Title: Combined Partial External FRP-Internal Steel Ties Confinement Modeling in Rectangular RC Columns

Author(s): Al-Rahmani

Publication: Web Session

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Date: 10/17/2021

Abstract:
Fiber reinforced polymers (FRPs) have become a popular choice for design professionals in strengthening and retrofit applications for concrete structures. This can be attributed to their relative ease of installation and their superb properties such as high strength-to-weight ratio, high energy absorption and excellent corrosion resistance. Traditionally confinement in concrete columns is provided by steel ties. FRP wrapping of concrete columns contributes to the confinement effect and enhances its ultimate strength. The introduction of FRP complicates the nature of the confinement system, and necessities specialized nonlinear analysis to model and determine the upgraded ultimate capacity. This work proposes a combined confinement model that accounts for both steel and FRP systems in rectangular concrete columns. Effective lateral pressures are determined based on Mander model and Lam and Teng model for steel ties and FRP wraps, respectively. Load eccentricity is utilized as a parameter to model the compression zone, which represents the level of confinement in the section. Infinite eccentricity indicates unconfined behavior, while zero eccentricity indicates full confinement under compression. The model is then used to generate interaction curves for the full range of combined confinement levels.