Bond behaviour of substandard splices in RC beams externally confined with CFRP

Abstract

Bond splitting is investigated using flexuraltests ontwelve RCbeams with substandard laps(25 bar diameters)at midspan.Differentconfinementconfigurationsof the splice region, concrete coversand bar sizesare examined.The resultsshow thatCFRP confinement enhancesthe splicebond strength by up to 65%compared to unconfined specimens.Predictiveequationsfrom the literature are shown to yield a large scatter in results and tooverestimate the strain developedin theCFRPconfinement. Analternative approach to calculatetheconfinement strain and theadditional bond strength provided byCFRP confinementis proposedand validated.

Fibre-reinforced polymer strengthening of substandard lap-spliced reinforced concrete members: A comprehensive survey

“…More recently, Garcia et al (2014Garcia et al ( , 2015 proposed a practical strain control approach (model 12 in Table 1) to calculate the bond strength enhancement due to FRP confinement. The effect of the CFRP confinement is considered through an additional confining pressure f o assumed to act over a split cross sectional area equal to (c min(x,y) +d b )•l b , as shown in Figure 9.…”

“…More recently, Garcia et al (2014Garcia et al ( , 2015 investigated the bond strength enhancement resulting from the confinement provided by CFRP sheets in 24 beam splice specimens tested in flexure, similar to those tested by Harajli et al (2006) and Hamad et al (Hamad et al 2004a, Hamad et al 2004b, Hamad et al 2004c). Lap lengths of 10d b and 25d b were used to examine the mobilised "local" and average bond strengths, respectively.…”

“…Moreover, it is more convenient to compare the relative improvement that the FRP provides to confined specimens over unconfined specimens in terms of bond strength and ductility for different rib areas, rather than comparing the absolute bond improvement. It has been also argued that FRP-strengthened lap-spliced elements have highly variable properties of concrete in tension, but tests performed by the authors (Garcia et al 2014(Garcia et al , 2015 and by other researchers (Hamad et al 2004a(Hamad et al , 2004b(Hamad et al , 2004c on beam splice specimens indicate that the FRP strengthening reduced the concrete variability in tension, thus providing more consistent bond strengths. In summary, the influence of concrete strength and bar characteristics on require further investigation.…”

“…Whilst the Greek code is adequately progressing towards a general bond strength approach, the adopted model suggests ignoring the contribution of the concrete cover around the lap ( s =0), which may actually account for most of the existing bond strength of the lap as demonstrated experimentally (e.g. Hamad et al 2004a, 2004b, 2004c, Hamad and Rteil 2006, Garcia et al 2014.…”

Seismic retrofitting of RC buildings using CFRP and post-tensioned metal straps: shake table tests

“…The article details the adopted retrofitting strategy, and discusses global and local results from the shake table tests on the retrofitted structure. This study is part of a comprehensive research effort focusing on the seismic retrofitting of substandard RC buildings using PTMS (Garcia et al 2014a) and FRP composites (Garcia et al 2014b(Garcia et al , 2015.…”