Browsing by Author "Anil, Ö"

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    Evaluation of blast-induced ground vibration effects in a new residential zone
    Dogan, O; Anil, Ö; Akbas, SO; Kantar, E; Erdem, RT
    The results from an experimental blasting program that was performed at the special explosives training field of the General Directorate of Security in Ankara, where new residential blocks are planned to be constructed nearby, are presented. With the objective of estimating the blast-induced ground vibration effects on the proposed structures, various blasting parameters of nineteen surface and underground explosions were recorded in two directions at three measurement stations. Site-specific empirical relationships between peak particle velocity, the amount of explosive and the distance were developed. These relationships were used to construct a practical blasting chart, which gives the maximum amount of explosive to be used as a function of distance, for future underground and surface blasting operations in the training field. Since the use of peak particle velocity in the field of civil engineering has been limited so far, site-specific parameters were also estimated to predict the blast-induced horizontal peak ground acceleration. Then, an attempt was made to investigate the dynamic responses of four and six storey reinforced concrete structures that consist of frame and shear wall type structural systems under the measured accelerations using finite element analysis. The limitations of this approach were discussed within the context of damage estimation. (C) 2013 Elsevier Ltd. All rights reserved.
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    Estimation of compression strength of polypropylene fibre reinforced concrete using artificial neural networks
    Erdem, RT; Kantar, E; Gücüyen, E; Anil, Ö
    In this study, Artificial Neural Networks (ANN) analysis is used to predict the compression strength of polypropylene fibre mixed concrete. Polypropylene fibre admixture increases the compression strength of concrete to a certain extent according to mix proportion. This proportion and homogenous distribution are important parameters on compression strength. Determination of compression strength of fibre mixed concrete is significant due to the veridicality of capacity calculations. Plenty of experiments shall be completed to state the compression strength of concrete which have different fibre admixture. In each case, it is known that performing the laboratory experiments is costly and time-consuming. Therefore, ANN analysis is used to predict the 7 and 28 days of compression strength values. For this purpose, 156 test specimens are produced that have 26 different types of fibre admixture. While the results of 120 specimens are used for training process, 36 of them are separated for test process in ANN analysis to determine the validity of experimental results. Finally, it is seen that ANN analysis predicts the compression strength of concrete successfully.
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    Experimental and numerical investigation of reinforced concrete beams with variable material properties under impact loading
    Anil, Ö; Durucan, C; Erdem, RT; Yorgancilar, MA
    In this study, behaviors of reinforced concrete beams manufactured from several concrete types are experimentally and numerically investigated under dynamic impact loading. In the experimental part of the study, 12 beams manufactured using low strength concrete, normal strength concrete and engineered cementitious composites (ECC) containing polyvinyl alcohol (PVA) fibers are tested under dynamic impact loading. The dimensions of the manufactured reinforced concrete beams are also used as a variable to observe the effect of beam size on the behavior under dynamic impact loading. After the experimental study, finite element analyses of the tested beams are also conducted by using commonly used finite element software to observe the stress distribution under the impact loading. The results obtained from the experimental study illustrated that material type significantly affected the width of the observed cracks on the test specimens. Generally the smallest cracks formed on the test specimens manufactured using ECC and the largest cracks formed on the test specimens manufactured using low strength concrete. The results of the finite element study showed that the crack patterns on the test specimens are in good agreement with the stress distributions obtained from the impact loading simulations. (C) 2016 Elsevier Ltd. All rights reserved.
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    Vibration measurement and vulnerability analysis of a power plant cooling system
    Anil, Ö; Akbas, SO; Kantar, E; Gel, AC
    During the service life of a structure, design complications and unexpected events may induce unforeseen vibrations. These vibrations can be generated by malfunctioning machinery or machines that are modified or placed without considering the original structural design because of a change in the intended use of the structure. Significant vibrations occurred at a natural gas plant cooling structure during its operation due to cavitation effect within the hydraulic system. This study presents findings obtained from the in-situ vibration measurements and following finite-element analyses of the cooling structure. Comments are made on the updated performance level and damage state of the structure using the results of these measurements and corresponding numerical analyses. An attempt was also made to assess the applicability of traditional displacement-based vulnerability estimation methods in the health monitoring of structures under vibrations with a character different from those due to seismic excitations.
