13 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 10 / 13
Yayın Comparison study on the effect of diaphragm types and slab voids on planner irregular asymmetrical structures using time history analysis(Işık Üniversitesi, 2022-09-06) Aldaddou, Amin Ammar; Umut, Önder; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıIn the past years plan-irregular structures with different diaphragm types have been limitedly studied regarding their seismic performance using nonlinear static procedures, which limited the application of those methods to existing irregular structures. In this study, the effect of gap existing and flexibility in the diaphragms on asymmetrical irregular structures is studied by free vibration analysis, equivalent lateral force method, and nonlinear time history analysis approach using 11 different earthquake records comparing two two-story similar steel structures, one with rigid diaphragm for both stories, and the other with flexible diaphragm in the second story and a large void in its second story slab. Both are irregular structures with re-entrant corner. It is found that the existence of the large void and diaphragm flexibility affect the period and natural frequency of the structures, increase the joint displacements and joint drifts, increase the base shear, increase the internal forces in beams and columns significantly specially in the critical places such as re-entrant corners. So overall, the study showed that irregular structures can be highly influenced and dramatically change its behavior when the existence of voids in the diaphragms, and when the diaphragms act as flexible diaphragm rather than rigid diaphragms.Yayın Seismic performance assessment of a post tensioned box girder viaduct(Işık Üniversitesi, 2022-01-31) Arslanboğan, Emir; Umut, Önder; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıIn the 1999 Marmara earthquakes (Kocaeli and Düzce earthquakes), some of the existing bridges and viaducts were completely or partially destroyed and the earthquake performance of the existing bridges and viaducts began to be questioned. Evaluating the seismic performance of existing structures is one of the most important preliminary steps before seismic retrofitting of structures, as well as a way to validate the analysis and design specifications. The subject of this study is the seismic performance evaluation of the Molla Gürani Viaduct, located in front of the Elmalı Dam on the TEM (O-2 highway) in Istanbul, according to the Turkey Bridge Earthquake Code published in 2020 and its annexes. First of all, all kinds of information, documents, projects, reports and test results related to the viaduct were examined, analyzed and tried to be verified. It has been tried to obtain healthy information about the current situation of the viaduct by making visual inspections in the region where the viaduct is located. The seismic performance assesment of the existing viaduct were made with the Nonlinear Time History Analysis method described in TBEC 2020. The three dimensional model of the viaduct was prepared using the SAP2000 software. The moment-curvature relationship of the sections were determined with the XTRACT section analysis program, using the axial loads obtained from the non-linear static analysis results performed under non-seismic loads. The cracked section stiffnesses and other section properties were modified before dynamic analyses. Due to the large stirrup spacing in the columns, unconfined concrete properties were used in the moment-curvature analyses. The bending cracked section stiffnesses of each column were calculated separately and included in the model. The nonlinear behavior has been tried to be characterized by the acceptance of lumped plastic hinges. For each of the pier columns, 2 plastic hinges in both directions are defined in the foundation-column junction area and just below the 1.4 m solid part at the top end of the columns. The Nonlinear Time History analyses was carried out using 7 earthquake records selected by considering earthquake magnitudes, fault distances, source mechanisms and local ground conditions compatible with DD1 and DD2a earthquake ground motion levels defined in TBEC-2020 Chapter 2. Selected ground motion records are scaled according to TBEC-2020 Section 2.5. As a result of the existing situation analysis of the viaduct, it has been observed that the deformations occurring in the elastomeric bearings in the longitudinal and transverse directions for the DD-1 Earthquake Ground Motion Level are higher than the values allowed in the TBEC-2020 section 5.4.5.1. The fact that the superstructure is continuous and that it is anchored to the abutment by tie bars eliminates the possibility of falling off the support in the longitudinal direction. As a result of possible ruptures that may occur because of high deformations in elastomeric bearings, elastomeric bearings may not fulfill their function. In this case, the viaduct superstructure beams are likely to be free in the transverse direction and may pound each others under the effects of earthquakes, despite the 1.50 m gap between them. In the seismic performance evaluation analyses of the viaduct, it has been determined that the shear keys on the abutments do not have the capacity to meet the earthquake loads. In the observations made in the field, it is seen that macro cracks are formed in the shear keys on the abutments. Limiting elastomeric bearings deformation and strengthening shear keys before a possible Istanbul earthquake in the Molla Gürani viaduct are among the some of the most important precautions to be taken immediately before an earthquake.Yayın Analyzing the freeway capacity and examining the improvements via connected and autonomous vehicles(Işık Üniversitesi, 2022-09-05) Küçükoğlu, Berkcan; Aksoy, Göker; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıTechnology is getting better and improving each and every day. Transportation systems are getting smarter and more tolerant of human errors. In the near future, it won't be surprising to see