Konuralp Girgin | Istanbul Technical University (original) (raw)
Papers by Konuralp Girgin
Acta Mechanica, 2018
The purpose of this study is to calculate the torsional rigidity and maximum shear stresses of ar... more The purpose of this study is to calculate the torsional rigidity and maximum shear stresses of arbitrarily shaped orthotropic composite or functionally graded material sections on the basis of a hybrid finite element approach. A hybrid finite element based on a Hellinger-Reissner functional is presented. A set of numerical examples is solved to verify the proposed method, and a parametrical study is also performed.
JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT, 2017
In spread footings, the rotational spring constants, which represent the soil-structure interacti... more In spread footings, the rotational spring constants, which represent the soil-structure interaction, play an important role in the structural analysis and design. To assign the behaviour of soil, which is generally represented via Winkler-type tensionless springs, necessitates time consuming iterative computing procedures in practice. In this study, a straightforward approach is proposed for the soil-structure interaction of rigid spread footings especially subjected to excessive eccentric loading. By considering the uplift of footing, the rotational spring constants of those type footings under axial load and biaxial bending are easily attained through the proposed simplified formulations. Since these formulations enable manual calculation, iterative computer efforts are not required. The formulations under consideration can be applicable to symmetric and non-symmetric rigid spread footings. The numerical results of this study are verified with SAP2000.
Dokuz Eylül Üniversitesi-Mühendislik Fakültesi Fen ve Mühendislik Dergisi, 2017
Bu çalışmada, İstanbul’da başlayan ve sürmekte olan kentsel dönüşüm projesi kapsamında inşa edile... more Bu çalışmada, İstanbul’da başlayan ve sürmekte olan kentsel dönüşüm projesi kapsamında inşa edilen konut türü binaların hemen hemen tümünde kullanılan taşıyıcı sistem modelinin deprem performansının araştırılması amaçlanmıştır. Bahsedilen taşıyıcı sistem modelinde, kolon ve perdelerden oluşan düşey ve yatay yük taşıyıcı elemanlar, dişli döşemeler ve bu döşemeler içinde teşkil edilen yassı kirişler ile birbirine bağlanmaktadır. Bu tür binaları temsil edecek şekilde seçilmiş orta yükseklikte bir betonarme bina güncel yönetmeliklere göre boyutlandırılmıştır. Daha sonra bu binanın deprem performansı araştırılmıştır. Bu çalışmadan elde edilen sonuçlar bu tür binaların yeterli deprem güvenliğini sağlamadığı yönündedir.
Polymers, 2015
This study addresses a design oriented combined model to predict the ultimate strengths and ultim... more This study addresses a design oriented combined model to predict the ultimate strengths and ultimate strains in an extensive range of unconfined strength (7 to 190 MPa) for the axially loaded fiber-reinforced polymer (FRP)-wrapped circular short columns. Modified Hoek-Brown strength criterion, which was previously extended to FRP-confined concrete from 7 to 108 MPa, is revisited and verified. An empirical strength model beyond 108 MPa encompassing ultra-high strength concrete (UHSC) and ultra-high performance concrete (UHPC) data, as well as empirical strain models, are defined to accomplish the design oriented combined model. This article especially focuses on the verification of the proposed strain models. The assessment performances of those models for carbon FRP (CFRP) and glass FRP (GFRP) confinement are compared with specific models in the current literature. Strength and strain predictions for UHSC and UHPC are integrated into the design oriented combined model as well. The assessments on this model agree with the experimental results in high accuracy.
Pamukkale Universitesi Muhendislik Bilimleri Dergisi, 2013
There are different approaches in the performance based design of the existing reinforced concret... more There are different approaches in the performance based design of the existing reinforced concrete structures, regarding the determination of the intersection point of capacity and demand curves. While the equivalent displacement approach is employed in Turkish Earthquake Code (TEC2007), a successive approximation technique based on the effective period and damping is suggested in FEMA440. Frame type and wall-frame type regular structures with different number of stories are selected to discuss the approaches on the performance point determination techniques proposed in TEC2007 and FEMA440. The resulting earthquake demands are compared with each other and also those obtained from the nonlinear time history analyses. Top displacement, base shear, relative story drift are amongst the discussed demand parameters. It is shown that for the structures considered in this study, the demands obtained from the TEC2007
procedure are more close to the nonlinear time history analyses results.
Teknik Dergi, 2008
In several design codes and specifications, simplified formulae, nomographs or charts are given f... more In several design codes and specifications, simplified formulae, nomographs or charts are given for determining the effective lengths of frame columns. It is shown that these
simplified approaches may yield rather erroneous results in most of the cases. This is due to the fact that, the code formulae utilize only local stiffness distributions, thus ignoring the general behaviour of the system. In this paper, a simplified procedure for determining approximate values for the effective lengths of braced multi-storey frame columns is developed. The procedure utilizes a simple average calculation and yields errors less than 10 %, which may be considered suitable for practical purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range.
