Abstract
Typically, the stress-strain relationship of confined lightweight aggregate concrete (LWAC) exhibits lower stiffness in the ascending branch and more brittleness in the descending branch compared to counterpart confined normal-weight concrete (NWC). To describe the rational stress-strain relationship of confined LWAC according to these trends, the concept of concrete brittleness number (ξb) was introduced. Specifically, ξb values were determined as constants in the existing size effect equation. The constants were fitted via regression analysis of 164 datasets compiled in extant studies. The models of elastic modulus, strength gain factor, strain at maximum stress, and strain at 85% of the maximum stress in descending branch were proposed, including ξb to describe the lower stiffness and more brittle behavior in confined LWAC when compared to those of counterpart confined NWC. Other existing models showed significant differences when compared with the test results in the descending behavior. These differences were significant in LWAC and counterpart NWC. Conversely, the proposed stress-strain relationship of confined concrete was in excellent agreement with the test results, irrespective of concrete type, compressive strength of concrete, and volumetric transverse reinforcement index.
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Abbreviations
- A sh :
-
Amount of transverse reinforcement
- b c :
-
Section size of confined concrete
- c s :
-
Spacing of the longitudinal reinforcement
- d :
-
Characteristic dimension of the specimen or structure
- d a :
-
Maximum aggregate size
- d o :
-
Transition value for a structure of a given geometric size
- E c :
-
Elastic modulus of concrete
- E cc :
-
Elastic modulus of confined concrete
- E s :
-
Elastic modulus of transverse reinforcement
- f 0 :
-
Reference value (= 10 MPa) of maximum confined stress
- f c :
-
Stress of confined concrete at εc
- \(f_{c}^{\prime}\) :
-
Compressive strength of concrete
- \(f_{cc}^{\prime}\) :
-
Maximum stress of confined concrete
- f hcc :
-
Tensile stress of the transverse reinforcement
- f LE :
-
Lateral confining pressure
- f t :
-
Tensile strength of concrete
- f yh :
-
Yield strength of transverse reinforcement
- (f cc)EXP :
-
Measured stresses
- (f cc)m :
-
Mean stress of points in measured stress-strain relationship of confined concrete
- (f cc)PRE :
-
Predicted stresses
- G f :
-
Fracture energy
- g f(α o):
-
Non-dimensional energy release rate
- h :
-
Height of cylindrical specimen
- k :
-
Factor to section shape of specimen (π/4 for cylindrical section, and 1.0 for cubic section)
- k 1 :
-
Factor of efficiency of the transverse reinforcement arrangement
- K s :
-
Strength gain factor
- n :
-
Number of points in measured stress-strain relationship of confined concrete
- s h :
-
Spacing of transverse reinforcement
- β 1 :
-
Slope factors of ascending and descending branches
- ε c :
-
Strain of confined concrete
- ε cc :
-
Strain at maximum stress of confined concrete
- ε c85 :
-
Strain at 85% of the maximum stress in descending branch of confined concrete
- γ m :
-
Mean of NRMSE
- γ s :
-
Standard deviation of NRMSE
- ρ 0 :
-
Reference value (= 2,300 kg/m3) of ρc
- ρ c :
-
Unit weight of concrete
- γ sh :
-
Volumetric transverse reinforcement ratio
- σ N :
-
Stress of the horizontal line for the strength criterion and inclined straight line for energy failure criterion
- ω sh :
-
Volumetric transverse reinforcement index
- ξ b :
-
Concrete brittleness number
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Acknowledgments
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (No. NRF-2017R1A2B3008463 and NRF-2018R1D1A1B07050275).
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Yang, KH., Mun, JH. & Hwang, SH. Compressive Stress-Strain Model for Confined Lightweight Concrete Based on Brittleness Number. KSCE J Civ Eng 25, 3041–3053 (2021). https://doi.org/10.1007/s12205-021-1840-9
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DOI: https://doi.org/10.1007/s12205-021-1840-9