autonomous vehicles on our roads. However, this can not happen in one night and there will be a transition phase where conventional and automated vehicles will coexist. Connected vehicle technology will provide many opportunities. Reduced accident rates, reduced emissions, reduced parking requirements, reduced congestion and reliable journeying times are some of these advantages. Micro simulations have been broadly adopted for many evaluations, and there are serious challenges that should be answered. In this regard, simulation model calibration and validation are crucial for evaluating the potential improvements offered by connected car technology. In this research, possible changes happening on the freeway merge sites through the usage of connected vehicle technology tried to be investigated by using a VISSIM simulation model that meets current peak capacities. As a result of the experiments and investigations, it has been found that, when compared to traffic with only conventional vehicles, the vehicle capacity in the research area increases by an average of 5% for every 10% increase in autonomous vehicles. Additionally, it was shown that penetration rates up to 40% had the best results, outperforming all other percentages by a considerable margin. To conclude, the addition of autonomous vehicles for the enhancement of effective traffic management made a significant improvement to the transportation study. However, additional studies and applications of the same logics with various models is advised to improve future studies.Yayın Comparative study for earthquake performance of steel buildings with seismic isolator and fixed based steel buildings with damper(Işık Üniversitesi, 2022-01-28) Abdi, Abdullahi Abdiaziz; Umut, Önder; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıEarthquake causes huge loss of lives and enormous damages to properties every year. In order to understand and avoid such damages, different types of seismic isolators have been used. To get the optimal and effective types of seismic isolators, a comparison study of three same-sized 12-storey steel buildings with conventional steel braced frames, and lead rubber bearing (LRB) fixed-based with fluid viscous dampers (FVD) is conducted and their seismic performance enhancements are evaluated using SAP2000 software. Researchers suggest that the seismic isolator building can survive seismic agitation behaviors such as uplifts, stress against ruptures, shears, cracking and displacements. In the study, three same-sized steel structures with different seismic isolator models, special moment and concentric moment frames of all three structures (SMF and SCBF) respectively, earthquake location (Kocaeli Turkey, Yarimca, 8/17/1999) have been selected, performing non-linear time history analysis, non-linear evaluation of dynamic behavioral building response spectrum analysis under load varying time function and design parameters are conducted. As a result of this study, conventional buildings, lead rubber bearing buildings and fluid viscous damper building storey displacement, inter-storey drifts, mode shape, shear force, axial force, base shear, and time history analysis for nonlinear dynamic structural responses are evaluated and compared with the conventional, lead rubber bearing and fluid viscous damper building, according to American Institute of Steel Construction (AISC 360-16).Yayın The statistical analysis of the relationship between particulate matter with traffic and meteorological parameters(Işık Üniversitesi, 2023-06-07) Panhwar, Mehran; Kesten, Ali Sercan; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıParticulate matter (PM) pollution has become a pressing concern due to its detrimental effects on human health and the environment. Understanding the relationship between PM and meteorological parameters, as well as the impact of traffic, is crucial for effective pollution control strategies. This thesis aims to analyze these relationships by employing an Ordinary Least Squares (OLS) regression model for PM1.0, PM2.5, and PM10 concentrations. A comprehensive dataset of PM measurements, meteorological data, and traffic-related variables is collected from various monitoring stations over a specific time period. Meteorological parameters such as temperature and wind speed, are obtained from corresponding meteorological stations, while traffic data includes vehicle counts and road characteristics. The initial analysis reveals significant associations between PM concentrations, meteorological parameters, and traffic impact. The OLS regression model is used to investigate the individual and combined effects of meteorological variables and traffic on PM levels. The results show that temperature, highway traffic and wind speed changes the PM concentrations, indicating that higher temperatures and traffic contribute to increased PM1.0, PM2.5, and PM10 levels. Wind speed demonstrates a negative correlation, suggesting that higher wind speeds are associated with lower PM concentrations due to dispersion effects. Furthermore, the model reveals that traffic-related variables, significantly influence PM pollution, with increased traffic leading to higher PM concentrations. The findings of this study provide valuable insights into the complex relationships between PM pollution, meteorological parameters, and traffic impact. These finding can assist policymakers and environmental agencies in formulating targeted measures to mitigate PM pollution, such as implementing traffic management strategies and improving urban planning. Moreover, the OLS regression model developed in this study can serve as a useful tool for predicting PM levels based on meteorological conditions and traffic patterns, facilitating proactive pollution control efforts.Yayın On some of the factors influencing the engineering properties of improved clayey soils(Işık Üniversitesi, 2022-07-04) Göçkün, Beste Seyla; Etminan, Ehsan; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıAlternative materials and techniques are constantly being investigated