Abstract
The use of cementitious grout to enlarge the member size represents a method for strengthening RC columns, addressing limitations inherent in traditional section enlargement techniques. This study conducted experiments on the eccentric compression behavior of RC columns reinforced by enlarging the member size through the application of cementitious grout. The effects of eccentricity, strengthening thickness, new steel bars, and strengthening position on the bearing capacity of columns strengthened with cementitious grout were investigated. The results show that increasing the size of the members with cementitious grout can significantly improve the bearing capacity of columns under eccentric loads, with improvement ranging from 16% to 237%. Strengthening in the compression zone had a notably greater impact compared to strengthening in the tension zone for eccentric compression members. The ultimate compressive load of the strengthened columns experienced varying degrees of improvement with the increase in strengthening thickness and area of new steel bars. In addition, the study established a calculation formula for the bearing capacity of a strengthened column under eccentric load based on the plane section assumption and verified the availability of the calculation method by comparing the calculation results with the experimental results.
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Abbreviations
- A sn :
-
Area of new tensile steel bars
- a sn :
-
Thickness of concrete cover for new tensile steel bars
- A′sn :
-
Area of new compressive steel bars
- a′sn :
-
Thickness of concrete cover for new compressive steel bars
- A so :
-
Area of existing tensile steel bar
- a so :
-
Thickness of concrete cover for existing tensile steel bars
- A′so :
-
Area of existing compressive steel bar
- a′so :
-
Thickness of concrete cover for existing compressive steel bars
- b:
-
Width of column section
- e i :
-
Distance between axial load and geometrical centroid of section
- E s :
-
Elastic modulus of steel bars
- E sn :
-
Elastic modulus of new tensile steel bars
- E′sn :
-
Elastic modulus of new compressive steel bars
- E so :
-
Elastic modulus of existing tensile steel bars
- E′so :
-
Elastic modulus of existing compressive steel bars
- f c :
-
Axial compressive strength of concrete
- f cu :
-
Cubic compressive strength of concrete
- f g :
-
Axial compressive strength of cementitious grout
- f gu :
-
Cubic compressive strength of cementitious grout
- f y :
-
Yield strength of steel bars
- f yn :
-
Yield strength of new tensile steel bars
- f yn′:
-
Yield strength of new compressive steel bars
- f yo :
-
Yield strength of original tensile steel bars
- f yo′:
-
Yield strength of original compressive steel bars
- h :
-
Height of original column section
- h g :
-
Strengthening thickness
- h g1, h g2, h g3, h g4 :
-
Critical strengthening thickness
- n :
-
Shape coefficient
- N cu :
-
Ultimate axial load
- x b :
-
Critical depth of compressive zone
- x n :
-
Depth of compressive zone of section
- y cc :
-
Distance between section edge near axial load and resulting force of concrete
- y cg :
-
Distance between section edge near axial load and resulting force of cementitious grout
- σ c :
-
Compressive stress of concrete
- σ cb :
-
Stress of concrete at boundary between concrete and cementitious grout
- σ cn :
-
Stress of concrete at section edge near axial load
- σ cf :
-
Stress of concrete at section edge far from axial load
- σ g :
-
Compressive stress of cementitious grout
- σ gb :
-
Stress of cementitious grout at boundary between concrete and cementitious grout
- σ gf :
-
Stress of cementitious grout at section edge far from axial load
- σ gn :
-
Stress of cementitious grout at section edge near axial load
- σ s :
-
Stress of steel bars
- σ sn :
-
Stress of new tensile steel bars
- σ′sn :
-
Stress of new compressive steel bars
- σ so :
-
Stress of original tensile steel bars
- σ′so :
-
Stress of original compressive steel bars
- ε 0 :
-
Compressive strain of concrete when compressive stress reaches fc
- ε b :
-
Strain at boundary between concrete and cementitious grout
- ε c :
-
Compressive strain of concrete when compressive strain is εc
- ε cu :
-
Ultimate compressive strain of concrete
- ε f :
-
Strain at section edge far from axial force
- ε g :
-
Compressive strain of cementitious grout
- ε g0 :
-
Compressive strain of cementitious grout when compressive strain is εg
- ε gu :
-
Ultimate compressive strain of cementitious grout
- ε s :
-
Strain of steel bars when stress is εs
- ε n :
-
Strain at edge of section near axial force
- ε sn :
-
Strain of new tensile steel bars
- ε′sn :
-
Strain of new compressive steel bars
- ε so :
-
Strain of existing tensile steel bars
- ε′so :
-
Strain of existing compressive steel bars
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Acknowledgments
The authors would like to acknowledge the National Natural Science Foundation of China (Grant Nos. 52078412, 51678473), Key Scientific Research Foundation of Education Department of Shaanxi Province of China (Grant No.23JS030) and Program for Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT_17R84) for financial support.
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Zhong, S., Hu, X., Peng, G. et al. The Effect of Section Enlargement with Cementitious Grout on the Eccentric Compression Behavior of RC Columns. KSCE J Civ Eng (2024). https://doi.org/10.1007/s12205-024-1211-4
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DOI: https://doi.org/10.1007/s12205-024-1211-4