7. Conclusions
The present experimental campaign was carried out to investigate the fatigue performance of orthogonally reinforced concrete slabs wherein the principal moment and reinforcement direction do not coincide. On the basis of the experimental results, a number of conclusions could be drawn with regards to the load-carrying behaviour of slabs under high levels of cyclic loading. The main conclusions can be summarised as follows:
7.1. General
Fatigue represents a realistic hazard scenario for reinforced concrete slabs with a typical reinforcement content. For predominant bending action, a relatively gradual but continuous deterioration of the loaddeformation behaviour is observed. Measurable changes in structural response occur upon failure of individual bars; especially pronounced were the increases in reinforcing steel strains. A detailed inspection of the exposed bar fractures in all four tests indicate that the local milling of the instrumented bars along the longitudinal rib, as indicated in Fig. 5, was not significantly detrimental for the fatigue properties. Out of a total of 50 bar fractures, only two occurred within the milled regions. Changes in the concrete deformations on the slab top surface and soffit were also observed upon reinforcement rupture. The occurrence of bar failures was characterised by localisations of concrete strains and curvatures in the critical cross-sections. Furthermore, local increases in crack widths were observed in the proximity of bar fractures as well as the formation of secondary cracks in some cases. Global failure in bending occurs when the residual flexural strength, following rupture of individual reinforcing bars, falls below the bending demand. Such a mode of failure was observed in all four tests.
