Outline

  • Abstract
  • Keywords
  • 1. Introduction
  • 1.1. Shear Failure
  • 1.2. Seismic Reinforcement
  • 1.3. Frp Shear Reinforcement of Columns
  • 2. Experimental Procedure
  • 2.1. Materials of Reinforcement
  • 2.2. Specimens Design
  • 2.3. Loading Device
  • 2.4. Loading Diagram
  • 2.5. Instrumentation
  • 3. Results
  • 3.1. Load and Failure Mode
  • 3.1.1. Influence of the Width and Spacing of the Bands
  • 3.1.2. Influence of Reinforcement Material (carbon or Glass)
  • 3.1.3. Influence of the Reinforcement Type (continuous or Discontinuous)
  • 3.2. Ductility
  • 3.3. Stiffness
  • 4. Energy Analysis
  • 4.1. Elastic Energy
  • 4.1.1. Influence of the Width and the Spacing of the Bands
  • 4.1.2. the Influence of Material Reinforcement (carbon or Glass)
  • 4.1.3. Influence of the Reinforcement Type (continuous or Discontinuous)
  • 4.2. Dissipated Energy
  • 4.2.1. Influence of the Width and the Spacing of the Bands
  • 4.2.2. Influence of the Reinforcement Material (carbon or Glass)
  • 4.2.3. Influence of the Reinforcement Type (continuous or Discontinuous)
  • 5. Conclusions
  • Acknowledgements
  • References

رئوس مطالب

  • چکیده
  • کلید واژه ها
  • 1. مقدمه
  • 1.1. تسلیم برشی
  • 1.2. مقاوم سازی لرزه ای
  • 1.3. مقاوم سازی برشی ستون ها با FRP
  • 2. رویه آزمایشگاهی
  • 2.1. مصالح مقاوم سازی
  • 2.2. طراحی نمونه ها
  • 2.3. دستگاه بارگذاری
  • 2.4. دیاگرام بارگذاری
  • 2.5. تجهیزات
  • 3. نتایج
  • 3.1. بار و مود تسلیم
  • 3.1.1. اثر عرض و فاصله تسمه ها
  • 3.1.2. تاثیر مصالح مقاوم سازی (کربن یا شیشه)
  • 3.1.3. تاثیر نوع مقاوم سازی (سراسری یا منفصل)
  • 3.2. شکل پذیری
  • 3.3. سختی
  • 4. تحلیل انرژی
  • 4.1. انرژی ارتجاعی
  • 4.1.1. تاثیر عرض و فاصله تسمه ها
  • 4.1.2. تاثیر مصالح مقاوم سازی (کربن یا شیشه)
  • 4.1.3. تاثیر نوع مقاوم سازی (سراسری یا منفصل)
  • 4.2. انرژی مستهلک شده
  • 4.2.1. تاثیر عرض و فاصله تسمه ها
  • 4.2.2. تاثیر مصالح مقاوم سازی (کربن یا شیشه)
  • 4.2.3. تاثیر نوع مقاوم سازی (سراسری یا منفصل)
  • 5. نتیجه گیری

Abstract

Nowadays, reinforcing buildings or bridges against earthquake damage is a real technico-economic challenge. Composite materials applied by the wet lay-up method have been the main reinforcement technology for civil engineering structures since the 1990s. The research developed in this paper concerns seismic reinforcement. The main objectives are to evaluate CFRP’s contribution to mechanical and energetic performance and to the modification of the cracking pattern on short columns. During earthquakes, short columns undergo shear stress due to their low resistance to high imposed horizontal displacements.

Eight short columns were tested; their longitudinal reinforcement was higher than the Eurocode 8 upper limit whereas transverse reinforcement was insufficient, in order to ensure shear failure. Seven were continuously or discontinuously reinforced by CFRP or GFRP. They were tested under a constant compression load combined with a horizontal quasi-static cyclic load. It was therefore possible to evaluate the efficiency of such reinforcement by measuring the gain in terms of load and ductility.

Keywords: - -

Conclusions

FRP reinforcement completely changed the failure mode of the columns. For the two entirely wrapped columns brittle shear failure changed to ductile bending failure, while in the strip-reinforced column failure was due to shear-bending. The strategy of FRP reinforcement in this study involves the increase of both resistance and ductility.

Reinforcement by strips provides a more advantageous dissipative behaviour than the fully wrapped columns. This is due to the ductility gained through the following two mechanisms:

  • Damage to the concrete by cracking between the FRP strips.
  • Yielding of the reinforcements in all column sections.

For the columns which were fully wrapped in FRP, ductility was increased, mainly due to transfer to the embeddings, creating a hinge by advanced yielding of the longitudinal reinforcements. The FRP reinforcement allowed rotation in the embedding sections, without buckling of the compressed reinforcements, although they greatly exceeded their elastic limit. Even for the short columns, the central section was less solicited that the embedding sections. So it seemed that using a different thickness of reinforcement would be advantageous.

Composite material reinforcement endowed the short columns with ductile behaviour, although the columns did not contain the necessary transversal reinforcement ratio. Care must be taken not to oversize the FRP reinforcement, as this results in a transfer of effort to the nodes. Finally, the strategy of reinforcement must be total and non-local.

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