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    Improving the impact behavior of pipes using geofoam layer for protection
    Anil, Ö; Erdem, RT; Kantar, E
    In scope of this study performances of protective layers, proposed to protect the pipes from sudden impact loads such as rock falls, are aimed to be compared. In this study, performance, strength and energy absorption capability of geofoam structures against impact forces are investigated by using drop weight impact testing apparatus. Pipes that are manufactured from steel and composite materials are tested with only 130 mm thick sand protecting layer without any geofoam structure, and with two different geofoam with different thicknesses. Results are presented in a comparative form and the effect of geofoam on the impact behavior of sand layer is investigated. Impact load and accelerations on the pipes are measured with respect to time during experiments. Absorbed energy by the pipes are calculated and compared with each other for determining performance of the different protective structures. From the study, it was observed that the sand and geofoam layers used as protective layers were generally successful by reducing the detrimental effects of impact loads in terms of dissipating impact effects on the pipes and the measured acceleration and displacement levels. The best result is obtained from the 50 mm thick geofoam with sand layer. Finite elements analyses are performed by using ABAQUS software and both test and analysis results are compared to obtain a model that can give an idea to designers. (C) 2015 Elsevier Ltd. All rights reserved.
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    Load displacement behavior of concrete beam under monotonic static and low velocity impact load
    Yilmaz, MC; Anil, Ö; Alyavuz, B; Kantar, E
    Experiments were carried out to observe the influence of loading type on concrete beam specimens. Beam specimens made of similar concrete mixture with the same geometry were tested under three point static loading and low velocity drop weight impact loading. Load displacement behavior, absorbed energy dissipation capacity, stiffnesses, failure modes of beam specimens were obtained and discussed. A finite element (FE) model was prepared in ANSYS Explicit STR software and the results of FE analysis were compared with experimental results. The loading type and loading rate have significant influence on the maximum load, stiffness and energy dissipation capacity. Numerical results obtained from ANSYS Explicit STR FE models are consistent with the experimental results.
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    EFFECT OF CONCRETE COMPRESSIVE STRENGTH VARIATION ON IMPACT BEHAVIOUR
    Kantar, E; Arslan, A; Anil, Ö
    The least well known loading type is the impact loading that are affecting on to RC structures. For these reason an experimental study is conducted, and the effect of concrete compression strength variation on impact behavior of concrete investigated. Total ten beam specimens at which five of them are manufactured with normal compression strength concrete without reinforcement are prepared. Remaining five had high concrete compression strength. These specimens are tested under the impact loading that is applied by dropping constant weight hammer from five different heights. The acceleration due to impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. The increase in compression strength of concrete is significantly affected on the impact behaviors of the specimen, and as the compression strength increase impact behavior improved. Dissipated energy, the number of the hammer drops, and accelerations are increased, and displacement is dropped.
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    Investigation of lateral impact behavior of RC columns
    Anil, Ö; Erdem, RT; Tokgöz, MN
    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.
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    Low velocity impact behavior of concrete beam strengthened with CFRP strip
    Kantar, E; Anil, Ö
    Nowadays CFRP (Carbon Fiber Reinforced Polymer) became widely used materials for the strengthening and retrofitting of structures. Many experimental and analytical studies are encountered at literature about strengthening beams by using this kind of materials against static loads and cyclic loads such as earthquake or wind loading for investigating their behavior. But authors did not found any study about strengthening of RC beams by using CFRP against low velocity impact and investigating their behavior. For these reasons an experimental study is conducted on totally ten strengthened RC beams. Impact loading is applied on to specimens by using an impact loading system that is designed by authors. Investigated parameters were concrete compression strength and drop height. Two different sets of specimens with different concrete compression strength tested under the impact loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. Impact behaviors of beams are positively affected from the strengthening with CFRP. Measured accelerations, the number of drops up to failure and dissipated energy are increased. Finite element analysis that are made by using ABAQUS software is used for the simulation of experiments, and model gave compatible results with experiments.
