Structural properties of steel-concrete composite joints

The performance of steel and concrete composite frames is influenced by the structural
properties of beam-to-column composite joints. The accurate assessment of these properties
constitutes therefore an important element for a realistic representation of the structural
behaviour at serviceability and ultimate limit state. However, the structural joint properties
are not equally covered by current design standards; analytical guidance is provided to
assess the resistance and stiffness of composite joints, whereas for the rotation capacity an
experimental proof is required. Due to the additional effort required to determine the rotation
capacity, the global plastic analysis finds little application in the design of composite frames,
resulting in a lack of efficiency and material optimization in the final design.
In the present work, an analytical model to calculate the rotation capacity of composite joints
is derived. Based on the knowledge developed in this research, an improvement of the
current design rules for the joint stiffness is proposed.
This model is based on an experimental test campaign comprising eight full-scale beamto-
column joints with composite slim-floor beams. Besides, a finite element model was
developed with the software Abaqus, which has been validated by the experimental tests.
Numerical simulations were performed to investigate in-depth the conducted experiments and
to analyse the behaviour of additional composite joints with different reinforcement properties.
This research has resulted in new analytical design rules for the joint stiffness and rotation
capacity. The reliability of these new design rules has been demonstrated for different
joint typologies using experimental and numerical data. The development of an analytical
method for the rotation capacity of composite joints allows composite beams with composite
beam-to-column joints to be designed according to the global plastic analysis without need
of experimental evidence. Furthermore, the improvement of the current design rules for the
stiffness of composite joints induces a more accurate assessment of the action effects at
serviceability and ultimate limit state. This thesis provides therefore a complete methodology
to design beam-to-column composite joints.