 0  1  2  3  4  5  6  7  8  0  0.2  0.4  0.6  0.8  1 average bond stress [MPa] slip [mm] 0 % 3.2 % 16.8 % analysis experiments (a) (b) Figure 8: Crack patterns for the pullout analysis for the corrosion-free case at (a) peak and (b) end of the aver- age bond stress slip curve. Cracks initiate at the interface between reinforcement and concrete and propgate to the specimen surface. Figure 7: Comparison of predicted average bond stress-slip curves and experimental data reported by Lee et al. (2002) for three corrosion percentages ρ$_{c}$ = 0 , 3 . 2 and 16 . 8 %. post-peak response might be expected across all three cases. More studies are required to explore this obser- vation. For the analyses without corrosion, the crack pat- terns for the peak bond stress and the maximum slip (presented in Figure 7) are shown in Figure 8. Crack patterns are visualised as those middle cross-sections of lattice elements in which the norm of the crack opening vector is greater than 10 µ m and increasing. Thus, only active cracks are presented. At the peak of the average bond stress-slip curve, the concrete cover is cracked at its thinnest section (Figure 8a). With further slip, additional cracks initi- ate from the reinforcement and propagate radially into the specimen as shown in Figure 8b. In Figure 9 the crack patterns are shown, for the two corrosion cases, at the end of the corrosion pro- cess. For both corrosion cases, cracking of the con- crete cover occurs before the pullout, which corre- sponds to the observations reported in the literature (Lee et al. 2002). the decrease of the bond strength if the concrete is pre-cracked. Very good agreement with experimental results in the pre-peak regime of the bond stress-slip curves was obtained. More studies are required to in- vestigate the post-peak response of the bond stress- slip curves. Also, further studies will be performed to investigate the influence of the element length of the interface between reinforcement and concrete on the analyses results. Also, we will study the influence of the stiffness of the lattice elements on corrosion in- duced cracking and its interplay with lateral confine- ment. The simulations were performed with the object-oriented finite element package OOFEM (Patz´ak 1999; Patz´ak and Bittnar 2001), extended by the present authors. Andrade, C., C. Alonso, and F. Molina (1993). Cover cracking as a function of bar corrosion: Part I- In the present work a lattice approach is used to de- scribe the mechanical interaction of a corroding rein- forcement bar, the surrounding concrete and the inter- face between steel reinforcement and concrete. The cross-section of the ribbed reinforcement bar is taken to be circular, assuming that the interaction of the ribs of the deformed reinforcement bar and the surround- ing concrete is included in a cap-plasticity interface model. This lattice approach is capable of represent- ing many of the important characteristics of corrosion induced cracking and its influence on bond. The ide- alisation of the corrosion expansion as an eigenstrain allows for the modelling of corrosion induced crack- ing. Furthermore, the frictional bond law can model ACKNOWLEDGEMENTS REFERENCES 4 CONCLUSIONS