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    Low velocity impact behavior of RC slabs with different support types
    Anil, Ö; Kantar, E; Yilmaz, MC
    Studies focused on the effects of supporting conditions on the behavior of reinforced concrete slabs subjected to static and dynamic loadings may be found in the literature. However, in the literature no study was found about the effect of variation of the support conditions on the behavior of slabs subjected to impact loads. Consequently, an experimental study was performed on the behavior of reinforced concrete slabs subjected to impact loading. Eight (8) square reinforced concrete slabs with dimensions 500 x 500 x 50 mm were tested by changing two parameters; (i) support type, (ii) support layout. In scope of the experimental study, 4 different support layouts were considered on 2 main support types (i.e. fixed and hinge supports). In the experimental study, impact loadings were applied to the specimens using a drop weight impact test set up. Acceleration-time responses of those specimens were measured by dropping a standard-weighing hammer from a height of 500 mm. Effects of the parameters on the damage distribution, number of drops, acceleration-time, velocity-time and displacement-time responses were investigated. Variations of velocities and displacements were calculated for all specimens by using measured accelerations. Finite element analyses conducted using ANSYS Explicit STR software was used to simulate the experiments. It was observed that the results obtained using the numerical model was in good agreement with those obtained from the experimental study. (C) 2015 Elsevier Ltd. All rights reserved.
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    Impact behavior of low strength concrete slab strengthened with fan type anchored carbon fiber-reinforced polymer strips
    Çaliskan, Ö; Aras, M; Yilmaz, T; Anil, Ö; Erdem, RT
    This study investigated the behavior of slabs produced with low compressive strength concrete without reinforcements under the effect of sudden dynamic impact loading. In addition, an experimental study was conducted by proposing a strengthening method with anchored carbon fiber-reinforced polymer (CFRP) strips to strengthen the nonreinforced slabs with low-strength concrete against sudden dynamic impact loads to improve their performance. The variables examined in the experimental study were the placement of the CFRP strips adhered to the concrete slabs for strengthening purposes and anchors in the strips. A constant energy level of impact loading was applied to the concrete slab test specimens with the authors' free weight drop test setup. The acceleration-time, displacement-time, strain-time, and applied impact loading-time measurements on the concrete slabs were examined, and comments were made about the strengthening method applied to the slab test specimens. In addition, numerical analysis of the tested concrete slabs with ABAQUS finite element software was performed, and the results were compared with the experimental results. In the comparison, it was investigated to what extent numerical analysis and this type of impact analysis can be done realistically and compatible with the experimental results. Within the scope of the study, the strengthening method applied with fan- type anchored CFRP strips significantly improved and increased the impact performance of concrete slabs produced with low-strength concrete.
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    Investigation of impact behavior of shear deficient RC beams using nonlinear FEA
    Yilmaz, T; Erdem, RT; Kishi, N; Anil, Ö
    In the scope of this study, the impact behavior of shear deficient RC beam was investigated by performing numerical analysis based on the finite element method and comparing it with the experimental results. The explicit dynamic analysis of 27 shear-deficient RC beams of which experiments were previously carried out by one of the authors has been conducted by utilizing ABAQUS software, and also it is aimed to establish the reasonable finite element model that is accordant with the experimental results. The variables of the experimental study were the ratio of longitudinal reinforcement on the tension side of the member, the shear-span ratio, and impact velocities. The time histories of impact load, reaction forces on supports, and the displacements measured from the mid-span of the beams were recorded during the experiments, and the energy absorption capacities of RC beams were evaluated based on an area enclosed by the impact load vs. displacement loops. It is investigated and interpreted to what extent the proposed nonlinear finite element method could be successful for analyzing the values of impact load and mid-span displacements and to what extent the explicit dynamic solution technique could be successful for simulating experiments. It is found that the maximum differences between the results obtained by numerical analysis using ABAQUS and the experimental results are 7% and 14% for impact loads and mid-span displacements, respectively.
