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Sustainable soil stabilization using colemanite: experimental and numerical analysis of sandy soils for improved geotechnical properties
(Springer Nature, 2025-06-12) Koçak Dinç, Beste; Dehghanian, Kaveh; Etminan, Ehsan
This paper discusses the use of colemanite, a boron compound, which is a natural additive to geotechnically improved sandy soils, thus providing an eco-friendly alternative to conventional soil stabilization. Clean angular sand was the base material with the addition of colemanite in amounts of 0%, 5%, 10%, and 15% by dry mass. Various laboratory tests, such as Atterberg limits, void ratio, specific gravity, compaction, permeability, and unconsolidated undrained triaxial tests, were carried out to determine the physical and mechanical characteristics of the produced mixtures. Numerical modeling, adopted by the PLAXIS finite element program, was used to carry out simulations under various conditions for soil profiles to determine and compare soil behavior. The findings revealed that the addition of colemanite significantly reduced permeability and void ratios while enhancing stiffness and strength, with 15% colemanite yielding the best performance. This study is one of those that focuses on the introduction of colemanite, which can also act as an effective stabilizer and is a much greener and more environmentally friendly option. Apart from this, it has other advantages both economically and ecologically by reducing the amount of cement, which is a high carbon source required for building based on this. The discoveries bring in the further development of green geotechnical engineering, which also includes the construction of sustainable infrastructures.
Drought analysis based on nonparametric multivariate standardized drought index in the Seyhan River Basin
(Springer Science and Business Media B.V., 2025-05) Terzi, Tolga Barış; Önöz, Bihrat
Drought is a detrimental natural hazard that is a threat to the social and ecological aspects of life. Unlike other natural hazards, drought occurs slowly and gradually, making it difficult to detect its formation, leading to severe consequences in the affected area. Therefore, precise and reliable monitoring of drought is crucial to implement effective drought mitigation strategies. Drought indices are significant tools for drought monitoring; single variable indices are quite frequently used in the literature to assess drought conditions. Although these indices are generally accurate at characterizing the specific type of drought they were developed for, they fail to provide a comprehensive representation of drought conditions. Hence, this study applies a nonparametric multivariate standardized drought index (MSDI) that integrates meteorological and hydrological drought to investigate the dynamics of drought events within the Seyhan River Basin (SRB). Trend analyses were conducted to detect any directional changes in the drought patterns within the SRB. Additionally, this study examined the potential effects of El Nino-Southern Oscillation events on the MSDI series to determine their impact on drought conditions in the SRB. The results indicate that the MSDI outperforms the single variable indices in characterizing drought conditions within the basin. The calculations conducted for 5 different time scales 1, 3, 6, 9 and 12-months showed satisfactory results in multivariate analysis of drought. Upon examining the trend analyses, MSDI series showed an insignificant negative trend in all stations within the SRB. The MSDI series was strongly influenced by Nino 3.4 and Arctic Oscillation (AO) indices while sunspot activities had a relatively weak impact on the MSDI series.
DroughtStats: a comprehensive software for drought monitoring and analysis
(Springer Science and Business Media Deutschland GmbH, 2025-01) Terzi, Tolga Barış; Önöz, Bihrat
The significance of drought monitoring and prediction systems has grown substantially due to the escalating impacts of climate change. However, existing tools for drought analysis face several limitations, including restricted functionality to single-variable indices, reliance on predefined probability distributions, lack of flexibility in choosing distributions, and the need for advanced programming expertise. These constraints hinder comprehensive and accurate drought assessments. This study introduces DroughtStats, a novel, user-friendly software designed to overcome these challenges and enhance drought analysis capabilities. DroughtStats integrates advanced statistical tools to analyze hydrometeorological data, compute both single-variable and multivariable drought indices using empirical and parametric methods, and evaluate drought characteristics with improved accuracy. Notably, it supports a broader range of probability distributions, performs copula-based analyses, and estimates potential evapotranspiration using multiple methods, including Penman–Monteith. Additionally, DroughtStats can analyze the relationship between different datasets using techniques like copula-based Kendall’s tau. By addressing the limitations of existing tools, DroughtStats provides a more flexible and comprehensive approach to drought monitoring. Its versatility and global applicability are demonstrated through a case study in Turkey’s Çoruh River Basin (CRB), where drought indices based on precipitation and streamflow are calculated to characterize drought conditions. The results show that DroughtStats can successfully identify and characterize drought events at various time scales, providing valuable insights into drought severity, frequency, and recovery, and offering a reliable tool for ongoing drought monitoring and management.
