Organizational Unit: Department of Civil Engineering
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Master ThesisPublication Metadata only Extrusion and rheological characterization of cement-based materials containing different types of clays(2021-01) Aydın, Eylül Mina; Bundur, Zeynep Başaran; Bundur, Zeynep Başaran; Öztürk, Hande; Zihnioğlu, N. Ö.; Department of Civil Engineering; Aydın, Eylül MinaRecently, digital manufacturing has been termed the fourth industrial revolution (Industry 4.0). Implementation of digital manufacturing revolutionizes the construction industry with the potential of freeform architecture, less raw material consumption, reduced construction costs, and increased worker safety. Thus, for the last decade methods on digital manufacturing of concrete gained a significant interest compared to conventional concrete. While the studies mainly focus on the development of specially designed 3-D printers, at this current technology readiness lever the main challenge is to design the highly thixotropic material and the software enabling heterogenous material flow. In terms of material design, the printable mortars must be extrudable through a nozzle without clogging and retain its shape right after the printing and when another layer is deposited, in short, it must be buildable. To be able to provide layer deposition on top of each other, the consistency of mortar should increase fast upon extrusion. The thixotropic nature of cement paste enables this rapid viscosity change. Time dependent viscosity and shear stress of the material limits the extrusion rate and the height of the construction, fast extrusion rates reduce the buildability, whereas slow extrusion rates create cold joints between the layers and decreases the interlayer bond strength, resulting the overall strength to decrease. These properties could be adjusted by using appropriate materials with appropriate mix design. This study aims to investigate the influence of 2 different clays, nano-montmorillonite and sepiolite, on rheological properties of fly-ash (FA) amended cement-based systems adapted for 3D printing. Herein, the clays were incorporated at 0.5 and 1% of the cement content. The effects of these clays on rheological properties such as static and dynamic yield stress, apparent viscosity and thixotropy were analysed. The performance of clays was compared to a commercially available viscosity modifying agents (VMA). Finally, selected mixes were printed through extrusion. The results showed that both clays were compatible with polycarboxylate ether based (PCE) superplasticizer and FA. In fact, the impact of clays on rheological properties were much more pronounced in samples containing 20% FA by weight of cement at a dosage of 0.5% of the cement weight.Master ThesisPublication Metadata only Comparitive energy simulation for high-rise residential building envelope materials: Heating and cooling efficiency analysesAzima, Mahshad; Seyis, Senem; Seyis, Senem; Deniz, Derya; Erten, D.; Department of Civil Engineering; Azima, MahshadThe interest in building energy performance and efficiency has been increasing in the last decades. Although several studies on energy-efficient buildings exist in the architecture, engineering, and construction (AEC) literature, none of them addressees the heating and cooling performance of high-rise building envelope materials. Such research would be a valuable guideline for the early decision-making process in energy-efficient high-rise building design. This study aims to (1) build up a knowledge base for exploring the optimal building envelope components based on the relevant aspects of energy performance to design energy-efficient high-rise buildings and (2) analyze and compare the effects of three different building envelope materials (i.e., reinforce concrete, timber wall, and curtain wall) on energy performance of a high-rise residential building. For this purpose, first, Cite Space, VoSViewer, and Gephi were used for building up a knowledge base in building energy performance. Then, various scenarios for evaluating the impact of envelope components (e.g., wall structure, window-to-wall ratio, and site orientation) were developed and analyzed. Efficient scenarios were opted for developing analyses in terms of floor, roof, and glazing type to decrease the heat loss/gain in the roof, floor, and glazing. Design Builder was utilized to design and model the case study building based in Istanbul, Turkey, and perform energy analysis for its heating and cooling efficiency by focusing on walls, roof, and ceiling (considering the building's orientation), window-to-wall ratio (WWR), and insulation. This research contributes to the AEC literature and industry by providing (1) detailed information about influential factors in heat loss/gain, (2) the factors to achieve energy efficiency and to decrease heating and cooling demand in high-rise buildings, (3) combinations for energy efficient building envelope materials, and (4) knowledge base for an efficient heating ventilation air conditioning system design for high-rise residential buildings. Accordingly, the results would be very useful for assisting professionals in the decision-making process of energy-efficient high-rise residential building design. Further, this study reveals promising topics in this scope for future research.Master ThesisPublication Metadata only A parametric study on the influence of boundary frame flexibility in steel plate shear