Recommendation of RILEM TC 212-ACD: acousticemission and related NDE techniques for crack detectionand damage evaluation in concrete. Measurement method for acoustic emission signals in concrete

The text presented hereafter is a draft for general consideration

Recommendation of RILEM TC 212-ACD: acousticemission and related NDE techniques for crack detectionand damage evaluation in concrete.Test method for damage qualification of reinforced concrete beams by acousticemission

The text presented hereafter is a draft for general consideration

Special issue on compressive failure of concrete and rock

Stevin laboratoryCivil Engineering and Geoscience

Fracture mechanics of concrete: Will applications start to emerge?

Fracture mechanics of concrete has developed into an active field of research in the past decades. It promises a rational solution technique to structural problems in reinforced concrete in the limit state. Numerical tools have been developed on the basis of fracture mechanics theories. The question to be addressed is how much of the early promise, i.e. the promise of a powerful rational numerical tool having predictive capabilities, has come true, and whether additional research is needed in order to further extend the range of applicability of the new tools. Essential for new applications, both at the structural and the materials engineering level seems a combined experimental and numerical approach. Both experimentation and numerical simulation have grown to a level where highly advanced techniques are applied, often too complex and of a scope too wide to be comprehended by a single researcher. Structural engineering applications of fracture mechanics must be sought in problems where the concrete reaches its limit state, and where knowledge of softening becomes eminent. Examples are the minimum reinforcement ratio in reinforced concrete structures, or structural details like anchor pull-out. Other recent developments point towards applications at the material level, where numerical models at the meso-level (particle level) of the concrete are used to develop materials for specific structural applications. At best numerical analyses and testing should be carried out in dose cooperation. A meaningful development seems one where the softening response of the material (for example by adding fibres to increase the ductility) is optimised in conjunction with new structural applications. The development of a SKFCON truss systems is a recent example.Stevin LaboratoryCivil Engineering and Geoscience

Examples of Non-Linear Analysis of Reinforced Concrete Structures with DIANA

Stevin LaboratoryCivil Engineering and Geoscience

Field evidences and theoretical analysis of the gravity-driven wetting front instability of water runoffs on concrete structures

A series of field observations of the evolution of water runoffs over several vertical concrete walls directly exposed to rain falls is reported in this note. In all the cases, the main water flow originated from the top horizontal surface of the walls. The observations show that the gravity-driven wetting front may propagate in a very unstable way by developing well defined and quite regularly spaced vertical finger-like features. The mean width and the mean growth's velocity of the fingers appear locally constant, but may vary from a wall surface to another. A simple relationship between and is deduced from the field data and the narrower the fingers the higher the growth's velocity. The fingering process is tentatively interpreted by using the theoretical analysis developped by Glass et al (1989b) for the wetting front instability of infitration in unsaturated homogeneous layered soils. It is shown the model accounts qualitatively well for our observations. The variation in the geometry and kinematics of the instabilities from a wall surface to another may therefore be related to variations of the concrete structure at the microscopic scale. The relationship between and reflects the effects of the microstructure. The gravity driven-wetting front instability provides a powerful echanism for a fast and over large distance moisture transfer along concrete constructions. It also leads to an heterogeneous distribution of the moisture content along the wall surface, which may eventually result in large spatial variations of the moisture-induced damages of the building structures.Civil Engineering and Geoscience