Advanced drought analysis using a novel copula-based multivariate index: a case study of the Ceyhan River Basin
(Springer Science and Business Media Deutschland GmbH, 2025-02) Terzi, Tolga Barış; Önöz, Bihrat
Drought is a severe natural disaster that poses significant risks to both social and ecological systems. Detecting drought is challenging due to its gradual development, which makes it difficult to identify and predict, often resulting in significant impacts on the affected regions. Therefore, accurate and dependable monitoring of drought conditions is essential for the development and implementation of effective mitigation strategies. Drought indices play a crucial role in monitoring drought conditions, with single-variable indices commonly employed in the literature to evaluate drought severity. While these indices are typically effective at characterizing the specific type of drought for which they were designed, they often fall short in offering a comprehensive view of overall drought conditions. The multivariate standardized drought index (MSDI) is a comprehensive tool that assesses drought conditions by integrating multiple hydrometeorological variables. Widely employed in the literature in both parametric and empirical forms, the MSDI is recognized for its effectiveness in detecting drought in an integrated manner. This study focuses on a particular challenge related to the calculation of MSDI using copula families. The novel methodology introduced in this paper involves selecting the most suitable copula family for each data subset using AIC and BIC criteria. Rather than applying a single copula family to the entire dataset, this approach utilizes multiple copula families for different subsets, thereby ensuring optimal modeling for each distinct group of data. The Ceyhan River Basin (CRB) is used as a case study to apply the proposed methodology. The drought characteristics of the basin are analyzed using both the newly developed MSDI and conventional single-variable indices, and the performance of the new methodology is evaluated. The application of this approach in the CRB demonstrated its effectiveness in identifying both concurrent and isolated occurrences of meteorological and hydrological droughts, thereby facilitating a more integrated and precise assessment of drought characteristics. Results indicated that the proposed MSDI detected drought events that were overlooked by single-variable indices and improved classification accuracy over the conventional MSDI.
Drought analysis in the Seyhan River Basin based on standardized drought indices using a new approach considering seasonality
(Springer Science and Business Media Deutschland GmbH, 2025-01) Terzi, Tolga Barış; Önöz, Bihrat
Drought is a significant natural disaster with adverse effects on both social and ecological systems. Unlike other natural disasters, drought develops slowly and gradually, complicating its early detection and often resulting in severe impacts on affected regions. Consequently, accurate and dependable drought monitoring is essential for devising effective mitigation strategies. Standardized drought indices are vital tools in drought monitoring, providing a means to quantify and characterize drought events. Most standardized drought indices utilize the Standardized Precipitation Index (SPI) method, which is valued for its simplicity and flexibility. However, this study contends that the SPI method lacks several critical elements, particularly in practice, such as determining the most suitable probability distribution for hydrometeorological variables. Therefore, this study proposes a novel methodology for calculating standardized drought indices and assesses its performance against conventional and nonparametric standardized indices, employing various methods capable of capturing complex dependencies. The novel methodology involves identifying the best-fit probability distributions for each data group through various goodness-of-fit tests. This approach ensures that each group is modeled optimally, considering the seasonal variations inherent to each group. The Seyhan River Basin has been chosen as a case study for the proposed methodology. The drought characteristics of the basin are analyzed using indices derived from the new methodology, the conventional SPI method, and the nonparametric method. Additionally, trend analyses were performed on the calculated indices to identify any directional changes in drought patterns within the Seyhan River Basin. The performance of the proposed methodology was evaluated by analyzing its relationship with nonparametric standardized indices and comparing it to the relationship between conventional standardized indices and nonparametric standardized indices. The results show that the newly proposed methodology outperforms the conventional SPI method across various dependence measures, suggesting it captures the underlying data structure more effectively than the SPI method.