walls(2020-01-17) Benam, Shaghayegh Sadeghzadeh; Özçelik, Ahmet Yiğit; Özçelik, Ahmet Yiğit; Altay, Gülay; Müderrisoğlu, Z.; Department of Civil Engineering; Benam, Shaghayegh SadeghzadehSteel plate shear walls (SPSWs) are known to be a reliable lateral force-resisting system, particularly attractive for high-seismic regions, due to their high lateral strength and stiffness and stable hysteretic behavior. SPSWs comprise thin infill plates that are connected to the beams and columns of the surrounding boundary frame on all four edges. Being the primary element resisting the lateral load, thin infill plates buckle almost immediately when the SPSW is loaded laterally. Despite shear buckling of thin infill plates, thin infill plates exhibit substantial post-buckling strength and stiffness due to a mechanism called tension field action. To take advantage of tension field, the surrounding boundary frame is required to anchor thin infill plates by resisting the diagonal tension forces exerted by thin infill plates due to the formation of tension field and by limiting the inward deflection of thin infill plates to enable them to yield in tension. Pursuant to this goal, it is necessary to capacity-design the boundary frame to ensure thin infill plates yield prior to hinging in the boundary frame. In addition to the capacity design requirement, a stiffness limit for the boundary frame, based on elastic behavior, is provided by design codes to minimize pull-in of boundary frame. Furthermore, for preventing excessive plastic deformation in the horizontal boundary elements (HBEs) a limit for plastic section modulus of HBEs is provided. In this study, a parametric study is undertaken to quantify the effect of boundary frame flexibility (or stiffness) on the development of diagonal tension and the variation of tension stresses in thin infill plates of SPSWs. The web plate thicknesses are chosen, and relevant boundary frame elements are designed according to the forces applied by web plate without considering seismic actions. 27 one story one bay SPSWs with 3 different aspect ratios (ratio between width and length) and 9 different plate thickness using lightest sections for beams and columns are designed following the capacity design principles. Later for each design, 2 additional bigger column sections are assigned while beam sections remained constant. In total, 81 designs are provided. In addition to the capacity design requirements, these designs also fulfill the stiffness requirement given for boundary frame in design codes. Nonlinear pushover analyses are performed using a simplified model known as strip model (validated against experimental data available in literature) representing the cyclic behavior of thin infill plates. It is observed that column stiffness does not affect the distribution of the stresses in the web plates. Additionally, in pushover analysis it is observed that the capacity design method underestimates the shear forces. Results showed that the accumulation of plastic deformation at the mid- span of the HBE is critical for designs with aspect ratios of 1 and web plates with thickness less than 1.3 mm. Finally, the closed-form expression for uniformity of the stresses in the web plates is also obtained as a function of flexibility of beams and columns, aspect ratios and drifts.Master ThesisPublication Metadata only Seismic performance of self-anchored tanks located in high seismic regions in Turkey(2023) Koçraş, İrsen Nihan; Erkmen, Bülent; Erkmen, Bülent; Yılmaz, Taner; Yazgan, U.; Department of Civil Engineering; Koçraş, İrsen NihanThis study examines the seismic performance of three unanchored industrial liquid storage tanks that are located in the Kocaeli industrial area, which has a significant earthquake risk. One of the tanks is an existing tank in an industrial facility located in the region, while the other two were designed to have different anchorage ratios. The finite element analysis software ABAQUS was used to build 3-D finite element models in order to assess the seismic performance of the tanks. The seismic behaviour of the tanks was studied by performing time-history analyses using the recorded earthquake records that were scaled for the tank location. The spring-mass model, on which the developed tank models are based, models liquid content as two-point masses that were spring-adjusted to the tank wall. This approach was based on American Petroleum Institute (API 650). Tank-liquid interaction, base uplift, tank sliding off its foundation, damage to the tank's wall shell plates as well as bottom base plates, and the tank earthquake performance were all analysed. In addition, the effects of different friction coefficients between tank base and its foundation on tank seismic performance were studied. The seismic analyses were carried out using data related to eleven earthquakes. This data was scaled to meet the seismic design spectrum for the tank location and chosen in compliance with the Turkish Building Earthquake Code. Tank base sliding, base uplift and material damage were monitored to assess potential tank damages. The main objective of the study was to investigate the effects of tank anchorage ratio on seismic performance of unanchored tanks located in high seismic regions. This was achieved by performing time history analysis of the tanks using 11 earthquake records. Also, tank base uplift and sliding over the foundation failure modes were also evaluated on the basis of the effect of anchorage ratio on