Axial behavior of carbon fiber-reinforced polymer–confined recycled aggregate concrete-filled steel tube slender square columns

2021 ◽  
pp. 136943322110339
Author(s):  
Jiongfeng Liang ◽  
Siqi Lin ◽  
Mizan Ahmed
Keyword(s):  
Steel Tube ◽  
Recycled Aggregate Concrete ◽  
Fiber Reinforced Polymer ◽  
Recycled Aggregate ◽  
Fiber Reinforced ◽  
Replacement Ratio ◽  
Aggregate Concrete ◽  
Concrete Filled Steel Tube ◽  
Reinforced Polymer ◽  
Axial Behavior

The behavior of fiber-reinforced polymer (FRP)–confined recycled aggregate concrete-filled steel tube (RACFT) columns is barely studied. Especially, that of slender specimens has not been investigated so far. In this article, an experimental test of FRP-confined RACFT slender square columns was conducted to study the influences of recycled aggregate (RA) replacement ratios, FRP thicknesses, and wrapping schemes on their axial behavior. Results in this article suggest that the RA replacement ratio barely affects the initial stiffness of load-deflection curves of specimens. Moreover, the specimen with a higher RA replacement ratio has a lower axial stress but larger strain at the peak point. The external FRP jackets (either partial or full wrap) can effectively improve the performance of axially loaded RACFT columns, and the improvement of ductility due to the increase of the FRP thickness is more significant than that of axial compressive strength. Additionally, it was found that the axial strength and ultimate axial strain decrease with increasing slenderness ratios. Furthermore, the influences of slenderness ratios on the behavior of such columns are more significant for the column with a larger length-to-width ratio. Finally, a design model for FRP-confined RACFT slender square columns is developed, which can predict the results of the present test accurately.

scholarly journals Ductility Evaluation of Damaged Recycled Aggregate Concrete Columns Repaired With Carbon Fiber-Reinforced Polymer and Large Rupture Strain FRP

2020 ◽  
Vol 7 ◽  
Author(s):  
Pengda Li ◽  
Yao Zhao ◽  
Xu Long ◽  
Yingwu Zhou ◽  
Zhenyuan Chen
Keyword(s):  
Concrete Columns ◽  
Recycled Aggregate Concrete ◽  
Fiber Reinforced Polymer ◽  
Confined Concrete ◽  
Recycled Aggregate ◽  
Carbon Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Aggregate Concrete ◽  
Reinforced Polymer ◽  
Concrete Cylinders

The inherent defects of recycled aggregate concrete (RAC) include the complex interfacial transition zone (ITZ) and the many micro-cracks that appear during its producing process, which result in some inferior mechanical properties compared with natural aggregate concrete (NAC). This drawback usually prevents RAC from being selected for structural purposes. Existing research has shown that the strength and ductility of damaged concrete in compression members can be significantly enhanced through external confinement using fiber-reinforced polymer (FRP) wraps. This application has been widely used in concrete structural repair and retrofitting technology. However, research on the effects of RAC damage coupled with different load damage conditions is rare, as is information on the mechanical properties of RAC reinforced with FRP jackets. This paper presents the results of an experimental study on the behavior of pre-damaged recycled aggregate concrete cylinders that were repaired with carbon fiber-reinforced polymer (CFRP) or large rupture strain (LRS)-FRP jackets. Tests were conducted on 58 concrete cylinders with variations in the replacement ratio, damage levels, and FRP properties. Test results demonstrated that the ultimate strain and strength of damaged recycled aggregate concrete could be significantly enhanced by FRP jackets and that aggregate quality plays a vital role in the strength of confined concrete. Also, the energy absorption of CFRP- and LRS-FRP-confined RAC were evaluated. The analysis indicated that, compared with CFRP-confined RAC, LRS-FRP can greatly improve the energy absorption capacity of RAC; thus, LRS-FRP confined concrete has a good potential to achieve a ductile design for concrete columns, especially when used in seismic reinforcement.

Compressive Strength of Steel Fiber Reinforced Polymer Modified Recycled Aggregate Concrete

2021 ◽  
Vol 1166 ◽  
pp. 81-94
Author(s):  
Ganesh D. Awchat
Keyword(s):  
Compressive Strength ◽  
Steel Fiber ◽  
Recycled Aggregate Concrete ◽  
Fiber Reinforced Polymer ◽  
Recycled Aggregate ◽  
Fiber Reinforced ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Reinforced Polymer ◽  
Strain Behaviour

Demolish existing structures for better economic gains, functional and structural performance, and non-availability of land or disposal sites in nearby areas of all major cities worldwide turned as a significant reason for the crushing demolished concrete instead of using it as landfill. Research work aimed at arriving Recycled Concrete (RC) with the help of two materials, i.e. Steel Fibers (SF) and Styrene-Butadiene Rubber (SBR) latex, as additives to improve strength parameters of it. SF and SBR added in RC to examine & strengthen and termed as Steel Fiber Reinforced Polymer Modified Recycled Aggregate Concrete (SFRPMRAC). For this purpose, 198 cubes each of M20 (trial-1) and M25 (trial-2) cast separately to check compressive strength and its stress-strain behaviour for Natural Concrete (NC), RC & SFRPMRAC. The volume fractions of SF added 0.5%, 1% & 1.5% m3 of concrete and dosages of SBR latex varied from 2.5%, 5% and 7.5% by cement weight for preparation of cubes made of RC. From experimental results, SFRPMRAC with SF volume fraction of 1% m3 of concrete and 5% by cement weight provides an improvement in compressive strength by 8.62 % & 10.73 % for trial -1 and 11.51 % & 12.57 % for trial - 2 at 28 & 90 days when compared with NC. Compression stress-strain behaviour for SFRPMRAC with SF 1% m3 of concrete and 5% by weight of cement shows higher strain values at the peak stress. SFRPMRAC arrests the sudden drop of load due to co-matrix bond formation between SF and SBR in a linear direction compared to a similar NC & RC mix for both trials. It reflects significant improvement and approval of compressive strength for the desired purpose.

Reliability Analysis on Load-Bearing Capacity of Axially Loaded of Recycled Aggregate Concrete-Filled Steel Tube

2014 ◽  
Vol 711 ◽  
pp. 438-443
Author(s):  
Rong Hua Yang ◽  
Gao Bo Mai
Keyword(s):  
Reliability Index ◽  
Coarse Aggregate ◽  
Great Influence ◽  
Steel Tube ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Order Moment ◽  
Aggregate Concrete ◽  
Concrete Filled Steel Tube ◽  
Recycled Coarse Aggregate

The first degree second order moment method (JC method) is applied to analyze the reliability of recycled aggregate concrete-filled steel tube (RACFST). Several performances are studies, which are the influences of different load combinations, specific values of loads,confinement coefficients and recycled coarse aggregate replacement percentage on the reliability of the column. It is found that the reliability index varied with the load combination and specific value of loads. The analytical results indicate that the reliability index of the round steel tube is higher than square steel tube and the influence of recycled coarse aggregate replacement percentage can almost be ignored It can be concluded that the formula had great influence on reliability index and the revised formula can meet the requirements of the ductility of structure reliability.

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