within the scope of innovative solutions for the construction of earth structures. Improvement of soft soils for the structures, such as subgrades of highway embankments and shallow foundation soils, can be critical for implementing sustainable and economic applications, especially in the cases where alternative materials are used in soft soils. During this thesis, the high plasticity clay was mixed with class C fly ash which is a recycled material, and two different synthetic fibers in order to stabilize clayey soil. Furthermore, fly ash combined with each copolymer and polypropylene fiber was added to the high plasticity clay to observe more effective improvement. In this thesis, findings from both laboratory and numerical analysis executed with particular emphasis on the use of mentioned alternative materials were represented. First, the compaction and unconfined compression tests were performed on all mixtures. On the other hand, the influence of adding alternative materials to high plasticity clayey soil was studied from analytical aspects by modifying and suggesting new versions of the Duncan-Chang hyperbolic model for the unconfined compression test results. After gathering the unconfined compression test results of mentioned mixtures, the initial tangent modulus (Ei) and the tangent modulus at half of the maximum stress (Et50) were found using the modified Duncan-Chang model. Then, the secant modulus at failure point (Esf) and the secant modulus at half of the maximum stress (Es50) were determined by suggested new equations in terms of the initial tangent modulus and the tangent modulus at half of the maximum stress. The relationship between each soil moduli and the unconfined compression strength of all tested samples were also presented. Finally, obtained soil moduli values of high plasticity clay mixtures improved that mentioned alternative materials and increased the strength and load-deformation properties of high plasticity clayey soil with different percentages.Yayın Comparison between Turkish and Jordan standards from geotechnical earthquake engineering aspects(Işık Üniversitesi, 2024-01-31) Hawa, Shafeeq Mohammad; Etminan, Ehsan; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans ProgramıThis thesis focuses on a comparative analysis of geotechnical earthquake engineering standards in Turkey and Jordan. The importance lies in ensuring that these standards are safe and economically viable, meeting each country's specific geotechnical and ground motion requirements. The study comprehensively examines both nations' earthquake and ground motion characteristics, reviewing relevant papers. The research is organized into six chapters, including recommendations. The thesis delves into the evolution of standards in both countries, considering feedback from researchers and the impact of past earthquakes on human life and infrastructure. It also explores the geotechnical earthquake phenomena resulting from earthquakes, such as landslides and liquefaction. The study reveals differences in codes due to variations in geological conditions, soil properties, and seismic locations. However, it also identifies noteworthy similarities. Additionally, the research analyzes the impact of earthquakes on soil by simulating two seismic events: the Düzce earthquake in Turkey and the Dead Sea earthquake in Jordan. PLAXIS 3D software, as a finite element method, is employed to observe deformations in the mesh, foundation, and piles, providing insights into the effects of seismic activity on these structural elements. The study emphasizes that Turkey encounters more frequent ground motion events than Jordan, and earthquakes in Turkey demonstrate a higher peak ground acceleration. Furthermore, even though Jordan experiences fewer earthquakes, the potential impact could be severe in the event of their occurrence. The similarities in earthquake effects identified through PLAXIS analysis indicate the presence of high peak ground acceleration, posing a significant risk in Turkey. This risk extends to Jordan, particularly during moderate earthquakes. This observation sheds light on why Jordan may have implemented stringent requirements in its building codes, aligning with the standards set by Turkey in some sections.Yayın Addressing delays in construction projects in Somalia : mitigation of contributing factors(Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2024-08-07) Hassan, Abdelrahman Ahmed; Akşar, Bora; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans Programı; Işık University, School of Graduate Studies, Master’s Program in Civil EngineeringDelays are a common issue in construction projects, characterized by the late completion of work compared to the planned or contract schedule. Identifying the causes of delays is crucial for minimizing them. This study aimed to identify the factors causing delays, the effects of delays, and the mitigation strategies for construction projects in Somalia. Data were collected through a questionnaire survey involving 50 respondents from Grade (A) contractor companies in Somalia. The survey identified 32 factors contributing to delays, 37 effects of delays, and 27 mitigation strategies. Data analysis was conducted using the Statistical Package for the Social Sciences (SPSS) software with descriptive statistical methods. The study found that delays in construction projects in Somalia were caused by consultant factors, material factors, client factors, equipment factors, labor factors, and contractor factors. The effects of these delays included cost overruns, legal disputes, time overruns, lost profit, and project abandonment. Most respondents agreed on several significant mitigation strategies: ensuring resource availability, having competent personnel, appointing a competent project manager, and making accurate initial cost and time estimates. The study concludes that the best way to mitigate delays is to proactively address these factors. Implementing strategies such as employing a competent Project manager and making accurate cost and