Prediction of Shear Transfer in High-strength Concrete Crack Interfaces

P Gatheeshgar,A J Dammika,H D Yapa,P Silojan

doi:10.4038/engineer.v51i3.7303

P Gatheeshgar, A J Dammika + Show 2 more

Open Access

https://doi.org/10.4038/engineer.v51i3.7303

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Abstract

Shear behaviour of concrete is still a riddle, accurate prediction of concrete shear capacity is therefore a challenge. Shear transfers across concrete cracks primarily via aggregate interlocking based shear friction and via dowel action, amongst the former is considered as the major factor. It is found that the Contact Density Function (CDF) has the potential to quantify shear friction at cracked concrete interfaces. This function has mainly been used for normal strength concrete (NSC) (<60 MPa) and recent investigations show that it has to be modified when it is used for high strength concrete (HSC) , different aggregate sizes and large crack widths. The current study focussed on the modification of the CDF to suit high-strength concrete using the experimental results of nine pre-cracked push-off specimens which comprised of compressive strength up to 90 MPa, maximum aggregate sizes of 12.5/20 mm, and comparatively large initial crack width of about 0.5 mm. The results indicate a significant prediction inaccuracy when the existing model is used for HSC specimens. However, incorporation of a modification into the formulae is found to improve the prediction accuracy for HSC reasonably.

Highlights

Accurate prediction of the shear capacity of Reinforced Concrete (RC) structures is a challenge, as shear behaviour in RC has not been fully understood as yet
It is an Original Contact Density (OCD) model which can deal with the complex nature of shear stress transfer in concrete by dividing the crack surface into infinitely small pieces called contact units
The current study was conducted in that context to validate the model proposed by Moradi et al [4] for high strength concrete (HSC) using a push-off experimental series which comprised of high-strength concrete of wide range of strength and different sizes of locally available coarse aggregate

Summary

Introduction

Accurate prediction of the shear capacity of Reinforced Concrete (RC) structures is a challenge, as shear behaviour in RC has not been fully understood as yet. The current study was conducted in that context to validate the model proposed by Moradi et al [4] for HSC using a push-off experimental series which comprised of high-strength concrete of wide range of strength and different sizes of locally available coarse aggregate. For high strength concrete (HSC) applications, this CDF needs to be modified, because in NSC, cracks propagate around the coarse aggregate whereas in HSC cracks generally go through the aggregate. Moradi et al [4] further modified the prediction approach to obtain more accurate predictions by including more parameters in the formulae. They introduced a normal distribution function (NDF) to represent the probability distribution of the contact units. Four basic governing parameters: compressive strength of concrete (fcu); maximum aggregate size (Gmax); initial crack width (wo); and crack asperity degradation, were

Shear Stress Transfer Concept

Factor F3

Experimental Programme

Evaluation of Push-off Test Results

Conclusions