Browsing by Author "Altiok, TY"

Now showing 1 - 9 of 9
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    Proposal for a novel technological damper system (TDS) for the retrofit of reinforced concrete frame structures
    Suk, R; Demir, A; Altintas, G; Altiok, TY
    Considering the severe earthquakes that have occurred worldwide, it has been observed that even buildings which are constructed in compliance with the seismic regulations, have suffered heavy damage or collapsed. Similarly, in earthquake on February 6, 2023, in Kahramanmaras,, Turkey, many old and new structures were damaged or even collapsed. This situation has compelled researchers to focus on the most current and technological applications for earthquake protection. In the latest research topics, there has been a growing emphasis on the impact of new technological systems targeted at improving the seismic performance of structures constructed with reinforced concrete systems, given the notable occurrence of collapsed buildings with such structural systems in this earthquake. In this study, the developed Technological Damper System (TDS) was employed to enhance the earthquake performance of reinforced concrete structures. TDS is a versatile and adjustable frictiontype damper. For this reason, two identical 1/2 scaled reinforced concrete frames were fabricated for the study, one representing a traditional structure as a reference frame (REF), and the other a frame with the TDS device. After applying quasi -static cyclic tests to the frames, the force -displacement, and force -rotation relationships, as well as energy dissipation capacities were determined for both frames. In addition, the damage conditions of the columns during the tests were assessed based on the plastic rotation limit conditions outlined in Turkish Building Earthquake Code (TBEC 2018). As a result, the frame retrofitted with the TDS device exhibited a significant increase in horizontal load -carrying capacity, ranging from 42.04% to 75%, when compared to the REF. Additionally, it was observed that energy consumption increased between 85% and 220%. The REF reached significant damage levels at 1% and 2% story drift ratios and an advanced damage state at about 3%, in accordance with TBEC 2018. Finally, the behavior of the frame retrofitted with TDS considerably improved according to REF and it reached a significant damage state at 3% story drift ratio.
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    Advancing earthquake resistance: Hybrid retrofitting of RC frames with FRP and TDS
    Suk, R; Demir, A; Altiok, TY; Altintas, G
    Traditional and technological retrofitting methods have been proposed over time to enhance earthquake resistance in structures. Friction-type dampers have attracted considerable interest from both researchers and the construction industry because of their versatility in retrofitting, quick installation, and non-destructive characteristics. Moreover, the integration of damping systems with various retrofitting elements and the resulting impact of these hybrid systems on building performance have consistently been subjects of interest. This study involved the construction of three identical half-scale reinforced concrete (R.C) frames. One frame served as the reference (REF), the second was wrapped with Fiber Reinforced Polymers (FRP) material (REF-FRP), and the third was retrofitted using both FRP wrapping and the developed Technological Damper System (TDS-FRP). Quasi-static cyclic experiments were performed on the three structural frames, providing force-displacement and force-rotation relationships. The acquired data were then used to assess the damage states of the frames according to the Turkish Building Earthquake Code (TBEC 2018), and energy consumption rates were determined. Moreover, Finite Element Method (FEM) analyses were performed on REF, REF-FRP, and TDS FRP frames to derive force-displacement relationships, which were subsequently compared with experimental findings. The experiment results indicate that the horizontal load-carrying capacity of the TDS-FRP frame increased by 76 % to 122 % compared to the REF frame, while the REF-FRP frame showed a maximum increase of 14 %. Additionally, the cumulative energy consumption capacity of the REF-FRP frame increased by a maximum of 42 % compared to the REF frame, and the TDS-FRP increased between 51 % and 156 %. At a 1 % drift ratio, shear cracks at the beam ends and column-beam intersections of the REF frame were observed to be significantly reduced in the REF-FRP frame and eliminated in the TDS-FRP frame. Additionally, upon reaching a 3 % drift ratio, it was observed that the TDS-FRP frame remained within acceptable limits as per TBEC 2018, whereas the REF and REF-FRP frames exceeded the advanced damage limit. Additionally, it has been observed that the results obtained from FEM analyses coincide with the experimental results. In this context, the TDS-FRP hybrid application can be considered as an effective and alternative solution for the R.C buildings.
