How do you compare the different methods of shear design for composite steel-concrete beams?

1 Eurocode 4 method

The Eurocode 4 method is based on the plastic theory of composite beams, which assumes that the steel and concrete act as a single material with a common neutral axis and a rectangular stress block. The shear resistance of the beam is calculated by summing the contributions of the steel web, the concrete flange, and the shear connectors. The method also accounts for the effects of longitudinal reinforcement and transverse stirrups on the shear capacity and ductility of the beam. The Eurocode 4 method is suitable for beams with moderate shear spans, continuous or simply supported boundary conditions, and adequate shear connectors.

2 AISC-LRFD method

The AISC-LRFD method is based on the elastic theory of composite beams, which assumes that the steel and concrete act as separate materials with different neutral axes and parabolic stress distributions. The shear resistance of the beam is calculated by applying the shear flow concept, which relates the shear force in the beam to the shear stress in the interface between the steel and concrete. The method also accounts for the effects of longitudinal reinforcement and transverse stirrups on the shear strength and stiffness of the beam. The AISC-LRFD method is suitable for beams with large shear spans, variable or complex boundary conditions, and variable or insufficient shear connectors.

3 ACI 318 method

The ACI 318 method is based on the strut-and-tie model of composite beams, which assumes that the beam behaves as a truss composed of diagonal concrete struts, longitudinal steel ties, and nodal regions. The shear resistance of the beam is calculated by applying the equilibrium and compatibility conditions to each node of the truss, and checking the strength and ductility of each strut and tie. The method also accounts for the effects of longitudinal reinforcement and transverse stirrups on the shear transfer and crack control of the beam. The ACI 318 method is suitable for beams with high shear forces, discontinuous or irregular boundary conditions, and critical or congested regions.