1,721,075 research outputs found
Seismic Strengthening with Precast Concrete Panels - Theoretical Approach
Get PDFCanbay, Erdem/0000-0001-6798-0144; Baran, Mehmet/0000-0001-6674-7308An economical, structurally effective and practically applicable seismic retrofitting technique has been developed on the basis of the principle of strengthening the existing hollow brick infill walls by using high strength precast concrete panels. The technique would not require evacuation of the building and would be applicable without causing much disturbance to the occupant. For this purpose, a total of eighteen reinforced concrete frames with hollow brick infill walls were tested under reversed cyclic lateral loading simulating earthquake. The specimens were strengthened by using six different types of precast concrete panels. In the present study, hollow brick infill walls strengthened by using high strength precast concrete panels were modeled once by means of equivalent diagonal struts and once as monolithic walls having an equivalent thickness. The experimental results were compared with the analytical results of the two approaches mentioned
Modelling of strengthened hollow brick infills
No full textCanbay, Erdem/0000-0001-6798-0144; Baran, Mehmet/0000-0001-6674-7308Strengthening the existing hollow brick infill walls by bonding high-strength precast concrete panels or applying steel fibre reinforced mortar was found to be an occupant-friendly seismic retrofitting technique for the buildings in use with deficient reinforced concrete structural systems. Both techniques convert the existing non-structural hollow brick infill walls into load-carrying structural members. To verify the effectiveness of the techniques, 20 reinforced concrete frames with hollow brick infill walls were tested under reversed cyclic lateral loading simulating earthquake. In the present study, hollow brick infill walls strengthened by these techniques were modelled by means of two equivalent diagonal struts in the analytical studies. Analytical results matched well with the experimental results. A performance-based rehabilitation case study of an existing building showed that both techniques offer a sound and practical solution for rehabilitation studies
Use of steel fiber reinforced mortar for seismic strengthening
No full textBilir, Turhan/0000-0003-0317-026X; Canbay, Erdem/0000-0001-6798-0144; Baran, Mehmet/0000-0001-6674-7308The objective of this research was to develop an economical, structurally effective, and practically applicable steel fiber reinforced mortar (SFRM) which could be applied onto the hollow brick infills of a reinforced concrete (RC) structure. Masonry walls were almost converted into strong and rigid infills with the application of SFRM. Two different mix proportions were produced with the composition of Portland cement, fine aggregate, water, and plasticizer or bonding agent as the chemical admixture. Tests were carried out to determine the optimum steel fiber content (1%, 2%, or 4% by volume) and to clarify the use of plasticizer or bonding agent in the mortar in the context of sticking ability, flexural, compressive, and adhesion strengths. As a result, mortar with plasticizer and 2% steel fiber (by volume) came out to be the optimum mortar mixture as strengthening material. The performance of RC frame strengthened with SFRM containing plasticizer and 2% steel fiber by volume was compared to those of the hollow brick infilled RC frame without strengthened mortar and the hollow brick infilled RC frame with reference mortar. It was observed that the specimen strengthened with the optimum mortar mix satisfied the target objectives of this study. (C) 2010 Elsevier Ltd. All rights reserved
Comparison of code provisions on lap splices
No full textThe code provisions on lap splices are critically assessed in the light of 203 beams without transverse reinforcement and 278 beams with transverse reinforcement. For comparison, the provisions given in the ACI 318, Eurocode 2, and TS 500 Codes are considered. The ACI Committee 408 recommended provision and a new proposal are also taken into account throughout the assessment. The comparison with real beam tests where the splice region was subjected to constant moment indicates that current provisions in the Codes do not agree acceptably with test results. The steel stress prediction graphs calculated by means of the Code provisions show high scatter and remain unsafe especially for test data without transverse reinforcement. Both the recent recommended provision by ACI Committee 408 and a new design expression proposed by the author have much less scatter with fewer unsafe predictions. The simplified design provision proposed by ACI Committee 408 does not yield similar results to that of the advanced design provision proposed by the same committee and therefore it could conveniently be replaced with the simpler equation proposed by the author
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Kendinden yerleşen betonda bindirmeli eklerin aderansı.