time estimates can significantly reduce delays in construction projects.Yayın Design of a high-rise reinforced concrete building according to TBDY 2018(Işık Üniversitesi, 2023-04-05) Qaiqab, Obaidallah Ahmed Balghait Ali; Umut, Önder; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans Programı; Işık University, School of Graduate Studies, Master’s Program in Civil EngineeringDue to the demand for additional livable space and lodging options for the urban population, towering structures (high-rises) are becoming more and more necessary as the world's population grows every day. For generations, people have had the need to construct big buildings. Tall structures used to be extremely difficult to construct because of a lack of seismic knowledge and computer technology. However, modern advancements in computer technology, amenities like lifts, and engineers' familiarity with earthquake movements are the main factors in the success of tall skyscraper construction. Tall structures are a problem in both industrialized and developing nations today. Engineers now employ norms and guidelines created for normal buildings for tall skyscrapers. Engineers are limited in their ability to apply easy structural solutions for tall buildings since these laws are based on the structure's strength-based design and linear elastic analysis. Engineers may choose earthquake-resistant designs and conduct more complex analyses thanks to the emergence of non-linear behavior in structural systems. Due to a lack of understanding of the non-linear behavior of buildings and the adoption of laws based on the strength that is developed under seismic threat, engineers are forced to build low-rise and mid-rise structures. According to earthquake legislation from 2007 that is largely recognized until 2019, high-rise buildings are not distinguishable from other structures and are equated with them. The Turkish Building Earthquake Regulation is published in 2019, and it analyzed high-rise buildings separately from other types of construction. High-rise structures are divided into three separate level classes under the Turkish Building Earthquake Regulation, and it has been determined to check them in accordance with that content when it comes to design issues. There are five chapters in the research. The introduction is in the first chapter, while information on earthquake-resistant design is in the second. The third chapter is mostly made up of the variables that will be used in this thesis, such the projected computation and design of high-rise structures in the Turkish Building Earthquake Regulation in 2019. The fourth chapter compares the outcomes of linear calculations with the Turkish Building Earthquake Regulation from 2007 and looks at the performance analysis and design of buildings up to 94 meters tall and 30 floors in compliance with the Turkish Building Earthquake Regulation in 2019. A list of resources and annexures follows the fifth chapter's conclusion part.Yayın Enhancing simulation accuracy in building energy modeling through data-driven approaches(Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2025-06-26) Merchad, Hadi; Umut, Önder; Işık Üniversitesi, Lisansüstü Eğitim Enstitüsü, İnşaat Mühendisliği Yüksek Lisans Programı; Işık University, School of Graduate Studies, Master’s Program in Civil EngineeringThis thesis investigated the contribution of occupant behavior towards residential building energy consumption by comparing deterministic and probabilistic schedule models. 170 in-depth survey responses were obtained across Türkiye in an effort to record daily residential activities every 15 minutes. These were augmented into 1000 high-resolution daily occupant schedules with the incorporation of variation in behavior into energy simulations. Two residential building models, a high-rise and a low-rise configuration were simulated using Energy Plus with fixed (deterministic) and variable (probabilistic) schedule methods. Importantly, the occupant schedules used in both models were identical; the only difference between the two scenarios was the building form, allowing analysis of geometry-driven energy variations. The methodology used consisted of realistic probabilistic Schedule creation using MATLAB and Python, automated interfacing with EnergyPlus as CSV inputs, and simulation of 50 randomized runs per scenario. The deterministic models built on standard daily routines from the literature and duplicated over all days of the year. The outputs of the simulations were evaluated in five categories of energy consumption: lighting, HVAC, other electrical uses, total electricity, and total utility consumption. The outcomes revealed that probabilistic values tend to occur around the average of probabilistic distributions but could not capture extreme behaviors that play a significant role in system sizing and peak load. Probabilistic models had wider variability in plug loads and electricity consumption but less varied HVAC loads that still remained influenced by changing patterns of occupant presence. The results highlighted the necessity for real occupant behavior to be included within building performance simulation for better energy demand representation. Total average energy usage for probabilistic simulation ranged between 63.9–79.5 kWh/m² for the two scenarios, compared to 74.2 and 71.4 kWh/m² under deterministic values. Variability was seen to be restricted for loads under HVAC, but varied considerably for other plug loads and lighting based on different behavior patterns. These observations reinforce the fact that internal variation is hidden under deterministic modeling, and that probabilistic simulation gives better insight into actual occupant impact on energy usage. The research brought a culturally informed, fact-based modeling approach applicable in Turkish residential buildings and confirmed that probabilistic simulation methods offer a stronger and more realistic platform for analyzing the energy supply and demand, evaluation of policies, and optimization of sustainable designs.
