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Sürdürülebilir Kalkınma Amaçları

• 4

• MakaleYalnız künye2025/r/gumushane/12378
  Influences of chord pre-stress on CHS X-joints with high-strength-steel at various temperatures

  Ozyurt, E.; Wang, Y.C.

  This study examines the influence of chord pre-stress on the behaviour and load resistance of Circular Hollow Section (CHS) X-joints with High Strength Steel (HSS) at various temperatures. This investigation uses a total number of seven hundred and four Finite Element simulation results to evaluate the level of accuracy of current Eurocode and CIDECT design guidelines in predicting the high-temperature resistance of these joints. The numerical simulations investigate the effects of changing brace-to-chord diameter (β), chord semi-diameter-to-thickness (γ), and brace-to-chord thickness (τ) ratios, as well as different prestressing levels (np) and temperatures (θ). The γ and τ ratios have a limited effect on the normalised joint strength, but the β ratio, and the prestressing level are highly influential. At ambient temperature, the CIDECT design approach is a more suitable method for calculating the chord pre-stress reduction factors for S355 joints. For HSS X-joints, the constant modification coefficient of 0.80 is inadequate, and this paper has proposed a new modification coefficient as a function of the pre-stress level. At elevated temperatures, the ambient temperature resistance of CHS X-joints can be modified by the reduction factor of the Young's modulus for S355 steel and that of the yield stress for S960 steel.

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• MakaleYalnız künye2025/r/gumushane/11755
  Assessment of Seismic Responses of Square-Hollow-Section Joints in a Lattice Girder with Soil-Structure Interaction

  Ozturk, Kasif Furkan; Ozyurt, Emre; Araz, Onur; Cakir, Tufan

  The fixed base approach is widely used to obtain the seismic behaviour of Square Hollow Section (SHS) joints in a lattice girder. However, in some cases where soil-structure interaction (SSI) can be relatively significant, this approach may result in incorrect acquisition of the natural periods and dynamic responses of the lattice girders using welded tubular joints. This situation may negatively affect the safety of the structure by causing an underestimation of the dynamic loads acting on the structure. Therefore, this study evaluates the seismic behaviour of SHS joints in a typical lattice girder exposed to different ground motions considering SSI. A nonlinear finite element analysis software, Abaqus, performs the dynamic analyses considering six earthquake excitations with three different frequency contents (a ratio of peak ground acceleration (PGA) to peak ground velocity (PGV)) and four different soil types. After verifying the numerical model, it is determined that 3D solid elements should be used to capture the actual seismic behaviour of the tubular joints in a steel truss frame with or without SSI. A comprehensive parametric study is then carried out to evaluate the peak displacement and stress values on the SHS joints with and without SSI under different ground motions with different PGA/PGV ratios. The findings show that the stresses are concentrated around the column and bottom chord connection region. Besides, the SSI mechanism significantly affects the peak stress and displacement values of the SHS joints, especially in soft soil types. Furthermore, it is observed that the PGA/PGV ratio significantly changes the seismic responses of the steel truss frame.

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• MakaleYalnız künye2024/r/gumushane/14291
  Hysteretic behaviour of square-hollow-section T- and X-joints with in-plane bending moment

  Ozyurt, E.; Gunaydin, M.

  This study examined the hysteretic behaviour of Square Hollow Section (SHS) T- and X-joints subjected to cyclic in-plane bending moments. A nonlinear finite element software, Abaqus, was used to investigate SHS T- and X-joint seismic performance. Prior to the parametric study, the numerical model was validated based on the available test results in the literature. A comprehensive parametric study employed validated finite element models to evaluate the influence of critical geometric parameters, including the brace-to-chord width ratio (β) and the chord width-to-thickness ratio (γ). The results of the finite element analyses regarding ductility, flexural strength, and energy dissipation behaviour of SHS T- and X-joints under quasi-static cyclic in-plane bending were evaluated. Based on the hysteretic curves, increasing β generally leaded to higher initial stiffness and moment capacity in SHS joints, considerably reducing joint rotation. Conversely, the joints with larger γ exhibited reduced initial stiffness and moment capacity. Besides, the Eurocode 3 EN1993-1-8 predictions for the ultimate flexural strength of the joints are found to be conservative compared to finite element results. The results also revealed that the SHS T- and X-joints showed satisfactory ductility levels under in-plane bending load. It was observed that the SHS T- and X-joints with high β and low γ are advantageous for absorbing energy under seismic loads. These findings offered valuable insights for the seismic-resistant design of structures incorporating SHS joints, aiding in selecting optimal configurations based on specific performance requirements.

