Open Access

ARTICLE

Bond Behavior of NPR Bar/Steel Strands with Ultra-High-Performance Concrete

Qinfeng Pan¹, Wei Zhang¹, Hao Chen¹, Lin Pang², Xiang Liu^1,*, Chun Chieh Yip³

1 School of Civil Engineering, Fujian University of Technology, Fuzhou, China
2 China Railway Eryuan Engineering Group Co., Ltd., Chengdu, China
3 Department of Civil Engineering, Universiti Tunku Abdul Rahman, Bandar Sungai Long, Cheras, Kajang, Selangor, Malaysia

* Corresponding Author: Xiang Liu. Email:

Structural Durability & Health Monitoring 2026, 20(4), 18 https://doi.org/10.32604/sdhm.2026.083328

Received 01 April 2026; Accepted 06 May 2026; Issue published 30 June 2026

Abstract

Ultra-high-performance concrete (UHPC) exhibits high strength, toughness, and durability, making it an excellent candidate for integration with novel high-ductility, high-strength negative Poisson’s ratio (NPR) steel bars. This combination shows promising applications in the fields of bridges and buildings. This study investigates the bonding performance of various types of NPR bars (smooth NPR bars, spiral rib NPR bars, and NPR steel strands) with UHPC as the concrete matrix. It examines the effects of bond length, bar diameter, and NPR bar type on bonding performance, comparing these results with those of normal concrete (NC). A predictive model for the bonding performance of NPR bars with UHPC was developed. Results show that in the UHPC matrix, all types of NPR bars primarily exhibit pullout failure, with bond strength exceeding that of the NC matrix group by 47.07%. The use of NPR bars improves ductility, with all groups demonstrating better ultimate slip compared to traditional steel bars. An increase in bond length reduces the ultimate strength of all NPR bar types while simultaneously increasing ultimate slip. Similarly, a larger bar diameter decreases the ultimate strength of NPR steel strands by 32.32% and increases slip. During this process, the expansion effect of the strand wires complicates the loading conditions during pullout. Among the three NPR bar types, spiral rib NPR bars exhibit the highest ultimate strength but relatively low slip. In contrast, smooth NPR bars and NPR steel strands have lower ultimate strength but allow for greater slip. The parameter, empirical, and composite models developed in this study demonstrate strong predictive accuracy, with most models achieving an R² value above 0.7. These models reliably estimate the ultimate strength and slip of NPR bars in UHPC. These findings provide a solid theoretical foundation and practical guidance for the application of NPR bars in UHPC.

---

Keywords

---