The twisting rigidity of pre-cast slabs with a statically acting layer of site-mixed concrete

The twisting rigidity was examined in the course of three series of tests. In stage II it is considerably lower than the flexural strength in the field, due to the fact that the direction of reinforcement differs from the direction in which stress is applied. This result is not specific to pre-cast slabs, it is also true for site-mixed concrete slabs. If pre-cast slabs joints are used in the area being twisted, there is a clear reduction in the twisting rigidity and in the twisting moment which can be absorbed. The horizontal joint between the pre-cast slabs and the site-mixed concrete has no influence. Favourable twisting moments may be taken into account in the design if there are no pre-cast slab joints in the twisting area.