No full textSelf-compacting concrete is an innovative construction material; its priority to normal vibrated concrete is that there is not any vibration requirement. Bond strength of reinforcement is one of the key factors that ensures the usefulness of any reinforced concrete structure. In this study, 6 full-scale concrete beams spliced at the mid-span were tested under two-point symmetrical loading. Test variables were bottom cover, side cover, free spacing between longitudinal reinforcement, lap-splice length and presence of transverse reinforcements within the lap-splice region. Specimen SC_22_44_88_800 had cover dimensions close to the code limits and had 36db lap splice length. This specimen showed flexural failure. Specimen SC_44_44_44_710 had 32db lap splice and cover dimensions greater than code minimums. This specimen showed yielding primarily. With the increasing loading, however, bond failure occurred with side splitting. ACI 408 descriptive equation for normal vibrated concrete predicted bar stresses of the unconfined specimens produced with self-compacting concrete acceptably well. The predicted values were lower than the measured values to be on the safe side. The error varied between 3.4% and 6.5%. All predictions of the ACI408 descriptive equation was higher than the measured bar stresses of the confined specimens produced with SCC. All the calculated values were unsafe. The error varied between 10.6% and 34.5%. Specimen SC_44_22_22_530_T4 with 24db lap splice length had side cover and spacing between bars 63.3% and 56.7% less than the ACI 318 limits. The calculated bar stress was 21.6% higher than the measured value. The main reason of the deviation was inadequate cover dimensions. In specimen SC_44_22_22_530_T6, number transverse reinforcement was increased to 6 stirrups to overcome the small cover and spacing problem. However, increased number of stirrups inside a small side and face cover caused weak plane and measured bar stress decreased.M.S. - Master of Scienc
TBDY 2018 YÜKSEK DAYANIMLI BETON GERİLME DAĞILIMI ÜZERİNE BİR ÖNERİ
No full textThe use of high-strength concrete (HSC) has become increasingly popular since the beginning of the current millennium. Thanks to the greater strength per unit volume, it found widespread use in the construction of high-rise buildings and long-span prestressed bridges. In the 1960s, researchers started adding supplementary materials, initially superplasticizers, to the concrete mix to increase the strength of concrete. The theoretical research of the material on the academic level is older than its practical use. It dates back to the 1980s when researchers started to examine the mechanical properties of the material. Although it has been more than forty years since researchers began experimenting with structural elements of HSC, the major international codes have not made extensive additions to the code requirements regarding HSC. One of the design codes not including requirements for HSC extensively is TBEC 2018, which refers to Eurocode 2 for the use of equivalent rectangular stress-block parameters for concrete grades over 50 MPa. The current study aims to eliminate this need and propose a new expression for stress-block parameters for structural elements with concrete grades over 50 MPa. Additionally, a new factor of reduction is proposed for the overall axial and bending moment capacity of HSC columns of over 80 MPa due to premature cover spalling, the effect that is present in HSC columns. The results of ultimate section capacity calculations due to proposed expressions are examined and verified against experimental results of research publications from 1995 to 2021.Yüksek dayanımlı beton kullanımı (YDB), mevcut binyılın başından bu yana giderek daha popüler hale gelmiştir. Birim hacim başına daha yüksek mukavemet sayesinde, yüksek binaların ve uzun açıklıklı öngerilmeli köprülerin yapımında yaygın kullanım alanı bulmuştur. 