Seyhan Havzası’nda düşük akımların analizi
(Balıkesir Üniversitesi, 2025-07-15) Baysal, Selman; Yılmaz, Selahattin Utku; Kaçar, Furkan Sencer; Önöz, Bihrat
Bu çalışmada Seyhan Havzası’nda yer alan istasyonlarda düşük akım analizi gerçekleştirilmiştir. Bu doğrultuda kısa, orta ve uzun vadeli kuraklık tespiti için d = 1, 7, 10 ve 15 günlük yıllık ortalama minimum debi değerleri kullanılarak düşük akım frekans analizi yapılmıştır. İki parametreli Log-Normal (LN2), Gamma (G2), Weibull (W2), Üstel (E2), Gumbel (GEV-I), Lojistik (L2) dağılımları ile üç parametreli GEV (GEV-III), Log-Normal (LN3), Pearson Tip III (P3), Log-Pearson Tip III (LP3) ve Genel Lojistik (GL3) dağılımları kullanılarak farklı dönüş aralıklarına sahip düşük akım tahminleri gerçekleştirilmiştir. Kolmogorov-Smirnov (K-S) uygunluk testi ile farklı istatistiksel dağılımların mevcut zaman serilerine uygunluğu tespit edilmiştir. Elde edilen düşük akımlardaki eğimin (trend) belirlenmesi için Mann-Kendall (MK), Trend-Free PreWhitening (TFPW) ve yenilikçi trend analizi (ITA) testleri uygulanmıştır. Çalışmada altı farklı istasyon ölçümleri kullanılarak elde edilen bulgular, Seyhan Havzası’nda en iyi tahminlerin LN2, P3, GEV-III ve LN3 dağılımları ile elde edildiğini göstermiştir. Seçilen anlamlılık düzeyinde üç istasyonda azalan trend bulunmuş olup, anlamlı bir trend tespit edilemeyen diğer istasyonlarda ITA testleri ile azalan bir eğilim belirlenmiştir. Elde edilen bulgular doğrultusunda, bu istasyonlarda özellikle son 10-15 yıllık süreçte ölçülen debilerin önemli miktarda azaldığı ve dolayısıyla küresel iklim değişikliği de göz önüne alındığında kuraklık riskinin olabileceği sonucuna ulaşılmıştır.
Structural analysis of steel truss and masonry bridge interaction: a case of Ali Fuat Pasha bridge in Sakarya, Türkiye
(2023-10-02) Akşar, Bora; Özdemir, Muhammed Alperen; Tutar, Ali İkbal; Çakır, Ferit
Restoration of historical structures using new materials and techniques is widespread worldwide. In these applications, relatively new materials such as steel, concrete, reinforced concrete (RC), or composite are generally preferred. However, it is often ignored whether old materials and new materials work in compatibility. In this respect, Ali Fuat Pasha Bridge (or Bayezid II Bridge), which was built by Bayezid II in 1495 over the Sakarya River in Geyve-Sakarya, was examined. The bridge is 196.50 meters long and consists of 15 arches with different spans and three arches of the bridge were destroyed as a result of the earthquake. Then, the bridge has been restored by constructing a steel truss system in place of the destroyed arches. Within the scope of this study, the structural performance of the bridge, which is currently serving vehicle and pedestrian traffic, is examined by using finite element analyses (FEAs). Moreover, this research examines the combined behavior of steel and masonry materials and investigates the structural behavior of steel truss and masonry bridge interaction. According to the results of the analyses, there are significant behavioral differences between the masonry structure and the steel structure. The main cause for this disparity is thought to be the varying levels of stiffness and ductility in steel and masonry sections.