tanks. The second objective of the research was to examine the impact of friction between the tank base plate and tank foundation on tanks seismic performance. For this purpose, the tank's seismic performance was evaluated by considering two different friction coefficients. The findings of this study contribute new and valuable insights into the existing literature on the seismic performance of unanchored tanks and the effects of anchorage ratio on their seismic performance. In addition, the study provided a better understanding of the effects of unanchored tanks base friction on their seismic performance. Consequently, these findings will contribute to procedures used for seismic design of unanchored tanks and enhance the seismic performance of tanks at highly seismic regions.Master ThesisPublication Metadata only Performance and loss assesment of industrial buildings under flood and earthquake actionsÖlmez, Hasan Numan; Deniz, Derya; Ölmez, Hasan Numan; Altay, Gülay; Karaman, H.; Department of Civil Engineering; Ölmez, Hasan NumanFlooding and earthquake are the two most-costliest hazard events that significantly affect communities in Turkey. Especially, their impacts on industrial facilities can trigger fire or release of toxic substances, resulting in extensive environmental pollution, enormous economic losses and even significant health effects on the communities around the facilities. To mitigate with impacts of disasters and reduce associated damage on industrial structures, assessment of hazard performance and loss of the facilities is the first crucial step. This study presents a probabilistic methodology to make reliable seismic and flood impact estimate for industrial buildings considering any potential structural, non-structural damage, and equipment and/or inventory losses and associated uncertainties. As a case study, the common one-story precast concrete industrial buildings in Turkey were considered. Several field trips were conducted to industrial facilities in different sectors to investigate and understand their hazard damage potential. Using the field notes and literature review results, numerous analytical damage models were built to analyze behavior of typical precast reinforced concrete industrial buildings under lateral seismic and flood forces. Damage state matrices were established for the industrial facilities to connect possible damage levels under earthquake and flood load actions to functionality of the facilities. Considering uncertainties in the key parameters for the built damage models, sensitivity analyses were performed to develop probabilistic earthquake and flood loss models. Both structural and non-structural damages and equipment/inventory losses were considered to establish holistic loss models. While the proposed models have been developed for the industrial structures in Turkey, the methodology can be adopted to the facilities in other nations and regions using similar industrial construction practices.Master ThesisPublication Metadata only Seismic performance evaluation of semi-rigid composite cold-formed steel-rubberised concrete buildingsIraguha, Dieudonne; Deniz, Derya; Deniz, Derya; Altay, Gülay; Akbaş, B.; Department of Civil EngineeringOver the past few years, cold-formed steel (CFS) structural elements have been extensively used as a cost-effective and fast way of achieving sustainable buildings thanks to their low embodied carbon. Besides, the increased demand for CFS systems in multi-story construction has led to the development of competent CFS lateral force-resisting systems with moment-resisting connections. These rigid connections are implemented to compensate for the shortcomings of traditional CFS framing systems that use simply supported floor-to-wall connections and hence cannot adequately dissipate large moments present in multi-story structures. With this in mind, this study focuses on the seismic performance evaluation of rubberised concrete-filled cold-formed steel (CFS-RuC) tube frames equipped with a recently developed semi-rigid moment-resisting connection. A numerical study is carried out in ABAQUS to examine the effect of different dimensions for CFS-RuC sections and side plates on the behavior of the semi-rigid connection adopted herein. A validation study of the semi-rigid connection is conducted in SAP2000 to come up with a practical plastic hinge model to use at frame-level analysis. Design of case studies of 2, 5, and 8 story- CFS-RuC buildings is accomplished per the TBEC 2018 and AISI-S100-16 codes. Seismic performance evaluation of the case study buildings at the performance point is investigated through nonlinear static pushover analyses. Alternatively, the seismic behavior of CFS-RuC buildings is probabilistically assessed through fragility curves generated by a fragility tool, SPO2FRAG. Results indicate that these new composite systems possess higher stiffnesses and adequate energy absorption capability in comparison to their bare counterparts. They also displayed a ductile deformation which enabled the fulfillment of the code-prescribed performance level of life safety.Master ThesisPublication Metadata only Determination of effective breadth width of stiffened steel plate structures based on nonlinear finite element analysis(2019-08-19) Kılıç, Burak Talha; Erkmen, Bülent; Erkmen, Bülent; Özçelik, Yiğit; Şeker, O.; Department of Civil Engineering; Kılıç, Burak TalhaAn economical and effective design of plates loaded by out-of-plane loads such as