Publications

Eşdeğer Deprem Yükü Yöntemi Kullanılarak Tarihi Bir Yığma Yapının Sismik Performans Düzeyinin Belirlenmesi

Tarih boyunca Anadolu toprakları, birçok medeniyete ev sahipliği yapmıştır. Bu sebeple ülkemizde tarihi yapılar azımsanmayacak sayıdadır. Bununla birlikte ülkemizin, aktif deprem kuşağı içerisinde yer alması sebebiyle birçok tarihi yapı, meydana gelen depremlerden zarar görmüş veya yıkılmıştır. Kültür mirası açısından önem arz eden tarihi yapılarımızın, gelecek kuşaklara güvenle aktarılabilmesi için sismik performans seviyelerinin doğru ve hızlı bir şekilde belirlenerek gerekli müdahalelerin yapılması oldukça önemlidir. Çalışma kapsamında örnek olarak ele alınan Tarihi Yanıkoğlu Camisinde yapılan ölçümler ve gözlemlere dayalı olarak yapının analitik modeli oluşturulmuştur. Yapı konumuna özel olarak seçilen deprem spektrumları ile eşdeğer deprem yükü hesaplanmıştır. Yapının kendi ağırlığı ve hesaplanan deprem kuvvetleri altında yapılan analizlerden elde edilen sonuçlara bağlı olarak yapının sismik performans düzeyi 2017 yılında Vakıflar Genel Müdürlüğünce yayımlanan Tarihi Yapılar İçin Deprem Risklerinin Yönetimi Kılavuzuna göre belirlenmiştir. Bu çalışma ile tarihi yığma yapıların sismik performanslarının değerlendirilmesinde eşdeğer deprem yükü yöntemi kullanılarak pratik bir yaklaşım ortaya konulmuştur.

Flexural behaviour of old wooden beams strengthened with CFRP: Experimental and numerical investigations

The flexural performance of old wooden beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) strips was investigated through a combination of experimental and numerical analyses. Timber specimens were sourced from three historic wooden structures in Türkiye. CFRP strips were bonded to the tension zone of the beams to enhance flexural performance, while transverse CFRP strips were applied at regular intervals to improve shear resistance. A total of thirty-one beam specimens, varying in wood type, span length, and CFRP strip spacing, were tested under three-point bending. Key variables included chestnut and elm wood, span lengths of 300–700 mm, and CFRP strip spacings of 50 mm, 75 mm, and 100 mm. Beams with 50 mm strip spacing (S5) exhibited the highest values with load capacity (52.7 kN), stiffness (3.55 kN/mm) occurred in elm beams, while the largest displacement (25.3 mm) and energy dissipation (494 kN-mm) occurred in chestnut beams. Digital Image Correlation (DIC) was employed to assess strain distributions, while numerical models were developed using finite element analysis (FEA) to validate experimental results. DIC analysis confirmed that peak strains occurred near the loading point, while minimum strains were observed at the supports. FEA models closely matched experimental data, with parameter ratios mostly ranging between 0.64 and 1.16, confirming their reliability. The numerical analysis aligned closely with experimental outcomes, showcasing its effectiveness in modelling the anisotropic and heterogeneous nature of timber. These findings highlight CFRP’s effectiveness in strengthening and preserving historic wooden structures, offering a sustainable solution for modern timber engineering applications.

Korozyonlu betonarme kolonlarda donatı korozyonunun plastik mafsal boyu üzerine etkisinin araştırılması.

