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IntroductionConstruction company MATIERE has developed a new type of reinforcement based on ribbed flat steel in recent years. To verify that the use of this new reinforcement satisfies the relevant Eurocodes, a major experimental study was carried out by the Polytech Clermont-Ferrand Laboratory. The objective is to obtain information concerning, on the one hand, the bending behaviour of RC structural elements reinforced with these flat steel bars and, on the other, the cracking process they induce (number of cracks and crack opening), especially at the serviceability limit state.The structural element chosen in the scope of this work is a small slab-beam (330 × 15 × 80 cm) subjected to three-point central bending.Concurrent with this experimental study, a numerical finite element model was developed at IFSTTAR to consolidate the experimental results. This numerical modelling takes into account: -Cracking of concrete through a probabilistic discrete cracking model -Concrete/steel bond through an interface element exhibiting damage behaviour -Elasto-plastic behaviour of steel (Von Mises law)

The simulation of the behaviour of the rebar-concrete bond is of primary importance for an accurate description of cracking processes in reinforced concrete structures and an improved prediction of their durability. In this paper, the methodology used to identify the mechanical behaviour of a rebar-concrete bond in the case of a particular steel reinforcement is first mentioned. The methodology consists in simulating the probabilistic mechanical behaviour of RC tie-beams (170 x 10 x 10 cm), subjected to tension, using a probabilistic approach for the mechanical behaviour of the concrete and a deterministic model for the concrete/rebar bond.The tie-beams are reinforced by a flat steel rebar with a rectangular cross section (25 x 3.5 mm). This approach at macro-scale level is compared to another one at micro-scale level in which notches/indentations of the flat steel rebar are explicitly taken into account in the simulation, the bond behaviour being considered through the local concrete cracking around the rebar.The following conclusions can be made from this study: 1

The paper focuses on stress analyses of structures subjected to excitation forces operating at resonant frequencies. The structures are analysed experimentally using the Thermoelastic Stress Analysis (TSA) technique. Experiments are carried out for fixed-free beams of different dimensions and materials, and also for a steel rectangular plate with clamped edges. These structures are excited by a shaker via a stinger. For materials with low thermal conductivity, the agreement between the theory, numerical results and experimental results is excellent. As the thermal conductivity of the material is increased, the correspondence is not as close. This is because of nonadiabatic behaviour. The implications of these results are discussed in detail in the paper and a means of deriving the severity of heat transfer is provided. Other factors that influence the TSA results from structures under natural loading are also discussed.

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