Effect of Sheath Modeling on Unbonded Post-Tensioned Concrete under Blast Loads

Hyeon-Sik Choi¹, Min Kyu Kim¹, Jiuk Shin², Thomas H.-K. Kang^1,*
1 Department of Architecture and Architectural Engineering, Seoul National University, Seoul, 08826, Republic of Korea
2 Department of Architectural Engineering, Gyeongsang National University, Jinju, 52828, Republic of Korea
* Corresponding Author: Thomas H.-K. Kang. Email: email
(This article belongs to the Special Issue: Modeling and Simulation of Explosive Effects on Structural Elements and Materials)

Computer Modeling in Engineering & Sciences https://doi.org/10.32604/cmes.2025.074029

Received 30 September 2025; Accepted 30 December 2025; Published online 14 January 2026

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Abstract

Unbonded post-tensioned (PT) concrete systems are widely used in safety-critical structures, yet modeling practices for prestress implementation and tendon-concrete interaction remain inconsistent. This study investigates the effects of sheath (duct) implementation and confinement assumptions through nonlinear finite element analysis. Four modeling cases were defined, consisting of an explicit sheath without tendon-concrete confinement (S) and three no-sheath variants with different confinement levels (X, N, A). One-way beams and two-way panels were analyzed, and panel blast responses were validated against experimental results. In both beams and panels, average initial stress levels were similar across models, through local stress concentrations appeared when the sheath was modeled. Under blast loading, these local effects became critical, and the sheath-implemented model reproduced experimental behavior most accurately, whereas non-implemented models deviated. Reduced blast intensity diminished the differences among models, thereby reaffirming that sheath-induced localization and damage propagation are critical factors. These findings highlight the importance of explicit sheath implementation for realistic numerical assessment of unbonded PT structures under extreme loads.