Designing Tendon and Reinforcement Configurations for Punching and Postpunching Performance Demands of Posttensioned Concrete Flat Plate Slab–Column Joints

Abstract

The punching shear and postpunching strengths of slab–column joints (SCJs) are the critical indicators of the resistance of posttensioned concrete flat plate structures to progressive collapse. These two capacities, however, are governed by distinct failure mechanisms and typically require different design strategies. To identify accurate analytical prediction methods for both punching shear and postpunching strengths, this study first validated the prediction accuracy of current design provisions in the Australian, Chinese, American, and European (Euro) codes, using the results of a series of experimental and numerical studies on posttensioned SCJ specimens. Given that Euro code explicitly accounts for the effects of in-plane restraint on the enhancement of punching shear strength, this study presents a calculation approach to quantify the contribution of in-plane forces, based on the specimen design and test setup. Among the various codes, Euro code was found to provide the most reliable predictions. Secondly, an analytical model was proposed to predict the postpunching strength of the SCJs. Building on the Euro code approach and the proposed analytical model, a design methodology was developed to assist engineers in determining rational reinforcement and tendon configurations that satisfy various progressive collapse design requirements under a common design condition. A workflow is presented to illustrate the procedures involved in progressive collapse design, incorporating the proposed prediction methods and design methodology.