Next Article in Journal
Liquid Crystal Ordering in the Hexagonal Phase of Rod-Coil Diblock Copolymers
Next Article in Special Issue
Defect Characteristics and Online Detection Techniques During Manufacturing of FRPs Using Automated Fiber Placement: A Review
Previous Article in Journal
Less Reactive Thiol Ligands: Key towards Highly Mucoadhesive Drug Delivery Systems
Previous Article in Special Issue
Reliability Analysis of FRP-Confined Concrete at Ultimate using Conjugate Search Direction Method
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Polymers
Volume 12
Issue 6
10.3390/polym12061261
polymers-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns

by
Cheng Jiang
1,2 and
Yu-Fei Wu
1,3,*
1
School of Engineering, RMIT University, 376-392 Swanston St, Melbourne, VIC 3001, Australia
2
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon 999077, Hong Kong, China
3
Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University, Shenzhen 518060, China
*
Author to whom correspondence should be addressed.
Polymers 2020, 12(6), 1261; https://doi.org/10.3390/polym12061261
Submission received: 24 April 2020 / Revised: 28 May 2020 / Accepted: 29 May 2020 / Published: 31 May 2020
(This article belongs to the Special Issue Fiber Reinforced Polymers)
Browse Figures
Versions Notes

Abstract

:
This paper presents an experimental program that includes 78 fiber reinforced polymer (FRP)-confined square concrete columns subjected to eccentric loading. The degradation of the axial strength of FRP-confined short concrete columns due to the load eccentricity is investigated in this work. A larger load eccentricity leads to a greater decrease in the axial strength. From the test results, it is found that FRP confinement can cause less strength degradation compared with that of unconfined concrete specimens. For FRP-confined square concrete specimens, the strength enhancement due to FRP confinement increases with increasing load eccentricity. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. The relationship between the strength of eccentrically loaded FRP-confined square columns and their corner radii is evaluated.

1. Introduction

Fiber reinforced polymer (FRP) jacketing or confinement has been widely adopted and used in rehabilitation work on concrete structures [1,2,3,4]. The confinement can not only enhance the strength and ductility of a concrete structure [5,6] but also increase the bond between the concrete and internal steel reinforcement [7,8,9]. In addition to the structural rehabilitation, the concept of FRP confinement has also been adopted in the constructions of new structures, such as the applications of concrete filled FRP tubes [10,11,12]. Various models for concrete columns strengthened with FRPs under concentric loading have been proposed in the past three decades. These stress-strain and strength models have covered different sections of circular (e.g., [13,14,15,16,17,18,19]), square (e.g., [20,21]), rectangular (e.g., [22,23,24]), and cross-sectional unified (e.g., [25,26,27]) types. In practical engineering applications, most existing concrete columns with noncircular cross-sections are subjected to eccentricity loading. However, concentrically loaded models have usually been used to analyze cases with eccentrically loading. It is well established in the literature that the load eccentricity affects the confinement behavior of FRP jacketed concrete columns [28,29,30,31] because the eccentric loading causes a variation in the confinement pressure across the section, thereby leading to a stress state that differs from that under concentric loading for a certain axial strain.
Many experimental investigations on eccentrically loaded FRP confined columns have been carried out on circular columns [30,32,33,34,35,36,37,38,39,40,41] and noncircular columns [28,42,43,44,45,46,47,48,49,50]. Other investigations [29,31,51] focused on finite element modeling (FEM) to investigate the effect of the load eccentricity on FRP-confined concrete columns. It is found that the eccentric loading highly influences the mechanical behaviors of FRP-confined concrete. There is no doubt that the global response has a degradation trend due to load eccentricity. More recently, the effect of load eccentricity on the stress-strain relationship for cross-sectional analysis was deeply investigated and discussed. For example, Maaddaw [28] developed a simple theoretical stress-strain model considering load eccentricity, which has a reduction effect on the stress-strain relationship. However, other researchers found that load eccentricity enhanced the stress-strain behavior from both experimental [30] and numerical [31] analyses.
Overall, the available tests on eccentrically loaded FRP-confined concrete columns are limited in the open literature, especially for square cross-sections. As the confinement mechanism for square columns is different with that of circular columns, it is necessary to clearly understand the relationship between column section and confinement efficiency under eccentric loading. This work aims to investigate the degradation of the axial load capacity due to the load eccentricity on FRP-confined square and circular short concrete.