Steel and Composite Structures, 2007
The purpose of this study is to calculate the torsional rigidity of arbitrarily shaped composite ... more The purpose of this study is to calculate the torsional rigidity of arbitrarily shaped composite sections on the basis of hybrid finite element approach. An analogy is used between the torsion problem and deformation of a plate which exhibits only shear behavior. In the analysis a simple hybrid finite element based on Hellinger-Reissner functional is presented and a set of numerical examples are performed to demonstrate and asses the performance of the developed element in practical applications.
Advances in Structural Engineering, 2007
In this paper, the torsional rigidity of the composite sections formed by different materials is ... more In this paper, the torsional rigidity of the composite sections formed by different materials is obtained by using a finite element procedure. In the derivation of the differential equation, the Saint-Venant's stress function was used. The obtained partial differential equation was discretized by finite elements to get the potentials in the nodal points. After the calculations of the unknown potentials on the composite cross-section, the torsional rigidity is calculated by integrating the potentials on the solution domain. To test the validity of the proposed algorithm, the available analytical and numerical results from the previous studies were studied. It was seen that this new algorithm is efficient and simpler than the previous ones.
Structural Engineering & Mechanics, 2011
This study introduces a new load increment method for the ductile reinforced concrete (RC) frame ... more This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.
ARI Bulletin of the Istanbul Technical University, 2007
Structural frames are often filled with infilled walls serving as partitions. Although the infill... more Structural frames are often filled with infilled walls serving as partitions. Although the infills usually are not considered in the structural analysis and design, their influence on the seismic behaviour of the infilled frame structures is considerable. In the present study, a parametric study of certain infilled frames, using the strut model to capture the global effects of the infills was carried out. Three concrete planar frames of five-stories and three-bays are considered which have been designed in accordance with Turkish Codes. Pushover analysis is adopted for the evaluation of the seismic response of the frames. Each frame is subjected to four different loading cases. The results of the cases are briefly presented and compared. The effect of infill walls on seismic behavior of two sample frames with different infill arrangements was investigated. The results yield that it is essential to consider the effect of masonry infills for the seismic evaluation of moment-resisting RC frames, especially for the prediction of its ultimate state, infills having no irregularity in elevation have beneficial effect on buildings and infills appear to have a significant effect on the reduction of global lateral displacements.
Yedinci Uluslararası İnşaat Mühendisliğinde Gelişmeler Kongresi,11-13 Ekim 2006, Yıldız Teknik Üniversitesi, İstanbul, Türkiye., 2006
Bu çalışmada silindirik olmayan helislerin serbest titreşimi Timoshenko kiriş teorisinin gözönüne... more Bu çalışmada silindirik olmayan helislerin serbest titreşimi Timoshenko kiriş teorisinin gözönüne alındığı karışık sonlu elemanlar yöntemi ile incelenmektedir. Bu amaçla değişken eğrilikli eğrisel uzay çubukların eleman ve yayılı kütle matrisleri geliştirilmiştir. Hareket denklemleri Timoshenko kiriş kuramı ve Gatéaux diferansiyeli kullanılarak elde edilen karışık sonlu eleman formülasyonuna uygun bir fonksiyonelden yararlanmak suretiyle yazılmaktadır. Silindirik olmayan helis geometrisi, silindirik helisten uyarlanan yaklaşık geometri ile ifade edilmiştir. Silindirik olmayan helislerin serbest titreşim analizinde yaklaşık geometri ile elde edilen frekanslar, literatürde kesin geometri kullanılarak elde edilen frekanslar ile karşılaştırılmış, sayısal sonuçların uyum içinde olduğu görülmüştür.
Sixth International Congress on Advances in Civil Engineering, 6-8 October 2004, Bogazici University, Istanbul, Turkey, 2004
The nonlinear behavior of existing low rise reinforced concrete buildings with structural deficie... more The nonlinear behavior of existing low rise reinforced concrete buildings with structural deficiencies was examined in this study. A set of push over analyses has been done for hypothetically defined four representative different types of widely used frames with four, five and six stories. The structural deficiencies such as the low compressive strength of concrete in existing buildings, low percentage of reinforcement in column sections, lack of proper lap splicing in critical regions of columns and beams in existing buildings are all grouped and have been taken into consideration in push over analyses. Also, possible structural changes such as alterations in the orientations of columns, having additional stories on top of the existing building and changing the demand of live loads on the existing structure are idealized for representative frames to obtain load-top deflection curves. All graphs achieved can be utilized in quick assessment work to evaluate earthquake load resisting capacities of the huge amount of existing low rise similar reinforced concrete structures constructed in earthquake prone areas.
