Bu caly?mada, tersinir yuklere ve momentlere maruz elastic zemine oturan serbest bir kiri?in dina... more Bu caly?mada, tersinir yuklere ve momentlere maruz elastic zemine oturan serbest bir kiri?in dinamik analizi incelenmi?tir. Temel modeli Winkler hipotezine dayalydyr. Yayyly yukler icin belirlenen diferansiyel denklemin kullanylabilmesi amacyyla, kiri?teki tekil deformasyonlar Dirac da?ylym teorisi kullanarak yayyly yuklere donu?turulmu?tur. Caly?mayy acyklamak amacyyla tanymlayycy bir ornek sunulmu?tur ve elde edilen bazy sonuclar tablo ve ?ekillerde verilmi?tir.
In this study, the dynamic analysis of a free beam subjected to transverse forces and moments on ... more In this study, the dynamic analysis of a free beam subjected to transverse forces and moments on an elastic soil are investigated. The foundation model is based on the Winkler hypothesis. Using Dirac distribution theory, concentrated disturbances on beams are transformed to distributed loads in order to be able to use the governing differential equation established for distributed loads. An illustrative example is presented in order to demonstrate the use of the study and some of the obtained results are given in tables and figures.
Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods estimation o... more Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods estimation of modal parameters. The calibrated model in the future can be used to assess the parameters affecting modal parameter estimation therefore accurate damage identification
The seismic performance of steel moment-framed buildings has been of particular interest after th... more The seismic performance of steel moment-framed buildings has been of particular interest after the 1994 Northridge earthquake because brittle fractures were discovered at the beam-column connection. This paper examines the problem of identifying the dynamic character stics of an instrumented building using an input-output system identification method. The building studied was a six-story steel moment-resisting frame (SMRF) instrumented by the California Strong Motion Instrumentation Program (CSMIP). The building was shaken by several earthquakes and strong motion data of the building response was recorded during these earthquakes and were made available through SMIP. The identified modal properties of the structure were compared and verified with the spectral analysis of the response of the structure excited by three different earthquakes.
Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods Civil engine... more Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods Civil engineering structures are exposed to different external effects which change their dynamic characteristics. The fact that damage can alter stiffness, and/or energy dissipation capacity of a structure which in turn results in detectable changes in its vibration signature is the underlying principle of vibration-based structural health monitoring (SHM). An important step of SHM process is the estimation of modal parameters. In this study, modal parameters of a steel bridge are estimated using ERA and NExT-ERA system identification techniques. A calibrated finite element model of the bridge is obtained using the estimated modal parameters. Accurate damage identification of a structure depends on accurate
In earthquake-prone regions, it is still a challenge for predicting seismic resilience of existin... more In earthquake-prone regions, it is still a challenge for predicting seismic resilience of existing building inventory subjected to possible major magnitude earthquakes. This study presents results for pilot project “Establishment of Building Stock Inventory and Seismic Evaluation of Seismic Safety of Buildings” conducted in Balçova and Seferihisar regions in Izmir (Turkey) with the collaboration of Metropolitan Municipality, Dokuz Eylul University and Chamber of Civil Engineers Izmir Branch. For this purpose, construction plans of 10.550 existing buildings were scanned, digitized and evaluated and augmented with field observations. Field evaluations were performed by 84 civil engineers who attended a core training program in Chamber of Civil Engineers and certified after a series of exams prepared by the trainers. It is obvious that required time spent and economic resources to collect the data are not sufficient for. Therefore, a necessity arises for performing rapid screening asse...
The structures are challenged by earthquakes, material degradations and other environmental facto... more The structures are challenged by earthquakes, material degradations and other environmental factors. In order to protect the lives, assets, and for maintenance planning, structural health monitoring (SHM) is important. In SHM applications, strain gages are widely used which have low durability, low sensitivity while they have high cost. To monitor a structure, large number of strain gages have to be used that increases the cost. In this study, seven coal reinforced concrete mixtures with 0, 0.35, 0.5, 0.8, 1, 1.5 and 2 volume % of coal were designed; three cubic samples for each mixture were fabricated. Simultaneous strain and electrical resistance measurement of the samples during the compression test was conducted. A strong linear piezoresistive relationship between strain and electrical resistance change with a correlation coefficient of 0.99 was determined. The concrete mixture having 0.8 volume % coal had the highest strain sensitivity of K=44, which was 22 times the strain sensitivity of commercial metal strain gages while it had a linearity error of LE=6.9% that was low. This mixture with 0.8 volume % coal is a candidate to be smart concrete which can sense its strain. As a contribution to the literature, a phenomenological model for the relationship between gage factor and coal volume % was explained in details. The multifunctional smart concrete will be used as a smart material, which can sense its strain in SHM applications while acting as a load bearing material.
