Title: Simplified Analytical Models for Progressive Collapse Assessment of Precast RC Beam-Column Assemblies Upgraded with Hybrid NSM/FRP System

Abstract:-- Due to discontinuity at beam-column joints, precast concrete structures are vulnerable to the potential of progressive collapse under the removal of one or more columns. Hence, efficient techniques are needed to strengthen existing precast beam-to-column connections for prohibiting (or diminishing) the risk of progressive collapse under column-removal event. This paper presents simplified analytical models for estimating the progressive collapse resistance of precast beam-column assemblies upgraded with a hybrid system having steel NSM (near-surface mounted) bars combined with FRP (fiber reinforced polymer) sheets. The developed models were validated with the help of available test data on half-scale 2D frame assemblies – comprising of three columns and two beams – tested under the loss of the middle column. Test assemblies included unstrengthened reference precast specimen, cast-in-situ concrete frame, and NSM/FRP-upgraded precast specimen. Parametric studies were also performed for assessing the influence of different variables on the progressive collapse capacity of retrofitted precast assembly in the event of column removal.