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Reduction of Residual Displacement of Concrete Structures by use of High Strength Rebars

Tazarv, Mostafa | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39065 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khalu, Alireza
  7. Abstract:
  8. Reinforced concrete bridge columns located in regions of high seismicity are designed with large ductility capacity for adequate protection against collapse. This type of design tends to result in large permanent displacements. To maximize post-event operability and to minimize repair costs, new design strategies to reduce these residual displacements are necessary. Even though seismic codes ensure life safety for bridges, large residual displacement after severe earthquake may make the bridge useless. For example, after 1995 Hyogo-ken Nanbu earthquake (Japan), more than 100 reinforced concrete bridge columns experienced a tilt angle of more than 1 degree (1.75% drift). These columns had to be removed and new columns built because of the difficulty of setting the superstructure back to the original alignments and levels. So, controlling the residual displacement of bridges would keep fundamental infrastructures safe and functional. In this research, a new method is proposed to reduce residual displacements of concrete columns by the use of High Strength Rebars (MMFX). This method is different from the most researched method for reduction of residual displacement, i.e., post-tensioning technique. The result of numerous cyclic and dynamic analysis, carried out by OpenSees, shown that high strength rebars distributed near the core of column section will give the column a selfcentering tendency. Simultaneously consideration of cyclic and dynamic analyses indicates that the best position for HSR is the center of the column section. But, due to construction difficulties, radial distribution of HSR in the radius of 25% radius of column section was selected. Adding 40% area of mild reinforcements as HSR to the concrete column will dissipate adequate energy to restrict residual displacements in acceptable range. Dynamic analyses indicated that proposed method can reduce residual displacements of RC column more than 50% that is comparable to the previous innovative method in this field. Therefore, proposed method is an efficient method for reduction of residual displacement of concrete structures
  9. Keywords:
  10. Concrete Structures ; Permanent Displacement ; High Strength Rebars

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