Civil Engineering / İnşaat Mühendisliği
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Conference Object The Challenges and Advantages of Macro Modeling in Ansys Software for Seismic Vulnerability Assessment of Historic Masonry Structures(National Technical University of Athens, 2023) Demir, Hatice Ayşegül; Yücetürk, Kutay; Aktaş, Engin; Hamamcıoğlu Turan, MineThis study aims at creating an advancement guideline for a software which can be used for seismic vulnerability assessment of historic masonry structures by revealing the results of an experience related to the macro modeling of a historic masonry building. The case study structure is Bergama Bedesten (15th-16th centuries) located in Bergama, Izmir, Turkey. ANSYS software is used for the Finite Element Modeling of the structure. The seismicity at its location is determined and the structural response under lateral loads is obtained together with the dynamic characteristics. Mesh design, component creation according to the used material change in structural elements, contact surface identification, the arrangement of the stress scales, and result interpretation are realized. For these stages, the challenges are discussed with the solutions. The advantageous aspects of the software are explained. For the challenges, in mesh design, the ineffectiveness of cartesian method for some elements was detected and tetrahedrons method was chosen. In contact surface identification, the overlapping portions of structural components could not be detected by the software exactly, so the manual surface separation was realized. In the stress level interpretation, the lack of assignment for material limit strength values to the analysis scale was experienced and the addition of limit values was carried out. The scale also needs manual arrangement for the increase of interval numbers of stress values to emphasize vulnerable zones. This flexibility of scale to be arranged can be seen as an advantage, as well. The 3d section and axonometric view creation provide the presentation of stress changes at inner and outer surfaces of the structure which is another positive side. © 2023 COMPDYN Proceedings. All rights reservedConference Object Citation - Scopus: 1Decoding and Predicting the Attributes of Urban Public Spaces With Soft Computing Models and Space Syntax Approaches(Education and research in Computer Aided Architectural Design in Europe, 2023) Yönder, Veli Mustafa; Doğan, Fehmi; Çavka, Hasan Burak; Tayfur, Gökmen; Dülgeroğlu, ÖzümPeople spend a considerable amount of time in public spaces for a variety of reasons, albeit at various times of the day and during season. Therefore, it is of utmost importance for both urban designers and local authorities to try to gain an understanding of the architectural qualities of these spaces. Within the scope of this study, squares and green parks in Izmir, the third largest city in Turkey, were analyzed in terms of their dimensions, landscape characteristics, the quality of their semi-open spaces, their landmarks, accessibility, and overall aesthetic quality. Using linear predictor, general regression neural networks, multilayer feed-forward neural networks (2-3-4-5-6 nodes), and genetic algorithms, soft computing models were trained in accordance with the results of the conducted analyses. Meanwhile, using space syntax methodologies, a visibility graph analysis and axial map analysis were conducted. The training results (i.e., root mean square error, mean absolute error, bad prediction rates for testing and training phases, and standard deviation of absolute error) were obtained in a comparative table based on training times and root mean square error values. According to the benchmarking table, the network that most accurately predicts the aesthetic score is the 2-node MLFNN, whereas the 6-node MLFN network is the least successful network. © 2023, Education and research in Computer Aided Architectural Design in Europe. All rights reserved.Book Part Design and Construction of a Test Setup To Investigate Ground Settlement Response of Large-Scale Masonry Building Models(Springer, 2023) Liu, Yiyan; Dalgıç, Korhan Deniz; Yeşilyurt, Cennet; Gülen, Burcu; Açıkgöz, Sinan; Maraşlı, Muhammed; İlki, AlperUnderground construction activities such as tunnelling and deep excavations in urban areas may impact a significant number of surface structures and cause damage. Tunnelling-induced damage can often be repaired, but at great expense, due to significant repair costs and associated project delays. Within this context, damage caused by excavation-induced ground movements on heritage masonry buildings requires further attention, due to the cultural value and vulnerability of these assets. There is a need for experimental studies to better understand