Experimental investigations of size effect in reinforced concrete beams failing by shear

• We investigate a size effect in reinforced concrete beams failing by shear.
• We use the Digital Image Correlation technique to measure displacements.
• The measured size effect is strong in concrete beams with both basalt and steel bars.
• Our experimental results match well the size effect law by Bazant.

Laboratory tests were carried out on concrete beams with longitudinal bars and without shear reinforcement. Slender concrete beams with steel bars were subjected to four-point bending with the ratio of the shear span to the effective depth equal to α/D = 3.0 while short concrete beams with basalt bars were subjected to three-point bending with α/D = 1.0. The beams were geometrically similar. Load–deflection curves and cracks were registered. In addition, the Digital Image Correlation (DIC) technique was used to measure displacements on the outer surface of concrete to visualize localized zones. A pronounced size effect was measured in concrete beams.

Graphical AbstractSize effect on shear strength V/(tD) versus beam depth D in 9 slender concrete beams with steel bars and in 3 short concrete beams with basalt bars as compared with size effect law by Bazant.Laboratory tests were carried out on concrete beams with longitudinal bars and without shear reinforcement. Slender concrete beams with steel bars were subjected to four-point bending with the ratio of the shear span to the effective depth equal to a/D = 3.0 while short concrete beams with basalt bars were subjected to three-point bending with a/D = 1.0. The beams were geometrically similar. Load–deflection curves and cracks were registered. In addition, the Digital Image Correlation (DIC) technique was used to measure displacements on the outer surface of concrete to visualize localized zones. A pronounced size effect was measured in concrete beams.Figure optionsDownload as PowerPoint slide