pressure or blast can be obtained by using stiffeners instead of increasing plate thickness. Therefore, stiffened steel plates are widely used in many different industries for different purposes and structures. For marine structures, for instance ships, stiffened steel plate walls are used as ship skeleton for resisting wind, hydrostatic and dynamic pressures. In aerospace engineering, these systems are used to resist especially wind pressure. Similarly, such steel wall systems are also widely used in petrochemical industry especially in offshore and onshore platforms as blast walls and blast resistant steel structures as control rooms, office buildings, and living quarters in areas with a high risk of explosion, fire, or danger from toxic materials in petrochemical industry. For such steel wall structures ultimate strength capacity, wall stiffness, and requirement for weld connection between the wall plate and stiffeners depends on effective breadth of plate, which is the part or breadth of plate working with each stiffener as its flange. This breadth width is typically predicted based on plate nonlinear stress distribution occurring due to out-of-plane loading such as pressure, blast, wind etc. Although there are a number of studies for such cold formed plate systems, they are mainly focused on effective width concept, which is based on in-plane loading only. In other words, there is a need for research to generate engineering design guidelines for predicting effective breadth width for stiffened steel plates subjected to out-of-plane loads. In the first part of this study, nonlinear finite element models of stiffened plate structures subjected to uniform out-of-plane pressure loading was generated by using purpose finite element program Abaqus CAE. The effective breadth of these wall systems was calculated using nonlinear stress distribution through plate thickness and along plate width to determine axial load carried by plate. The effective breadth width was calculated as the plate width needed to carry the same axial load but with a uniform stress, which is equal to the maximum computed stress from the model, along the plate width as defined in the literature. A parametric study was also conducted to determine effects of walls design parameters such as spacing of stiffeners, plate thickness and type of stiffener. For this purpose, a wide range of plate thickness from 30 mm to 10 mm was studied. Similarly, for stiffener angle, flat, boxed and tee sections were also considered. Additionally, seven different spacing ranging 150 cm to 75 cm for the stiffeners were included in the parametric study. In the second part, effective breadth of the walls was investigated by using simple beam method. In this method, such structures were modeled as a simple beam because modelling and analyzing of these walls require a lot of computational time, high-performance computer, costly finite element software package as well as expert engineering judgment. For this purpose, three prototype walls for different cases; plate yields first, flange yields first, both yield at the same time, were created. At the same time, the walls that have the same geometric and material properties were modeled as simple beams. The correlation between walls and simple beams were discussed by using support reaction per stiffener versus vertical displacement curve. In summary, this part investigates how close the behavior of different featuring walls can be modeled by simple beam method.Master ThesisPublication Metadata only Building information modelling based on-site 3D printer position optimization for digital fabricationBaş, Sercan; Bundur, Zeynep Başaran; Işın, Gürşans Güven; Bundur, Zeynep Başaran; Işın, Gürşans Güven; Bartın, Bekir Oğuz; Seyis, Senem; Pehlevan, E. E.; Department of Civil EngineeringDigital fabrication, Additive Manufacturing (AM), and Building Information Modeling (BIM) has recently been advancing in the Architecture, Engineering, and Construction (AEC) industry and have been leading to increasing number of applications of digital fabrication technologies for three-dimensional (3D) printed structures such as tiny houses, shelters, or even bridges. The 3D printing processes of structures provide advantages in terms of time, cost, and energy efficiencies, as well as health, safety, and environment (HSE) aspects. The on-site integration of 3D printing and Building Information Modeling (BIM) has shown potential to improve the production processes of digital fabrication with concrete. So far, the utilization of building models by 3D printers has been the focus of this integration for more effective digital fabrication applications. BIM can be used in the site planning and optimization of the digital fabrication process by optimally positioning the 3D printers on the construction site. In this work, a BIM-based 3D printer position optimization tool was developed using the Dynamo plugin of the Autodesk Revit software. Similar to the optimization of the site layout with BIM for major construction equipment (e.g., cranes); this tool looks at the design and geometry of the elements to be printed as well as the fresh and hardened state properties of the concrete mix. This tool considers the physical properties of a 3D printer, such as its dimensions and printing range, the geometry and location of the elements to be printed on-site, and the properties of printable concrete mixture, such as initial setting time. In the case study, the tool significantly