Self-centering braces, in the current stage of development can accommodate large deformation and ... more Self-centering braces, in the current stage of development can accommodate large deformation and force levels. However, there is still a need for improvement of the energy dissipation mechanisms commonly incorporated in these braces. Yield based energy dissipation systems can overcome some of the problems faced with friction-based devices, such as susceptibility to bolt relaxation, long-term creep of friction material and excessive flexing arising in the outer tubes due to friction bolts. However, in these alternative systems multi-wave buckling of the yielding core is present, which is the leading cause of an asymmetric hysteresis of the brace. Hence, in this study, U-shape flexural plates (UFPs) are analyzed as an alternative energy-dissipating device in real scale self-centering braces with a finite element modeling approach. UFP plates yield in flexure and when comparing to direct tension/compression yielding members, they show lower strain demand, resulting in a larger displacement capacity. Implementation of the UFP units in the brace produces a flag shape hysteresis with minimal residual deformation. The proposed system provides some advantages when compared to previous models in terms of increased redundancy, symmetric hysteresis and a more gradual stiffness change.
AbstractThis paper presents modal parameter estimation work on a steel railway bridge at three di... more AbstractThis paper presents modal parameter estimation work on a steel railway bridge at three different temperature conditions using ambient vibration test data. The bridge was built at the end of...
Earthquakes, material deteriorations and other environmental factors challenge the structural saf... more Earthquakes, material deteriorations and other environmental factors challenge the structural safety. In order to protect the lives, structural health monitoring is crucial. The metal foil strain gages have low durability, low sensitivity and can get point wise measurements which are disadvantages. In this study six different concrete mixtures were designed; one without any copper powder, the rest five having different copper powder volume fractions. Three cube samples from each mixture were cast and cured. Simultaneous measurement of electrical resistance and strain were conducted during the compression tests. A strong linear relationship between strain and electrical resistance change was obtained for copper powder reinforced concrete. The results are contribution to the development of “Smart Concrete” which can sense its strain and damage.
International Journal of Concrete Structures and Materials
Post-earthquake observations revealed that seismic performance of beam-column connections in prec... more Post-earthquake observations revealed that seismic performance of beam-column connections in precast concrete structures affect the overall response extensively. Seismic design of precast reinforced concrete structures requires improved beamcolumn connections to transfer reversed load effects between structural elements. In Turkey, hybrid beam-column connections with welded components have been applied extensively in precast concrete industry for decades. Beam bottom longitudinal rebars are welded to beam end plates while top longitudinal rebars are placed to designated gaps in joint panels before casting of topping concrete in this type of connections. The paper presents the major findings of an experimental test programme including one monolithic and five precast hybrid half scale specimens representing interior beam-column connections of a moment frame of high ductility level. The required welding area between beam bottom longitudinal rebars and beam-end plates were calculated based on welding coefficients considered as a test parameter. It is observed that the maximum strain developed in the beam bottom flexural reinforcement plays an important role in the overall behavior of the connections. Two additional specimens which include unbonded lengths on the longitudinal rebars to reduce that strain demands were also tested. Strength, stiffness and energy dissipation characteristics of test specimens were investigated with respect to test variables. Seismic performances of test specimens were evaluated by obtaining damage indices.
The structures are challenged by earthquakes and other environmental factors. Structural health m... more The structures are challenged by earthquakes and other environmental factors. Structural health monitoring is crucial to protect the lives. The strain gages used in structural health monitoring have low durability and can get point wise measurements which limit their use. In this study, five different concrete mixtures with different brass fiber volume fractions were designed. Along with the control mixture which does not have brass fiber, six mixtures were designed and three cube samples from each mixture were cast and cured. Compression test was conducted with simultaneous measurement of electrical resistance. The brass fiber reinforced concrete has strong linear relationship between the electrical resistance change and strain. Important progress was achieved in development of “Smart Concrete” which can sense its strain and damage.
Abstract Moment-resisting beam-column connections including emulative and mechanical components a... more Abstract Moment-resisting beam-column connections including emulative and mechanical components are widely used solutions in precast construction practice. Hybrid connections are constructed by welding of corbel plates to beam end plates where beam longitudinal rebars are welded, and casting of concrete through the designated gaps in beam tops and column elements at site. This study presents the development of a numerical model for hybrid connections to be used to assess seismic performance of multi-storey precast concrete structures. The numerical model includes truss-based elements for beam-column connections and fiber-based elements for beams and columns. Lateral load-drift ratio relations for the measured and computed cyclic responses of a precast connection are compared. In addition, two-dimensional three- and five- storey precast concrete frames are designed for seismic performance evaluation. Frame models are analysed by performing nonlinear static pushover analyses and incremental dynamic analyses with representative ground motions. Response modification factors are obtained and evaluated for seismic design of precast concrete buildings.