2. Experimental Program

The experimental program included 78 square confined columns with different FRP confinements (32 specimens without confinement, 32 specimens with 1-ply FRP confinement, and 14 specimens with 2-ply FRP confinement), corner radius ratios (12 specimens with 15 mm, 42 specimens with 30 mm, 12 specimens with 45 mm, and 12 specimens with 60 mm), and a full range of load eccentricities (12 specimens each for 0, 10, 20, 30, 40 and 50mm, and 6 specimens with 60 mm). The details of the specimen design are given in Table 1. All the specimens were tested in the Heavy Structure Testing Laboratory in the City University of Hong Kong.
All the specimens were designed with a width of 150 mm (b), a depth of 150 mm (d) and a height of 300 mm with different corner radii (r). To independently study the behaviors of the confined concrete, no internal reinforcement was used for the specimens. The corner radius ratio ρ is a key factor that affects the confining effect of FRP wrapping and is determined as [25,26,27,52]:
ρ = 2r/b
where b is the length of the side for square cross-sections and the diameter for circular sections. The effect of the corner radius ratio ρ and the steel molds for concrete casting can be found in Figure 1.
As the specimens in this work could not be cast with one single batch of concrete, they were carefully grouped to minimize the unavoidable differences caused by the variations between the concrete properties of different batches. Specimens with the same FRP layers but different load eccentricities were grouped in one batch. Hence, the variation in the eccentricity could be isolated from the variation due to other factors.
A carbon fiber reinforced polymer (CFRP) was used for the FRP wrapping, which had a nominal thickness of 0.167 mm. A two-part Sikadur-300 was used as the saturant resin. Flat coupon tensile tests were conducted following ASTM D3039 [53] to determine the mechanical properties of the CFRP sheets. The ultimate strength, tensile modulus and ultimate strain of the CFRP sheets in this work were 4192 MPa, 254 GPa, and 1.84%, respectively. The CFRP sheets were wrapped around the specimens using the manual lay-up procedure in the hoop direction. Each CFRP jacket had a single overlap of 150 mm in length.
For the specimen IDs in Table 1, the number after the letter R represents the corner radius with units of mm; subsequently, the two identical specimens are separated into two different groups identified by the letter A or B in the specimen IDs for the specimens with 30 mm of corner radius; the second figure of specimen ID (0, 1 or 2) denotes the number of CFRP layers; and the remaining indicators, E0, E10, E20, E30, E40 or E50, represent a load eccentricity of 0, 10,20, 30, 40 and 50 mm, respectively. For example, R45B2E30 indicates the FRP-confined square concrete specimen with a corner radius of 45 mm in group B, which was applied with 2-ply CFRP sheets and a load eccentricity of 30 mm.
All the specimens were tested after 28 days of curing. The test setup is shown in Figure 2. Eccentric loading was applied by a knife edge at the top of the specimen (Figure 2). The specimen was placed on a flat and greased plate at the bottom so that friction at the end was minimized. The vertical displacements of the specimen at both the compression and tension sides were measured by two 50 mm-travel linear variable differential transformers (LVDTs), which were mounted on an aluminum frame with a 200 mm gauge length in the middle. A total of 75 mm was left between the specimen surfaces and the LVDTs. The specimens were tested under monotonically increasing loading until failure, controlled with a displacement rate of approximately 0.3 mm/min. The load was measured by a load cell placed at the bottom of the specimen (Figure 2).

3. Test Results and Discussion

3.1. Failure Modes and Cross-Sectional Strength

For unconfined concrete specimens with concentric loading, the concrete mainly split longitudinally on the side surface, and the cone appearance could also be found on the failure surface. For unconfined columns with relatively larger load eccentricities, the failure of the specimens was generally marked by concrete crushing at the compression side at or near the mid-height of the specimen, and a horizontal crack at approximately mid-height or at the top of the column was clearly observed on the tensile side. For the columns with the largest eccentricity of 60 mm, the specimens crushed at the top of the specimen on the compression side. The typical images of failure modes of the tested FRP-confined square short columns are shown in Figure 3.
The failure of all FRP-confined specimens was always caused by FRP rupture, and no delamination of the FRP at the overlapping zone was observed. Clicking sounds could be heard during the loading stage, and the failure occurred suddenly with an explosive sound. The fracture of the CFRP jacket was mainly near the corner of the compression side due to the stress concentration. On the tensile side, horizontal cracks along the fiber hoop direction were observed at mid-height or in adjacent areas. Furthermore, crushing of the concrete core occurred in the specimens with a relatively large load eccentricity. The test results for the axial strength, which refer to the peak load for a section in the tests (Ne), of all the specimens are listed in Table 1. The typical load-displacement curves for eccentrically loaded FRP-confined square columns in this work and FRP-confined circular columns reported in [30] are illustrated in Figure 4. Each specimen in Figure 4 has two curves from two LVDTs on the compression side and tension side. Similarly to the circular columns, the degradation due to the load eccentricity is substantial, as observed in Figure 4. The sudden load loss or drop in the load-displacement curves indicates the occurrence of FRP rupture.

