Comparison of Dynamic Characteristics of Prestressed and Reinforced Concrete Beams

Yıl 2019, , 37 - 44, 31.01.2019

Barbaros Atmaca

https://doi.org/10.29130/dubited.421496

Öz

To determine the dynamic characteristics of bridges built with prestressed and reinforced concrete beams, the
dynamic properties of such beams should be known. Prestressing force is applied to the prestressed concrete (PSC)
beam, unlike reinforced concrete (RC) beam. In this study, it is aimed to compare the dynamic properties of PSC
and RC beams with the same material, section properties and effective span length. Dynamic properties such as
the mode shapes and periods of the PSC and RC beam were determined by means of the formulation found in the
literature and a computer program that uses the finite element method. For this study I-beam with 0.90m height
and 15m effective span length was selected as an example. The selected beam was considered separately as PSC
and RC. In the PSC beam, eight low-relaxation Grade270 prestressing strand with 15mm (0.6 in.) diameter were
used, unlike reinforced concrete beams. Three dimensional finite element models (FEM) of PSC and RC beam
were constituted using SAP2000 software. At the end of the study, mode shapes and periods of PSC and RC beams
obtained from analytical prediction by formulation and numerical by FEM were compared with each other.

Anahtar Kelimeler

Prestressed beam, Reinforced beam, Natural frequency, Mode shapes, Prestressing force

Öngerilmeli ve Betonarme Kirişlerin Dinamik Karakteristiklerinin Karşılaştırılması

Öz

Öngerilmeli ve betonarme kirişler kullanılarak inşa edilen köprülerin dinamik karakteristiklerini belirlemek için
köprülerde kullanılan kirişlerin dinamik özelliklerinin bilinmesi gerekmektedir. Öngerilmeli kirişlere, betonarme
kirişlerden farklı olarak öngerilme kuvveti uygulanmaktadır. Bu çalışmada malzeme, kesit özellikleri ve efektif
açıklık değerleri aynı olan öngerilmeli ve betonarme kirişlerin dinamik karakteristiklerinin karşılaştırılması
amaçlanmıştır. Öngerilmeli ve betonarme kirişlerin dinamik karakteristiklerinden mod şekilleri ve periyodların
belirlenmesinde, literatürde bulunan bağıntılar ve sonlu elemanlar yöntemine dayalı bilgisayar programı
kullanılmıştır. Bu çalışma için 15m uzunluğa 0.90m yüksekliğe sahip I kiriş örnek olarak seçilmiştir. Seçilen kiriş,
öngerilmeli ve betonarme olarak ayrı ayrı dikkate alınmıştır. Öngerilmeli kirişte, betonarme kirişten farklı olarak
15mm (0.6in.) çaplı sekiz tane 270K sınıfı öngerme kablosu kullanılmıştır. Kirişlerin sonlu eleman modelleri SAP2000 programı kullanılarak oluşturulmuştur. Çalışmanın sonunda öngerilmeli ve betonarme kirişlerin analitik
ve sayısal olarak elde edilen dinamik karakteristikleri birbiriyle karşılaştırılmıştır.

Anahtar Kelimeler

Öngerilmeli kiriş, Betonarme kiriş, Doğal frekans, Mod şekilleri, Öngerme kuvveti

Kaynakça

• [1] S. Ates, B. Atmaca, E. Yildiri, and N. A. Demiroz, “Effects of soil-structure interaction on construction stage analysis of highway bridges.” Computers and Concrete, vol. 12, no. 2, pp.169-186, 2013.
• [2] F. Ubertini, A. L. Materazzi, A. D’Alessandro and S. Laflamme, “Natural frequencies identification of a reinforced concrete beam using carbon nanotube cement-based sensors” Engineering Structures, no. 60, pp. 265-275, 2014.
• [3] F. Magalhes, A. Cunha and E. Caetano, “Vibration based structural health monitoring of an arch bridge: from automated oma to damage detection.” Mech Syst Signal Process, no. 28, pp. 212–28, 2012.
• [4] F.S. Tse, I. E. Morse and R.T. Hinkle Mechanical vibrations: theory and applications, 2rd ed., Boston, USA: Allyn and Bacon series in mechanical engineering and applied mechanics, 1978.
• [5] M. Saiidi, B. Douglas and S. Feng, “Prestress force effect on vibration frequency of concrete bridges”, ASCE Journal of Structural Engineering, vol. 120, no. 7, pp. 2233–2241, 1994.
• [6] T. H. T. Chan and T. H. Yung, “A theoretical study of force identification using prestressed concrete bridges” Engineering Structures, vol. 22, no. 11, pp. 1529–1537, 2000.
• [7] N. F. Grace and B. Ross, “Dynamic characteristic of post-tensioned girders with web openings,” J. Structural Engineering, vol. 122, no. 6, pp. 643-650, 1996.
• [8] A. Miyamoto, K. Tei, H. Nakamura, and J.W. Bull, “Behavior of prestressed beam strengthened with external tendons”, ASCE Journal of Structural Engineering, vol. 126, no. 9, pp. 1033–1044, 2000.
• [9] Timoshenko, S., Young, D.H., Weaver, W.J.R., Vibration Problems in Engineering, New York, USA: Wiley, 1974.
• [10] G. Deak, “Prestress force effect on vibration frequency of concrete bridges discussion”, ASCE Journal of Structural Engineering, vol. 122, no. 4, pp. 458–459, 1996.
• [11] E. Hamed and Y. Frostig, “Natural frequencies of bonded and unbonded prestressed beams–prestress force effects”. Journal of sound and vibration, vol. 295, no. 1-2, pp. 28-39, 2006.
• [12] A. Pavic, P. Reynolds, P. Waldron and K. Bennett, “Dynamic modelling of post-tensioned concrete floors using finite element analysis”, Finite elements in analysis and design, vol. 37, no. 4, pp. 305-323, 2001.
• [13] D. Noble, M. Nogal, A. J O’Connor and V. Pakrashi, “The effect of prestress force magnitude on the natural bending frequencies of prestressed concrete structures” 23rd Australasian Conference on the Mechanics of Structures and Materials, Byron Bay, Australia, 2014.
• [14] L. Fengge and L. Rong “Theoretical analysis of natural vibration frequency for unbonded prestressed concrete beams”, Advanced Materials Research, vol. 594, no. 597, pp. 882-885, 2012.
• [15] Computers and Structures Inc., SAP 2000 Static and dynamic finite element analysis of structures, Berkeley, CA, USA, 2016.
• [16] AASHTO LRFD Bridge design specifications, 6th Ed., Washington, D.C., 2012.