Third European Workshop on the Seismic Behaviour of Irregular and Complex Structures, International Conference in Earthquake Engineering, Skopje & Ohrid, R. Macedonia, 2003
Huge amount of low rise reinforced concrete buildings have been constructed with important struct... more Huge amount of low rise reinforced concrete buildings have been constructed with
important structural deficiencies, which cause substantial decrement in the expected safety against earthquakes. Concrete compressive strengths of these buildings are low, the amount of longitudinal reinforcement bars are lower than the code requirements, heavy corrosion in certain sections is commonly observed, lack of sufficient confinement and poor detailing and construction are also among the common deficiencies encountered. Not only because of these factors but the earthquake code requirements, which were valid at the period of construction, was not good enough to provide the performance levels prescribed in recent codes also.
Most of those 25, 30, 40 or more years old buildings have been structurally altered in their life. Sometimes additional stories have been placed on top of the buildings, beams even columns have been removed and dynamic behaviour of those buildings have been changed. If those buildings are evaluated according to any one of the current assessment method used in America, Japan or Europe, it is strongly probable that most of them will fail to satisfy the lowest level of requirements. Unfortunately they are used and they have to be used in near future as well. The problem becomes more severe when the probability of occurrence of an expected earthquake starts to
get bigger. If this is case a powerful realistic quick assessment method is urgently needed to inspect millions of buildings located in earthquake prone areas in a relatively short time to identify the units which have to be strengthened. A proposed quick assessment method based on the dimensions of columns in critical storeys and the collected common structural features of collapsed and existing building, is presented in this paper together with a strengthening technique which can be utilised in a prescriptive manner. Four walls are proposed for each 100 m2 floor area of buildings in this technique. The problems pertinent to the altered structural behaviour and foundations of wall are discussed in this paper.
A short review of the current research projects going on in ITU Structural and Earthquake Engineering Laboratory on the construction of these walls are presented for the sake of completeness and to show the need of co-operative both experimental and theoretical research.
SPEAR (Seismic Performance Assessment and Rehabilitation of Existing Buildings) INTERNATIONAL WORKSHOP, An event to honour the memory of Prof. Jean Donea Ispra, 4-5 April 2005., 2005
The seismic evaluation and the retrofit design of existing buildings due to seismic loads is a ve... more The seismic evaluation and the retrofit design of existing buildings due to seismic loads is a very important problem of most of the earthquake prone countries. In this paper, existing four and seven story RC buildings are evaluated according to the 1998 Earthquake Code of Turkey and found to be weak and strengthened by adding shear walls and/or jacketing some columns, then results have been tested using ATC–40 guidelines and the capacity spectrum method. Moreover, in order to see the effect of near fault earthquakes, a nonlinear time history analysis has been carried out for seven story building using five ground motions of recent earthquakes in Turkey. As a conclusion, the buildings strengthened according to the code are over-designed and the near fault effects have to be introduced to the existing Turkish Earthquake Code.
The 2011 World Congress on Advances in Structural Engineering and Mechanics (ASEM'11+) Seoul, Korea, 18-22 September, 2011 , 2011
In this paper, a numerical method based upon the effective utilization of Mohr method is proposed... more In this paper, a numerical method based upon the effective utilization of Mohr method is
proposed for non-uniform beam-columns fully or partially resting on Winkler type elastic
foundation. This method presents a unified approach to determine buckling load and to derive the stiffness matrix and nodal load vector. The algorithm enables the non-uniform members to regard as a sub-structure, which all the variable characteristics are incorporated, in the analysis of large complex structures. The numerical examples to analyze some engineering problems as well as to verify the efficiency of the numerical method are included in this paper.
The 2011 World Congress on Advances in Structural Engineering and Mechanics (ASEM'11+) Seoul, Korea, 18-22 September, 2011, 2011
In this paper, a numerical method is proposed for arbitrarily or abruptly variable non-uniform co... more In this paper, a numerical method is proposed for arbitrarily or abruptly variable non-uniform columns under concentrated and distributed axial loads. The algorithm enables the non-uniform column to regard as a sub-structure. This method presents a unified approach based on Mohr method to determine the stiffness matrix and nodal load vector. Stability and free-vibration analysis can also be carried out through this method. The numerical examples confirm the efficiency of the method.