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    Numerical assessment of a slender structure damaged during October 30, 2020, Izmir earthquake in Turkey
    Demir, A; Altiok, TY
    The minarets, which have a tall and slender structure, are quite vulnerable to dynamic forces, i.e. earthquakes and winds. In mainly concrete minarets, since the bond between the concrete blocks is provided by only mortar, the damages caused by high tensile stresses may emerge. This study aims to simulate the behaviour of the concrete Selimiye minaret damaged during the Izmir (Seferihisar-Samos) earthquake on October 30, 2020. The nonlinear finite element model of the Selimiye minaret is created using the Concrete Damage Plasticity failure model. In the nonlinear time history analyses, the Izmir earthquake records obtained from the Bayrakli station, located the closest to the minaret, are used. The damages occurring in the transition segment of the minaret are verified with the finite element method. This study also aims to strengthen insufficient concrete minarets with an innovative, cost-effective, and better workability method. The proposed strengthening method is based on a Fabric Reinforced Concrete Mixture. Finite element models are strengthened from the inner surface using Fabric Reinforced Concrete Mixture composites reinforced with glass and steel fibers. As a result of the finite element analyses, it is concluded that the concrete minarets can be strengthened from the inner surface with the Steel Fabric Reinforced Concrete Mixture method in safety. In addition, with a parametric study, it has been determined that partial strengthening applications, which are more economical and aesthetic, can be more effective on structural performance than full strengthening applications.
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    Investigation of the effect of damper location and slip load calculation on the behavior of a RC structure
    Sevik, M; Altiok, TY; Demir, A
    Energy dissipation systems increase the energy dissipation capacity of buildings considerably. In this study, the effect of dampers on a typical 10-storey reinforced concrete structure with a ductile moment-resisting frame was investigated. In this context, 5 different models were created according to the calculation of the slip load and the positions of the dampers in the structure. Nonlinear time-history analyzes using 11 different earthquake acceleration records were performed on the models using the ETABS program. As a result of the analyses, storey displacements, energy dissipation ratios, drift ratios, storey accelerations, storey shears, and hysteretic curves of the dampers on the first and last storey and overturning moments are presented. In the study, it was determined that friction dampers increased the energy dissipation capacities of all models. In addition, it has been determined that positioning the dampers in the outer region of the structures and taking the base shear as a basis in the slip load calculation will be more effective.
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    Damping impact with different water level on structural behaviour of elevated water towers
    Altiok, TY; Yigit, ME; Eser, CB; Demir, A
    Water towers with tall and delicate geometry are highly susceptible to seismic actions. This study aims to develop a fast, reliable and cost-effective method for examining the seismic behaviour of such structures, by taking a reinforced concrete water tower with known material parameters and dimensions as an example. The impact of water absorption on structural response under dynamic loading at empty, half full and full capacity was investigated. Ideal finite element models of the water tower were constructed using operational modal analysis. Linear time history analyses were conducted using the finite element software. The structure was modelled with the Lagrangian approach, while the fluid was modelled using the Eulerian approach in finite element analysis. The coupled Eulerian Lagrangian technique was employed for the analysis. Results obtained from the analyses indicate that an increase in tank fill level led to enhanced structural damping, resulting in reduced displacement and stress values.
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    Collapse mechanism estimation of a historical masonry minaret considered soil-structure interaction
    Altiok, TY; Demir, A
    Cultures and lifestyles of past communities can be transferred to the next generations through historical structures. Accordingly, these structures should be carefully preserved against devastating events i.e. earthquakes, wind, and fire. Seismic performances of historical structures can be determined with destructive and nondestructive methods. As destructive methods are quite difficult and complex, easier and reliable methods should be used to determine the seismic behaviors of these structures. In this study, the seismic behavior of the historical Lala Mehmet Pasha minaret is investigated by considering Soil Structure Interaction (SSI). Dynamical properties of the minaret are experimentally obtained with the operational modal analysis (OMA) method and the initial finite element (FE) model is updated. Embedded and SSI models are generated by Abaqus, then linear (LTH) and nonlinear time history (NLTH) analyses are performed. As a result of analyses, displacements, damage, and stress distributions are obtained and interpreted. These analyses show that SSI is quite effective on the structural behavior and results obtained from the nonlinear analysis are more realistic than that of linear analysis.