3.2. Effect of the Load Eccentricity and FRP Confinement

The strength factor Ne/Nc0 is defined and analyzed to study the effect of the load eccentricity on the degradation of the axial strength, where Ne is the load capacity of the sections for FRP-confined concrete specimens with/without load eccentricity and Nc0 is the load capacity for concentrically loaded unconfined concrete specimens. This type of load capacity comparison has been widely adopted in confined concrete analysis [54].
A nondimensionalized term 2e/b is adopted to show the magnitude of the load eccentricity. By comparing the values of Ne/Nc0, it is obvious that the axial strength decreases with increasing load eccentricity, as shown in Figure 5. When the eccentricity is small (e.g., 10 mm or 2e/b = 0.13), the cross-sectional strength reduction degree is limited and is occasionally close to 0. However, when the load eccentricity increases, the decrease in the axial strength is more significant. Additionally, a greater confinement (or number of FRP layers) results in a higher strength.
To better understand the strength degradation due to the load eccentricity, another comparison of Ne/Nc is carried out by modifying the results in Figure 5, where Nc is the axial strength for concentrically loaded specimens with the same confinement level as that of Ne. The results are shown in Figure 6. It can be concluded that the degradation of FRP-confined circular columns due to the load eccentricity (Figure 6e) is insensitive to the FRP confinement. However, for square columns (Figure 6a–d), FRP confinement can cause less axial strength degradation compared with that of unconfined concrete specimens. Different confinement levels (i.e., 1 layer and 2 layers) do not have a significant influence on the strength degradation, as can be observed in Figure 6b.
The contribution from the FRP confinement can be further investigated by studying the effect of the load eccentricity on Ne/Nf0, where Nf0 is the axial strength for unconfined concrete with the same load eccentricity as that of Ne. The comparison results are shown in Figure 7. The confinement efficiency can be easily revealed for the term Ne/Nf0. A high value of Ne/Nf0 represents a higher efficiency due to the FRP confinement because this ratio represents the strength enhancement by the FRP confinement. For most FRP-confined square concrete specimens, it can be found in Figure 7 that the value of Ne/Nf0 increases when the load eccentricity increases. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. This is reasonable because the circular section has less compressive area than that of square columns for a fixed load eccentricity or natural axis. This trend is more significant for a large eccentricity because of the small height of the natural axis.

3.3. Effect of the Corner Radius

When 2e/b = 0, which means the concrete is under concentric loading, a greater corner radius can result in a higher value of Ne/Nf0, as shown in Figure 7. An exception to this trend is the case where r = 15 mm (Figure 7a). This is because the specimens with r = 15 mm have the lowest unconfined concrete strength, as shown in Table 1. The lower concrete strength leads to a higher confinement effect for the fixed FRP wrapping layers.
The reduction in the confinement effectiveness due to the corner radius of an FRP-confined square-shaped column under concentric loading can be accounted for with an accurate shape factor ks [24,25,26] as:
ks = (2r/b)0.72
However, Equation (2) was proposed for the ultimate strength of the stress-strain relationship of FRP-confined concrete. Jiang et al. [55] extended and summarized a general relationship for the influence of the corner radius on the structural indexes (e.g., axial strength and plastic hinge length) of FRP-confined concrete structures, as shown in Equation (3).
Ssf/Ss0 = 1 + (2r/b)0.72(Scf/Sc0 − 1)
where Ssf and Ss0 are the structural indexes of FRP-confined square concrete and unconfined square concrete, respectively; Scf and Sc0 are the performances of FRP-confined circular concrete and unconfined circular concrete, respectively. If Equation (3) is applied to determine the axial strength of FRP confined concrete under eccentric loading, Equation (3) can be written as:
Ne/Nf0 = 1 + (2r/b)0.72(Nc-f/Nc-0 − 1)
where Nc-f and Nc-0 are the Ne and Nf0 values for 2r/b = 1 (i.e., circular section), respectively.
The Ne/Nf0 values for the various corner radii with a fixed number of FRP layers are plotted in Figure 8. It can be found from Figure 8 that the relationship for Equation (4) can basically describe the effect of the corner radius for FRP-confined concrete subjected to eccentric loading. Here, Nc-f/Nc-0 in Equation (4) takes the average test values in Figure 8 in the analysis. This finding provides a foundation for developing an eccentricity-based stress-strain model of FRP-confined square columns, which requires future study.

