İnşaat Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/395

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A New Novel Model Proposal For Bond-Slip Behavior Between Angular CFRP Fan Type Anchoraged CFRP Strip and Concrete Surface
(2020) Ghoroubi, Rahim; Mercimek, Ömer; Anıl, Özgür; Özgür, A. C. Anıl
In the reinforced concrete, masonry or steel structures should be strengthened or repaired. Carbon fiber reinforced polymers (CFRP) have been widely used for the last 20 years for repairing and strengthening of inadequate earthquake performance of the structures. One of the most important developed design criteria in the retrofit and strengthening details are using CFRP to delay the debonding of the CFRP reinforcement elements. For this reason, the uses of anchors in the reinforcement details developed by using CFRP and also researches on this subject have increased substantially. In the literature, research on bond-slip models developed for fan type CFRP anchors and anchored CFRP strips used in reinforcement details are limited in comparison to non-anchored strips. However, in studies on this subject, anchors are placed at 90o to the axial tensile force applied to the CFRP strips. Axial force-bearing strength and bond-slip models of CFRP strips with the different anchored angle under axial tensile strengths have not been found in the literature. For this reason, an experimental study was carried out and 28 specimens of angled anchored CFRP strip test specimen, which was bonded to the concrete surface, was tested under the influence of axial tensile force with an experimental setup designed by the authors. The variables studied in the experimental study are the CFRP strip width and the fan type CFRP anchor angle placed on the CFRP strip. As a result of the experimental study, an equation was proposed for calculating the bearing strength values of angled anchored CFRP strips and a new proposal for the bond-slip model was developed.
Citation - WoS: 2
Citation - Scopus: 3
Effects of Collars on Local Scour Around Semi-Circular End Bridge Abutments
(Emerald Group Publishing Ltd, 2023) Gogus, Mustafa; Daskin, Sueyla; Gokmener, Serkan
The occurrence of scour around bridge elements due to the transportation of bed material during flood events can cause serious structural damage and loss of life. Increased uncertainties in precipitation and runoff predictions due to climate change make this phenomenon more complex and dangerous. Bridge scour countermeasures should thus be more focused on decreasing scour formation around bridge elements. In this study, abutment scour under clear-water conditions with constant flow intensity was conducted and collars were tested as scour countermeasures around semi-circular end bridge abutments. The experimental study was performed in a rectangular channel with an almost uniform cohesionless bed material for 3 h with and without collars. Collars of various lengths located at different elevations around the abutments were tested to investigate the effect of collars on scour development. The results of the study showed that the scour depth decreased with increasing collar width and when the collar was placed below the bed level for a given abutment length. The results were compared with those of similar earlier studies to show the effect of abutment shape, size of the bed sediment and test durations on the development of scour depth around abutments.
Citation - WoS: 14
Citation - Scopus: 17
Experimental and Numerical Investigation of Rc Column Strengthening With Cfrp Strips Subjected To Low-Velocity Impact Load
(Techno-press, 2021) Mercimek, Omer; Anil, Ozgur; Ghoroubi, Rahim; Sakin, Shaimaa; Yilmaz, Tolga
Reinforced concrete (RC) square columns are vulnerable to sudden dynamic impact loadings such as the vehicle crash to the bridges of highway or seaway, rock fall, the collision of masses with the effect of flood and landslide. In this experimental study RC square columns strengthened with and without CFRP strip subjected to sudden low velocity lateral impact loading were investigated. Drop-hammer testing machine was used to apply the impact loading to RC square columns. The test specimens were manufactured with square cross sections with 1/3 geometric scale. In scope of the study, 6 test specimens were manufactured and tested. The main variables considered in the study were the application point of impact loading, and CFRP strip spacing. A 9.0 kg mass was allowed to fall freely from a height of 1.0 m to apply the impact loading on the columns. During the impact tests, accelerations, impact force, column mid-point displacements and CFRP strip strains measurements were taken. The general behavior of test specimens, collapse mechanisms, acceleration, displacement, impact load and strain time relationships were interpreted, and the load displacement relationships were obtained. The data from the experimental study was used to investigate the effect of variables on the impact performances of RC columns. It has been observed that the strengthening method applied to reinforced concrete columns, which are designed with insufficient shear strength, insufficient shear reinforcement and produced with low strength concrete, using CFRP strips significantly improves the behavior of the columns under the effect of sudden dynamic impact loading and increases their performance. As a result of the increase in the hardness and rigidity of the specimens strengthened by wrapping with CFRP strips, the accelerations due to the impact loading increased, the displacements decreased and the number of shear cracks formed decreased and the damage was limited. Moreover, the finite element analyses of tested specimens were performed using ABAQUS software to further investigate the impact behavior.
Citation - WoS: 78
Citation - Scopus: 92
Finding the Most Suitable Existing Hydropower Reservoirs for the Development of Pumped-Storage Schemes: an Integrated Approach
(Pergamon-elsevier Science Ltd, 2014) Kucukali, Serhat
This study aims to evaluate existing hydropower reservoirs for the development of pumped-storage schemes by using multi-criteria scoring technique. This method enables a screening of existing hydropower reservoirs, in order to assess and rank potential sites for pumped-storage development. This analysis is based on the documented evidence, measured data, and site surveys. The site assessments are categorized in 6 criteria namely geometrical conditions (maximum head, head to water way length ratio, distance to grid connection), geological conditions, environmental, and social conditions. In the context of the study, 7 existing hydropower reservoirs in Turkey, each with a catchment area of more than 50 km(2), are evaluated in order to be utilized as the lower reservoirs of pumped-storage facilities. The overall score of each candidate site is obtained and, their performance is compared. The results indicate that Turkey have suitable existing hydropower reservoirs for the development of pumped-storage facilities. However, the country lacks from legal and market framework for the establishment of pumped-storage power plants. (C) 2014 Elsevier Ltd. All rights reserved.
High-velocity impact of large caliber tungsten projectiles on ordinary Portland and calcium aluminate cement based HPSFRC and SIFCON slabs. Part I: experimental investigations
(Techno-Press, 2011) Polat, Gülkan; Korucu, Hasan
Impact experiments have been carried out on concrete slabs. The first group was traditionally manufactured, densely reinforced concrete targets, and the next were ordinary Portland and calcium aluminate cement based HPSFRC (High performance steel fiber reinforced concrete) and SIFCON (Slurry infiltrated concrete) targets. All specimens were hit by anti-armor tungsten projectiles at a muzzle velocity of over 4 Mach causing destructive perforation. In Part I of this article, production and experimental procedures are described. The first group of specimens were ordinary CEM I 42.5 R cement based targets including only dense reinforcement. In the second and third groups, specimens were produced using CEM I 42.5 R cement and Calcium Aluminate Cement (CAC40) with ordinary reinforcement and steel fibers 2 percent in volume. In the fourth group, SIFCON specimens including 12 percent of steel fibers without reinforcement were tested. A high-speed camera was used to capture impact and residual velocities of the projectile. Sample tests were performed to obtain mechanical properties of the materials. In the companion Part II of this study, numerical investigations and simulations performed will be presented. Few studies exist that examine high-velocity impact effects on CAC40 based HPSFRC targets, so this investigation gives an insight for comparison of their behavior with Portland cement based and SIFCON specimens
On the properties of piezoelectric materials based upon orthonormal representations
(CRC Press-Taylor, 2013) Dinçkal, Çiğdem
For piezoelectric tensor, the decomposition method based upon irreducible orthogonal representation is overviewed. Besides, orthonormal tensor basis method is improved to express any third rank tensors such as piezoelectric tensor showing the piezoelectric effect of the material properties on the structures. Numerical examples for materials from different crystal symmetry classes serve to illustrate and verify the orthonormal tensor basis method. The differences and similarities are stated by comparing the methods presented in this work and the others in literature. It is also demonstrated that for hexagonal symmetry, each decomposed parts obtained from orthonormal tensor basis method has physical meaning. Furthermore, the norm based upon orthonormal tensor basis representation of piezoelectric tensor is obtained explicitly for each crystal symmetry classes and those results are used to study the piezoelectric effect of different materials. It is also shown that one can determine in which material the piezoelectric effect is stronger by using the norm concept for any material from various crystal symmetry classes.
Citation - WoS: 45
Citation - Scopus: 51
Risk Assessment of River-Type Hydropower Plants Using Fuzzy Logic Approach
(Elsevier Sci Ltd, 2011) Kucukali, Serhat
In this paper, a fuzzy rating tool was developed for river-type hydropower plant projects, and risk assessment and expert judgments were utilized instead of probabilistic reasoning. The methodology is a multi-criteria decision analysis, which provides a flexible and easily understood way to analyze project risks. The external risks, which are partly under the control of companies, were considered in the model. A total of eleven classes of risk factors were determined based on the expert interviews, field studies and literature review as follows: site geology, land use, environmental issues, grid connection, social acceptance, macroeconomic, natural hazards, change of laws and regulations, terrorism, access to infrastructure and revenue. The relative importance of risk factors was determined from the survey results. The survey was conducted with the experts that have experience in the construction of river-type hydropower schemes. The survey results revealed that the site geology and environmental issues were considered as the most important risks. The new risk assessment method enabled a Risk Index (R) value to be calculated, establishing a 4-grade evaluation system. The proposed risk analysis will give investors a more rational basis to make decisions and it can prevent cost and schedule overruns. (C) 2011 Elsevier Ltd. All rights reserved.
Seismic behavior of a four-legged masonry minaret
(2012) Kazaz, İ.; Akansel, V.; Gülkan, Polat; Kazaz, E.
The four-legged Minaret of Sheikh Mutahhar Mosque has been constructed in the early 16th century during the Aq Qoyunlu Period in Diyarbakır, Turkey, which is located in the second most hazardous zone of the Turkish Seismic Zones Map. This is a special structure, because the minaret body has been placed on four cylindrical stone columns. Therefore, this minaret is seemingly vulnerable though it has survived for five centuries. We use the square cross sectioned minaret as a possible large-scale seismograph to examine the possible limits of ground motion that must have affected it without causing its collapse. In order to investigate the likely seismic performance and strength of the four-legged minaret, a model, which is very close to real structure, was generated with explicit dynamic code LS-DYNA. The developed model takes into account the material nonlinearities and the interface friction and contact behavior between the masonry units. It was displayed that the amplitude of the ground motion in Diyarbakır could not be 0.15g.

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