Abstract
In an attempt to mitigate the high cost of FRP composite strengthening, an experimental investigation was carried out that sought to achieve efficient and most favorable FRP strengthening using CFRP composite strips. 50 mm wide CFRP composite strips were used in two different spacings (20 mm and 40 mm) to confine columns. The test results of the column confined with smaller spacing (20 mm) showed significant restraint of axial deformation of the column and enhanced the strength capacity to a maximum of 99.20% compared to that of reference column. In contrast, the column confined by strips with larger spacing (40 mm) failed by crushing of concrete alone, which occurred even before the CFRP strips reached their ultimate strain. In addition, the embodied energy that exists in the CFRP strips could not be utilized effectively. The stress and strength enhancement ratio of this present study was compared with the previous research that has been conducted on columns confined with full wrapping. From the obtained results, it is recommended that CFRP strips with a spacing of 20 mm be used to improve the strength capacity of the RC column; in addition, this wrapping technique provides economic benefits compared to a column confined with full wrapping.
Highlights
Over the past several decades, the innovative application of fibre reinforced polymer (FRP) composites has gained popularity as a method of upgrading/strengthening the deteriorated RC structures in the construction industry due to their high resistance to corrosion and their high strength-to-weight ratio
For the column confined with 50 mm CFRP strips with 20 mm spacing (NC-20-2 and NC-20-3), at the respective 60% (155 kN) ultimate load of the reference column, there were no cracks observed in the unbonded area; a cracking sound was observed due to the removal of excessive resin on the outside of the CFRP strips
Among the few models [14, 39, 58,59,60,61,62, 67, 68], the model proposed by Miyauchi et al [39] was considered in this study to evaluate the ultimate strength capacity of the FRP confined RC column, since the models proposed by various studies showed a lower prediction, which is shown in Figure 22; in addition, the percentage of difference of the studies was very high
Summary
Over the past several decades, the innovative application of FRP composites has gained popularity as a method of upgrading/strengthening the deteriorated RC structures in the construction industry due to their high resistance to corrosion and their high strength-to-weight ratio. Even though the technique was successful in practice, it had some problems, including the addition of self-weight, corrosion of the steel plate, the need for skilled labour, and a higher cost. This method can be applied only to the square and rectangular columns and is not possible to apply to the circular columns. The test results of the columns confined by CFRP strips were compared with the previous studies, Abdollahi et al [27], Au and Buyukozturk [28], Pon et al [29], Bisby et al [30], Aire et al [31], Silva [32], Almusallam [33], Silva and Rodrigues [34], Benzaid et al [35], Smith et al [36], Erdil et al [37], Akogbe et al [38], Miyauchi et al [39], Wang and Wu [40], Hosotani et al [41], Shehata et al [42], Santarosa et al [43], Theriault et al [44], Valdmanis et al [45], Wang and Wu [46], Wang and Hsu [47], Hadi [48], Punurai et al [49], Quiertant and Clement [50], Pham et al [51], Li et al [52], Siddiqui et al [53], and Sharma et al [54] conducted on RC columns externally confined by full wrapping, in terms of stress and strength enhancement ratio
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