Flexural strain and crack width measurement of steel-fibre-reinforced concrete by optical grid and electrical gauge methods

Robins, Peter J.; Austin, Simon A.; Chandler, Jim H.; Jones, P. A.

doi:10.1016/s0008-8846(01)00465-3

Cited by 44 publications

(22 citation statements)

References 11 publications

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“…This paper presents work undertaken to investigate the reinforcing mechanisms and fracture processes associated with SFRC under flexural load, in order to develop an alternative stress-profile model to predict flexural behaviour in the form of a load-deflection response using strain, crack-width and fibre pull-out data as the principal modelling parameters. The work formed the final stage of a larger research project investigating sprayed and cast SFRC under flexural load [8][9][10][11][12]. …”

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confidence: 99%

Predicting the flexural load–deflection response of steel fibre reinforced concrete from strain, crack-width, fibre pull-out and distribution data

2007

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A semi-analytical model is presented, based on conventional principles of mechanics, to predict the flexure behaviour of steel fibre reinforced concrete. The model uses a stress-block approach to represent the stresses that develop at a cracked section by three discrete stress zones: (a) a compressive zone; (b) an uncracked tensile zone; and (c) a cracked tensile zone. It is further shown that the stress-block, and hence flexural behaviour, is a function of five principal parameters: compressive stress-strain relation; tensile stress-strain relation; fibre pull-out behaviour; the number and distribution of fibres across the cracked section in terms of their positions, orientations and embedment lengths; and the strain/crack-width profile in relation to the deflection of the beam. An experimental investigation was undertaken on both cast and sprayed specimens to obtain relationships for use in the model. The results of the study showed a reasonable agreement between the model predictions and experimental results. However, the accuracy of the model is probably unacceptable for it to be currently used in design. A subsequent analysis highlighted the single fibre pull-out test and the sensitivity of the strain analysis tests as being the main cause of the discrepancies. IntroductionSteel fibre reinforced concrete (SFRC) continues to grow in specialist applications that can utilise its flexibility and enhanced toughness performance, notably sprayed concrete and industrial floors. However, its continued development has been hindered by a general lack of confidence in its design, particularly under flexural load. This is mainly due to a lack of suitable analytical design methods and appropriate material property tests that measure flexural toughness (or strength) parameters. This need is highlighted by the recent RILEM TC162-TDF [1] proposals for test and design methods.Although recent developments in flexural toughness characterisation have attempted to address the latter of these shortcomings, flexural behaviour of SFRC will be better understood, and thereby predicted, if crack formation and the associated fibre reinforcing mechanisms at the critical section can be explicitly considered in terms of the strain distribution, crack-width and deflection of the beam. To this end, the stress-profile concept potentially offers the most acceptable flexural modelling approach because it is simple to understand; uses conventional principles of structural mechanics, and could, therefore, be incorporated into a design rationale similar to that used for conventional reinforced concrete.A variety of stress-profile models have been proposed for predicting the load-deflection behaviour of SFRC by utilising the equilibrium of forces at the cracked section [2][3][4][5]. These models have generally adopted a semi-analytical approach, whereby failure is assumed to occur at a single crack with rigid-body motion of the two broken halves, rotating about a plastic hinge, being the dominant mechanism.The kinematics of failure has bee...

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Predicting the flexural load–deflection response of steel fibre reinforced concrete from strain, crack-width, fibre pull-out and distribution data

2007

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“…Image-based monitoring has proven its application in the past to monitoring structural tests [5][6][7][8]. A structure is measured using photogrammetric techniques and data compared at different time intervals to calculate displacements.…”

Section: Imagery-based Monitoring Of Structuresmentioning

confidence: 99%

“…Demonstrations give laboratory-scale examples of monitoring complex deformation in beam load tests as well as measuring the width of small scale hairline cracks in concrete [6][7][8]. Mass and Hampel [8] also give examples of large scale monitoring of complex structures such as buildings, bridges and reservoir dams.…”

Section: Imagery-based Monitoring Of Structuresmentioning

confidence: 99%

Monitoring Dynamic Structural Tests Using Image Deblurring Techniques

McCarthy

Chandler

Palmeri

2013

KEM

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Photogrammetric techniques have demonstrated their suitability for monitoring static structural tests. Advantages include scalability, reduced cost, and three dimensional monitoring of very high numbers of points without direct contact with the test element. Commercial measuring instruments now exist which use this approach. Dynamic testing is becoming a convenient approach for long-term structural health monitoring. If image based methods could be applied to the dynamic case, then the above advantages could prove beneficial. Past work has been successful where the vibration has either large amplitude or low frequency, as even specialist imaging sensors are limited by an inherent compromise between image resolution and imaging frequency. Judgement in sensor selection is therefore critical. Monitoring of structures in real-time is possible only at a reduced resolution, and although imaging and computer processing hardware continuously improves, so the accuracy demands of researchers and engineers increase. A new approach to measuring vibration is introduced here, whereby a long-exposure photograph is used to capture a blurred image of the vibrating structure. The high resolution blurred image showing the whole vibration interval is measured with no need for high-speed imaging. Results are presented for a series of small-scale laboratory models, as well as a larger scale test, which demonstrate the flexibility of the proposed technique. Different image processing strategies are presented and compared, as well as the effects of exposure, aperture and sensitivity selection. Image processing time appears much faster, increasing suitability for real-time monitoring.

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“…DIC has been applied successfully to obtain the cohesive interface fracture behavior of the FRP-concrete bond (Ali-Ahmad et al 2006;Subramaniam et al 2007;Subramaniam 2010, 2013;Carloni et al 2012). Limited number of application of DIC technique for studying the crack growth in fiber reinforced concrete have also been attempted (Robins et al 2001;Subramaniam et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Crack Propagation and Post-cracking Hinge-type Behavior in the Flexural Response of Steel Fiber Reinforced Concrete

Gali

Subramaniam

2017

Int J Concr Struct Mater

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An experimental evaluation of crack propagation and post-cracking behavior in steel fiber reinforced concrete (SFRC) beams, using full-field displacements obtained from the digital image correlation technique is presented. Surface displacements and strains during the fracture test of notched SFRC beams with volume fractions (V f ) of steel fibers equal to 0.5 and 0.75% are analyzed. An analysis procedure for determining the crack opening width over the depth of the beam during crack propagation in the flexure test is presented. The crack opening width is established as a function of the crack tip opening displacement and the residual flexural strength of SFRC beams. The softening in the post-peak load response is associated with the rapid surface crack propagation for small increases in crack tip opening displacement. The load recovery in the flexural response of SFRC is associated with a hinge-type behavior in the beam. For the stress gradient produced by flexure, the hinge is established before load recovery is initiated. The resistance provided by the fibers to the opening of the hinge produces the load recovery in the flexural response.

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Flexural strain and crack width measurement of steel-fibre-reinforced concrete by optical grid and electrical gauge methods

Cited by 44 publications

References 11 publications

Predicting the flexural load–deflection response of steel fibre reinforced concrete from strain, crack-width, fibre pull-out and distribution data

Predicting the flexural load–deflection response of steel fibre reinforced concrete from strain, crack-width, fibre pull-out and distribution data

Monitoring Dynamic Structural Tests Using Image Deblurring Techniques

Evaluation of Crack Propagation and Post-cracking Hinge-type Behavior in the Flexural Response of Steel Fiber Reinforced Concrete

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