4. Conclusions

The compression tests on a total of 78 FRP-confined square concrete columns subjected to eccentric loading were reported in this work. The degradation of the axial load capacity due to the load eccentricity was investigated. After analyzing the test results, the following conclusion can be drawn.
(1)
When the load eccentricity is small (e.g., 10 mm or 2e/b = 0.13), the axial strength reduction degree is limited and is occasionally close to 0. However, when the load eccentricity increases, the decrease in the axial strength is more significant.
(2)
FRP confinement can reduce the axial strength degradation compared with that of unconfined concrete specimens. While different confinement levels (i.e., 1 layer and 2 layers) do not have a significant influence on the strength degradation.
(3)
For FRP-confined square concrete specimens, the strength enhancement due to FRP confinement increases with increasing load eccentricity. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. This is because the circular section has a much less compressive area than that of square columns for a fixed natural axis.
(4)
The relationship between the structural behavior of FRP-confined square columns and their corner radii (Equation (4)) can basically describe the effect of the corner radius on the axial strength of FRP-confined concrete subjected to eccentric loading.

Author Contributions

Conceptualization, Y.-F.W.; methodology, C.J. and Y.-F.W.; validation, C.J.; formal analysis, C.J.; investigation, C.J.; resources, Y.-F.W.; data curation, C.J.; writing—original draft preparation, C.J.; writing—review and editing, Y.-F.W.; visualization, C.J.; supervision, Y.-F.W.; project administration, Y.-F.W.; funding acquisition, Y.-F.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Victoria-Jiangsu Program for Technology and Innovation R&D, from the Department of Economic Development, Jobs, Transport and Resources, the state of Victoria, Australia, and the Australian Research Council (DP200100631).

Acknowledgments

The experimental tests in this work were undertaken by the former Ph. D. student Leiming Wang, and his contribution is acknowledged.

Conflicts of Interest

The authors declare no conflict of interest.

Nomenclature

blength of the side for square cross-sections and the diameter for circular sections
ddepth of the cross-section, = b for square cross-sections
eload eccentricity
fcounconfined concrete strength
hheight of the specimens
ksshape factor for the corner radius, = (2r/b)0.72
Ncaxial strength for the concentrically loaded specimens
Nc0axial strength for the concentrically loaded unconfined concrete specimen.
Nc-0Nf0 value for 2r/b = 1 (i.e., circular section)
Nc-fNe value for 2r/b = 1 (i.e., circular section)
Neaxial load capacity (or axial strength) of short columns
Nf0axial strength for the unconfined concrete specimens
rcorner radius
Sc0structural index of the unconfined circular concrete
Scfstructural index of the FRP-confined circular concrete
Ss0structural index of the unconfined square concrete
Ssfstructural index of the FRP-confined square concrete
ρcorner radius ratio, = 2r/b

