To research the influence of concrete slab on the behavior of panel zone in steel moment frame structures,the effective width of composite connections was proposed by finite element analysis.Based on analysis within elastic and post-elastic range of the panel zone,a new model,which is particularly suited for modelling steel and composite joints within frame analysis procedures,is proposed,and the formulae calculating the shearing stiffness and ultimate strength of the composite joints are derived.The results demonstrate that the approach provides a more realistic representation of the behavior in comparison with the available models,especially in the case of composite connections.Shear force in panel zone with slab is smaller than that without slab under the same moment loads.