The proposed research has an experimental and a theoretical component. A series of new tests on deck slab elements aims at studying two unforeseen effects observed within project AGB2009/008 and also in other recent research in Germany (lower strength of cantilevers when the load acts at a large distance from the web and overestimation by calculation models when several concentrated loads act on the cantilever). A test series to determine the fatigue strength of naked reinforcing bars is also planned as a complement to project AGB2009/008, as several unforeseen bar fractures have been observed during experimental testing.
The theoretical part of the study aims at a better quantification of the bending and shear internal forces distribution in the critical zone of the slab. Bending is strongly influenced by the redistribution of internal forces induced by cracking and by the loading and unloading cycles. Measurements performed seem to imply that the stress variation in reinforcing bars is overestimated in the calculation, leading to an under-estimation of the actual fatigue strength for practical applications. Bending- and shear-induced cracking also strongly influences shear in the critical zone. Furthermore, several simulations show that, because of cracking, significant compressive membrane forces can develop in the critical zone. This phenomenon is likely the reason why, in realistic tests, the measured strength is significantly larger that the calculated values.