References

  1. Wu, Y.F.; Jiang, C.; Yuan, F.; Zhao, X.M.; Wang, J.S. Labor and Cost Efficient Construction Method for Retrofitting RC Columns with FRP; Construction Industry Council: Hong Kong, China, 2020. [Google Scholar]
  2. Keshtegar, B.; Gholampour, A.; Ozbakkaloglu, T.; Zhu, S.P.; Trung, N.T. Reliability analysis of FRP-confined concrete at ultimate using conjugate search direction method. Polymers 2020, 12, 707. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  3. Zhou, Y.; Hu, J.; Li, M.; Sui, L.; Xing, F. FRP-confined recycled coarse aggregate concrete: Experimental investigation and model comparison. Polymers 2016, 8, 375. [Google Scholar] [CrossRef] [PubMed]
  4. Li, P.D.; Wu, Y.F.; Zhou, Y.; Xing, F. Stress-strain model for FRP-confined concrete subject to arbitrary load path. Compos. Part B Eng. 2019, 163, 9–25. [Google Scholar] [CrossRef]
  5. Zeng, J.J.; Guo, Y.; Li, L.; Chen, W. Behavior and three-dimensional finite element modeling of circular concrete columns partially wrapped with FRP strips. Polymers 2018, 10, 253. [Google Scholar] [CrossRef] [Green Version]
  6. Feng, P.; Cheng, S.; Bai, Y.; Ye, L. Mechanical behavior of concrete-filled square steel tube with FRP-confined concrete core subjected to axial compression. Compos. Struct. 2015, 123, 312–324. [Google Scholar] [CrossRef]
  7. Jiang, C.; Yuan, F.; Wu, Y.F.; Zhao, X.M. Effect of interfacial bond on plastic hinge length of FRP-confined RC columns. J. Compos. Constr. 2019, 23, 04019007. [Google Scholar] [CrossRef]
  8. Jiang, C.; Wu, Y.F.; Dai, M.J. Degradation of steel-to-concrete bond due to corrosion. Constr. Build. Mater. 2018, 158, 1073–1080. [Google Scholar] [CrossRef]
  9. Lin, H.; Zhao, Y.; Ozbolt, J.; Feng, P.; Jiang, C.; Eligehausen, R. Analytical model for the bond stress-slip relationship of deformed bars in normal strength concrete. Constr. Build. Mater. 2019, 198, 570–586. [Google Scholar] [CrossRef]
  10. Idris, Y.; Ozbakkaloglu, T. Seismic behavior of high-strength concrete-filled FRP tube columns. J. Compos. Constr. 2013, 17, 04013013. [Google Scholar] [CrossRef]
  11. Mohamed, H.M.; Masmoudi, R. Axial load capacity of concrete-filled FRP tube columns: Experimental versus theoretical predictions. J. Compos. Constr. 2010, 14, 231–243. [Google Scholar] [CrossRef]
  12. Huang, L.; Sun, X.; Yan, L.; Zhu, D. Compressive behavior of concrete confined with GFRP tubes and steel spirals. Polymers 2015, 7, 851–875. [Google Scholar] [CrossRef] [Green Version]
  13. Lam, L.; Teng, J.G. Design-oriented stress-strain model for FRP-confined concrete. Constr. Build. Mater. 2003, 17, 471–489. [Google Scholar] [CrossRef]
  14. Ozbakkaloglu, T.; Gholampour, A.; Lim, J.C. Damage-plasticity model for FRP-confined normal-strength and high-strength concrete. J. Compos. Constr. 2016, 20, 04016053. [Google Scholar] [CrossRef]
  15. Zeng, J.J.; Ye, Y.Y.; Guo, Y.C.; Lv, J.F.; Ouyang, Y.; Jiang, C. PET FRP-concrete-high strength steel hybrid solid columns with strain-hardening and ductile performance: Cyclic axial compressive behavior. Compos. Part B Eng. 2020, 190, 107903. [Google Scholar] [CrossRef]
  16. Jiang, C.; Wu, Y.F.; Jiang, J.F. Effect of aggregate size on stress-strain behavior of concrete confined by fiber composites. Compos. Struct. 2017, 168, 851–862. [Google Scholar] [CrossRef]
  17. Ozbakkaloglu, T.; Vincent, T. Axial compressive behavior of circular high-strength concrete-filled FRP tubes. J. Compos. Constr. 2014, 18, 04013037. [Google Scholar] [CrossRef]
  18. Pham, T.M.; Hadi, M.N. Confinement model for FRP confined normal-and high-strength concrete circular columns. Constr. Build. Mater. 2014, 69, 83–90. [Google Scholar] [CrossRef] [Green Version]
  19. Zhou, A.; Qin, R.; Chow, C.L.; Lau, D. Structural performance of FRP confined seawater concrete columns under chloride environment. Compos. Struct. 2019, 216, 12–19. [Google Scholar] [CrossRef]
  20. Wu, G.; Wu, Z.S.; Lü, Z.T. Design-oriented stress–strain model for concrete prisms confined with FRP composites. Constr. Build. Mater. 2007, 21, 1107–1121. [Google Scholar] [CrossRef]
