Smeared crack models of RC beams with externally bonded CFRP plates

Abstract

Concrete, a complex mix of variously sized aggregates, sand, water, additives and cement binder, is one of the more common engineering materials used for the design and construction of structures and bridges. Concrete is characterised by good compressive strength properties but it demands the use of internal reinforcement, generally in the form of round steel bars, to carry tensile stresses. The strength of the resulting element is dependent on the amount and distribution of steel reinforcement included during construction. It is not however possible to include additional internal reinforcement after construction in the event of the applied loading being increased and therefore consideration must be given to strengthening the structure externally, demolishing it, or con®ning it to speci®c usage, for example a maximum weight restriction on a bridge. In circumstances where restricted usage is not practicable structural strengthening is generally more favourable than demolition and replacement. Research in the area of strengthening of existing bridge beams is currently topical in the European Union given recent EU directives, aimed at encouraging free trade and movement of goods and services, which require all bridges to take 40 tonne vehicles.This paper describes the numerical modelling procedures employed, using smeared crack models available in ANSYS V5.4, to capture the load-deformation response and modes of failure, of reinforced concrete beams which have been strengthened, using carbon ®bre reinforced polymer (CFRP) composite material plates. Experimental veri®cations of these simulations have also been performed and are discussed in the present paper.

Tensile stress-strain relaxation as a failure precursor for FRP-strengthened RC beams

“…In only a few studies, experimental recordings identified tensile strain relaxation in the FRP plate anchorage region before the concrete cover failure [35,36,8]. The tensile relaxation is a consequence of the gradual cohesion loss in the concrete cover layer when the pull-out force from the FRP plate exceeds the elastic strain limit of concrete in tension.…”

Modeling of ultimate load for R.C. beams strengthened with Carbon FRP using artificial neural networks

“…R/C members resist bending moment using several mechanisms. Experimental investigations to predict the flexural strength of R/C members have been carried out by several researchers and several empirical formulas [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], based on experimental results, have been developed, Some of these formulas are used in prominent design codes such as the American Concrete Institute (ACI 440 R2) [6]. These formulas are used to predict the bending moment of concrete beams strengthen by CFRP, carry two point load as shown in figure (2) and they are functions of several flexural parameters.…”

“…During the collection of the data, specimens that do not have flexural failures have been excluded from the training set. The basic parameters that control the ultimate load of beams, based on previous research works are listed in table (1) The experimental data include 85 beam results, which are taken from the tests carried out by references [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], the data are rearranged in such a way that 17 basic parameters are listed as input values and the ultimate load is included as the corresponding output value. The data collected contain the ranges as in table 1.…”

Investigation of Structural Response of Reinforced Concrete Beams Strengthened with Anchored FRPs

“…Specifically, it has been shown that the CFRP post-strengthening can lead to a catastrophic brittle failure in the form of plate or sheet peeling in the absence of end sheet anchorages [7], [14] and [15]. The ratio of the length of bonded plate within the shear span of the beam to the length of shear span has been considered as a parameter affecting the plate anchorage of strengthened RC beams with CFRP plates [16]. Some researchers have recommended that, to prevent a catastrophic brittle failure mode of strengthened beams by strip detachment, mechanical anchorage should be provided at the strip ends [13].…”