reduced the number of steps required for printing the walls of a single-floor office building with a robotic arm 3D printer. The main objective of this research is creating an algorithm examining relocation step counts of a robotic arm 3D printer in a real case office building construction and decreasing this relocation counts from 20 to lower values with determining optimal places over the slab. The outcome of this research will enable decreasing the relocation step counts for printer to 7 from 20 and unnecessary 13 steps are eliminated. As a result of this optimization work, 65% yield is gained in terms of labor force, time and energy consumption for relocation process of the printer.Master ThesisPublication Metadata only Implementation of microwave curing system to adapt metakaolin based geopolymer binders for 3d-printingAtalay, Yiğit Alper; Bundur, Zeynep Başaran; Bundur, Zeynep Başaran; Fındıkçı, İlknur Eruçar; Gülgün, M. A.; Department of Civil Engineering; Atalay, Yiğit AlperThree-dimensional (3D) printing techniques of the construction materials such as contour crafting and additive manufacturing are being developed in the construction sector and replace the conventional building techniques used for generations. To achieve successful printing in large scale, it is necessary to develop advanced printing systems and compatible software. Another main challenge in 3D printing is to design a suitable material feasible with the requirements of the 3D printing in terms of its extrudability and buildability. It is also known that extrudability and buildability are also contradicting factors, as high workability causes more extrudability while the low workability provides more buildability. Therefore, the designed material should exhibit high level of workability as it is required to be extruded through the printer nozzle and sustain its shape without major deformation while subsequent layers are printed on top of each other. To obtain such structural reliability and applicability, fresh and hardened properties of the material such as tensile and compressive strength, static and dynamic yield stress obtained by rheological experiments, thixotropic behavior, flowability etc. should be evaluated. The goal of this study was to adapt metakaolin-based geopolymer mortar to 3D printing through a novel microwave curing approach. To achieve this goal, 3 types of precursor materials and 2 types of different curing regimes which are microwave and oven curing were utilized to enhance the materials' characteristic properties by triggering the rapid strengthening and buildability. The experimental design was established for samples with 3 different molar ratios (MR; 1.3,1.5 and 1.7) containing metakaolin, fly ash and silica fume. Samples were subjected to 3 different curing regimes: oven curing, microwave curing and hybrid curing (combination of optimized microwave and oven curing). Results showed that replacing a portion of applied oven curing with microwave curing in hybrid approach can increase operation speed and increase the rate of hardening. While the use of microwave curing in the geopolymer binders did not affect the alkali leaching, it increased the drying shrinkage in the material. Moreover, it was found that the samples can be hardened in 120 minutes once they are subjected to microwave curing while it was 60 minutes for hybrid curing. The use of microwave curing increased the green strength and dimensional stability without sacrificing from workability of the sample. Implementation of microwave curing improved the printability of metakaolin based geopolymers by affecting the buildability of the material. The outcomes of this study will pave a better design of set-on-demand geopolymer binders for advanced applications such as 3D printing by reducing the total duration of heat curing.Master ThesisPublication Metadata only Implementing artificial neural network based gap acceptance models in the simulation model of a traffic circle in SUMOBagheri, Mohammad; Bartın, Bekir Oğuz; Bartın, Bekir Oğuz; Yılmaz, Taner; Şahin, İ.; Department of Civil Engineering; Bagheri, MohammadThe impact of various operational and design alternatives at roundabouts and traffic circles can be evaluated using microscopic simulation tools. Most microscopic simulation softwares utilize default underlying models for this purpose, which may not be generalized to specific facilities. Since the effectiveness of traffic operations at traffic circles and roundabouts is highly affected by the gap rejection–acceptance behavior of drivers, it is essential to accurately model driver's gap acceptance behavior using location-specific data. The objective of this paper was to evaluate the feasibility of implementing an Artificial Neural Network (ANN)-based gap acceptance model in SUMO, using its application programming interface. A traffic circle in New Jersey was chosen as a case study. Separate ANN models for one stop-controlled and two yield-controlled intersections were trained based on the collected ground truth data. The output of the ANN-based model was then compared with the SUMO model, calibrated by modifying the default gap acceptance parameters to match the field data. Based on the analyses results it was concluded that the advantage of the ANN-based model lies not only in the accuracy of the selected output variables in comparison to the observed field values, but also in the realistic vehicle crossings at the uncontrolled intersections in the simulation model.