  21. Al-Salloum, Y.A. Influence of edge sharpness on the strength of square concrete columns confined with FRP composite laminates. Compos. Part B Eng. 2007, 38, 640–650. [Google Scholar] [CrossRef]
  22. Ozbakkaloglu, T. Axial compressive behavior of square and rectangular high-strength concrete-filled FRP tubes. J. Compos. Constr. 2013, 17, 151–161. [Google Scholar] [CrossRef] [Green Version]
  23. Lam, L.; Teng, J.G. Design-oriented stress-strain model for FRP-confined concrete in rectangular columns. J. Reinf. Plast. Compos. 2003, 22, 1149–1186. [Google Scholar] [CrossRef]
  24. Wu, Y.F.; Wei, Y.Y. Effect of cross-sectional aspect ratio on the strength of CFRP-confined rectangular concrete columns. Eng. Struct. 2010, 32, 32–45. [Google Scholar] [CrossRef]
  25. Wei, Y.Y.; Wu, Y.F. Unified stress–strain model of concrete for FRP-confined columns. Constr. Build. Mater. 2012, 26, 381–392. [Google Scholar] [CrossRef]
  26. Wu, Y.F.; Wang, L.M. Unified strength model for square and circular concrete columns confined by external jacket. J. Struct. Eng. 2009, 135, 253–261. [Google Scholar] [CrossRef]
  27. Cao, Y.G.; Jiang, C.; Wu, Y.F. Cross-sectional unification on the stress-strain model of concrete subjected to high passive confinement by fiber-reinforced polymer. Polymers 2016, 8, 186. [Google Scholar] [CrossRef] [Green Version]
  28. El Maaddawy, T. Strengthening of eccentrically loaded reinforced concrete columns with fiber-reinforced polymer wrapping system: Experimental investigation and analytical modeling. J. Compos. Constr. 2009, 13, 13–24. [Google Scholar] [CrossRef]
  29. Hu, B.; Wang, J.G.; Li, G.Q. Numerical simulation and strength models of FRP-wrapped reinforced concrete columns under eccentric loading. Constr. Build. Mater. 2011, 25, 2751–2763. [Google Scholar] [CrossRef]
  30. Wu, Y.F.; Jiang, C. Effect of load eccentricity on the stress-strain relationship of FRP-confined concrete columns. Compos. Struct. 2013, 98, 228–241. [Google Scholar] [CrossRef]
  31. Lin, G.; Teng, J.G. Three-dimensional finite-element analysis of FRP-confined circular concrete columns under eccentric loading. J. Compos. Constr. 2017, 21, 04017003. [Google Scholar] [CrossRef]
  32. Li, J.; Hadi, M.N.S. Behaviour of externally confined high-strength concrete columns under eccentric loading. Compos. Struct. 2003, 62, 145–153. [Google Scholar] [CrossRef]
  33. Fam, A.; Flisak, B.; Rizkalla, S. Experimental and analytical modeling of concrete-filled fiber-reinforced polymer tubes subjected to combined bending and axial loads. ACI Struct. J. 2003, 100, 499–509. [Google Scholar]
  34. Tao, Z.; Teng, J.G.; Han, L.H.; Lam, L. Experimental behaviour of FRP-confined slender RC columns under eccentric loading. In Proceedings of the 2nd International Conference on Advanced Polymer Composites for Structural Applications in Construction, Surrey, UK, 20–22 April 2004; pp. 203–212. [Google Scholar]
  35. Hadi, M.N.S. Comparative study of eccentrically loaded FRP wrapped columns. Compos. Struct. 2006, 74, 127–135. [Google Scholar] [CrossRef]
  36. Hadi, M.N.S. Behaviour of FRP wrapped normal strength concrete columns under eccentric loading. Compos. Struct. 2006, 72, 503–511. [Google Scholar] [CrossRef]
  37. Hadi, M.N.S. Behaviour of FRP strengthened concrete columns under eccentric compression loading. Compos. Struct. 2007, 77, 92–96. [Google Scholar] [CrossRef] [Green Version]
  38. Hadi, M.N.S. The behaviour of FRP wrapped HSC columns under different eccentric loads. Compos. Struct. 2007, 78, 560–566. [Google Scholar] [CrossRef] [Green Version]
  39. Hadi, M.N.S. Behaviour of eccentric loading of FRP confined fibre steel reinforced concrete columns. Constr. Build. Mater. 2009, 23, 1102–1108. [Google Scholar] [CrossRef] [Green Version]
  40. Bisby, L.; Ranger, M. Axial-flexural interaction in circular FRP-confined reinforced concrete columns. Constr. Build. Mater. 2010, 24, 1672–1681. [Google Scholar] [CrossRef]
  41. Cao, Y.; Wu, Y.F.; Jiang, C. Stress-strain relationship of FRP confined concrete columns under combined axial load and bending moment. Compos. Part B Eng. 2018, 134, 207–217. [Google Scholar] [CrossRef]