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• MakaleYalnız künye2024/r/gumushane/11418
  Axial resistance of elliptical hollow section K-joints made of high strength steel

  Ozyurt, E.

  The present study examined the axial resistance of welded elliptical hollow section (EHS) K-joints made of high-strength steel (HSS). The axial resistance of EHS K-joints was affected by a range of factors, including the geometrical parameters, orientations, chord pre-stress levels, and the mechanical properties of the high-strength steel grades. This research aimed to investigate the performance of welded EHS K-joints made of HSS under axial loading conditions with or without chord pre-stresses. Finite element analysis was employed for numerical simulations to analyze the nonlinear behaviour of EHS K-joints with HSS. It was observed from the numerical results that the orientation types significantly affected normalised resistance ratios. In contrast, β, γ, θ, and chord pre-stress levels had minimal impact, as comparisons were based on normalised resistance ratios. However, non-dimensional geometric parameters and chord pre-stress levels notably influenced the axial joint resistance of the HSS K-joints. As for predicting the axial resistances of EHS K-joints with HSS, the numerical results indicated that the existing reduction factor might be unsafe for the equivalent RHS method to be applied in the current design guides. Therefore, a new reduction factor was proposed for EHS K-joints with HSS that yield unsafe results.

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• MakaleAçık Erişim2023/r/gumushane/17035
  Eksenel Yüke Maruz Çelik Boru ve Kutu T-birleşimlerinin Yangın sonrası Davranışı

  Ozyurt, Emre

  Bu çalışma, boru ve kutu profillerden oluşmuş kafes sistem T-birleşimlerinin eksenel yük altında yangın sonrası davranışlarını sonlu elemanlar yöntemi kullanarak incelemeyi amaçlamaktadır. Bunu için farklı geometrik özelliklere sahip T-birleşimler sonlu elemanlar programı kullanılarak modellenildi. Öncelikle ısı transfer analizi yapılarak, oluşturulan sayısal modeller ISO 834 yangın eğrisine bağlı olarak ısıtıldı ve sonra soğutuldu. Yangın sonrası artık gerilmelere ve deformasyonlara maruz kalmış birleşimlere, maksimum dayanıma ulaşıncaya kadar örgü elemanı ucundan eksenel yük uygulanıldı. Tüm birleşimlerde göçme sınır durumu başlık elemanı cidarında plastikleşme olarak tespit edildi. Yangın öncesi ve sonrası birleşimlerin dayanımları karşılaştırıldı. Sayısal sonuçlardan elde edilinen bilgilere göre yangın sonrası tübüler T-birleşimlerin dayanımları %23,5 ’a kadar düşmektedir. Ayrıca, birleşimler üzerindeki sıcaklık dağılımları, örgü-başlık eleman oranlarına ve başlık elemanının et kalınlıklarına bağlı olarak değişmektedir. Yangın sonrasında oluşan artık gerilme ve deformasyonlar boru ve kutu T-birleşimlerin dayanımlarına önemli derecede etki etmektedir.

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• MakaleYalnız künye2023/r/gumushane/12622
  A Numerical Study to Evaluate the Changes in Dynamic Properties of Various Steel Truss Types Under Fire Conditions

  Sibil, R.; Ozyurt, E.

