Title: Implications of Sustained Load for Behavior of CFRP-Confined Columns

Author(s): Yail J. Kim

Publication: Structural Journal

Volume: 120

Issue: 1

Appears on pages(s): 75-88

Keywords: carbon fiber-reinforced polymer (CFRP); modeling; strengthening; sustained loading; time-dependent behavior

DOI: 10.14359/51734826

Date: 1/1/2023

Abstract:
This paper presents the long-term behavior of reinforced concrete (RC) columns confined with carbon fiber-reinforced polymer (CFRP) sheets when subjected to sustained loading for 100 years. Through analytical modeling formulated with effective modulus and tangent modulus theories alongside the time-dependent characteristics of constituent materials, the performance of full-scale columns is studied with and without CFRP confinement. Of interest are the stress, strain, constraining pressure, core displacement, and stability of these columns. The creep dependency of CFRP on time is negligible, and the confinement improves the effective modulus of the concrete. Under the default sustained stress level of 40% of the unconfined core strength, the integrity of the CFRP system is not influenced. While a transition of stress becomes obvious from the core concrete to the reinforcing steel over time, the axial rigidity of the confined column increases by up to 24%. The intensity of sustained loading is instrumental in altering the critical stress of the confined column, which determines material failure or stability failure. The moment magnifier of existing design specifications is assessed against analytical solutions. Parametric investigations with variable geometric and material properties clarify the effects of sustained loading, effective length factors, concrete strength, reinforcement configurations, and confining layers. Design recommendations are suggested to conveniently evaluate the stability of CFRP-confined columns.