  42. Chaallal, O.; Shahawy, M. Performance of fiber-reinforced polymer-wrapped reinforced concrete column under combined axial-flexural loading. ACI Struct. J. 2000, 97, 659–668. [Google Scholar]
  43. El Maaddawy, T. Behavior of corrosion-damaged RC columns wrapped with FRP under combined flexural and axial loading. Cem. Concr. Compos. 2008, 30, 524–534. [Google Scholar] [CrossRef]
  44. El Maaddawy, T. Post-repair performance of eccentrically loaded RC columns wrapped with CFRP composites. Cem. Concr. Compos. 2008, 30, 822–830. [Google Scholar] [CrossRef]
  45. Elwan, S.K.; Rashed, A.S. Experimental behavior of eccentrically loaded R.C. short columns strengthened using GFRP wrapping. Struct. Eng. Mech. 2011, 39, 207–221. [Google Scholar] [CrossRef]
  46. Hadi, M.N.S.; Widiarsa, I.B.R. Axial and flexural performance of square RC columns wrapped with CFRP under eccentric loading. J. Compos. Constr. 2012, 16, 640–649. [Google Scholar] [CrossRef] [Green Version]
  47. Hajsadeghi, M.; Alaee, F.J. Numerical analysis of rectangular reinforced concrete columns confined with FRP jacket under eccentric loading. In Proceedings of the 5th International Conference on FRP Composites in Civil Engineering, Beijing, China, 27–29 September 2010; pp. 658–661. [Google Scholar]
  48. Quiertant, M.; Clement, J.L. Behavior of RC columns strengthened with different CFRP systems under eccentric loading. Constr. Build. Mater. 2011, 25, 452–460. [Google Scholar] [CrossRef]
  49. Sadeghian, P.; Rahai, A.R.; Ehsani, M.R. Experimental study of rectangular RC columns strengthened with CFRP composites under eccentric loading. J. Compos. Constr. 2010, 14, 443–450. [Google Scholar] [CrossRef]
  50. Shaheen, E.; Shrive, N.G. Sprayed glass fibre reinforced polymer masonry columns under concentric and eccentric loading. Can. J. Civ. Eng. 2007, 34, 1495–1505. [Google Scholar] [CrossRef]
  51. Csuka, B.; Kollár, L.P. FRP-confined circular columns subjected to eccentric loading. J. Reinf. Plast. Composit. 2011, 30, 1167–1178. [Google Scholar] [CrossRef]
  52. Li, P.; Sui, L.; Xing, F.; Li, M.; Zhou, Y.; Wu, Y.F. Stress–strain relation of FRP-confined predamaged concrete prisms with square sections of different corner radii subjected to monotonic axial compression. J. Compos. Constr. 2019, 23, 04019001. [Google Scholar] [CrossRef]
  53. ASTM Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials; D3039/D3039M-95; Annual Book of ASTM Standards: Philadelphia, PA, USA, 1995.
  54. Wei, Y.; Jiang, C.; Wu, Y.F. Confinement effectiveness of circular concrete-filled steel tubular columns under axial compression. J. Constr. Steel Res. 2019, 158, 15–27. [Google Scholar] [CrossRef]
  55. Jiang, C.; Wu, Y.F.; Wu, G. Plastic hinge length of FRP-confined square RC columns. J. Compos. Constr. 2014, 18, 04014003. [Google Scholar] [CrossRef]
Polymers 12 01261 g001 550
Figure 1. Cross-sections in this work: (a) Cross-sectional unification by the factor ρ; (b) Prefabricated steel molds with various corner radii.
Figure 1. Cross-sections in this work: (a) Cross-sectional unification by the factor ρ; (b) Prefabricated steel molds with various corner radii.
Polymers 12 01261 g001
Polymers 12 01261 g002 550
Figure 2. Test setup.
Figure 2. Test setup.
Polymers 12 01261 g002
Polymers 12 01261 g003 550
Figure 3. Typical failure mode.
Figure 3. Typical failure mode.
Polymers 12 01261 g003
Polymers 12 01261 g004a 550Polymers 12 01261 g004b 550
Figure 4. Typical load-deformation curves: (a) ρ = 0.4, unconfined, Group A; (b) ρ = 0.4, unconfined, Group B; (c) ρ = 0.4, 1-ply FRP, Group A; (d) ρ = 0.4, 1-ply FRP, Group B; (e) ρ = 0.4, 2-ply FRP, Group A; (f) ρ = 0.4, 2-ply FRP, Group B; (g) ρ = 1, 1-ply FRP, Group A in [30]; (h) ρ = 1, 2-ply FRP, Group A in [30].
Figure 4. Typical load-deformation curves: (a) ρ = 0.4, unconfined, Group A; (b) ρ = 0.4, unconfined, Group B; (c) ρ = 0.4, 1-ply FRP, Group A; (d) ρ = 0.4, 1-ply FRP, Group B; (e) ρ = 0.4, 2-ply FRP, Group A; (f) ρ = 0.4, 2-ply FRP, Group B; (g) ρ = 1, 1-ply FRP, Group A in [30]; (h) ρ = 1, 2-ply FRP, Group A in [30].
