Browsing by Author "Tuğrul Erdem R."

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    Non-linear performance analysis of existing and concentric braced steel structures
    (Techno Press, 2015) Tuğrul Erdem R.
    Since there are several places located in active seismic zones in the world, serious damages and losses have happened due to major scaled earthquakes. Especially, structures having different irregularities have been severely damaged or collapsed during these seismic events. Behavior of existing structures under several loading conditions is not completely determined due to some uncertainties. This situation reveals the importance of design and analysis of structures under seismic effects. Several non-linear static procedures have been developed in recent years. Determination of the seismic safety of the existing structures and strengthening techniques are significant civil engineering problems Non-linear methods are defined in codes to determine the performance levels of structures more accurately. However, displacement based ones give more realistic results. These methods provide more reliable evaluation possibilities for existing structures with developing computer technology. In this study, non-linear performance analysis of existing and strengthened steel structures by X shaped bracing members with 3, 5 and 7 stories which have soft story irregularity is performed according to FEMA-356 and Turkish Earthquake Code-2007. Damage ratios of the structural members and global performance levels are determined as well as modal properties and story drift ratios after non-linear finite elements analysis for each structure. Copyright © 2015 Techno-Press, Ltd.
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    Influence of the air-entraining admixture with different superplasticizers on the freeze-thaw resistance of cement mortars; [Influenţa aditivului antrenor de aer combinat cu diferiti superplastifianţi asupra rezistenţei la îngheţ – dezgheţ a mortarelor de ciment]
    (Procema SA, 2016) Uğur Ozturk A.; Tuğrul Erdem R.
    Compatibility of different based superplasticizers with air-entraining admixture has been investigated. Physical and mechanical properties such as flow, setting time and compressive strength of cement mortars incorporating an air-entraining admixture (HS) with naphthalene sulfonate (SPNS) and modified polymer (SPMP) based admixtures have been determined. Also, the effects of their combinations on the freeze-thaw resistance of cement mortars have been determined. All admixtures are used with three different ratios and one of them is for overdosage effect. Results indicate that cement mortars having lowest early strength values are mortars incorporating 1.5% SPMP and 2.0% SPNS by mass of cement. The most effective series for the ultimate highest strength values were series with 0.05% HS and 0.8% SPMP. The freeze-thaw resistances of cement mortars were investigated for 50, 100, 150 and 200 freeze-thaw cycles. Indeed, the most effective series for freeze-thaw resistance were series with 0.05% HS and 0.8% SPMP. © 2016, Procema SA. All rights reserved.
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    Estimation of compressive strength of cement mortars; [Estimarea rezistenței la compresiune a mortarelor de ciment]
    (Procema SA, 2016) Tuğrul Erdem R.; Uğur Ozturk A.; Gücüyen E.
    Due to several advantages of cementitious materials especially mortars, they are widely used in construction works. It is important to determine the mechanical properties of cementitious materials to understand their behavior under different effects. In this study, Artificial Neural Networks (ANN) analysis is used to predict the 7 and 28 days compression strength values of cement mortars. Physical-mechanical properties such as flow, setting time and compressive strength of cement mortars incorporating of different chemical admixtures such as air-entraining admixture (HS), naphthalene sulfonate based (SPNS) and modified polymer (SPMP) based admixtures have been determined. The aim of the usage of combinations of air-entraining admixture with two different based superplasticizers is to form different inner structure affecting on compressive strength. All admixtures are used with three different ratios by cement weight and one of them is for overdosage effect. ANN analysis has been performed to predict the compression strength values after 7 and 28 days, in correlation with experimental part of the study. According to this view, 28 sets have been prepared with different combination of admixtures. At early ages, HS015-SPNS2.0 series had the lowest strength whereas the highest compressive strength at 28 days were obtained for HS005-SPMP0.8 series. Obtained compression strength values after 7 and 28 days have also been predicted by ANN analysis. It is stated that the established ANN model indicates a great capacity to predict the compressive strength values in the end. © 2016, Procema SA. All rights reserved.
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    Investigation of lateral impact behavior of RC columns
    (Techno Press, 2018) Anil Ö.; Tuğrul Erdem R.; Tokgöz M.N.
