Experimental investigation of seismic strengthening of reinforced concrete short columns using externally bonded reinforcement, near surface mounted, and hybrid techniques

2019 ◽  
Vol 54 (9) ◽  
pp. 1177-1195 ◽  
Author(s):  
A Kargaran ◽  
A Kheyroddin
Keyword(s):  
Reinforced Concrete ◽  
Fiber Reinforced Polymer ◽  
Dissipated Energy ◽  
Fiber Reinforced ◽  
Near Surface ◽  
Short Columns ◽  
Reinforced Polymer ◽  
Shear Rupture ◽  
Externally Bonded ◽  
Near Surface Mounted

Nowadays, the existence of short columns is a major factor in the failure and collapse of structures during the earthquake. In this article, 10 reinforced concrete short columns are prepared and experimentally investigated under cyclic lateral displacements. Since failure in short columns under earthquake was in the form of diagonal cracks and shear rupture, two new techniques are proposed to strengthen short columns against seismic loads. These techniques include externally bonded reinforcement with carbon fiber-reinforced polymer sheets and near surface mounted with glass fiber-reinforced polymer bars in the form of transverse, diagonal, and hybrid strengthening techniques. The experimental results demonstrated that the above-mentioned strengthening techniques in short columns lead to a change in the type of failure from shear to flexural, and the change of crack patterns and columns failure. The mentioned strengthening methods lead to an increase of ductility, increase of load carrying capacity and increase of dissipated energy.

Retrofitting of reinforced concrete columns using near-surface-mounted steel rebars and fiber-reinforced polymer straps under eccentric loading

2019 ◽  
Vol 23 (4) ◽  
pp. 687-701 ◽  
Author(s):  
Sayed Behzad Talaeitaba ◽  
Ehsan Barati ◽  
Abolfazl Eslami
Keyword(s):  
Reinforced Concrete ◽  
Concrete Columns ◽  
Fiber Reinforced Polymer ◽  
Small Scale ◽  
Fiber Reinforced ◽  
Reinforced Concrete Columns ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Steel Rebars

This experimental study focuses on the retrofitting of reinforced concrete columns subjected to axial compression loading with different eccentricities. The proposed hybrid retrofitting technique incorporates two components: near-surface-mounted longitudinal steel rebars and transverse carbon-fiber-reinforced polymer straps. The latter was implemented to preclude buckling of the near-surface-mounted steel rebars under compression, to postpone debonding of near-surface-mounted steel rebars, to increase shear capacity of columns, and to improve the confinement level of concrete. The efficiency of the adopted retrofitting technique was evaluated through experimental testing of undamaged and damaged columns. Toward this, a total of 20 small-scale reinforced concrete circular columns including 5 control, 5 repaired, and 10 strengthened specimens were tested. All specimens were built to be identical with a diameter of 150 mm and a height of 500 mm. The specimens were tested under pure compression, combined axial–flexural (with eccentricities of 30, 60, and 90 mm), and four-point flexural loadings. Comparison of the results showed the efficacy of the proposed retrofitting strategy in enhancing the structural performance of both the undamaged and damaged columns in terms of loading capacity, ultimate displacement, and ductility factor. Finally, the axial load–bending moment interaction curves were discussed for all the tested columns.

scholarly journals Debonding Detection of Reinforced Concrete (RC) Beam with Near-Surface Mounted (NSM) Pre-stressed Carbon Fiber Reinforced Polymer (CFRP) Plates Using Embedded Piezoceramic Smart Aggregates (SAs)

2019 ◽  
Vol 10 (1) ◽  
pp. 50 ◽  
Author(s):  
Yang Liu ◽  
Ming Zhang ◽  
Xinfeng Yin ◽  
Zhou Huang ◽  
Lei Wang
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fiber ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Rc Beam ◽  
Fiber Reinforced ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Carbon Fiber Reinforced

The application of reinforced concrete (RC) beam with near-surface mounted (NSM) pre-stressed carbon fiber reinforced polymer (CFRP) plates has been increasingly widespread in civil engineering. However, debonding failure occurs easily in the early loading stage because of the prestress change at the end of CFRP plate. Therefore, it is important to find reliable, convenient and economical technical means to closely monitor the secure bonding between CFRP and concrete. In this paper, an active sensing approach for generating and sensing stress wave by embedded smart aggregates (SAs) is proposed, which provides a guarantee for the secure connection between CFRP and concrete. Two specimens with different non-pre-stressed bond lengths were fabricated in the laboratory. Six SAs were installed at different positions of the structure to monitor the degree of debonding damage during the loading process. The experiments showed that the optimal length of non-pre-stressed CFRP bond section (300 mm) can significantly improve the load characteristics and enhance the service performance of the structure. The theoretical analysis of wavelet packet shows that increasing the length of non-pre-stressed CFRP bond section can slow down the occurrence and propagation of debonding cracks. The debonding crack in the tension end region is earlier than that in the bond end region. The research results reflect that the developed approach can monitor the damage process caused by debonding cracks and provide early warning for the initial damage and the debonding failure.

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