Collapse performances of 3D post-tensioned RC frame structures considering combined influences of infill walls and floor slabs

This paper investigates the combined influences of infill walls and floor slabs on mechanical behaviors of post-tensioned (PT) reinforced concrete (RC) frame structures against collapse. Four PT frame structures modified from experimental specimens are studied. Applied loads, horizontal displacements, failure modes and resisting mechanisms are analyzed, and the roles that infill walls and floor slabs play are discussed. Parametric analyses are performed to study influences of opening in infill walls, diameter of wires in floor slabs and PT force in beams on collapse resisting capacity of PT frame structures. Results indicate that infill walls behave as equivalent compressive struts, increasing the horizontal deformation, changing the failure mode of PT frame structures; Floor slabs provide restraints on all columns and reducing the horizontal deformations of structures. Out-of-plane deformation develops in infill walls due to the two-way bending effect of floor slabs. The opening decreases the influence of infill walls, and the resisting capacity of PT frame structures enhances with increasing diameter of wires in floor slabs and PT forces in beams. A design method is developed to estimate collapse resistance of PT frame structures with good accuracy and efficiency.