Numerical Analysis of Mode I Fracture Toughness for Plain Concrete Beams

Abstract

Fracture mechanics is based on the assumption that all engineering materials contain cracks from which failure starts. Structures have sizeable existing cracks that may or may not grow, depending on the load level. When a material has an existing crack, this leads to high stresses near the crack tip. Stress field type in the region of the crack tip can be defined as mode I, where two fracture surfaces are displaced perpendicular to each other in the opposite direction where crack growth takes place. The crack tip stress and displacement field can be uniquely characterized by the stress intensity factor, SIF; it is neither the magnitude of stress nor strain, but it is a unique parameter that describes the effect of loading at the crack tip region and the resistance of the material. The stress intensity factor is valid for a small region around the crack tip. It depends on both the values of stress and crack size. In the present work, numerical models were designed to study the effect of specimen thickness, crack-depth ratio and concrete compressive strength on the SIF in concrete beams. Nine beams were idealized with dimensions of 1500 mm length, 400 mm depth and different thicknesses 120, 250 and 400 mm. The crack-depth ratios were 0.1, 0.2 and 0.3 and the concrete compressive strengths were 25, 40 and 55 MPa. The results proved that there is a decrease in the SIF with increasing the specimen thickness. On the other

The effect of beam width and crack-depth ratio on mode I fracture toughness of RCB: an experimental and numerical study

“…When the a/d increases in plain concrete beams, the number of cracks generated by a head and surrounding main crack decreases. This behavior results in a significant decrease in the fracture resistance and toughness of concrete, which has been confirmed by previous studies such as [42][43][44]. However, in reinforced concrete beams, the existence of reinforcing steel bars increases the closing effect due to the compressive force generated by the steel bars.…”