Title:
Thermomechanical Hysteresis of Reinforced Concrete Beams Retrofitted with Carbon Fiber-Reinforced Polymer and Ultra-High-Performance Concrete
Author(s):
Yail J. Kim and Ibrahim Bumadian
Publication:
Structural Journal
Volume:
121
Issue:
5
Appears on pages(s):
189-202
Keywords:
carbon fiber-reinforced polymer (CFRP); hysteresis; retrofit; strengthening; thermomechanical loading
DOI:
10.14359/51740864
Date:
9/1/2024
Abstract:
This paper presents the behavior of reinforced concrete beamsretrofitted with carbon fiber-reinforced polymer (CFRP) sheets andultra-high-performance concrete (UHPC) jackets in a multi-hazardenvironment. Following the procedural protocol of a publishedstandard, the beams are cyclically loaded under thermomechanicaldistress at elevated temperatures, varying from 25 to 175°C (77to 347°F), to examine their hysteretic responses alongside ancillarytesting. The thermal conductivity of UHPC is higher than thatof ordinary concrete by more than 62% and, according to a theoretical inference, premature delamination would not occur within the foregoing temperature range. The difference in load-carrying capacities between the strengthened and unstrengthened beams declines with temperature. While the UHPC+CFRP retrofit scheme is beneficial, CFRP plays a major role in upgrading the flexural resistance. The thermomechanical loading deteriorates the hysteretic loops of the beams, thereby lowering the stiffness and capacity. Elevated temperatures are concerned with the pinching, plasticity, characteristic rigidity, stress redistributions, and energy-release patterns of the beams. Due to the retrofit, the configuration of plastic hinges alters, and the localized sectional deformations form a narrow damage zone. The adverse effects of the temperatures on rotational stiffness are pronounced during the early loading stageof the beams.