Polymers 12 01261 g004aPolymers 12 01261 g004b
Polymers 12 01261 g005 550
Figure 5. Effect of the load eccentricity on Ne/Nc0: (a) r = 15 mm; (b) r = 30 mm; (c) r = 45 mm; (d) r = 60 mm; (e) r = 75 mm [30].
Figure 5. Effect of the load eccentricity on Ne/Nc0: (a) r = 15 mm; (b) r = 30 mm; (c) r = 45 mm; (d) r = 60 mm; (e) r = 75 mm [30].
Polymers 12 01261 g005
Polymers 12 01261 g006 550
Figure 6. Effect of the load eccentricity on Ne/Nc: (a) r = 15 mm; (b) r = 30 mm; (c) r = 45 mm; (d) r = 60 mm; (e) r = 75 mm [30].
Figure 6. Effect of the load eccentricity on Ne/Nc: (a) r = 15 mm; (b) r = 30 mm; (c) r = 45 mm; (d) r = 60 mm; (e) r = 75 mm [30].
Polymers 12 01261 g006
Polymers 12 01261 g007 550
Figure 7. Effect of the load eccentricity on Ne/Nf0: (a) Specimens with 1-ply FRP confinement; (b) Specimens with 2-ply FRP confinement.
Figure 7. Effect of the load eccentricity on Ne/Nf0: (a) Specimens with 1-ply FRP confinement; (b) Specimens with 2-ply FRP confinement.
Polymers 12 01261 g007
Polymers 12 01261 g008 550
Figure 8. Effect of the corner radius on Ne/Nf0: (a) 1-ply FRP jacketing; (b) 2-ply FRP jacketing.
Figure 8. Effect of the corner radius on Ne/Nf0: (a) 1-ply FRP jacketing; (b) 2-ply FRP jacketing.
Polymers 12 01261 g008
Table
Table 1. Details of the test specimens.
Table 1. Details of the test specimens.
Specimen IDr (mm)fco (Mpa)e (mm)FRP LayersNe
(kN)		Specimen IDr (mm)fco (Mpa)e (mm)FRP LayersNe
(kN)
R15A0E01525.600571.8R30B0E603035.4600184.9
R15A0E101525.6100551.8R30B1E03035.601952.7
R15A0E201525.6200483.8R30B1E103035.6101878.7
R15A0E301525.6300438.8R30B1E203035.6201764.7
R15A0E401525.6400383.8R30B1E303035.6301802.7
R15A0E501525.6500292.9R30B1E403035.6401778.7
R15A1E01530.901826.7R30B1E503035.6501493.8
R15A1E101530.9101788.7R30B1E603035.6601509.8
R15A1E201530.9201732.7R30B2E03040.7021448.5
R15A1E301530.9301665.8R30B2E103040.71021383.5
R15A1E401530.9401589.8R30B2E203040.72021261.6
R15A1E501530.9501487.8R30B2E303040.73021215.6
R30A0E03035.400753.7R30B2E403040.74021034.6
R30A0E103035.4100671.7R30B2E503040.7502858.7
R30A0E203035.4200622.8R30B2E603040.7602645.8
R30A0E303035.4300523.8R45A0E04526.800555.8
R30A0E403035.4400460.8R45A0E104526.8100480.8
R30A0E503035.4500336.8R45A0E204526.8200452.8
R30A0E603035.4600203.9R45A0E304526.8300426.8
R30A1E03035.601950.7R45A0E404526.8400359.8
R30A1E103035.6101924.7R45A0E504526.8500271.9
R30A1E203035.6201886.7R45A1E04536.101997.7
R30A1E303035.6301831.7R45A1E104536.11011003.6
R30A1E403035.6401793.7R45A1E204536.1201937.7
R30A1E503035.6501447.8R45A1E304536.1301816.7
R30A1E603035.6601411.8R45A1E404536.1401729.7
R30A2E03040.7021420.5R45A1E504536.1501617.8
R30A2E103040.71021308.6R60A0E06027.600534.8
R30A2E203040.72021177.6R60A0E106027.6100497.8
R30A2E303040.73021086.6R60A0E206027.6200412.8
R30A2E403040.7402918.7R60A0E306027.6300372.8
R30A2E503040.7502591.8R60A0E406027.6400306.9
R30A2E603040.7602340.8R60A0E506027.6500205.9
R30B0E03035.400782.7R60A1E06036.8011052.6
R30B0E103035.4100677.7R60A1E106036.81011045.6
R30B0E203035.4200541.8R60A1E206036.8201999.7
R30B0E303035.4300498.8R60A1E306036.8301788.7
R30B0E403035.4400398.8R60A1E406036.8401703.7
R30B0E503035.4500276.9R60A1E506036.8501516.8
Note: r is the corner radius, fco is the unconfined concrete strength, e is the load eccentricity, and Ne is the axial load capacity (axial strength).

Share and Cite

MDPI and ACS Style

Jiang, C.; Wu, Y.-F. Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns. Polymers 2020, 12, 1261. https://doi.org/10.3390/polym12061261

AMA Style

Jiang C, Wu Y-F. Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns. Polymers. 2020; 12(6):1261. https://doi.org/10.3390/polym12061261

Chicago/Turabian Style

Jiang, Cheng, and Yu-Fei Wu. 2020. "Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns" Polymers 12, no. 6: 1261. https://doi.org/10.3390/polym12061261

APA Style

Jiang, C., & Wu, Y.-F. (2020). Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns. Polymers, 12(6), 1261. https://doi.org/10.3390/polym12061261

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop