Technical investigations carried out after the devastating earthquakes in Turkey in the last 25 years show that one of the main causes of damage to reinforced concrete structures is reinforcement bar corrosion. The deterioration caused by reinforcement corrosion in reinforced concrete elements reduces the parameters that define the performance level of the structure, such as ductility, stiffness, bond-slip relationship, load carrying capacity, and energy absorption capacity. Therefore, determining the specified performance levels of reinforced concrete structures exposed to corrosion before any seismic activity occurs is of great importance in preventing loss of life and property. Cross-section behavior in reinforced concrete structures represents the load-bearing element behavior In order to accurately determine the section behavior, the Moment-Curvature relationship must be defined. In this study, the structural behavior of reinforced concrete frames exposed to corrosion was examined experimentally and analytically. For this purpose, 4 of the 5 reinforced concrete frame specimens constructed were corroded at different ratios using the accelerated corrosion method. After the corrosion process was completed, in the experimental part of the study, all specimens were tested under the effect of a 20% constant axial load and reversal-cyclic loading. In the analytical study, as a result of the cross-sectional analyzes carried out by taking into account the material-mechanical properties changing with the effect of corrosion, it was determined that the calculated moment values were in high predicted with the experimentally measured moment values.
Betonarme elemanlarda oluşan donatı korozyonu sebebiyle, yapıların hedeflenen performans seviyeleri olumsuz yönde etkilenmektedir. Donatı kesit alanında azalma, korozyon ürünlerinin hacimsel genişlemesi ile betonun çatlaması, beton ve donatı arasındaki aderans kuvvetinin azalması korozyonun betonarme elemanlarda neden olduğu başlıca olumsuz etkilerdendir. Paslanmış betonarme kolonların yapısal performanslarının doğru bir şekilde değerlendirilebilmesi için yapılan araştırmalar önemini korumaktadır. Çalışma kapsamında yüksek seviyelerde donatı korozyonunun, betonarme kolonların yapısal davranışları üzerine etkisini incelemek üzere 5 adet tam ölçekli betonarme kolonu imal edilmiştir. Bir adet betonarme kolon referans tutularak korozyona maruz bırakılmamış olup, diğer numunelere tam ölçekli paslandırma havuzunda farklı seviyelerde hızlandırılmış korozyon süreci uygulanmıştır. Paslandırma sürecinin ardından numuneler üzerinde korozyon sebebiyle meydana gelen çatlak genişlikleri mikroskopla ölçülerek haritalandırma yapılmıştır. Tam ölçekli betonarme kolon numuneleri sabit eksenel yük altında, artırımsal tersinir tekrarlanır yanal yük uygulanarak teste tabi tutulmuştur. Yükleme deneylerinden sonra numunelerdeki boyuna donatılar ve etriyeler kırılarak çıkarılmış ve mekanik olarak beton artıklarından temizlenmiştir. Donatıların son ağırlıkları hassas terazi ile kayıt altına alınarak numunelerin gerçek korozyon oranları hesaplanmıştır. Elde edilen tüm deneysel verilerin ışığında korozyon etkisine maruz betonarme kolonların sismik performans seviyelerinin belirlenmesi için enerji bazlı ampirik modeller önerilmiştir.
When the existing structure stock is examined, it can be seen that the majority of buildings have reinforced concrete (RC) carrier systems. This case, combined with the increasing population and the increase in urbanization and industrialization, to be increased the need for concrete, which is the raw material of RC building production, day by day. In line with the stated need, the expected need must be met by taking into account both economic and ecological facts in concrete production without compromising the material mechanical properties of concrete (compressive strength, strain, ductility, etc. in concrete). Within the scope of the study, it is planned to fabricate a total of 4 RC beam specimens using both conventional and natural perlite aggregate. After the loading tests, the load-displacement relationship, energy consumption capacity and damage distributions of the specimens will be investigated. In the light of all test data, the usability of natural perlite aggregate in RC beams will be revealed.
Ductile behavior is one of the most important earthquake indicators that must be possessed by structures. Because of the limited tensile strength of concrete, alternative materials such as structural nanosynthetic fibers as three-dimensional reinforcement bars have gained increasing popularity over several decades. However, the contribution of fibers to the development length of reinforcement bars has not been investigated. Therefore, an experimental study was conducted to investigate the effects of polypropylene fibers on the development lengths of reinforcement bars. Thirty-three reinforced concrete (RC) slabs at three different volume fractions of fibers of 0.0, 1.0 and 1.5 % at different embedment lengths of reinforcement bars were investigated under four-point flexural strength tests. Load-displacement curves, energy absorption capacities, ductility ratios and bond-slip relationships were obtained for different embedment lengths of reinforcement bars with three different amounts of fibers in RC concrete slabs. The test results revealed that the predominant effects of fibers on structural behavior pertained to the energy absorption capacities at plastic deformation. It was found that resisting more strains by reinforcement bars with the help of added polypropylene fibers resulted in the regaining of ductile behavior due to the reduced embedment lengths of the reinforcement bars.
An experimental study was performed on fıve reinforced concrete (RC) columns to investigate the structural behavior of highly corroded RC columns. Four of the RC columns were corroded using an accelerated corrosion method for different corrosion levels at longitudinal bars as 15.4, 20.2, 27.3 and 28.3%. RC columns were tested under cyclic load for a constant axial load ratio of 0.40. After the loading test, the actual corrosion levels were obtained by extracting the longitudinal bars and stirrups following the breaking of the RC columns. Load-displacement curves, ductility ratios and energy absorption capacities oftested RC columns were obtained. Test results revealed that the ductility ratios of corroded RC columns should be determined in accordance with energy-based or bilateral failure criteria due to the misleading of increased ductility ratios of corroded RC columns based on the displacement method.
Carbonation and chloride penetration, which occur as a result of various environmental effects in reinforced concrete structures, cause reinforcement bar corrosion. Physical and chemical deterioration processes caused by corrosion lead to section losses in pitting or homogeneous forms of reinforcement bar. With section losses, decreases are observed in the material characteristic properties of the reinforcement bar such as yielding strength, ultimate/failure strength and strain property. Within the scope of the current study, it was aimed to examine the models used in the existing literature to predict the mechanical properties of corroded reinforcement bars such as yielding strength, ultimate/failure strength and elasticity modulus, as a function of the corrosion ratio. For this purpose, an analytical study will be carried out on reinforcement bars with different reinforcement diameters, corrosion ratios and corrosion types. From the research to be conducted, it is expected that the prediction performances of the corrosion ratios taken into account in the studies in which previous models were developed will show a appropriate harmony with different corrosion ratios.
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The high costs and environmental damage in conventional concrete production have led researchers to search for alternative materials. The aim of the studies carried out in this context is to improve the material mechanical properties of concrete and to progressive economical products. When the existing literature is examined; the changing material mechanical properties of concrete have been examined by adding materials such as fly ash, blast furnace slag, waste rubber, steel wire and plastic fiber in different volumetric ratios to concrete or by using light, sustainable and economical materials such as natural perlite instead of conventional aggregate in the concrete ingredient. The bond-reinforcement slip relationship between reinforcement bar and concrete depends on many factors such as concrete compression level, bar diameter, embedment depth, and concrete void structure. In this study; it was aimed to investigate the effect of concrete compression level, concrete cover and perlite usage parameters on the bond-reinforcement slip relationship between reinforcement bar and concrete by producing a total of 24 cube samples with 20 MPa and 40 MPa compressive strength and 2.0 mm and 4.0 mm concrete cover using conventional aggregate and natural perlite aggregate. From the research to be conducted; it is expected that the bond strength of conventional concrete and natural perlite concrete will be improved by increasing the concrete compressive strength and concrete cover parameters.
In the literature, only one empirical model is available as a nondestructive method for the prediction of seismic performance levels of corroded reinforced concrete (RC) columns as a function of the initial corrosion crack width at lower corrosion levels. Because of the ruptured transverse reinforcement bars at higher corrosion levels, the structural behavior may turn brittle in terms of shear failure. Therefore, in this study, higher corrosion levels for a different concrete strength level from that empirical model were studied. To do this, four RC columns were subjected to accelerated corrosion, and the widths of initial corrosion cracks were measured. The corroded RC columns were then tested under combined constant axial load and cyclic lateral displacement excursions. After the cyclic loading test, the actual corrosion levels at each reinforcement bar were obtained by extracting the reinforcement bars from the concrete. Test results showed that the prediction of seismic performance levels of corroded RC columns based on initial corrosion crack widths were limited owing to the nonlinear increase in the crack width with the increase in the corrosion levels. New empirical models were developed to predict the remaining energy capacities and seismic performance levels of the corroded RC columns.