Pamukkale University Journal of Engineering Sciences, 2013
Bu çalışmada, Deprem Bölgelerinde Yapılacak Binalar Hakkında Yönetmelik-2007 (DBYBHY-2007) ye gör... more Bu çalışmada, Deprem Bölgelerinde Yapılacak Binalar Hakkında Yönetmelik-2007 (DBYBHY-2007) ye göre boyutlandırılan altı katlı dış merkez çaprazlı bir çelik perdenin deprem performansı, zaman tanım alanında doğrusal olmayan hesap yöntemi kullanılarak değerlendirilmiştir. Bu değerlendirmede göreli kat ötelemeleri, kat kesme kuvvetleri, çapraz ve kolonların iç kuvvet istemleri ile bağ kirişi kesme kuvveti ve dönme istemleri dikkate alınmıştır. Zaman tanım alanında doğrusal olmayan analizler yedi adet deprem ivme kaydı kullanılarak gerçekleştirilmiştir. Analizler sonucu elde edilen istemlerin ortalama değerleri esas alınarak dış merkez çaprazlı çelik perdelerin kullanıldığı orta yükseklikteki binalar için DBYBHY-2007'de öngörülen kapasite tasarımı yaklaşımının yeterliliği araştırılmıştır. The goal of this paper is to investigate the non-linear response and to assess the seismic performance of a six story eccentrically braced steel frame (EBF). For this, split-K-braced EBF with high ductility level designed according to the Turkish Earthquake Code-2007 (TEC-07) is analyzed under seven selected earthquake records. The performance of the EBF is assessed considering drift, story and base shear demands, brace and column axial forces and bending moment demands, link beam shear force and rotation demands. Mean values of the demands are used in the performance assessment. The provisions based on capacity design approach specified in TEC-07 for EBFs with high ductility level are discussed by employing the findings..
Materials and Structures, 2014
In this study, the normality condition of the plastic strain vector to the yield surface utilized... more In this study, the normality condition of the plastic strain vector to the yield surface utilized for elastic-perfectly plastic materials is investigated for reinforced concrete (RC) sections. If the plastic strain vector can be assumed outward normal to the yield surface in RC sections under combined biaxial bending and axial load, the components of the vector can be expressed by a single parameter. Thus, the material nonlinearity can be simplified through the extended plastic hinge concept based on the normality condition. In this study the normality of the plastic strain vector is verified via numerical examples in symmetrically reinforced rectangular and circular RC sections subjected to biaxial bending and axial load for various configurations of longitudinal reinforcement.
International Journal of Advanced Structural Engineering (IJASE), 2014
The purpose of this study is first to determine the conditions for excessive torsional irregulari... more The purpose of this study is first to determine the conditions for excessive torsional irregularity and then to discuss the validity of code provisions. A parametric investigation is performed on six groups of typical structures with varying shear wall positions, story and axis numbers. It is found that torsional irregularity coefficients increase as the story numbers decrease, i.e. maximum irregularity coefficients occur for single-story structures. They reach maximum values when the asymmetrical shear walls are placed as close as possible to the centers of mass. However, the results obtained for floor rotations are quite contradictory. A new provisional definition for torsional irregularity coefficient based on floor rotations is proposed.
Structural Engineering and Mechanics, 2008
In several design codes and specifications, simplified formulae and charts are given for determin... more In several design codes and specifications, simplified formulae and charts are given for determining the effective lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of braced frames is developed. The procedure utilises a fictitious load analysis of frames and yields errors less than 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range.
Acta Mechanica, 2018
The purpose of this study is to calculate the torsional rigidity and maximum shear stresses of ar... more The purpose of this study is to calculate the torsional rigidity and maximum shear stresses of arbitrarily shaped orthotropic composite or functionally graded material sections on the basis of a hybrid finite element approach. A hybrid finite element based on a Hellinger-Reissner functional is presented. A set of numerical examples is solved to verify the proposed method, and a parametrical study is also performed.
JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT, 2017
In spread footings, the rotational spring constants, which represent the soil-structure interacti... more In spread footings, the rotational spring constants, which represent the soil-structure interaction, play an important role in the structural analysis and design. To assign the behaviour of soil, which is generally represented via Winkler-type tensionless springs, necessitates time consuming iterative computing procedures in practice. In this study, a straightforward approach is proposed for the soil-structure interaction of rigid spread footings especially subjected to excessive eccentric loading. By considering the uplift of footing, the rotational spring constants of those type footings under axial load and biaxial bending are easily attained through the proposed simplified formulations. Since these formulations enable manual calculation, iterative computer efforts are not required. The formulations under consideration can be applicable to symmetric and non-symmetric rigid spread footings. The numerical results of this study are verified with SAP2000.
