THE INFLUENCE OF BAR SPACING ON TENSION STIFFENING IN REINFORCED CONCRETE SLABS

The concrete between the cracks in the tension zone of a cracked flexural member makes a significant contribution to the flexural stiffness of the member. This paper describes tests which provide data on the tension stiffening effect and, in particular, the influence of bar spacing on tension stiffening in slabs. It is concluded that the tension stiffening can be calculated on the basis of an average tensile stress equal to a fraction of the tensile strength of the concrete acting over an effective area of concrete surrounding the bars in the tension zone. The tension stiffening reduces, with an increase in strain, at a rate which depends upon the bar spacing.