A point cloud filtering method based on anisotropic error model
(John Wiley and Sons Inc, 2023-12) Özendi, Mustafa; Akça, Devrim; Topan, Hüseyin
Many modelling applications require 3D meshes that should be generated from filtered/cleaned point clouds. This paper proposes a methodology for filtering of terrestrial laser scanner (TLS)-derived point clouds, consisting of two main parts: an anisotropic point error model and the subsequent decimation steps for elimination of low-quality points. The point error model can compute the positional quality of any point in the form of error ellipsoids. It is formulated as a function of the angular/mechanical stability, sensor-to-object distance, laser beam's incidence angle and surface reflectivity, which are the most dominant error sources. In a block of several co-registered point clouds, some parts of the target object are sampled by multiple scans with different positional quality patterns. This situation results in redundant data. The proposed decimation steps removes this redundancy by selecting only the points with the highest positional quality. Finally, the Good, Bad, and the Better algorithm, based on the ray-tracing concept, was developed to remove the remaining redundancy due to the Moiré effects. The resulting point cloud consists of only the points with the highest positional quality while reducing the number of points by factor 10. This novel approach resulted in final surface meshes that are accurate, contain predefined level of random errors and require almost no manual intervention.
An experimental study on RC beams shear-strengthened with Intraply Hybrid U-Jackets Composites monitored by digital image correlation (DIC)
(Elsevier Ltd, 2023-08-22) Çakır, Ferit; Aydın, M. Raci; Acar, Volkan; Aksar, Bora; Akkaya, Hasan Cem
Reinforced concrete (RC) beams are commonly strengthened using steel stirrups, but these materials have limitations such as added weight and susceptibility to corrosion. Fiber-reinforced polymers (FRPs) offer a promising alternative to steel stirrups with high mechanical performance, low density, and resistance to corrosion and chemicals. In particular, Intraply Hybrid Composites (IRCs), which comprise multiple fibers oriented in different directions within a single matrix, have recently gained attention in the construction industry. Cakir et al. [1] investigated the use of three types of IRCs (Aramid-Carbon (AC), Glass-Aramid (GA), and Carbon-Glass (CG)) for strengthening 2-meter-long RC beams (the ratio of shear span (a) to effective depth (d) equals 3 (a/d = 3)) against shear fractures. In this study, the effects of these IRCs on the shear strength of 1.5-meter-long RC beams (a/d = 2) without transverse reinforcement were examined. In this scope, four-point bending tests were conducted on the beams after U-shaped IRC strengthening, and the impact of IRCs on shear strength was evaluated using both digital image correlation and classical measurement equipment such as strain gauges and linear variable differential transducers. The maximum load measured in RC1.5 was 194.50 kN, while the ultimate load capacity reached 265 kN in AC1.5, 246 kN in GA1.5, and 229 kN in CG1.5 after strengthening, representing increases of 36%, 26%, and 18%, respectively, compared to RC1.5. Additionally, the maximum mid-span deflections were determined as 30.40 mm, 16.10 mm, 22.20 mm, and 36.40 mm for RC1.5, AC1.5, GA1.5, and CG1.5, respectively. Moreover, the experimental results were compared with the predictions obtained from the international codes. It should be noted that the failure modes of RC beams are directly affected by the type of IRCs used, highlighting the significant contribution these materials can make to the structural behavior of RC beams.
A novel nonlinear frequency modulated chirp signal for synthetic aperture radar and sonar imaging
(Millî Savunma Üniversitesi, 2016-01-20) Bayındır, Cihan
In order to maintain average power levels as well as high range resolution, phasecoded signals are used in radar and sonar signal processing. One of the most commonly used phase-coded signals is the linear frequency modulated chirp waveform. Various nonlinear frequency-modulated chirps are offered as alternatives to linear frequency modulated chirp. In this paper a new nonlinear frequency modulated chirp waveform is proposed. Properties like bandwidths, point spread functions and Fourier transforms are given for the proposed chirp signal. Synthetic imagery for spotlight imaging geometry is reconstructed by using the polar format and Stolt format processing techniques using the linear frequency-modulated (LFM) and proposed nonlinear frequency modulated chirp. Comparisons are presented, and it is shown that proposed waveform can improve the sonar image resolution.