1960'larda araştırmacılar, betonun mukavemetini arttırmak için beton karışımına başlangıçta süperakışkanlaştırıcılar olmak üzere ilave malzemeler eklemeye başlamışlardır. Malzemenin akademik düzeydeki teorik araştırması, pratik kullanımından daha eskidir. Araştırmacıların malzemenin mekanik özelliklerini incelemeye başladığı 1980'lere kadar uzanmaktadır. Araştırmacıların YDB’nin yapısal unsurlarını denemeye başlamasının üzerinden kırk yıldan fazla bir süre geçmesine rağmen, başlıca uluslararası yönetmelikler, YDB ile ilgili yönetmelik koşullarına kapsamlı eklemeler yapmamışlardır. YDB şartlarını kapsamlı olarak içermeyen tasarım kodlarından biri olan TBDY 2018’in 50 MPa'nın üzerindeki betonlar için eşdeğer dikdörtgen gerilme bloğu parametrelerinin kullanımı için Eurocode 2'ye atıfta bulunmaktadır. Bu çalışma, bu ihtiyacı ortadan kaldırmayı ve 50 MPa'nın üzerindeki betonlara sahip yapı elemanları için gerilme bloku parametreleri için yeni bir ifade önermeyi amaçlamaktadır. Buna ek olarak, 80 MPa üzeri YDB kolonların eksenel ve eğilme momenti kapasitesi için, YDB kolonlarda mevcut olan erken kabuk dökülmesi etkisinden dolayı yeni bir azaltma faktörü önerilmektedir. Önerilen ifadelere bağlı nihai kesit kapasitesi hesaplamalarının sonuçları incelenmiş ve 1995'ten 2021'e kadar olan araştırma yayınlarının deneysel sonuçlarına göre doğrulanmıştır.M.S. - Master of Scienc
Hasarlı tarihi bir caminin sonlu elemanlar analizi ile incelenmesi.
No full textHistoric structures form a very important part of our cultural heritage and should be well protected. Therefore, full comprehension of the structural behavior of historic structures is of prior importance. A seriously damaged single domed mosque of 16th century Classical Ottoman Architecture was investigated in this study. Serious damages have been observed at various structural elements including the dome and the structural masonry walls, recently leading the structure's closure to service. The main objective of this study is to find out the possible reasons of the damage. The Mosque was constructed on silty-clay soil and the water table has been changed considerably due to the drought in recent years causing soil displacements. The structure is modeled with linear finite element approach. The masonry walls are modeled with homogenized macro shell elements. The change in water table is imposed on the Mosque as displacement at foundation joints. The results of the analyses have been compared with the observed damage and the finite element model has been calibrated according to the observed damage. Some rehabilitation methods have also been proposed. Mini pile application up to firm soil (rock) was recommended to prevent the soil displacement. A steel ring around the damaged dome base was proposed to avoid any further propagation of cracks. Furthermore, the cracks on the masonry walls should also be repaired with a suitable material that is also compatible with the historic texture.M.S. - Master of Scienc
Dolgulu betonarme çerçevelerin çelik tel donatı uygulaması ile depreme karşı güçlendirilmesi.
No full textSeismic resistance of many buildings in Turkey is insufficient. Strengthening using R/C infills requires huge construction work. Feasible, easy strengthening techniques are being studied in Structural Mechanics Laboratory of METU. In this project, it was aimed to develop an economical strengthening method. This method is based on addition of steel fibers and/or PP fibers in mortar and application of mortar on masonry wall. Project was sponsored by the Scientific and Technical Research Council of Turkey (TÜBİTAK). Physical properties of cement, aggregate, and mortar used in tests were determined by material tests. After performing flexural strength and compressive strength tests, optimum mortar was obtained. R/C frames strengthened by applying the mortar to brick infilled walls were tested under reversed cyclic loads. Before the frame tests, two series of panel tests were performed to correctly model strengthened infill walls and to gather information about behavior of walls under load. Totally 10 frame tests were done. 4 tests were done as reference tests, and other 6 were done as strengthened frame tests. In the analytical part of study, the plastered hollow brick infill wall strengthened by FRM was modeled as two separate compression struts. First strut was used to model the plastered hollow brick infill wall. Second strut was used to model the FRM. This technique is effective in improving seismic behavior by increasing strength, initial stiffness, energy dissipation, and ductility. Moreover, the method provides strengthening of the buildings without evacuating the structure.Ph.D. - Doctoral Progra
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