the structural response of these buildings to excavation-induced ground movements. In this study, a test setup was designed and constructed to examine the response of an experimental building model, replicating historic masonry structures, against differential settlement effects. The settlement apparatus relies on controlled jacking of large steel beams to apply differential displacements to the building. A specific tunneling scenario was considered for the design of the settlement apparatus. The constructed test setup is validated by evaluating the displacement profiles of the steel beam for different tests, with or without building. Differences between the differential settlements experienced by the steel beam and the building highlights how building weight and progressive damage may increase compliance to ground movements. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.Conference Object Citation - Scopus: 2Experimental Study of the Evolution of the Breach and the Discharge Through the Breach Resulting From Piping Due To Seepage at the Earth-Fill Dam Bottom(Avestia Publishing, 2022) Güney, Mehmet Şükrü; Dumlu, Emre; Okan, Merve; Bor, Aslı; Aklık, Pelin; Tayfur, GökmenPiping is one of the main causes of the earth-fill dam failures. Most of the researchers realizing numerical analyses make some simplified assumptions concerning the shape of the breach and the discharge of water flowing through the breach. The aim of this study is to realize experiments to provide data needed to perform numerical analyses by making more realistic assumptions. The dam having a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m is built in a channel 1 m wide, 0.81 m high and 6.14 m long. The evolution of the breach and the discharge through the breach resulting from piping due to seepage at the earth-fill dam bottom was investigated experimentally. The evolution of the dam failure is recorded by six cameras located at different locations. The time-varied of the breach areas at upstream and downstream sides are determined by applying the Gauss Area functions. The discharge of water through the breach and average outflow velocity are determined by using the continuity equation.Conference Object Citation - Scopus: 3Seismic Performance of Cfrp Jacketed Sub-Standard Rc Columns Under High Axial Stress and Shear Demand(Springer, 2022) Demir, Merve Nur; Demir, Uğur; Demir, Cem; İlki, AlperIn the last decades, lessons learnt from the major earthquakes, that occurred in many countries, brought revisions in prevailing seismic design codes. As a consequence of this phenomenon, the current building stock in Turkey is mainly comprised of reinforced concrete (RC) buildings which were designed according to different seismic design codes. The presented paper is a component of a comprehensive investigation which containing three variables i) high axial load ratio defined as axial load divided by the axial capacity, ii) high shear demand defined as the ratio of shear demand at flexural yielding to shear resistance and iii) low transverse reinforcement ratio owing to large spacing among steel reinforcements. Thus, a total of four full-scale square RC columns comprised of i) one column designed to comply with the former Turkish Seismic Design Code (TSDC, 1975) and ii) three columns which are not compliant to any design codes (referred as sub-standard), were tested under high axial load ratio, 0.4 for code-conforming and 0.75 for sub-standard columns, combined with reversed cyclic lateral loading. The columns were also designed to have high shear demand in the order of 0.62 and 0.80 for bare sub-standard according to ACI 318 (2019) and TBEC (2018) design codes as sometimes observed in existing sub-standard structures. In addition to that, the ratio of shear demand for the code-conforming column is calculated 0.43 and 0.50 as per design codes, respectively. Besides, the ratio of transverse reinforcement area to the minimum required transverse reinforcement area was 0.19 and 0.77 for sub-standard columns according to ACI 318 (2019) and TBEC (2018), respectively. For the code-conforming column, the aforementioned ratio was 0.57 and 1.32 for both design codes, in the same manner. One of the sub-standard columns was kept as a reference column while the other two of them have been externally jacketed with one layer or two layers of carbon fiber-reinforced polymer (CFRP) sheets. Test results pointed out that the confinement provided by CFRP jacketing has remarkably improved the performance of seismically-deficient RC columns subjected to high axial compression under high shear demand in terms of lateral load capacity and ductility. The experimental results were also supplemented with theoretical work to evaluate the effects of CFRP jacketing on the