AbstractThe current seismic design of steel and composite frames relies on lateral frame stiffness and on the controlled failure mechanism of dissipative members or connections. The implementation of the slim‐floor solution in practice results in several advantages. But due to the reduced height of the slim‐floor beam – generally considered to result in lower flexural stiffness – the current practice disregards the usage of moment‐resisting slim‐floor beam‐to‐column joints in seismic applications. However, a previous study of the authors has experimentally and numerically confirmed the possibility of expanding the application of composite beams by developing inelastic behaviour in slim‐floor beams. The test results allowed the definition of the slim‐floor beam's mechanical characteristics and the evaluation of the structure's seismic performance through nonlinear static and dynamic analyses. The usage of the slim‐floor system resulted in a vertical space gain ‐ due to its reduced height ‐ and demonstrated the solution's effectiveness when implemented in seismic‐resistant structures.