مقاوم‌سازی لرزه‌ای ستون‌های کوتاه بتن‌آرمه به روش سطحی و نزدیک به سطح با صفحات CFRP و فولاد مقاومت بالا

نوع مقاله : Articles

نویسندگان

دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

چکیده

امروزه وجود ستون‌های کوتاه در ساختمان‌ها و پل‌ها به‌عنوان یک چالش جدی در زلزله مطرح می‌شود. این پدیدۀ مخرّب به دلیل اختلاف طول ستون در یک تراز مشخص رخ می‌دهد که عمدتاً به دلیل ملاحظات معماری از قبیل قرارگرفتن ساختمان روی سطح شیب‌دار یا محدود شدن ستون و دیوار با عناصر غیر سازه‌ای نظیر دیوارهای آجری و بازشوها و یا وجود اختلاف تراز طبقه در سازه‌های با دوبلکسی به دلیل قرارگیری پیلوت و واحدهای تجاری در همکف می‌باشد. در این مقاله با مدل‌سازی 9 نمونه ستون کوتاه بتن‌آرمه، بدون افزایش سختی، مقاومت برشی آنها به کمک الیاف کامپوزیتی و فولاد مقاومت بالا افزایش داده شده است. نتایج نشان می‌دهد به‌طورکلی مقاوم‌سازی نزدیک به سطح با فولاد مقاومت بالا، بر روی افزایش سطح زیر منحنی انرژی و ضریب شکل‌پذیری و مقاوم‌سازی سطحی بر روی افزایش سطح زیر منحنی بار– جابه‌جایی و ظرفیت باربری نهایی مؤثرتر می‌باشد.

کلیدواژه‌ها


عنوان مقاله [English]

Seismic Strengthening of RC Short Columns by EBR and NSM Methods Using CFRP Sheets and High Strength Steel

نویسندگان [English]

  • Ali Kargaran
  • Ali Kheyroddin
Department of Civil Engineering, Semnan University, Semnan, Iran
چکیده [English]

Existence of short columns in buildings and bridges is a serious challenge in earthquakes. This destructive phenomenon occurs due to the difference in length of the column at a certain level that is mainly because of architecture consideration, such as the placement of building on a slop or restriction of column with nonstructural walls and openings or difference in story level in structures because the existence of mezzanine floor.
Short columns have brittle shear failure in comparison with tall columns. This kind of failure causes a reduction in the energy dissipation capacity of the column. Shear failure is the most critical failure mode in RC short columns due to the none-observance of seismic details or sufficient transverse reinforcements against seismic loads. As concrete tensile stresses reach concrete tensile strength and the diagonal cracks appear, the concrete cover is detached and starts to shed. Then the failure and openings of transverse reinforcements and as a result the buckling longitudinal reinforcements occur. The above process leads to the disintegration of the core concrete and the sudden fracture and embrittlement of the column.
In externally bonded reinforcement by FRP composites, FRP materials are different from the materials of the RC (concrete and steel) parts. The use of FRP is limited to high temperatures and has a low resistance to fire. On the other hand, strengthening with FRP composite materials is economically expensive. Mostly, High Strength Steel (HSS) bars have been used in the design and construction of the RC structures and not in strengthening. Today, due to the growing population and increased demand for raw materials and energy, solutions have been taken to optimize standards and to save on consumables, production and cost reduction. Steel reinforcements are one of the most widely used building materials with a huge number of applications in a variety of structures. Due to the considerable cost of using steel in structures, the use of HSRs has been considered as one of the major options. The use of HSRs has economic justification because of reduced human resources, reduced consumption of materials, time and manufacturing efficiency, reduced environmental damage because of the optimal utilization of materials and reduced transportation costs. Because of the greater tensile strength of these bars than ordinary ones, it leads to a brittle failure in concrete prior to rebar flaking. It, therefore, limits their application in regions with high seismic hazard.
In this paper, with the modeling of nine RC short columns, without increasing the stiffness, their shear strength has increased with the help of composite and high strength steel. Two techniques were used to strengthen the diameter of the short columns against seismic loads. These techniques include EBR with FRP composite materials and NSM with HSS. The results show that in general, near surface mounted with high strength steel is more effective on increasing the dissipated energy and the ductility factor and externally bonded retrofitting is more effective on the increase of the load-displacement sub-curve and the peak load capacity.