Determining pull-out deformations by means of an online photogrammetry monitoring system
(Cem Gazioğlu, 2015-03-02) Avşar, Emin Özgür; Altan, Mehmet Orhan; Doğan, Ünal Anıl; Akça, Devrim
Chemical anchorages are applied in many engineering implementations, particularly strengthening of reinforced concrete structures. During strengthening procedure; chemical anchorages should be tested, since they supply to transfer the load between existing construction elements and newly added elements. Therefore; the study of the quality of chemical anchorages is an important issue in construction materials science. In this context; the most important experiment is to determine the pull-out loads of embedded anchorage reinforcement by applying axial loads. In this study; it is aimed to determine the displacements of steel reinforcements, embedded into concrete by using chemical anchorages, while applying axial pulling loads. In order to determine the displacements and load - deformation graphs; starting conditions and every 10 bar pressure applied conditions of the steel reinforcements were captured by the cameras. The obtained images were evaluated by using photogrammetric software. Based on the photogrammetric post-processing results, the load - deformation graphs were plotted and the loads at loss of adhesion were determined.
Examination of delay and travel time at highway toll booths using a micro simulation program: example of Northern Marmara Highway Kurnaköy
(2022-04) Özdemir, Ümitcan; Gürsoy, Mustafa; Aksoy, Göker
The aim of this study is to reveal that barrier toll booths are inefficient in terms of delay and travel time when compared to non-barrier toll booths. In our study, Kurnaköy toll booth, on the Northern Marmara Highway, was examined. The toll booth was modeled using the PTV Vissim micro simulation program. Currently, 8 toll booths are in active service and are operated with barriers. As an alternative to the current operation, 4 different operations were modeled: 8 toll booths without barriers, 10 toll booths without barriers, 12 toll booths without barriers and finally 4 toll booths with free passage system. The designed models were run under 3 different demand levels as low, medium and high, and compared using the PTV Vissim program. When the current barrier toll booth and the non-barrier operations were compared with medium demand, it was seen that there is a significant difference in delay. A bottleneck problem was also encountered due to the geometry of the barrier-free toll booth operation. The optimum operation was found by comparing the alternative operations.
Direct usage of occupancy data for multiregime speed-flow rate models
(American Society of Civil Engineers (ASCE), 2023-01) Aksoy, Göker; Öğüt, Kemal Selçuk
Early macroscopic traffic flow models were based on observations of volume, speed, and density. The invention of traffic sensors has supplied a wealth of data for the development of more accurate macroscopic flow models. However, traffic sensors typically collect volume, speed, and occupancy data. Researchers prefer to convert occupancy to density because of the density usage in earlier models; however, for this conversion, the average length of passed vehicles must be determined. This length is frequently estimated by researchers. However, because the explanatory variable (density) is not observed but produced, this estimation weakens the model results. Considering these challenges, this research proposes a novel traffic flow modeling approach based on occupancy. The proposed method was tested in three speed-flow rate relationship regions, one of which is congested and two of which are free flow. Free flow speed, capacity, queue discharge flow, breakpoint flow rate, and optimum speed can all be determined more precisely with this method. Furthermore, the nonlinear relationship between speed and flow rate was clarified. The proposed traffic flow model is extremely useful, especially for dynamic traffic management applications, because it is based on directly gathered data such as volume, speed, and occupancy.
Identification of sensor location and link flow reconstruction using turn ratio and flow sensors in an arterial network
(Taylor and Francis Ltd., 2024) Taşcıkaraoğlu, Fatma Yıldız; Aksoy, Göker
In this article, a quadratic programming problem is considered to identify all link flows in an arterial network when there are unmeasured link flows. A graphical method is provided to determine the minimum number of measurements and sensor locations required to obtain a fully observable model. It is shown that this method is also valid for the augmented graph with turn ratio measurements. If the minimum measurements required are met, a fully determined network can be obtained. If there is not enough measurement, a bound on the magnitude of the resulting inaccuracy in terms of vehicle kilometers traveled (VKT) can be calculated by the proposed linear programming method. The model is that of a queueing network; the parameters describe network geometry, saturation flow rates, turning ratios, timing plan and link flows. Three case studies are conducted to validate this approach. The first two cases are to calculate all missing flows by using a few numbers of measurements and minimum number of measurements required, respectively. Upper and lower bounds in terms of VKT are also calculated for these cases. Third case is to obtain a fully determined network with the minimum number of flow measurements when turn ratio sensors are included. Real measurements are collected from a network in Mugla including 55 links and 16 intersections. Vissim simulator is used to analyze the accuracy of the link flow calculations obtained from the proposed method. The results show that the proposed programming method can calculate the missing flows with a high accuracy and short computation time.
