Time-Variant Strength Capacity Model for GFRP Bars Embedded in Concrete

Abstract

Glass fiber-reinforced polymer (GFRP) concrete reinforcement exhibits high strength, is lightweight, can decrease time of construction, and is corrosion resistant. However, research has shown that chemical reactions deteriorate the GFRP reinforcing bars over time, resulting in a reduced tensile capacity. This paper develops a time-variant probabilistic model to predict the tensile capacity of GFRP bars embedded in concrete. The developed model is probabilistic to properly account for the relevant sources of uncertainties, including the statistical uncertainty in the estimation of the unknown model parameters (because of the finite sample size), the model error associated with the inexact model form (e.g., a linear expression is used when the actual and unknown relations are nonlinear), and missing variables (i.e., the model only includes a subset of the variables that influence the quantity of interest.) The proposed model is based on a general diffusion model, in which water or ions penetrate the GFRP bar matrix and degrade the glass fiber-resin interface. The model indicates that GFRP reinforcement bars with larger diameters exhibit lower rates of capacity loss. The proposed probabilistic model is used to assess the probability of not meeting the tensile strength requirement based on specifications over time and can be used to assess the safety and performance of GFRP reinforced systems. Sensitivity and importance analyses are carried out to explore the effect of the parameters and random variables on the probability estimates.

Long-Term Flexural Behaviors of GFRP Reinforced Concrete Beams Exposed to Accelerated Aging Exposure Conditions

“…Trejo et al [24] reported experimental tension test data for over one hundred GFRP reinforcement embedded in concrete and exposed to actual environmental conditions (mean annual temperature of 23 °C and average annual precipitation of 1008 mm) for seven years. Based on this study, Gardoni et al [25] developed the time-variant model. Later, time-dependent reliability analysis on a bridge deck was analyzed [26].…”

Experimental Investigation of the Effects of Concrete Alkalinity on Tensile Properties of Preheated Structural GFRP Rebar

“…In severe alkaline concrete environment, the mechanical performance degradation of the GFRP reinforcing bars is closely related to the alkaline solution diffusion coefficient [21][22][23][24][25][26]. Katsuki and Uomoto [21] suggest the relationship between the tensile strength variation and the alkaline diffusion coefficient of FRP reinforcing bars.…”

Design and predicting performance of carbon nanotube reinforced cementitious materials : mechanical properties and dispersion characteristics.

“…, the new models are formulated in a probabilistic manner (see Equations 7-9 and 7-10 for and , respectively) to account for the high degree of uncertainty while incorporating CNTs, statistical uncertainty in estimation of the unknown model parameters, model error associated with inexact form of the model, and missing of the possible influential variables that might influence the mechanical properties[222,234].= ɳ ( , ) × ɳ ( , ) × ɳ ( , ) × [1, ), ɳ ( , ), and ɳ ( , ) are dispersion relation, hydration age relation, and matrix relation, respectively, − is the volume fraction of CNTs within the cement matrix, and . Note that because − used in cementitious materials is very low (0.000038-0.001277; based on the database), the predicted elastic modulus of CNT-cement nanocomposites is almost the same as the matrix elastic modulus.…”