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    Seismic performance of retrofitted and non-retrofitted RC school buildings after the February 6th, 2023, Kahramanmaraş earthquakes
    Altiok, TY; Sevik, M; Demir, A
    On February 6, 2023, two significant earthquakes struck Pazarc & imath;k and Elbistan/Kahramanmara & scedil; with magnitudes of 7.7 and 7.6, respectively. These earthquakes are considered the most devastating disaster in Turkey in the last century. According to official records, these earthquakes affected 11 provinces, resulting in the loss of more than 50,000 lives. Additionally, numerous buildings collapsed or became unusable due to the impact of the earthquakes and the schools constitute an important part of these structures. The schools are important facilities that need to be functional and safe following an earthquake. This study contains both post-earthquake field observations and numerical studies for the retrofitted and non-retrofitted schools. It investigates the retrofitted and non-retrofitted conditions of a total of 7 blocks, which consist of 4 different schools located in Kahramanmara & scedil;. It is observed that the retrofitted school buildings weren't damaged after these earthquakes. The numerical models underwent nonlinear time history analyses using the ETABS program. The ground accelerations used in the analyses were obtained from the nearest station to the school buildings. The analyses yielded several results, including the natural periods, story displacements, story drifts, and seismic energy inputs of the structures. These results were then compared with the field observations to assess their accuracy and validity. With the retrofit application, story displacements, the interstory drifts and seismic energy input have decreased. Both field studies and numerical analyses have shown that even school buildings with insufficient material and engineering services can become resistant to major earthquakes with an appropriate retrofit method.
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    Experimental investigation of EBROG and bore-epoxy anchorage methods used for interior RC beam-column joints strengthened with CFRP sheets
    Cetin, K; Altiok, TY; Demir, A
    In severe earthquakes, the energy dissipation and ductility capacities of the structures depend on the performance of the beam-column joints where the load transfer is performed. Experiences in past earthquakes have shown that damage occurs in the beam-column joints that do not have sufficient strength and rigidity. In particular, the shear failure observed in deficient detailed joints has caused the collapse of many structures. Joints are effectively retrofitted with carbon fiber reinforced polymer (CFRP) sheets to increase the earthquake safety of the structures. However, the debonding problem experienced in CFRP sheets significantly affects the efficiency of the applied retrofit and the earthquake behavior of the member. In this study, the retrofit of reinforced concrete beam-column joints with deficient shear strength was carried out with CFRP sheets by using externally bonded reinforcement on grooves (EBROG) and bore-epoxy anchorage methods. These two retrofit methods were applied to effectively utilize the full capacity of CFRP sheets by delaying the debonding. Six 1/2 scaled reinforced concrete (RC) interior beam-column specimens without transverse reinforcement in the joint core were constructed. One reference and five retrofitted joints were subjected to displacement-controlled cyclic loading. The shear failures in the specimens were delayed until advanced displacement levels. The use of EBROG and bore-epoxy anchorage methods improved the yield load of the specimens by 32 % to 69.05 % compared to the reference specimen. Additionally, significant increases were observed in the initial stiffness, load-carrying, and energy dissipation capacities of the retrofitted specimens up to 68 %, 64 %, and 104 %, respectively. The ductility of the retrofitted specimens increased by approximately 7 % to 26 %. The EBROG and bore-epoxy anchorage methods proved to be highly successful in preventing the early debonding of CFRP sheets. In specimens strengthened with EBROG and bore-epoxy anchorage methods, the displacement values at which the FRP sheets began to debonding approximately doubled. It was concluded that EBROG and bore-epoxy anchorage methods were more effective than the externally bonded reinforcement (EBR) method in improving the overall structural performance of the joints.
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    Experimental and numerical investigation of RC beams strengthened with CFRP composites
    Demir, A; Ince, Y; Altiok, TY
    This study aims to strengthen reinforced concrete (RC) beams having insufficient shear capacity using Carbon Fibre Reinforced Polymer (CFRP) members and innovative anchorages. An innovative method is also proposed for strengthening beams in interaction site of adjacent structures. Test results show that the behaviour of beams has been improved with CFRP elements. The nonlinear finite element (FE) method, as well as American and Italian guidelines, are used to estimate theoretical capacity of the beams. Test results are compared with theoretical results. It can be concluded that proposed methods can be used reliably, and that the design of RC beams strengthened with these methods can be performed by design engineers based on simple calculations.