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    Experimental and numerical investigation of timber formwork beam under different loading type
    Dönmez, TÜ; Türer, A; Anil, Ö; Erdem, RT
    With the developing construction technologies, the formwork systems used in the manufacturing of the structures have also changed and developed significantly. Especially in the production of high-rise buildings, a special sliding formwork system that is quick-installation, resistant to external loads, can be used more than once, are widely used and preferred. Timber and composite timber materials are preferred due to their durability, ease of installation, lightness compared to steel systems, and easy to use more than one time. Within the scope of this study, it was aimed to investigate the performance and behaviors of timber beams of 1800 and 2450 mm length experimentally under the influence of different loading types in H20 top P-type, which is among the products of DOKA Company. During the use of timber formwork beams, various loading types such as static, fatigue, and sudden dynamic impact load can be affected. For this reason, an experimental study was carried out, and general load-displacement behaviors, initial stiffness, displacement ductility ratios, energy dissipation capacities, collapse mechanisms, acceleration, displacement, and impact load-time behaviors under the effect of monotonic static, repetitive fatigue and impact loading of two different length timber formwork specimens were examined. In addition to experimental study, nonlinear numerical analysis is made by using ABAQUS software for experimental specimens and compared with results with an experimental study. Communicated by Prof. Dr. Corina Sandu.
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    Investigation of damaged formwork timber beam retrofitting with anchoraged CFRP strip under different loading
    Türer, A; Anil, Ö; Çevik, A; Erdem, RT
    Construction of high -rise structures, formwork systems that can be installed quickly, resistant to external loads, can be used more than once, have become a necessity. Timber and composite timber materials are preferred in the formation of such formwork systems due to their durability, ease of assembly, light weight and easy to use more than one time. Formwork beams are the most commonly used structural component in the formation of such formwork systems, and these beams can be damaged for different reasons during their lifetime. In this study, H20 top P type timber formwork beams with 1800 and 2450 mm length which is among the products of DOKA(c) company is damaged under the effect of static loading up to a high load level of 85% of the maximum ultimate capacity and after being retrofitted using anchored CFRP strips, performance and behavior of the beams under the influence of various loading types such as static, fatigue and impact are investigated experimentally. Two different lengths of retrofitted timber formwork beams were tested by applying monotonic static, fatigue and impact loading and comments were made about the effects of the retrofit method on performance under different loading types.
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    Low-velocity impact behaviour of two way RC slab strengthening with CFRP strips
    Yilmaz, T; Kiraç, N; Anil, Ö; Erdem, RT; Sezer, C
    There are a lot of studies focused on behaviour of reinforced concrete (RC) slabs under static and dynamic loadings in the literature. However, investigations related to Carbon Fibre Reinforced Polymer (CFRP) strengthened RC slabs subjected to impact load are still relatively rare. Consequently, an experimental study was performed in order to determine impact behaviour of two way simply supported RC slabs strengthened with CFRP strips. The arrangement and width of CFRP strips were varied in an experimental study. The impact load was applied to slabs using moveable drop-weight test machine designed by the authors. A total of nine RC slabs that were 1000 x 1000 x 80 mm dimensions were manufactured. RC slabs were strengthened using CFRP strips with a width of 50 and 100 mm as orthogonally and diagonally in both one and two directions. One of the specimens was un-strengthened and manufactured as reference specimens. The time-history of the impact force, the accelerations of two points, the center displacement of slabs and the strains of four points on CFRP strips were measured. The crack patterns of slabs are also observed. In the light of experimental results, the effects of applied strengthening method on low-velocity impact behaviour of RC slabs were determined and interpreted. Besides, the finite element models of RC slabs strengthened with CFRP strips are generated using ABAQUS software. It is found out that the proposed finite element model could be used for evaluation of dynamic responses of RC slabs strengthened with CFRP strips subjected to low-velocity impact load. (C) 2018 Elsevier Ltd. All rights reserved.