Effectiveness of standalone simulation-based optimization software in optimizing the life cycle cost of residential buildings
(Dynamic Academy Yazılım İnşaat San. Tic. Ltd. Şti., 2021-12) Yiğit, Sadık; Ozorhon, Beliz
Designers aim to build nearly zero energy buildings and positive energy buildings to comply with regulations. However, due to many variables affecting the energy performance of buildings, energy-efficient building design is a challenging task. Among the proposed methods, simulation-based systems are promising. The proposed simulation-based systems are not suitable for the construction sector because of the long optimization periods. The primary goal of this study is to emphasize the necessity of standalone software packages in solving usability problems and to provide a tool for designers and architects to incorporate into their daily works. To demonstrate the advantages of standalone software a test study was conducted to find a cost-optimal configuration for a typical residential building. In addition, the obtained cost-optimal design was compared to the energy-optimal design obtained in previous studies and it was seen that the outcomes are in parallel with the results of previous studies. It was observed that the optimum insulation thickness obtained from the case study is significantly higher than the limiting values in the national regulation. The results of the parametric analysis demonstrated that wall type, window area, and window type have the highest influence on thermal performance. The results of the study have confirmed that stand-alone software performs optimizations faster overcomes the shortcomings of simulation-based optimization systems comprising integrated multiple software packages.
Analysis of the benefits, challenges and risks for the integrated use of BIM, RFID and WSN: a mixed method research
(Emerald Group Publishing Ltd, 2023-07-11) Seyis, Senem; Sönmez, Alperen Mert
Purpose The purpose of this study is to identify, classify and prioritize the benefits, challenges and risks for the integrated use of building information modeling (BIM), radio frequency identification (RFID) and wireless sensor network (WSN) in the architecture, engineering, construction and operation (AECO) industry. Design/methodology/approach This study relies on the mixed method approach which consists of systematic literature review, semistructured interviews and Delphi technique. A systematic literature review was performed and face-to-face semistructured interviews with seven subject matter experts (SMEs) were conducted for identification and classification purposes. Delphi method was applied in two structured rounds with eleven SMEs for prioritization purpose. These three research techniques were chosen to reach the most accurate data by combining different perspectives on the subject matter. Data gathered by these three methods was triangulated to increase the validity and reliability of this research. Findings Thirteen benefits, ten challenges and four risks for the integrated use of BIM, RFID and WSN were identified. The results could aid the practitioners and researchers comprehend the pros and cons of this integration by representing SMEs' valuable insights and perspectives about the current and future status, trends, limitations and requirements of the AECO industry. The identified risks and challenges show the requirements for future studies while the benefits demonstrate the capabilities and the potential contributions of this hybrid integration to the AECO industry. Originality/value The integration of BIM, RFID and WSN is still not commonly implemented in the AECO industry. Some studies focused on this topic; however, none of them reveals the benefits, risks and challenges for integrating BIM, RFID and WSN in a holistic manner. This research makes a significant contribution to the AECO literature and industry by uncovering the benefits, challenges and risks for the integrated use of BIM, RFID and WSN that could increase industry applications.
Investigation of the relationship between upstream and on-ramp flows at downstream capacity level on Istanbul freeway merges
(Muğla Sıtkı Koçman Üniversitesi Fen Bilimleri Enstitüsü, 2021-03-04) Aksoy, Göker; Öğüt, Kemal Selçuk
Traffic congestion usually occurs at freeway merges due to the inequality of lane numbers at upstream and downstream. The freeway entry, defined as on-ramp, is the main cause of this irregularity and in order to clarify its effect, three freeway merges are investigated in this study with macroscopic flow parameters where a variety of geometric properties are present. In each merge, when the capacity flow is achieved at downstream, the on-ramp and upstream flows are determined and the relationship between upstream flow rate and ‘on-ramp ratio’, which is calculated by dividing the on ramp flow rate to the sum of on-ramp and upstream flow rates, is investigated. An inverse relationship is determined between total upstream flows (upstream flow plus on-ramp flow) with respect to on-ramp ratio. As a result, the merge with one lane drop and three-lanes at downstream seems to be least influenced type while the merge with two lanes drop and four lanes at downstream is the highest. For the former, 1% increase in on-ramp ratio causes a reduction of 20 pcu/h/lane on sum of total upstream flows while for the latter 26 pcu/h/lane. It is seen that the term on ramp ratio, can be quite useful variable for establishing capacities of freeway merges with the help of upstream and on-ramp traffic demands.