    Reinforced concrete (RC) columns which are the main vertical structural members are exposed to several static and dynamic effects such as earthquake and wind. However, impact loading that is sudden impulsive dynamic one is the most effective loading type acting on the RC columns. Impact load is a kind of impulsive dynamic load which is ignored in the design process of RC columns like other structural members. The behavior of reinforced concrete columns under impact loading is an area of research that is still not well understood; however, work in this area continues to be motivated by a broad range of applications. Examples include reinforced concrete structures designed to resist accidental loading scenarios such as falling rock impact; vehicle or ship collisions with buildings, bridges, or offshore facilities; and structures that are used in high-threat or high-hazard applications, such as military fortification structures or nuclear facilities. In this study, free weight falling test setup is developed to investigate the behavior effects on RC columns under impact loading. For this purpose, eight RC column test specimens with 1/3 scale are manufactured. While drop height and mass of the striker are constant, application point of impact loading, stirrup spacing and concrete compression strength are the experimental variables. The time-history of the impact force, the accelerations of two points and the displacement of columns were measured. The crack patterns of RC columns are also observed. In the light of experimental results, low-velocity impact behavior of RC columns were determined and interpreted. Besides, the finite element models of RC columns are generated using ABAQUS software. It is found out that proposed finite element model could be used for evaluation of dynamic responses of RC columns subjected to low-velocity impact load. Copyright © 2018 Techno-Press, Ltd.
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    Experimental and numerical study of fiber reinforced concrete beams in four-point bending; [Badania doświadczalne i numeryczne beleczek betonowych wzmacnianych włóknami przy zginaniu czteropunktowym]
    (Foundation Cement, Lime, Concrete, 2021) Tuğrul Erdem R.
    In this study, the behavior of concrete beams with and without fiber was investigated. In the experimental part, a total of 16 beam specimens were manufactured having different section sizes. 12 specimens were reinforced with synthetic fibers, that provide toughness, impact, and fatigue strength to concrete. The fiber ratios of the samples varied between 0% and 0.20% by mass. The samples were subjected to a four-point bending test to obtain the maximum load and displacement values, until they reached the failure modes. Subsequently, the beam samples were modelled in the Abacus finite element analysis software. Due to the comparison of experimental and numerical values and stress distributions of the specimens, it is seen that numerical analysis could be an option when investigating the behavior of beams with different dimensions in four-point bending. © 2021, Foundation Cement, Lime, Concrete. All rights reserved.
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    Prediction of impact results on cement based mortar slabs
    (Fundatia Serban Solacolu, 2021) Tuğrul Erdem R.; Berberoğlu M.
    Grout mortars are non-permeable, non-shrink and flowing cement based construction materials. Due to reaching high strength values in a short time, grout mortars are used in construction works. However, behavior of cement mortars under sudden impact loading is complex. Because, loading duration is very short in impact scenarios, effect of strain rates is much higher than static loading. So, dynamic responses and failure modes of the materials are different. In this study, it is aimed to investigate the dynamic behavior of slabs that are produced by cement based grout mortars under impact loading. A drop test setup is developed for this purpose and several measurement devices utilized in the impact experiments. Acceleration, displacement and impact load values are obtained as well as drop durations and drop numbers. After completing the experimental part of the study, artificial neural networks (ANN) analysis which is used to model different physical dynamic processes depending on the experimental variables is performed to predict the impact results. So, ANN analysis is used in the verification of experimental study. Due to the comparison of experimental and analysis results, it is considered that proposed ANN model can be used for the evaluation of the dynamic responses of test specimens. © 2021, Fundatia Serban Solacolu. All rights reserved.
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    Experimental and numerical investigation of impact behavior of RC slab with different opening size and layout
    (Elsevier Ltd, 2022) Yılmaz T.; Anil Ö.; Tuğrul Erdem R.
    The present study intends to investigate the dynamic responses and failure modes of two-way reinforced concrete (RC) slabs that have openings in different sizes and locations under the impact load effect. RC slabs may include the openings due to the various architectural imperatives. Stair and elevator openings, ventilation openings, the openings left for the electricity, and the water installations can be given as examples of openings taken place in the RC slabs. Many studies related to RC slabs subjected to the static and the reversed-cyclic dynamic loads have existed in the literature. However, at the end of the detailed literature review conducted, the authors have not encountered a comprehensive study focused on the RC slabs' impact behavior that has openings in different sizes and locations. In the present experimental study's scope, the impact loading was applied to two-way RC slabs with the openings via the drop-weight test setup designed by the authors. The time-histories of acceleration and displacements measured from the RC slabs and impact forces acting on the RC slabs have been recorded during the tests to investigate the effect of opening sizes and locations on the RC slabs' impact performance. Furthermore, a finite element model (FEM) has been developed using ABAQUS software to calculate dynamic response and failure modes of the RC slabs with openings. Good agreement between experimental and numerical results has proven that the proposed FEM could be used to evaluate the impact behavior of the RC slabs that have the openings. © 2021 Institution of Structural Engineers
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    Investigation of impact behavior of glulam beam strengthened with CFRP
    (Elsevier Ltd, 2023) Karagöz İşleyen Ü.; Ghoroubi R.; Mercimek Ö.; Anıl Ö.; Tuğrul Erdem R.