Dokuz Eylül Üniversitesi-Mühendislik Fakültesi Fen ve Mühendislik Dergisi, 2017
Bu çalışmada, İstanbul’da başlayan ve sürmekte olan kentsel dönüşüm projesi kapsamında inşa edile... more Bu çalışmada, İstanbul’da başlayan ve sürmekte olan kentsel dönüşüm projesi kapsamında inşa edilen konut türü binaların hemen hemen tümünde kullanılan taşıyıcı sistem modelinin deprem performansının araştırılması amaçlanmıştır. Bahsedilen taşıyıcı sistem modelinde, kolon ve perdelerden oluşan düşey ve yatay yük taşıyıcı elemanlar, dişli döşemeler ve bu döşemeler içinde teşkil edilen yassı kirişler ile birbirine bağlanmaktadır. Bu tür binaları temsil edecek şekilde seçilmiş orta yükseklikte bir betonarme bina güncel yönetmeliklere göre boyutlandırılmıştır. Daha sonra bu binanın deprem performansı araştırılmıştır. Bu çalışmadan elde edilen sonuçlar bu tür binaların yeterli deprem güvenliğini sağlamadığı yönündedir.
Polymers, 2015
This study addresses a design oriented combined model to predict the ultimate strengths and ultim... more This study addresses a design oriented combined model to predict the ultimate strengths and ultimate strains in an extensive range of unconfined strength (7 to 190 MPa) for the axially loaded fiber-reinforced polymer (FRP)-wrapped circular short columns. Modified Hoek-Brown strength criterion, which was previously extended to FRP-confined concrete from 7 to 108 MPa, is revisited and verified. An empirical strength model beyond 108 MPa encompassing ultra-high strength concrete (UHSC) and ultra-high performance concrete (UHPC) data, as well as empirical strain models, are defined to accomplish the design oriented combined model. This article especially focuses on the verification of the proposed strain models. The assessment performances of those models for carbon FRP (CFRP) and glass FRP (GFRP) confinement are compared with specific models in the current literature. Strength and strain predictions for UHSC and UHPC are integrated into the design oriented combined model as well. The assessments on this model agree with the experimental results in high accuracy.
Pamukkale Universitesi Muhendislik Bilimleri Dergisi, 2013
There are different approaches in the performance based design of the existing reinforced concret... more There are different approaches in the performance based design of the existing reinforced concrete structures, regarding the determination of the intersection point of capacity and demand curves. While the equivalent displacement approach is employed in Turkish Earthquake Code (TEC2007), a successive approximation technique based on the effective period and damping is suggested in FEMA440. Frame type and wall-frame type regular structures with different number of stories are selected to discuss the approaches on the performance point determination techniques proposed in TEC2007 and FEMA440. The resulting earthquake demands are compared with each other and also those obtained from the nonlinear time history analyses. Top displacement, base shear, relative story drift are amongst the discussed demand parameters. It is shown that for the structures considered in this study, the demands obtained from the TEC2007
procedure are more close to the nonlinear time history analyses results.
Teknik Dergi, 2008
In several design codes and specifications, simplified formulae, nomographs or charts are given f... more In several design codes and specifications, simplified formulae, nomographs or charts are given for determining the effective lengths of frame columns. It is shown that these
simplified approaches may yield rather erroneous results in most of the cases. This is due to the fact that, the code formulae utilize only local stiffness distributions, thus ignoring the general behaviour of the system. In this paper, a simplified procedure for determining approximate values for the effective lengths of braced multi-storey frame columns is developed. The procedure utilizes a simple average calculation and yields errors less than 10 %, which may be considered suitable for practical purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range.
Steel and Composite Structures, 2007
The purpose of this study is to calculate the torsional rigidity of arbitrarily shaped composite ... more The purpose of this study is to calculate the torsional rigidity of arbitrarily shaped composite sections on the basis of hybrid finite element approach. An analogy is used between the torsion problem and deformation of a plate which exhibits only shear behavior. In the analysis a simple hybrid finite element based on Hellinger-Reissner functional is presented and a set of numerical examples are performed to demonstrate and asses the performance of the developed element in practical applications.
Advances in Structural Engineering, 2007
In this paper, the torsional rigidity of the composite sections formed by different materials is ... more In this paper, the torsional rigidity of the composite sections formed by different materials is obtained by using a finite element procedure. In the derivation of the differential equation, the Saint-Venant's stress function was used. The obtained partial differential equation was discretized by finite elements to get the potentials in the nodal points. After the calculations of the unknown potentials on the composite cross-section, the torsional rigidity is calculated by integrating the potentials on the solution domain. To test the validity of the proposed algorithm, the available analytical and numerical results from the previous studies were studied. It was seen that this new algorithm is efficient and simpler than the previous ones.
Structural Engineering & Mechanics, 2011
This study introduces a new load increment method for the ductile reinforced concrete (RC) frame ... more This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.