Strengthening of reinforced concrete beams without transverse reinforcement by using intraply hybrid composites
(Elsevier Ltd, 2021-12) Çakır, Ferit; Acar, Volkan; Aydın, Muhammet Raci; Akşar, Bora; Yıldırım, Pınar
Concrete is currently among the most widely used materials all around the world. The main advantages of concrete include durability, versatility, and high compressive strength, but significant disadvantages include low tensile strength, low shear strength, and low ductility. To eliminate these disadvantages, longitudinal and transverse reinforcements are usually preferred. Steel is widely used as a reinforcement material in the world, but there is still research underway to find alternative materials. In recent decades, composite materials have been used to reinforce concrete instead of steel materials. This study focuses on Intraply Hybrid Composites (IHCs), which are had an important place in the composite industry and examines how these composites affect concrete beams as far as their shear strength is concerned. For this purpose, A length of 2 m RC beams, with no transverse reinforcement (RC2.0), is prepared and then reinforced with three IHCs, Aramid-Carbon (AC2.0), Glass-Aramid (GA2.0) and Carbon-Glass (CG2.0). After U-shape strengthening, the specimens are inspected in four-point bending tests and the effects of the IHCs are investigated on the shear strength of the beams. The experimental results show that there is an increase of 4.36%, 10.62%, and 15.28% in the ultimate load capacity of AC2.0, CG2.0, and GA2.0, respectively, compared to reference specimen, RC2.0. Furthermore, the type of hybrid composite has a direct impact on the failure modes of the RC beams. Consequently, the IHCs can provide a significant contribution to the structural behavior of RC beams.
Improvement of seismic performance of precast frames with cladding panels fastened by energy dissipative steel cushions
(Springer, 2021-09) Özkaynak, Hasan; Khajehdehi, Arastoo; Yüksel, Ercan; Karadoğan, Hüseyin Faruk
Precast reinforced concrete panels are commonly used as wall claddings in precast buildings. The cladding panels are generally evaluated as non-structural members and are joined to structural systems via mechanical, welding, and bolted dry connections. Several failures were observed in the last seismic events in Southern Europe, which demonstrate the deficiencies of the cladding connections in terms of strength and ductility. A comprehensive research activity named SAFECLADDING was conducted in Europe to provide knowledge for proper seismic design of precast structures with cladding panels. In this context, energy dissipative steel cushions were developed and evaluated through the extensive experimental and numerical studies. Steel cushions can provide robust interaction of the structural system with the cladding panels. This paper numerically evaluates the effects of cladding panels with steel cushions on the global seismic behaviour of the buildings. An existing representative industrial building is selected to perform intensive nonlinear dynamic analyses. Analyses performed on the bare and hybrid systems showed that the hybrid system has high performance in terms of story drifts, internal forces, and deformations with respect to the bare system. The overall drifts in longitudinal and transversal directions of the building are reduced by about 78 and 54%, respectively. Average residual drifts of cladding panels and steel cushions indicated that the applied steel cushion placement scheme has a promising re-centring capability during seismic action.
A split-step Fourier scheme for the dissipative Kundu-Eckhaus equation and its rogue wave dynamics
(Işık University Press, 2021-01) Bayındır, Cihan; Yurtbak, Hazal
We investigate the rogue wave dynamics of the dissipative Kundu-Eckhaus equation. With this motivation, we propose a split-step Fourier scheme for its numerical solution. After testing the accuracy and stability of the scheme using an analytical solution as a benchmark problem, we analyze the chaotic wave fields generated by the modulation instability within the frame of the dissipative Kundu-Eckhaus equation. We discuss the effects of various parameters on rogue wave formation probability and we also discuss the role of dissipation on occurrences of such waves.

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