İnceltilmiş Uçlu Önüretimli Aşık Kirişlerinin Yük Taşıma Kapasitelerinin Deneysel ve Numerik Olarak İrdelenmesi ve Çözüm Önerileri

Yıl 2021, Cilt: 32 Sayı: 3, 10823 - 10858, 01.05.2021

Ceyhun Aksoylu , Yasin Onuralp Özkılıç , Şakir Yazman , Lokman Gemi , Musa Arslan

https://doi.org/10.18400/tekderg.667066

Cited By: 20

Öz

Türkiye’de inşaat sektörü 1960’lı yılların sonu itibari ile beton prefabrikasyon ile tanışmıştır. Prefabrike olarak üretilen yapılar seri üretimlerinin ve montajlarının hızlı olmasından dolayı özellikle sanayi yapılarında daha fazla tercih edilmişlerdir. Bu yapı türünün en büyük dezavantajı özellikle mafsallı birleşim bölgelerinde oluşan hasarlardır. Çatı kirişleri ile aşık kirişlerinin birleştiği bölgelerde de bağlantı genellikle mafsallı olarak gerçekleştirilir. Bundan dolayı mesnet bölgelerinde teorik olarak moment oluşmamakta ve bu tip kirişlerin kesit tesirleri basit mesnetli kirişlerde olduğu gibi hesaplanmaktadır. Ancak aşık inceltilmiş uç bölgelerinde yoğunlaşan kesme kuvveti, kesme gerilmelerinin artmasına neden olduğundan bu bölgenin detaylandırılması için bir takım özel tasarım kuralları ilgili standartlarda yer almıştır. Bu birleşim bölgelerinde özellikle etkili ve uzun süreli kar yağışlarından sonra çatıda biriken yoğun kar neticesinde hasarlar gözlemlenmektedir. Bu hasarlar nispeten daha eski prefabrike yapı stokunda bulunanlar başta olmak üzere inceltilmiş uçlu aşık kirişleri için önemli bir risk oluşturmaktadır. Bu çalışmada, şimdiye kadar kapsamlı olarak araştırılmamış olan inceltilmiş uçlu aşıkların düşey yük etkisi altında davranışları, aşıkların değişen mekanik parametrelerine göre deneysel ve numerik olarak incelenmiştir. İlk olarak yürürlükteki standartlara uygun olan ve olmayan iki adet aşık kirişinin deneyleri gerçekleştirilmiştir. Ardından yine standarda uygun bir adet aşık kiriş inceltilmiş uç hasarının önlenlenmesi amacıyla CFRP ile güçlendirilerek test edilmiştir. Daha sonra ABAQUS programıyla modellenen aşıklardan elde edilen sonuçlar ile deneysel çalışma sonuçları ile doğrulanmıştır. Tüm deneysel sonuçlarla numerik modelleme sonuçlarının oldukça yakın olduğu görülmüştür. Numerik model numunelerinde gözlenen hasarlar ile deneylerde oluşan hasarların benzer olması yeni parametrik çalışmalarda numerik modellerin kullanılabileceğini göstermiştir. Doğrulamanın ardından aşıkların mekanik özellikleri ile güçlendirme alternatiflerine bağlı bir dizi parametrik çalışma numerik olarak gerçekleştirilmiştir. Parametrik çalışmada; özellikle mevcut aşıklarda beton basınç dayanımı, donatı çekme dayanımı ve aşık kirişlerin üretiminde kullanılan öngerme seviyesinin tasarlanandan farklı olabileceği düşüncesiyle bir parametre olarak değerlendirilmiştir. Ayrıca karbon elyaf takviyeli polimer (CFRP) kumaş ile güçlendirilen ve yönetmeliğe göre tasarlanmayan aşıkların davranışı da yine parametrik çalışma kısmında incelenmiştir. Parametrik çalışmanın sonuçlarına göre beton basınç dayanımı daha etkin olmakla beraber beton ve çelik dayanımının artışı ile kesme kapasitesinde önemli ölçüde artış sağlandığı görülmüştür. Elde edilen sonuçlarda öngerme değeri artışının kapasiteye hatırı sayılır bir etki sağlamadığı görülmüştür. CFRP ile güçlendirilen numunelerde aşığın yük taşıma kapasitesinin %50’ye arttığı ve hasarın inceltilmiş uç bölgesi dışına kaydığı (inceltilmemiş bölgeye) görülmüştür. Parametrik çalışma ile farklı ve uygulanabilir CFRP alternatifleri de modellenerek en iyi güçlendirme alternatifi önerildi. Bununla beraber inceltilmiş uçlu aşıkların donatı tasarımına esas bazı öneriler getirilmiştir.

Anahtar Kelimeler

ABAQUS, CFRP malzeme, İnceltilmiş uç, aşık kiriş, prefabrik yapı

Experimental and Numerical Investigation of Load Bearing Capacity of Thinned End Precast Purlin Beams and Solution Proposals

Öz

The construction sector in Turkey has met concrete prefabrication at the end of the 1960s. Prefabricated structures have been preferred more especially in industrial buildings due to their rapid production and fast erecting. The biggest disadvantage of these structures is the damages that occurred at especially the region of hinged connection. The connection of roof beams and purlin beams are generally assembled with a hinged connection. Therefore, a moment does not occur theoretically in the support areas and the cross-sectional effects of these beams are calculated as in simple support beams. However, since the shear force concentrated in the thinned end regions causes an increase in shear stresses, a number of special design rules are included in the relevant standards for the detailing of this region. Damages are observed in these connections as a result of snow accumulated on the roof especially after effective and prolonged snowfall. These damages pose a significant risk for thinned end beams, especially those in the relatively older prefabricated building stock. In this present study, the behavior of thinned end purlins under vertical loading, which have not been investigated extensively before, has been numerically and experimentally examined according to varying mechanical parameters. First, experiments of two purlin beam, which are in accordance with current standards and not, were carried out. Then another purlin beam in accordance with the standard, which was strengthened with carbon fiber reinforced polymer (CFRP) in order to prevent thinned end damage, was tested. Then, the results obtained from the purlins modeled with ABAQUS program were verified with the results of the experimental study. The results of numerical modeling were found to be very close to all experimental findings. The similarities between the damages observed in the experiments and numerical modeling showed that numerical models can be used in new parametric studies. After the verificifation, a number of parametric studies related to the mechanical properties of the purlins and strengthening alternatives were performed numerically. In the parametric study, concrete compressive strength, reinforcement tensile strength and the pre-stressing level used in the production of purlin beams, especially in existing purlin, was evaluated as a parameter with the idea that it may differ from the designed one. In addition, the behavior of purlins which are not in accordance with standards and strengthened with CFRP was also examined in the parametric study section. According to the results of the parametric study, it has been observed that a significant increase in shear capacity has been achieved with the increase of concrete and steel strength although the concrete compressive strength is more effective. The results showed that increasing the pretension value does not have a significant effect on the capacity. In addition, the shear capacity of purlin strengthened with CFRP has increased up to 50% and the damage has shifted to out of the thinned end region. With the aid of parametric study, different and feasible CFRP alternatives were also modeled and the best strengthening alternative was recommended. In addition, some suggestions for the design of the reinforcements for the thinned ended purlins were made.

Anahtar Kelimeler

ABAQUS, CFRP, thinned end, purlin, prefabricated building

Kaynakça

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