek amacıyla irdelenecektir

A procedure on ground motion selection and scaling for nonlinear response of simple structural systems

This study presents a ground-motion selection and scaling methodology that preserves the basic seismological features of the scaled records with reduced scatter in the nonlinear structural response. The methodology modifies each strong-motion recording with known fundamental seismological parameters using the estimations of ground-motion prediction equations for a given target hazard level. It provides robust estimations on target building response through scaled ground motions and calculates the dispersion about this target. This alternative procedure is not only useful for record scaling and selection but, upon its further refinement, can also be advantageous for the probabilistic methods that assess the engineering demand parameters for a given target hazard level. Case studies that compare the performance of the proposed procedure with some other record selection and scaling methods suggest its usefulness for building performance assessment and loss models. Copyright (c) 2012 John Wiley & Sons, Ltd

Evaluation of a recently proposed record selection and scaling procedure for low-rise to mid-rise reinforced concrete buildings and its use for probabilistic risk assessment studies

This paper evaluates a recent record selection and scaling procedure of the authors that can determine the probabilistic structural response of buildings behaving either in the elastic or post-elastic range. This feature marks a significant strength on the procedure as the probabilistic structural response distribution conveys important information on probability-based damage assessment. The paper presents case studies that show the utilization of the proposed record selection and scaling procedure as a tool for the estimation of damage states and derivation of site-specific and region-specific fragility functions. The method can be used to describe exceedance probabilities of damage limits under a certain target hazard level with known annual exceedance rate (via probabilistic seismic hazard assessment). Thus, the resulting fragility models can relate the seismicity of the region (or a site) with the resulting building performance in a more accurate manner. Under this context, this simple and computationally efficient record selection and scaling procedure can be benefitted significantly by probability-based risk assessment methods that have started to be considered as indispensable for developing robust earthquake loss models. Copyright (c) 2013 John Wiley & Sons, Ltd