Out-of-Plane performance of masonry wallets strengthened with FRP-Reinforced prefabricated panels made from construction and demolition Waste-based mortars

This study investigated the out-of-plane performance of masonry wallets strengthened with prefabricated geopolymer panels produced using construction and demolition waste (CDW)-based mortars. The masonry wallets were constructed using three different types of masonry units: (a) aerated concrete blocks, (b) hollow bricks, and (c) clay bricks. Two geopolymer mortar mixtures were prepared using concrete waste, brick waste, and ground granulated blast furnace slag as precursor materials and recycled concrete aggregates as the primary aggregate source. The alkaline activators consisted of either sodium hydroxide (NaOH) solution alone or a combination of NaOH solution and sodium silicate. The panels were reinforced with three different types of fiber-reinforced polymer (FRP) meshes: (a) carbon, (b) glass, and (c) basalt. A total of 27 specimens, including control and strengthened samples, were subjected to three-point bending tests. Structural performance was evaluated based on load-bearing capacity, stiffness, and energy dissipation. In addition, measurements were taken during the experiments using the Digital Image Correlation (DIC) method, and the displacement and strain distributions of the specimens were determined. The results demonstrated significant improvements in the structural performance of the strengthened wallets, with load-bearing capacities increasing from 0.85 kN to 13.44 kN (an increase of approximately 1481%) for aerated concrete, from 1.03 kN to 17.93 kN (an increase of approximately 1641%) for hollow bricks, and from 0.62 kN to 21.04 kN (an increase of approximately 3293%) for clay bricks. Energy dissipation values also increased substantially for each type of masonry unit. Although there were some exceptions, the most favorable results were generally achieved with specimens strengthened with panels reinforced with carbon mesh and produced using sodium silicate.

Experimental and analytical investigation of moment-carrying capacities of reinforced concrete frame systems corroded by accelerated corrosion method

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.

A novel bond-slip model between TRM strips and different types of masonry walls: Experimental approach

Korozyona maruz kalmış betonarme kolonların yapısal davranışlarının deneysel olarak incelenmesi

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.

Experimental behavior of shear deficient RC beams strengthened with CFRP strips againts reversible cylic earthquake load

This study aims to prevent sudden and brittle shear failures in reinforced concrete beams, which are frequently caused by deficiencies in shear reinforcement. Following the Kahramanmaraş earthquakes in Turkey on February 6, 2023, inspections revealed that many reinforced concrete beams suffered severe damage due to design errors, high shear forces, and secondary effects. These issues are often a result of inadequate shear reinforcement and improper placement. The objective of this study is to enhance the overall load–displacement behavior of reinforced concrete beams with insufficient shear strength under cyclic loading conditions, transforming their failure mechanisms to exhibit ductile flexural failure. The developed strengthening method involves the use of CFRP strips with fan‐type anchors at their ends. This method has been applied to beams with both low and normal concrete compressive strength. The study investigates the maximum load capacity, initial stiffness, displacement ductility ratios, energy dissipation capacities, and overall load–displacement behavior of the tested beams under cyclic loading conditions. The impact of the strengthening method on beam performance is thoroughly evaluated. Additionally, the experimental results are compared with nonlinear finite element analyses conducted using ABAQUS software. The agreement between numerical analysis and experimental results is assessed, evaluating the reliability and accuracy of the finite element model. The findings of this study indicate that the proposed strengthening method is effective in enhancing the performance of reinforced concrete beams.

Retrofitting of squat RC column by using TRM strip under axial load

Seismic resilience of masonry buildings with a novel arch-type hollow brick (ArchBrick): Multi-scale numerical assessment from unit to building level

Investigation of the structural behavior of reinforced concrete beam with Perlite under the effect of monotonic load

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.

Experimental investigation of behavior of masonry wall under diagonal tension loading: Strengthening with CFRP versus TRM

An experimental study about unreinforced masonry panels strengthening with CFRP: Out-of-plane failure

Effect of polypropylene fibers on the development lengths of reinforcement bars of slabs

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.

Cyclic loading test on highly corroded reinforced concrete columns

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.

Investigation of experimental models for predicting mechanical properties of corroded reinforcement bars

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.

Bond-Slip Models for Textile Reinforced Mortar Strengthened Masonry Walls

No abstract is provided for this article.

Investigation of the bond-reinforcement slip relationship between conventional and natural perlite concrete and reinforcement bar

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.

An experimental study on seismic performance levels of highly corroded reinforced concrete columns

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.