PRC-440.14-25: Design of Circular Concrete-Filled Fiber-Reinforced Polymer Tubes—Guide

Abstract:

The circular concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) system is an alternative to traditional reinforced concrete structures. The pre-cured FRP tube, which comprises layers of engineered fibers oriented in different directions, provides a corrosion-resistant stay-in-place structural form to retain freshly cast concrete that speeds up construction while at the same time provides primary reinforcement in the two orthogonal directions instead of traditional longitudinal steel reinforcing bar, ties, and stirrups. Typical applications of CFFT include piles, columns, and poles used in building and bridge construction. The FRP tube provides confinement and environmental protection of the concrete core, increasing its strength, ductility, and durability, as well as protection of the minimum internal steel reinforcement. Due to the unique characteristics of CFFTs in which reinforcement in the orthogonal directions are integrated into one continuous membrane—namely, the tube—specific guidance on the design of members using this system is needed. This guide provides general information and background of CFFT technology, including applications and limitations, characteristics of circular FRP tubes, and the interface bond between tube and concrete. The guide provides provisions for design for flexure, axial load, shear, combined loading, connections, and a design approach aimed at mitigating the risk of accidental tube loss. This guide is based on the knowledge gained from experimental research, analytical work, and field applications of CFFTs.

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