ARI Bulletin of the Istanbul Technical University, 2007
Structural frames are often filled with infilled walls serving as partitions. Although the infill... more Structural frames are often filled with infilled walls serving as partitions. Although the infills usually are not considered in the structural analysis and design, their influence on the seismic behaviour of the infilled frame structures is considerable. In the present study, a parametric study of certain infilled frames, using the strut model to capture the global effects of the infills was carried out. Three concrete planar frames of five-stories and three-bays are considered which have been designed in accordance with Turkish Codes. Pushover analysis is adopted for the evaluation of the seismic response of the frames. Each frame is subjected to four different loading cases. The results of the cases are briefly presented and compared. The effect of infill walls on seismic behavior of two sample frames with different infill arrangements was investigated. The results yield that it is essential to consider the effect of masonry infills for the seismic evaluation of moment-resisting RC frames, especially for the prediction of its ultimate state, infills having no irregularity in elevation have beneficial effect on buildings and infills appear to have a significant effect on the reduction of global lateral displacements.
Yedinci Uluslararası İnşaat Mühendisliğinde Gelişmeler Kongresi,11-13 Ekim 2006, Yıldız Teknik Üniversitesi, İstanbul, Türkiye., 2006
Bu çalışmada silindirik olmayan helislerin serbest titreşimi Timoshenko kiriş teorisinin gözönüne... more Bu çalışmada silindirik olmayan helislerin serbest titreşimi Timoshenko kiriş teorisinin gözönüne alındığı karışık sonlu elemanlar yöntemi ile incelenmektedir. Bu amaçla değişken eğrilikli eğrisel uzay çubukların eleman ve yayılı kütle matrisleri geliştirilmiştir. Hareket denklemleri Timoshenko kiriş kuramı ve Gatéaux diferansiyeli kullanılarak elde edilen karışık sonlu eleman formülasyonuna uygun bir fonksiyonelden yararlanmak suretiyle yazılmaktadır. Silindirik olmayan helis geometrisi, silindirik helisten uyarlanan yaklaşık geometri ile ifade edilmiştir. Silindirik olmayan helislerin serbest titreşim analizinde yaklaşık geometri ile elde edilen frekanslar, literatürde kesin geometri kullanılarak elde edilen frekanslar ile karşılaştırılmış, sayısal sonuçların uyum içinde olduğu görülmüştür.
Sixth International Congress on Advances in Civil Engineering, 6-8 October 2004, Bogazici University, Istanbul, Turkey, 2004
The nonlinear behavior of existing low rise reinforced concrete buildings with structural deficie... more The nonlinear behavior of existing low rise reinforced concrete buildings with structural deficiencies was examined in this study. A set of push over analyses has been done for hypothetically defined four representative different types of widely used frames with four, five and six stories. The structural deficiencies such as the low compressive strength of concrete in existing buildings, low percentage of reinforcement in column sections, lack of proper lap splicing in critical regions of columns and beams in existing buildings are all grouped and have been taken into consideration in push over analyses. Also, possible structural changes such as alterations in the orientations of columns, having additional stories on top of the existing building and changing the demand of live loads on the existing structure are idealized for representative frames to obtain load-top deflection curves. All graphs achieved can be utilized in quick assessment work to evaluate earthquake load resisting capacities of the huge amount of existing low rise similar reinforced concrete structures constructed in earthquake prone areas.
Third European Workshop on the Seismic Behaviour of Irregular and Complex Structures, International Conference in Earthquake Engineering, Skopje & Ohrid, R. Macedonia, 2003
Huge amount of low rise reinforced concrete buildings have been constructed with important struct... more Huge amount of low rise reinforced concrete buildings have been constructed with
important structural deficiencies, which cause substantial decrement in the expected safety against earthquakes. Concrete compressive strengths of these buildings are low, the amount of longitudinal reinforcement bars are lower than the code requirements, heavy corrosion in certain sections is commonly observed, lack of sufficient confinement and poor detailing and construction are also among the common deficiencies encountered. Not only because of these factors but the earthquake code requirements, which were valid at the period of construction, was not good enough to provide the performance levels prescribed in recent codes also.
Most of those 25, 30, 40 or more years old buildings have been structurally altered in their life. Sometimes additional stories have been placed on top of the buildings, beams even columns have been removed and dynamic behaviour of those buildings have been changed. If those buildings are evaluated according to any one of the current assessment method used in America, Japan or Europe, it is strongly probable that most of them will fail to satisfy the lowest level of requirements. Unfortunately they are used and they have to be used in near future as well. The problem becomes more severe when the probability of occurrence of an expected earthquake starts to
get bigger. If this is case a powerful realistic quick assessment method is urgently needed to inspect millions of buildings located in earthquake prone areas in a relatively short time to identify the units which have to be strengthened. A proposed quick assessment method based on the dimensions of columns in critical storeys and the collected common structural features of collapsed and existing building, is presented in this paper together with a strengthening technique which can be utilised in a prescriptive manner. Four walls are proposed for each 100 m2 floor area of buildings in this technique. The problems pertinent to the altered structural behaviour and foundations of wall are discussed in this paper.