seismic behavior of sub-standard RC columns.Conference Object Citation - WoS: 1Citation - Scopus: 2Seismic Performance of Substandard Rc Columns Retrofitted With Sprayed Gfrm(Springer, 2022) Kian, Nima; Demir, Uğur; Demir, Cem; Maraşlı, Muhammed; İlki, AlperThere is a myriad amount of substandard reinforced concrete (RC) buildings in developing countries that do not comply with the requirements and instructions of the current building design codes. In particular, columns in these substandard buildings demonstrate unsatisfactory and undesired behavior against lateral loads, mainly due to low concrete compressive strength and poor reinforcement detailing. The problem is exacerbated when the axial load ratio (ratio of applied axial load to the axial load capacity) and/or the shear ratio (ratio of shear force corresponding to moment capacity (Ve) to the shear capacity (Vr)) is/are high, leading to brittle failure modes. In this study, three full-scale substandard RC columns subjected to high axial load ratio of 0.75 were tested under constant axial load combined with reversed cyclic lateral displacements. Shear ratio (Ve/Vr) of the substandard columns were 0.75 and 0.82 according to ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and (Turkish Building Earthquake Code (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), respectively. According to the TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), columns had a high Ve/(fctmbd) ratio of 1.12, where, fctm, b, and d are the direct tensile strength of concrete, width of the cross-section, and effective depth of the section. The ratio of transverse reinforcement to minimum required transverse reinforcement according to the ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey) was 0.19 and 0.77, respectively. Two of the columns were retrofitted with an innovative, cost-effective, and easily-applicable strengthening method, through external jacketing with sprayed glass fiber reinforced mortar (GFRM) of different characteristics. The remaining column was tested as the reference specimen to evaluate the efficiency of the strengthening method. The test results demonstrated the extremely poor performance of the reference substandard column as well as the remarkable lateral load capacity and ductility improvement provided by the adopted novel strengthening approach.Article An Experimental Study on Release Mechanism of Iron and Manganese From Sediments To the Water Column in Reservoirs(2021) Vural, Buse; Elçi, Şebnem; Ökten, Hatice EserIron and manganese accumulation in drinking water reservoirs is a challenging issue and should be controlled to prevent their adverse effects on human health. Accumulation of these elements not only clogs pipeline systems but also causes stains on fixtures and laundry. Also, high concentrations of iron and manganese may lead to various health problems when ingested. This study focuses on the release mechanism of iron and manganese from sediments to the water column in reservoirs and investigates methods to prevent this release. Effects of hypoxia, hypolimnetic aeration, alkalinity of water, and thermal stratification on iron and manganese concentrations were investigated through laboratory experiments. Experiments done simulating the water column showed that hypoxia caused more dissolution of ferrous iron when compared with that of manganese. Accordingly, aeration of the water column in hypoxic conditions lead to a significant decrease in ferrous iron concentrations (in our case reaching zero). However, manganese and total iron levels were not affected by the aeration of the water column. Alkalinity level of the water column was observed to have a great effect on the solubility of iron and manganese. Concentrations of total Fe and total Mn measured for acidic (pH = 5) conditions were considerably greater than concentrations measured at neutral conditions. As for alkaline (pH = 11) conditions, the opposite was observed with measured concentrations of total Fe and total Mn being lower than the ones measured for neutral conditions. Thermal stratification had an enhancing effect on the solubility of both iron and manganese ions. While aeration of the stratified water column slightly decreased the concentrations of Total Fe and Mn, it had a greater impact on decreasing $Fe^{2+}$ concentrations.Conference Object Citation - Scopus: 3Large Scale Experimental Settlement Tests To Evaluate Structural Models for Tunnelling-Induced Damage Analysis(Springer, 2021) Dalgıç, Korhan Deniz; Gülen, D. Burcu; Açıkgöz, Sinan; Burd, Harvey; Hendriks, Max A.N.; Giardina, Giardina; İlki, AlperUnderground construction activities, such as tunnelling, cause local ground movements to occur. Nearby surface structures interact with the moving ground, potentially