Yığma ya da Betonarme olarak inşa edilmiş bir yapının "göçme riski"nin ortaya konabilme... more Yığma ya da Betonarme olarak inşa edilmiş bir yapının "göçme riski"nin ortaya konabilmesi için öncelikle zemin ve malzeme parametrelerinin saptanması; yapının bilgisayar ortamında modellenerek, dolgu duvarların katkısını da göz önüne alabilen deprem yönetmeliğince belirlenmiş analizlerinin yapılması gereklidir. Ülkemizdeki mevcut yönetmeliklerin de öngördüğü bu değerlendirmeyi yapabilmek için öncelikle ayrıntılı deneysel ve analitik çalışmaların gerçekleştirilmesi gerekmektedir. Ancak, çok sayıda bina içeren bir yapı stoğu için böyle bir çalışma yükünü gerçekleştirmek, zaman ve finansman açısından neredeyse olanaksızdır. Envanteri yapılacak yapı stokunun büyüklüğü düşünüldüğünde, olası bir büyük depreme karşı yapı güvenliği ön değerlendirmesi yapılabilmesi amacıyla gerekli veri toplama, değerlendirme işlemleri için harcanacak zaman, ekonomik kaynak ihtiyacının karşılanmasının mümkün olmadığı görülmektedir. Bu nedenle, uygulanabilir, gerçekçi yaklaşımlarla durum tesbiti yap...
Yapı temel sistemlerinin projelendirilmesinde, yapı-temel-zemin üçlüsü arasındaki etkileşimin dik... more Yapı temel sistemlerinin projelendirilmesinde, yapı-temel-zemin üçlüsü arasındaki etkileşimin dikkate alınması, zemine aktarılan yükler nedeniyle zemin tabakalarında oluşan deformasyonların temel elemanı ve üstyapı taşıyıcı sistemindeki iç kuvvetler ve yük dağılımı üzerindeki ...
Bu caly?mada, tersinir yuklere ve momentlere maruz elastic zemine oturan serbest bir kiri?in dina... more Bu caly?mada, tersinir yuklere ve momentlere maruz elastic zemine oturan serbest bir kiri?in dinamik analizi incelenmi?tir. Temel modeli Winkler hipotezine dayalydyr. Yayyly yukler icin belirlenen diferansiyel denklemin kullanylabilmesi amacyyla, kiri?teki tekil deformasyonlar Dirac da?ylym teorisi kullanarak yayyly yuklere donu?turulmu?tur. Caly?mayy acyklamak amacyyla tanymlayycy bir ornek sunulmu?tur ve elde edilen bazy sonuclar tablo ve ?ekillerde verilmi?tir.
In this study, the dynamic analysis of a free beam subjected to transverse forces and moments on ... more In this study, the dynamic analysis of a free beam subjected to transverse forces and moments on an elastic soil are investigated. The foundation model is based on the Winkler hypothesis. Using Dirac distribution theory, concentrated disturbances on beams are transformed to distributed loads in order to be able to use the governing differential equation established for distributed loads. An illustrative example is presented in order to demonstrate the use of the study and some of the obtained results are given in tables and figures.
Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods estimation o... more Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods estimation of modal parameters. The calibrated model in the future can be used to assess the parameters affecting modal parameter estimation therefore accurate damage identification
The seismic performance of steel moment-framed buildings has been of particular interest after th... more The seismic performance of steel moment-framed buildings has been of particular interest after the 1994 Northridge earthquake because brittle fractures were discovered at the beam-column connection. This paper examines the problem of identifying the dynamic character stics of an instrumented building using an input-output system identification method. The building studied was a six-story steel moment-resisting frame (SMRF) instrumented by the California Strong Motion Instrumentation Program (CSMIP). The building was shaken by several earthquakes and strong motion data of the building response was recorded during these earthquakes and were made available through SMIP. The identified modal properties of the structure were compared and verified with the spectral analysis of the response of the structure excited by three different earthquakes.
Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods Civil engine... more Modal Parameter Estimation of Model Steel Bridge Using System Identification Methods Civil engineering structures are exposed to different external effects which change their dynamic characteristics. The fact that damage can alter stiffness, and/or energy dissipation capacity of a structure which in turn results in detectable changes in its vibration signature is the underlying principle of vibration-based structural health monitoring (SHM). An important step of SHM process is the estimation of modal parameters. In this study, modal parameters of a steel bridge are estimated using ERA and NExT-ERA system identification techniques. A calibrated finite element model of the bridge is obtained using the estimated modal parameters. Accurate damage identification of a structure depends on accurate
In earthquake-prone regions, it is still a challenge for predicting seismic resilience of existin... more In earthquake-prone regions, it is still a challenge for predicting seismic resilience of existing building inventory subjected to possible major magnitude earthquakes. This study presents results for pilot project “Establishment of Building Stock Inventory and Seismic Evaluation of Seismic Safety of Buildings” conducted in Balçova and Seferihisar regions in Izmir (Turkey) with the collaboration of Metropolitan Municipality, Dokuz Eylul University and Chamber of Civil Engineers Izmir Branch. For this purpose, construction plans of 10.550 existing buildings were scanned, digitized and evaluated and augmented with field observations. Field evaluations were performed by 84 civil engineers who attended a core training program in Chamber of Civil Engineers and certified after a series of exams prepared by the trainers. It is obvious that required time spent and economic resources to collect the data are not sufficient for. Therefore, a necessity arises for performing rapid screening asse...
The structures are challenged by earthquakes, material degradations and other environmental facto... more The structures are challenged by earthquakes, material degradations and other environmental factors. In order to protect the lives, assets, and for maintenance planning, structural health monitoring (SHM) is important. In SHM applications, strain gages are widely used which have low durability, low sensitivity while they have high cost. To monitor a structure, large number of strain gages have to be used that increases the cost. In this study, seven coal reinforced concrete mixtures with 0, 0.35, 0.5, 0.8, 1, 1.5 and 2 volume % of coal were designed; three cubic samples for each mixture were fabricated. Simultaneous strain and electrical resistance measurement of the samples during the compression test was conducted. A strong linear piezoresistive relationship between strain and electrical resistance change with a correlation coefficient of 0.99 was determined. The concrete mixture having 0.8 volume % coal had the highest strain sensitivity of K=44, which was 22 times the strain sensitivity of commercial metal strain gages while it had a linearity error of LE=6.9% that was low. This mixture with 0.8 volume % coal is a candidate to be smart concrete which can sense its strain. As a contribution to the literature, a phenomenological model for the relationship between gage factor and coal volume % was explained in details. The multifunctional smart concrete will be used as a smart material, which can sense its strain in SHM applications while acting as a load bearing material.
Self-centering braces, in the current stage of development can accommodate large deformation and ... more Self-centering braces, in the current stage of development can accommodate large deformation and force levels. However, there is still a need for improvement of the energy dissipation mechanisms commonly incorporated in these braces. Yield based energy dissipation systems can overcome some of the problems faced with friction-based devices, such as susceptibility to bolt relaxation, long-term creep of friction material and excessive flexing arising in the outer tubes due to friction bolts. However, in these alternative systems multi-wave buckling of the yielding core is present, which is the leading cause of an asymmetric hysteresis of the brace. Hence, in this study, U-shape flexural plates (UFPs) are analyzed as an alternative energy-dissipating device in real scale self-centering braces with a finite element modeling approach. UFP plates yield in flexure and when comparing to direct tension/compression yielding members, they show lower strain demand, resulting in a larger displacement capacity. Implementation of the UFP units in the brace produces a flag shape hysteresis with minimal residual deformation. The proposed system provides some advantages when compared to previous models in terms of increased redundancy, symmetric hysteresis and a more gradual stiffness change.
AbstractThis paper presents modal parameter estimation work on a steel railway bridge at three di... more AbstractThis paper presents modal parameter estimation work on a steel railway bridge at three different temperature conditions using ambient vibration test data. The bridge was built at the end of...
Earthquakes, material deteriorations and other environmental factors challenge the structural saf... more Earthquakes, material deteriorations and other environmental factors challenge the structural safety. In order to protect the lives, structural health monitoring is crucial. The metal foil strain gages have low durability, low sensitivity and can get point wise measurements which are disadvantages. In this study six different concrete mixtures were designed; one without any copper powder, the rest five having different copper powder volume fractions. Three cube samples from each mixture were cast and cured. Simultaneous measurement of electrical resistance and strain were conducted during the compression tests. A strong linear relationship between strain and electrical resistance change was obtained for copper powder reinforced concrete. The results are contribution to the development of “Smart Concrete” which can sense its strain and damage.