  This study numerically examines the changes in dynamic properties of fire-damaged steel trusses made of square hollow sections subjected to uniform and non-uniform heating scenarios. After verifying the numerical models at both ambient and elevated temperatures, a vast number of the simulations were analysed using non-linear finite element software to evaluate the effects of fire scenarios, truss types, and fire-damaged levels on the fire dynamic characteristics of square hollow section Warren, Howe, and Pratt trusses. The results indicated that the natural frequency of steel trusses significantly decreased as the fire-damaged level increased. In the case of local fire, the natural frequencies of the trusses began to drop suddenly at temperatures above 550 °C. Whereas the drop in the natural frequency of the uniformly heated trusses started at even much lower temperature levels. Moreover, the decrease in the natural fundamental frequencies of the uniformly heated trusses was lower than the reduction rate of the modulus of elasticity at high temperatures due to the large non-linear deformations. Since the modification of the stiffness of the truss by simply the reduction factor of the elastic modulus of the steel may be inappropriate to calculate the fundamental frequency of the trusses in the local and global fires, a new method was introduced to calculate the fundamental frequency value of the steel trusses in the fire.

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• MakaleYalnız künye2022/r/gumushane/16712
  A Parametric Study on Earthquake-Damaged Square Hollow Section T-Joints under Fire Conditions

  Ozyurt, E.

  This study numerically investigated the elevated temperature resistance of earthquake-damaged square hollow section (SHS) T-joints subjected to brace axial compressive load. The residual stresses and deformations due to the earthquake were obtained from a pushover analysis. The extensive numerical simulations were analyzed using nonlinear finite-element software to examine the effects of the beta ratio, gamma ratio, damage level ((D) over cap), and initial applied load (n(f)) on the fire resistance of SHS T-joints after verification of the numerical simulations based on the available test results in the literature. The results indicated that the fire resistance of SHS T-joints with axial compressive load in the brace member decreased significantly due to the residual stresses and deformations from the earthquake. This situation worsened in all numerical models as the damage level increased. The reduction rate of the critical temperature at various damage rates was independent of the initially applied load ratio, but the loading rate directly affected the fire resistance of the joint regardless of the earthquake. As the beta ratio decreased, the yielded area at the brace-to-chord intersection region increased. Thus, the critical temperature of the joints at a constant damage level was inversely proportional to the beta ratio. Joints with a large gamma ratio had larger residual stresses and deformations than those of corresponding joints with a small. ratio. Therefore, the fire resistance of the joints after the earthquake decreased as the chord-wall thickness decreased. The critical temperature of the joints with either a large beta or gamma ratio was limited by the deformation limit at high damage levels. The fire resistance of the SHS T-joints after the earthquake decreased due to residual stresses and deformations. That effect increased even more in joints with high beta and. ratios. (C) 2022 American Society of Civil Engineers.

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• MakaleYalnız künye2022/r/gumushane/14442
  Numerical studies on axially loaded doubler plate reinforced elliptical hollow section T-joints

  Saria, Busra; Ozyurt, Emre

  This paper presents results of numerical studies completed on unreinforced and doubler plate reinforced Elliptical Hollow Section (EHS) T-joints subjected to axial compressive loading on the brace member. Non-linear finite element (FE) models were developed using the finite element code, ABAQUS. Available test data in literature was used to validate the FE models. Subsequently, a parametric study was carried out to investigate the effects of various geometrical parameters of main members and reinforcement plates on the ultimate capacity of reinforced EHS T-joints. The parametric study found that the reinforcing plate significantly increases the ultimate capacity of EHS T-joints up to twice the capacity of the corresponding unreinforced joint. The thickness and length of the reinforcing plate have a positive effect on the ultimate capacity of Type 1 joints. This study, however, found that the capacity of Type 1 orientation is not dependent on the brace-to-chord diameter ratio. As for type 2 orientations, the thickness and length of the reinforcement have a minimal effect on the ultimate capacity. A new design method is introduced to predict the capacity of the reinforced EHS T-joints Type 1 and 2 based on the multiple linear regression analyses.

