Anchorage Effect for Steel Truss–Inserted Steel–Concrete Composite Wall Embedded in RC Foundation

Connections of steel–concrete composite walls (SCWs) to the foundation act essentially in seismic performances of buildings or constructions with SCW. A steel truss–inserted steel–concrete composite wall (STSCW) is often embedded in a RC foundation. The interaction between STSCW and RC foundation significantly influences the seismic performances of STSCWs, including the stiffness, strength, and hysteretic behavior. To examine such anchorage effect, a sophisticated finite-element model (FEM) is built and calibrated by experimental results. It was identified that four elements, including the stirrups, longitudinal rebars, steel anchoring plates, and interaction between concrete and STSCW, affect the anchorage performance significantly. A simplified mechanical model is then proposed, which modeled the four elements by nonlinear springs. Further, a general boundary condition model of STSCWs is developed, where the vertical, horizontal and rotation springs provide realistic constraints for STSCWs, with the stiffness error less than 6% compared with the experimental results. The embedding strength of the connection can be calculated by an iterative procedure. It was found that the yield of stirrups and longitudinal rebars would weaken the stiffness of the embedding connection. As the weld between the chord and the steel anchoring plate fails, the connection reaches the ultimate strength. The embedding strength is primarily determined by the embedded depth, hcon, and the axial force ratio, nd. It is concluded that the connection can be treated as full-strength connection except STSCW3 due to a large axial force ratio of 0.7. To prevent a premature failure to the embedding connection of STSCW3, the embedded depth should be increased to 1,000 mm.