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    Experimental Investigation of Impact Behaviour of RC Slab with Different Reinforcement Ratios
    Yilmaz, T; Kiraç, N; Anil, Ö; Erdem, RT; Kaçaran, G
    Reinforced concrete (RC) slabs may be exposed to the low-velocity impact load during their service periods. In low-velocity impact scenarios, the effect of strain rates has been remarkably higher than quasi-static loading because the loading duration is very short. Thus, structural responses and failure modes will be different. The present study aims to investigate dynamic response and failure modes of simply supported two-way RC slabs exposed to low-velocity impact load. In the experimental part of this study, nine RC slabs with the dimension of 1,000 x 1,000 x 80 mm were tested. The reinforcement ratio of RC slabs and the input impact energy applied to RC slabs were experimental variables investigated. A drop-weight test setup was utilized to apply impact load to RC slabs. By varying drop-height as 1,000, 1,250 and 1,500 mm, three different impact energies have been applied to RC slabs via a hammer of which weight is 84 kg. The time histories of the accelerations, displacements and impact loads were recorded. The dynamic responses obtained by tests and the failure modes observed has been interpreted in detail. Besides, a finite element model where explicit dynamic analysis is performed has been established for verification of the experimental results. There was observed good accordance between numerical and experimental results. Consequently, it is considered that the present finite element treatment can be used for the evaluation of the dynamic responses and failure modes of RC slabs exposed to low-velocity impact load.
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    Investigation of impact behavior of reinforced concrete beam to column connection strengthened with carbon fiber-reinforced polymer strips
    Kaya, T; Aras, M; Yilmaz, T; Çaliskan, Ö; Anil, Ö; Erdem, RT
    Reinforced concrete (RC) members may expose to impulsive dynamic loads due to the reasons such as the explosions occurring in the interior or exterior part of them, rockfall, the vehicle crash to the bridges, the collision of masses with the effects of floods and landslide. Many studies have investigated the effects of impulsive dynamic loads on the beam, column, and slab RC structural elements have been investigated in the literature. However, the authors have not encountered any study focused on the impact behavior of beam to column connections of the frames constructing the bearing system of reinforced concrete structures. Therefore, an experimental study has been planned to investigate RC beam impact behavior to column connections strengthened with carbon fiber-reinforced polymer (CFRP) strips. The concrete compressive strength, shear reinforcement spacing, CFRP strip spacing, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, displacements, and the strains measured from CFRP strips have been recorded in experiments. The experimental variables' effect on dynamic responses of RC beam to column connections strengthened with CFRP strips subjected to impact load has been interpreted in detail. The study's scope and improved numerical analysis procedure have also been introduced to verify experimental results. Good agreement between numerical and experimental results demonstrated that the presented numerical procedures could be safely used for evaluation of impact behavior of RC beam to column connections strengthened with CFRP strips.
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    Behavior of glulam timber beam strengthened with carbon fiber reinforced polymer strip for flexural loading
    Isleyen, UK; Ghoroubi, R; Mercimek, Ö; Anil, Ö; Erdem, RT
    In the last 20 years, the use of wooden structures and their dimensions have gradually increased. The wood application has increased in different structures such as multistory buildings, sports, industrial facilities, road and railway bridges, power transmission lines, and towers. The widespread use and size of wood structures have increased the research on developing special types of wood products supported by composite materials. Laminated wood elements are the leading composite wood materials. Laminated wooden beams allow making much larger openings than standard solid wood structural elements. The development of the sizes and usage areas of wooden structures has increased the capacity of glulam structural elements and reveals the need to improve their performance. Carbon fiber reinforced polymers (CFRPs) are the most suitable options for increasing the bearing capacity values of glulam beams and improving general load-displacement behaviors. In this study, the use of CFRP strips in different layouts to increase glulam wooden beams and the application of CFRP fan-type anchors in the CFRP strip endpoints are the studied variables. Anchored and non-anchored glulam wooden beams reinforced with CFRP strips with different layouts were tested using a three-point bending test. The ultimate load capacity, initial stiffness, displacement ductility ratio, energy dissipation capacity, failure mechanisms, and general load-displacement behavior of wooden beam test specimens were obtained and interpreted as a result of the experiments.
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    Experimental investigation of impact behaviour of shear deficient RC beam to column connection
    Aras, M; Yilmaz, T; Çaliskan, Ö; Anil, Ö; Erdem, RT; Kaya, T
    Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.
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    Investigation of impact behavior of glulam beam strengthened with CFRP
    Isleyen, ÜK; Ghoroubi, R; Mercimek, Ö; Anil, Ö; Erdem, RT
    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.