A post‐cracking kinematic compatibility model for axial thrust in restrained prestressed hollow‐core slabs

Abstract

Axial restraint can activate compressive membrane action and enhance the resistance of prestressed hollow‐core slabs while transferring horizontal forces to the surrounding structure. This paper proposes a mechanics‐based post‐cracking kinematic compatibility model for estimating axial thrust as a function of slab deflection. The thrust is treated as a compatibility force generated by restraint of the slab's free longitudinal extension, comprising a rotation‐induced component and geometric elongation of the deflected axis. The rotation‐induced component depends on the deflection increment, loading configuration, and an effective kinematic arm derived from concrete compression‐resultant positions obtained by nonlinear sectional analysis or experimentally informed equilibrium. The axial compliances of the slab and restraining system are combined in series. The model was evaluated against two full‐scale experimental datasets using thrust reconstructed from longitudinal tie‐member strains and directly measured horizontal reactions. The predicted curves reproduced the general post‐cracking thrust development. At a common deflection increment of 30 mm, signed deviations ranged from −9.1% to +11.1%. The model estimates the thrust transferred to the restraining system at a specified post‐cracking deformation state; ultimate resistance must be assessed separately.