Numerical Model for Flexural Analysis of Precast Segmental Concrete Beam with Internal Unbonded CFRP Tendons

Abstract

A new construction scheme was recently developed for precast segmental concrete beams by replacing steel tendons with internal unbonded carbon-fiber-reinforced polymer tendons. The discontinuous behaviors of the opening joints and unbonded phenomenon of tendons made their flexural behaviors more complicated than those of monolithic beams and members with bonded tendons. Currently, the knowledge on the structural performance of precast segmental concrete beams with internal unbonded carbon-fiber-reinforced polymer tendons is still limited. An efficient numerical model is urgently needed for the structural analysis and performance evaluation of this new construction scheme. In this paper, a new beam–cable hybrid model was proposed accounting for the mechanical behaviors of open joints and unbonded tendons. The numerical model was implemented in the OpenSees software with the proposed modeling method for joint elements and a newly developed element class for internal unbonded tendons. The effectiveness of the proposed model was verified by comparisons against two simply supported experimental tests. Then, the numerical model was employed to evaluate the flexural performance of a full-scale bridge with a span of 37.5 m. Compared with the precast segmental concrete beam with external steel tendons, the scheme with internal unbonded carbon-fiber-reinforced polymer tendons significantly improved the flexural capacity and ductility by almost 54.6% and 8.9%, respectively. The span-to-depth ratio and prestressing reinforcement ratio were the main factors affecting the flexural behaviors. With the span-to-depth ratio increasing by 23%, the flexural capacity decreased by approximately 38.6% and the tendon stress increment decreased by approximately 15.7%. With the prestressing reinforcement ratio increasing by 65.4%, the flexural capacity increased by 88.7% and the tendon stress increment decreased by approximately 25.2%.

Proposals for Flexural Capacity Prediction of Precast Segmental Concrete Beam Prestressed with Internal Un-Bonded CFRP Tendons

“…Internal un-bonded CFRP tendons Numerical model analysis is a practical method generally adopted as an alternative to expensive, time-consuming experimental tests. In previous studies [25,36], a high-efficiency nonlinear computational procedure for the numerical analysis of PSCB-IUCFRP was developed in OpenSees 2.5.0 software [37] by the authors [25]. The modeling scheme of the proposed model is shown in Figure 2.…”

“…We considered all critical mechanical behaviors in the model, such as material nonlinearity, geometric nonlinearity, open joint discontinuity, and tendon free-slip effects. Details on the finite element formulas, constitutive model, and developed procedure can be seen in the previous studies [25,36]. Numerical model analysis is a practical method generally adopted as an alternative to expensive, time-consuming experimental tests.…”

“…Nevertheless, its computational efficiency is limited due to the complicated contact relation and poor convergence. To solve this problem, Yan et al [25] developed a nonlinear high-efficiency fiber beam-tendon hybrid model to analyze the flexural performance of a full-scale PSCB-IUCFRP. The results showed that the flexural capacity of PSCB-IUCFRP was 75% of that of bonded members, and was improved by 55% compared with externally prestressed beams.…”