    This study's objective is to examine the general behavior of glulam timber beams strengthened with CFRP (Carbon Fiber Reinforced Polymers) strips and ascertain the impacts of the applied strengthening technique on the performance of timber beams under the influence of rapid dynamic impact loading. In the study, the innovative strengthening method developed with CFRP strips was placed on the lower tensile surface of glulam timber beams and positioned as more than one layer between laminated beam parts. In addition, placing CFRP fan-type anchors on the endpoints of the strips to delay the debonding of CFRP strips from the surface is an innovative application examined in this study that contributes to the literature. The glulam timber beams that strengthened with the developed method and non-strengthened reference test specimens were tested with the free-weight drop test setup. The acceleration, displacement, strain at the tensile surface, and the variations of the applied impact loading by the time were measured and interpreted. In this way, the performance level of the strengthening technique under the effect of the impact loading was investigated. The glulam timber beams strengthened with CFRP strips are modeled using ABAQUS finite element software to compare the numerical analysis with the experimental results and determine the extent to which the numerical analysis might produce realistic results. © 2023 Institution of Structural Engineers
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    Analyses of damaged effects on jacket type offshore platform; [Analize učinaka oštećenja na rešetkasto postolje izvanobalne platforme]
    (Croatian Association of Civil Engineers, 2023) Gücüyen E.; Coşkun S.; Tuğrul Erdem R.
    In this paper, an offshore platform subjected to dynamic loading for different damage cases was modelled via fluid-structure interaction (FSI) analysis. Different damage models were considered in the case where one leg was broken, and the Young’s modulus of the damaged member was reduced with four different severity ratios. In addition to the five damaged structures, the undamaged structure was modelled according to two different leg spacing conditions. Thus, the damaged models were compared among themselves as well as with undamaged models. In this study, models were investigated using a numerical FSI technique. The numerical technique was verified using semi-analytical modelling. At this stage, the equation of motion of one of the structural models was solved using a semi-analytical method based on a multi-degree-of-freedom system. In addition, the numerical environment model was verified using a semi-analytical solution of the free-surface motion equation and the wave velocity-wave force curve. An Abaqus finite-element analysis program was used to model the structures and their surroundings. While the structures were modelled using the Lagrangian technique, the fluid surroundings were modelled using the Eulerian technique. Both the conditions of leg spacing and different severity ratios were modelled, and the most negative damage type was revealed. © 2023, Croatian Association of Civil Engineers. All rights reserved.
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    Investigation of concrete slabs made with cement based mortars under impact loads; [Ponašanje betonskih ploča od cementnog morta pri udarnom opterećenju]
    (Croatian Association of Civil Engineers, 2023) Tuğrul Erdem R.; Berberoğlu M.; Gücüyen E.
    As structural members can be subjected to impact loading during their service life, impact experiments are applied for various materials and objects by taking different methods into consideration. The effect of impact load on concrete slabs prepared with cement-based mortars is investigated in this study. A total of nine slab specimens measuring 500 x 500 x 50 mm are tested within the experimental program. Test specimens are prepared to provide different strength values and tested under impact load using the drop test setup. The impact resistance values of the specimens are determined based on the acceleration, impact load and displacement values, as obtained by measurement devices. In addition, crack distribution of the specimens is observed during impact tests. It has been noted that mortar types have a significant effect on the impact behaviour of the specimens. The finite element analysis is generated for each specimen to verify experimental results. Time histories of the acceleration, displacement and impact load values of the selected test specimens are compared. The relationship between experimental and numerical analysis results is presented, which reveals that the finite element procedure can be used in the evaluation of dynamic response of test specimens under the low velocity impact loading. © 2023 Authors. All rights reserved.
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    A Simulation Study on the Performance of Jacket Type Offshore Structures Using Machine Learning Algorithms
    (Universidad de Cantabria, 2024) Gücüyen E.; Çiftçioğlu A.Ö.; Tuğrul Erdem R.
    In this study, the behaviors of jacket-type offshore structures are numerically investigated. The examined four-legged models with a total height of 60 m have four layers and three different cylindrical element sizes are fixed to the seabed. The structures are under the effect of environmental forces, including wind and wave loads, as well as operational loads. Three different marine environments have been generated in environmental modeling. Thus, the parametric study has been performed using bidirectional fluid-structure interaction (FSI) analyses of 36 models. Structural outputs such as displacement, reaction force, and stress values are determined by numerical analyses. In the second part of the study, the implementation of machine learning algorithms, including Xgboost, Random Forest, and Support Vector regressors, is employed to automate the assessment of performance in jacket-type offshore structures. The evaluation of these machine learning models in predicting the displacement, reaction force, and stress values of offshore jacket structures is conducted, revealing Xgboost as the most promising technique, although with satisfactory overall performance across all algorithms. These findings provide empirical evidence supporting the feasibility and applicability of employing machine learning methodologies in the analysis of performance for jacket-type offshore structures. © SEECMAR | All rights reserved.