کلیدواژه‌ها [English]

  • Reinforced Concrete
  • Short Column
  • Ductility
  • Hysteretic Curve
  • HSS
  • CFRP
  • EBR
  • NSM
  1. Kheyroddin, A., and Kargaran, A. (2009) Seismic behavior of short column in RC structures on slope surface. Journal of Modeling in Engineering, 7, 57-62.
  2. Kheyroddin, A., and Mirnezami, A.R. (2002) Seismic behavior steel buildings with different floor. Proc., 3rd National Conf. on Code of Practice for Seismic Resistant Design of Buildings, Tehran, Iran.
  3. Bayraktar, A., CanAltunisik, A., and Pehlivan, M. (2013) Performance and damages of reinforced concrete buildings during the October 23 and November 9, 2011 Van, Turkey, earthquakes. Soil Dynamics and Earthquake Engineering. 53, 49-72.
  4. Moretti, M., and Tassios, T.P. (2007) Behaviour of short columns subjected to cyclic shear displacements: Experimental results. Engineering Structures, 29, 2018-2029.
  5. Moretti, M., and Tassios, T.P. (2006) Behaviour and ductility of reinforced concrete short columns using global truss model. ACI Structural Journal, 103, 319-327.
  6. Haedir, J., and Zhao, XL. (2011) Design of short CFRP-reinforced steel tubular columns. Journal of Constructional Steel Research, 67, 497-509.
  7. Colomb, F., Tobbi, H., Ferrier, E., and Hamelin, P. (2008) Seismic retrofit of reinforced concrete short columns by CFRP materials. Composite Structures, 82, 475-487.
  8. Promis, G., Ferrier, E., and Hamelin, P. (2009) Effect of external FRP retrofitting on reinforced concrete short columns for seismic strengthening. Composite Structures, 88(3), 367-379.
  9. Promis, G. and Ferrier, E. (2012) Performance indices to assess the efficiency of external FRP retrofitting of reinforced concrete short columns for seismic strengthening. Constr. Build Mater., 26, 32-40.
  10. Galal, K., Arafa, A., and Ghobarah, A. (2005) Retrofit of RC square short columns. Engineering Structures, 27, 801-813.
  11. Ghobarah, A., and Galal, K. (2004) Seismic rehabilitation of short rectangular RC columns. Journal of Earthquake Engineering, 8, 45-68.
  12. Lieping, Y., Qingrui, Y., Shuhong, Zh., and Quanwang, L. (2002) Shear strength of reinforced concrete columns strengthened with carbon Fiber Reinforced plastic sheet. Journal of Structural Engineering, 128, 1527-1534.
  13. Galal, K., Ghobarah, A. (2003) Flexural and shear hysteretic behaviour of reinforced concrete columns with variable axial load. Engineering Structures, 25, 1353-1367.
  14. Bakhshi, A., and Tabeshpor, M.R. (2006) Evaluation of short column fracture calculation in earthquake. Research Bulletin of Seismology and Earthquake Engineering, 8(1), spring (in Persian).
  15. Barghi, M., and Abasnia, R. (2006) Augury of RC columns destruction type in cyclic lateral load. Proceedings of 7th Int. Conf. on Civil Eng., Tehran, Iran.
  16. Ghodrati Amiri, G.R., Kheyroddin, A., and Kargaran, A. (2011) Seismic vulnerability of RC structures with different floor under earthquake. Journal of Civil and Surveying Engineering, 45, 479-486.
  17. Kheyroddin, A., and Kargaran, A. (2011) Seismic behavior of short column in RC structures with different floor level. Journal of Civil Engineering, 22, 129-145.
  18. Kavir Steel Complex, www.kavirsteel.ir.
  19. Asplund, S.O. (1949) Strengthening bridge slabs with grouted reinforcement. J. Am. Concr. Inst., 20(6), 397-406.
  20. Warren, G.E. (1998) Waterfront Repair and Upgrade, Advanced Technology Demonstration site No. 2: Pier 12, NAVSTA San Diego. Site Specific Report SSR-2419-SHR, Naval Facilities Engineering Service Center, Port Hueneme (CA).
  21. Warren, G.E. (2000) Waterfront Repair and Upgrade, Advanced Technology Demonstration Site No. 3: NAVSTA Bravo 25, Pearl Harbour. Site Specific Report SSR-2567-SHR, Naval Facilities Engineering Service Center, Port Hueneme (CA).
  22. Garrity, S.W. (2001) Near-surface reinforcement of masonry arch highway bridges. Proceedings of the 9th Canadian Masonry Symposium, Fredericton (Canada), CD-ROM.
  23. Sika Group, Product Data Sheet: SikaWrap-300C (2006) Woven Carbon Fiber Fabric for Structural Strengthening. Zurich, Switzerland.
  24. Bungale, S. and Taranath, A. (1988) Structural Analysis and Design of Tall Building. McGraw-Hill Book Company.