leading to building damage. Although it is understood that the severity of building damage is influenced by the façade opening ratio (OpR) and the stiffness of the floors, experimental work in this area is lacking. This paper describes the specification and design of an experimental campaign on brick masonry buildings subjected to vertical base movements. The specimens are half-scale models of walls of two-storey buildings; models with different window arrangements and with/without floor slabs are examined. To design the experimental setup, 3D finite element analyses of the model walls were conducted. Key analysis results, presented in this paper, indicate how the examined structural properties (OpR, building weight, floor stiffness) are expected to influence the patterns of damage in the masonry. The finite element results are also used to design an instrumentation system comprising Fibre Bragg Grating (FBG) sensors and a digital image correlation (DIC) system. Data from the tests will support the formulation and validation of structural models for predicting tunnelling-induced damage in masonry buildings. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.Conference Object Experimental Investigation of the Stabilization Performance of Geogrids for Unpaved Roads with Low Bearing Capacity Subgrade(Springer International Publishing AG, 2022) Gokova, Suleyman; Saltan, Mehmet; Terzi, Serdal; Tutumluer, Erol; Uz, Volkan Emre; Karasahin, MustafaIn this study, laboratory experiments were carried out on real sized samples to investigate the reinforcement performance of geogrids in highway pavements constructed on low bearing capacity subgrade (California Bearing Ratio, CBR = 3%). In all prepared samples, Hot Mix Asphalt (HMA) layer was not applied. A moving wheel load was applied with Accelerated Pavement Tester (APT) device on representative pavement samples with and without geogrids. Two types of geogrids were used to construct the pavement sample configurations. Resistance to plastic (permanent) deformation was recorded as a performance indicator to compare structural performance trends of the pavement samples. For this objective, surface deformations were measured after certain wheel load repetitions. Rut depths have been calculated from surface profiles measured with a laser profiler and were plotted versus number of load repetitions. As a result of this study, the use of geogrid over soft subgrade with lowCBR values has been shown to extend the life of the pavement by reducing the rut depth.Conference Object Citation - WoS: 2Citation - Scopus: 3Micromechanical Modeling of Inter-Granular Localization, Damage and Fracture(Elsevier, 2018) Yalçınkaya, Tuncay; Özdemir, İzzet; Fırat, Ali Osman; Tandoğan, İzzet TarıkThe recent developments in the production of miniaturized devices increases the demand on micro-components where the thickness ranges from tens to hundreds of microns. Various challenges, such as size effect and stress concentrations at the grain boundaries, arise due to the deformation heterogeneity observed at grain scale. Various metallic alloys, e.g. aluminum, exhibit substantial localization and stress concentration at the grain boundaries. In this regard, inter-granular damage evolution, crack initiation and propagation becomes an important failure mechanism at this length scale. Crystal plasticity approach captures intrinsically the heterogeneity developing due to grain orientation mismatch. However, the commonly used local versions do not possess a specific GB model and leads to jumps at the boundaries. Therefore, a more physical treatment of grain boundaries is needed. For this purpose, in this work, the Gurtin GB model (Gurtin (2008)) is incorporated into a strain gradient crystal plasticity framework (Yalcinkaya et al. (2011), Yalcinkaya et al. (2012), Yalcinkaya (2017)), where the intensity of the localization and stress concentration could be modelled considering the effect of grain boundary orientation, the mismatch and the strength of the GB. A zero thickness 12-node interface element for the integration of the grain boundary contribution and a 10-node coupled finite element for the bulk response are developed and implemented in Abaqus software as user element subroutines. 3D grain microstructure is created through Voronoi tessellation and the interface elements are automatically inserted between grains. After obtaining the localization, the mechanical behavior of the GB is modelled through incorporation of a potential based cohesive zone model (see Park et al. (2009), Cerrone et al. (2014)). The numerical examples present the performance of the developed tool for the intrinsic localization, crack initiation and propagation in micron-sized specimens. (C) 2018 The Authors. Published by Elsevier B.V.