Reinforced concrete composite slab consists of a thin prefabricated slab
in which span reinforcement is located and of concrete joined with the
slab, with such concrete being laid on site.
The existence of a joint of two concretes in such floors is interpreted
as introducing a contact layer into a monolithic slab. In the paper
parameters of two models are estimated. The first is a model of a
contact layer and the second is a model of a composite slab with a
single degree of freedom. The models consider that the contact has
elastic properties and inelastic properties causing energy dissipation.
Experimental investigations are discussed further based on which the
parameters values of the contact layer model were determined.
Delamination was experienced for the slabs characterised by low contact
layer stiffness after applying a maximum load. In addition, the strains
of a contact layer having low stiffness are accompanied by lower energy
dissipation than of a layer with high stiffness.
The smaller stiffness of composite floors, as compared to monolithic
floors, occurs as a consequence of the existence of a joint. Such
decrease for a composite slab is interpreted in the model with a single
degree of freedom as the serial connection of stiffness of a monolithic
slab and an element considering the existence of a contact layer.
The stiffness of an element considering the existence of a contact layer
decreases along with a load, and the elements corresponding to the
higher stiffness of the contact layer are characterised by higher energy
The aforementioned results of the investigations confirm the assumptions
of the contact layer model and a composite slab model with a single
degree of freedom. The findings made represent a basis for establishing
a method of evaluating the condition of a joint in composite slabs
according to statistical investigations.