  İncele
• MakaleYalnız künye2021/r/gumushane/11321
  Static resistance of axially loaded multiplanar gap KK-joints of Circular Hollow sections at elevated temperatures

  Wang, Y.C.; Ozyurt, E.

  This paper presents the results of a numerical investigation of the behaviour, and proposes a method to calculate the static resistance of axially loaded Circular Hollow Section Double K-joints (DKK) at elevated temperatures. This type of joints is widely used in building construction, but currently, there is no method to calculate their static resistance at elevated temperatures. The numerical investigations of this paper cover a wide range of design parameters, including brace axial load combination, joint temperature, angles between brace members, longitudinal and transverse gap sizes, chord diameter to thickness ratio and brace diameter to chord diameter ratio. The results of this paper indicate that the ratio of joint elevated temperature resistance to ambient temperature resistance may be lower than the reduction factor for the yield strength of steel at elevated temperatures. There are two joint failure modes, one for small and one for large transverse gap. These failure modes and the demarcation between small and large gaps are independent of joint temperature. For joints with large gap, the ratio of joint resistance at elevated temperature to that at ambient temperature is close to the average of steel yield strength and Young's modulus reduction factors at elevated temperature. For joints with small gap, the joint resistance ratio follows the steel Young's modulus factor variation at elevated temperature if all four braces are under compression, but the trend changes to the average ratio of steel Young's modulus and yield strength reduction factors if the axial brace loads are balanced (compression in two brace members equal to tension force in the other two brace members). Linear interpolation can be applied between these two different loading cases.

  İncele
• MakaleAçık Erişim2020/r/gumushane/17779
  Çok Düzlemli Kaynaklı K-Birleşimlerin Dayanımları

  Ozyurt, Emre

  Boru enkesitli çelik profillerin yaygın olarak kullanılmaya başlanmasındaki önemli sebeplerden biri mimari açıdanestetik görünüme sahip olmaları, diğeri ise mühendislik avantajlarıdır. Bu yüzden, kullanım alanları çok geniştir,örneğin açık deniz yapıları, havaalanları, sergi salonları, köprüler, stadyumlar, vb. Bu tip yapılarda, çok düzlemlikaynaklı K-birleşimlerinden oluşan uzay kafes sistemler kullanılmaktadır. Ancak boru enkesitli profillerden oluşmuş,çok düzlemli kaynaklı K-birleşimlerin tasarım yöntemi, yeni çelik yapı yönetmeliğinde mevcut değildir. Bu çalışmanınamacı, yönetmelikteki düzlem kafes sistemleri için mevcut birleşim yönteminin, çok düzlemli K-birleşimler için uygunolup olmadığını incelemektir. Bu çalışma, doğrusal olmayan sonlu elemanlar yöntemi kullanılarak gerçekleştirilmiştir.Sayısal analizlerden önce sonlu elemanlar modeli mevcut bir test ile karşılaştırılarak doğrulaması yapılmıştır.Doğrulama çalışmasında belirlenen eleman ağ aralığı, eleman tipi, mesnet sınır koşulları ve yükleme yöntemine göre birdizi parametrik çalışma yapılmıştır. Parametrik çalışmalarda, dayanım kriteri, başlık ve örgü elemanlarının geometriközellikleri ve başlık ile örgü elemanı arasındaki açının etkileri incelenmiştir. Sayısal analiz sonuçlarına göre, mevcutyönetmelikteki düzlem K-birleşim yöntemleri aynı zamanda çok düzlemli K-birleşimlerinin dayanımlarını hesaplamakiçin kullanılabilir. Çok düzlemli K-birleşimlerinin dayanımlarını belirlemek için Lu’nun deformasyon sınırlamasıkullanılabilir. Başlık elemanına etkiyen ekstra eksenel yükler birleşimin dayanımını etkileyebilir.

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