A short review of the current research projects going on in ITU Structural and Earthquake Engineering Laboratory on the construction of these walls are presented for the sake of completeness and to show the need of co-operative both experimental and theoretical research.
SPEAR (Seismic Performance Assessment and Rehabilitation of Existing Buildings) INTERNATIONAL WORKSHOP, An event to honour the memory of Prof. Jean Donea Ispra, 4-5 April 2005., 2005
The seismic evaluation and the retrofit design of existing buildings due to seismic loads is a ve... more The seismic evaluation and the retrofit design of existing buildings due to seismic loads is a very important problem of most of the earthquake prone countries. In this paper, existing four and seven story RC buildings are evaluated according to the 1998 Earthquake Code of Turkey and found to be weak and strengthened by adding shear walls and/or jacketing some columns, then results have been tested using ATC–40 guidelines and the capacity spectrum method. Moreover, in order to see the effect of near fault earthquakes, a nonlinear time history analysis has been carried out for seven story building using five ground motions of recent earthquakes in Turkey. As a conclusion, the buildings strengthened according to the code are over-designed and the near fault effects have to be introduced to the existing Turkish Earthquake Code.
The 2011 World Congress on Advances in Structural Engineering and Mechanics (ASEM'11+) Seoul, Korea, 18-22 September, 2011 , 2011
In this paper, a numerical method based upon the effective utilization of Mohr method is proposed... more In this paper, a numerical method based upon the effective utilization of Mohr method is
proposed for non-uniform beam-columns fully or partially resting on Winkler type elastic
foundation. This method presents a unified approach to determine buckling load and to derive the stiffness matrix and nodal load vector. The algorithm enables the non-uniform members to regard as a sub-structure, which all the variable characteristics are incorporated, in the analysis of large complex structures. The numerical examples to analyze some engineering problems as well as to verify the efficiency of the numerical method are included in this paper.
The 2011 World Congress on Advances in Structural Engineering and Mechanics (ASEM'11+) Seoul, Korea, 18-22 September, 2011, 2011
In this paper, a numerical method is proposed for arbitrarily or abruptly variable non-uniform co... more In this paper, a numerical method is proposed for arbitrarily or abruptly variable non-uniform columns under concentrated and distributed axial loads. The algorithm enables the non-uniform column to regard as a sub-structure. This method presents a unified approach based on Mohr method to determine the stiffness matrix and nodal load vector. Stability and free-vibration analysis can also be carried out through this method. The numerical examples confirm the efficiency of the method.
Pamukkale University Journal of Engineering Sciences, 2013
Bu çalışmada, Deprem Bölgelerinde Yapılacak Binalar Hakkında Yönetmelik-2007 (DBYBHY-2007) ye gör... more Bu çalışmada, Deprem Bölgelerinde Yapılacak Binalar Hakkında Yönetmelik-2007 (DBYBHY-2007) ye göre boyutlandırılan altı katlı dış merkez çaprazlı bir çelik perdenin deprem performansı, zaman tanım alanında doğrusal olmayan hesap yöntemi kullanılarak değerlendirilmiştir. Bu değerlendirmede göreli kat ötelemeleri, kat kesme kuvvetleri, çapraz ve kolonların iç kuvvet istemleri ile bağ kirişi kesme kuvveti ve dönme istemleri dikkate alınmıştır. Zaman tanım alanında doğrusal olmayan analizler yedi adet deprem ivme kaydı kullanılarak gerçekleştirilmiştir. Analizler sonucu elde edilen istemlerin ortalama değerleri esas alınarak dış merkez çaprazlı çelik perdelerin kullanıldığı orta yükseklikteki binalar için DBYBHY-2007'de öngörülen kapasite tasarımı yaklaşımının yeterliliği araştırılmıştır. The goal of this paper is to investigate the non-linear response and to assess the seismic performance of a six story eccentrically braced steel frame (EBF). For this, split-K-braced EBF with high ductility level designed according to the Turkish Earthquake Code-2007 (TEC-07) is analyzed under seven selected earthquake records. The performance of the EBF is assessed considering drift, story and base shear demands, brace and column axial forces and bending moment demands, link beam shear force and rotation demands. Mean values of the demands are used in the performance assessment. The provisions based on capacity design approach specified in TEC-07 for EBFs with high ductility level are discussed by employing the findings..