International Journal of Concrete Structures and Materials
Post-earthquake observations revealed that seismic performance of beam-column connections in prec... more Post-earthquake observations revealed that seismic performance of beam-column connections in precast concrete structures affect the overall response extensively. Seismic design of precast reinforced concrete structures requires improved beamcolumn connections to transfer reversed load effects between structural elements. In Turkey, hybrid beam-column connections with welded components have been applied extensively in precast concrete industry for decades. Beam bottom longitudinal rebars are welded to beam end plates while top longitudinal rebars are placed to designated gaps in joint panels before casting of topping concrete in this type of connections. The paper presents the major findings of an experimental test programme including one monolithic and five precast hybrid half scale specimens representing interior beam-column connections of a moment frame of high ductility level. The required welding area between beam bottom longitudinal rebars and beam-end plates were calculated based on welding coefficients considered as a test parameter. It is observed that the maximum strain developed in the beam bottom flexural reinforcement plays an important role in the overall behavior of the connections. Two additional specimens which include unbonded lengths on the longitudinal rebars to reduce that strain demands were also tested. Strength, stiffness and energy dissipation characteristics of test specimens were investigated with respect to test variables. Seismic performances of test specimens were evaluated by obtaining damage indices.
The structures are challenged by earthquakes and other environmental factors. Structural health m... more The structures are challenged by earthquakes and other environmental factors. Structural health monitoring is crucial to protect the lives. The strain gages used in structural health monitoring have low durability and can get point wise measurements which limit their use. In this study, five different concrete mixtures with different brass fiber volume fractions were designed. Along with the control mixture which does not have brass fiber, six mixtures were designed and three cube samples from each mixture were cast and cured. Compression test was conducted with simultaneous measurement of electrical resistance. The brass fiber reinforced concrete has strong linear relationship between the electrical resistance change and strain. Important progress was achieved in development of “Smart Concrete” which can sense its strain and damage.
Abstract Moment-resisting beam-column connections including emulative and mechanical components a... more Abstract Moment-resisting beam-column connections including emulative and mechanical components are widely used solutions in precast construction practice. Hybrid connections are constructed by welding of corbel plates to beam end plates where beam longitudinal rebars are welded, and casting of concrete through the designated gaps in beam tops and column elements at site. This study presents the development of a numerical model for hybrid connections to be used to assess seismic performance of multi-storey precast concrete structures. The numerical model includes truss-based elements for beam-column connections and fiber-based elements for beams and columns. Lateral load-drift ratio relations for the measured and computed cyclic responses of a precast connection are compared. In addition, two-dimensional three- and five- storey precast concrete frames are designed for seismic performance evaluation. Frame models are analysed by performing nonlinear static pushover analyses and incremental dynamic analyses with representative ground motions. Response modification factors are obtained and evaluated for seismic design of precast concrete buildings.
Yığma ya da Betonarme olarak inşa edilmiş bir yapının "göçme riski"nin ortaya konabilme... more Yığma ya da Betonarme olarak inşa edilmiş bir yapının "göçme riski"nin ortaya konabilmesi için öncelikle zemin ve malzeme parametrelerinin saptanması; yapının bilgisayar ortamında modellenerek, dolgu duvarların katkısını da göz önüne alabilen deprem yönetmeliğince belirlenmiş analizlerinin yapılması gereklidir. Ülkemizdeki mevcut yönetmeliklerin de öngördüğü bu değerlendirmeyi yapabilmek için öncelikle ayrıntılı deneysel ve analitik çalışmaların gerçekleştirilmesi gerekmektedir. Ancak, çok sayıda bina içeren bir yapı stoğu için böyle bir çalışma yükünü gerçekleştirmek, zaman ve finansman açısından neredeyse olanaksızdır. Envanteri yapılacak yapı stokunun büyüklüğü düşünüldüğünde, olası bir büyük depreme karşı yapı güvenliği ön değerlendirmesi yapılabilmesi amacıyla gerekli veri toplama, değerlendirme işlemleri için harcanacak zaman, ekonomik kaynak ihtiyacının karşılanmasının mümkün olmadığı görülmektedir. Bu nedenle, uygulanabilir, gerçekçi yaklaşımlarla durum tesbiti yap...
Yapı temel sistemlerinin projelendirilmesinde, yapı-temel-zemin üçlüsü arasındaki etkileşimin dik... more Yapı temel sistemlerinin projelendirilmesinde, yapı-temel-zemin üçlüsü arasındaki etkileşimin dikkate alınması, zemine aktarılan yükler nedeniyle zemin tabakalarında oluşan deformasyonların temel elemanı ve üstyapı taşıyıcı sistemindeki iç kuvvetler ve yük dağılımı üzerindeki ...
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