Materials and Structures, 2014
In this study, the normality condition of the plastic strain vector to the yield surface utilized... more In this study, the normality condition of the plastic strain vector to the yield surface utilized for elastic-perfectly plastic materials is investigated for reinforced concrete (RC) sections. If the plastic strain vector can be assumed outward normal to the yield surface in RC sections under combined biaxial bending and axial load, the components of the vector can be expressed by a single parameter. Thus, the material nonlinearity can be simplified through the extended plastic hinge concept based on the normality condition. In this study the normality of the plastic strain vector is verified via numerical examples in symmetrically reinforced rectangular and circular RC sections subjected to biaxial bending and axial load for various configurations of longitudinal reinforcement.
International Journal of Advanced Structural Engineering (IJASE), 2014
The purpose of this study is first to determine the conditions for excessive torsional irregulari... more The purpose of this study is first to determine the conditions for excessive torsional irregularity and then to discuss the validity of code provisions. A parametric investigation is performed on six groups of typical structures with varying shear wall positions, story and axis numbers. It is found that torsional irregularity coefficients increase as the story numbers decrease, i.e. maximum irregularity coefficients occur for single-story structures. They reach maximum values when the asymmetrical shear walls are placed as close as possible to the centers of mass. However, the results obtained for floor rotations are quite contradictory. A new provisional definition for torsional irregularity coefficient based on floor rotations is proposed.
Structural Engineering and Mechanics, 2008
In several design codes and specifications, simplified formulae and charts are given for determin... more In several design codes and specifications, simplified formulae and charts are given for determining the effective lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of braced frames is developed. The procedure utilises a fictitious load analysis of frames and yields errors less than 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range.
Birsen Publication, 2011
Kitapta konular anlaşılır bir şekilde sunulurken, problem çözümlerinde ise ayrıntılara girilmiş v... more Kitapta konular anlaşılır bir şekilde sunulurken, problem çözümlerinde ise ayrıntılara girilmiş ve her konu başlığı altında yeterli sayıda problemin çözümü verilmiştir. Günümüzün bilgisayar çağı olması nedeniyle, kitap içinden seçilen bazı problemlerin SAP2000-V15 yapısal analiz programı ile adım adım açıklanarak hazırlanmış çözümlerine kitabın Ekler bölümünde yer verilmiştir. Yazarlar bu kitabın, İnşaat Mühendisliği ve Mimarlık bölümü öğrencileri için yararlı olacağına inanmaktadırlar. Web : https://hiperstatik-sistemler.blogspot.com/ Kitabın üçüncü baskısına ait kapak resmi Kitabın tükenen 2700 adet ikinci baskısına ait kapak resmi Kitabın tükenen 2700 adet ilk baskısına ait kapak resmi
Birsen Yayınevi, 2011
Bu kitapta, Yapı Statiği derslerinin başlangıç konularını oluşturan İzostatik Sistemler kolay izl... more Bu kitapta, Yapı Statiği derslerinin başlangıç konularını oluşturan İzostatik Sistemler kolay izlenebilir bir şekilde anlatılmaya çalışılmıştır. Böylelikle öğrencilerin Yapı Statiği`ne ilgi duymaları ve ileri düzey Yapı Statiği derslerine hazırlanmaları amaçlanmıştır. Aynı zamanda bu kitabın, ilgili dersleri veren öğretim elemanları için de temel bir kaynak olması hedeflenmiştir. Kitapta konular sade bir anlatım tarzı ile sunulurken, problem çözümlerinde ise ayrıntılara girilmiş ve her konu başlığı altında yeterli sayıda problemin çözümü verilmiştir. Günümüzün bilgisayar çağı olması nedeniyle, seçilen bazı problemlerin SAP2000 programının veri girişine uygun olarak hazırlanmış dosyalarına da kitabın Ekler bölümünde yer verilmiştir. Yazarlar bu kitabın; İnşaat Mühendisliği başta olmak üzere, Mimarlık ve diğer mühendislik bölümlerindeki öğrenciler için yararlı olacağına inanmaktadırlar. Web : https://izostatik-sistemler.blogspot.com/ Kitabın 4000 adet üçüncü baskısına ait kapak resmi Kitabın tükenen 3100 adet ikinci baskısına ait kapak resmi Kitabın tükenen 2700 adet ilk baskısına ait kapak resmi
TDV/TR 046-81, Süneklilik Düzeyi Normal Sistemlerde Taşıyıcı Sistem Davranış Katsayısı, 2003
TDV/TR 028-45, Deprem Bölgelerindeki Mevcut Betonarme Yapıların Deprem Güvenliklerinin Belirlenmesi ve Rehabilitasyonu, 1999