Vol. 16 No. 01 (2026): Journal of Materials & Construction
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JOURNAL OF MATERIALS & CONSTRUCTION

ISSN: 2734-9438

Website: www.jomc.vn

Modified space-truss model for predicting the torsional capacity of ultra-high-performance concrete beams

Nguyen Vu Luat , Nguyen Vinh Sang a:1:{s:5:"vi_VN";s:48:"Phân hiệu Trường đại học Thủy Lợi";}

Keywords:

torsion
torsional capacity
ultra-high-performance concrete
beam
modified space-truss model

Abstract

Ultra-high-performance concrete (UHPC) beams exhibit enhanced post-cracking stress transfer due to fiber bridging, a mechanism not adequately represented in conventional torsion design provisions. This study develops a modified space-truss model (MSTM) to predict the ultimate torsional capacity of UHPC beams under pure torsion. The proposed formulation retains the three-dimensional space-truss analogy and thin-walled tube idealization, while explicitly incorporating the tensile contribution of UHPC through equivalent longitudinal and transverse tensile components. In addition, the inclination angle of the concrete strut is refined using equilibrium and strain-compatibility considerations rather than fixed code-recommended values. The reliability of the MSTM is validated using a compiled database of 40 UHPC beams from previous experimental studies and benchmarked against the truss-based provisions in ACI 318-19 and GB 50010. The results indicate that both code-based approaches tend to provide conservative predictions. In contrast, the proposed MSTM achieves improved agreement with experiments (mean value = 0.90 for  Tu,cal/Tu,exp) while remaining slightly conservative for design.

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How to Cite

Nguyen Vu Luat, & Nguyen Vinh Sang. (2026). Modified space-truss model for predicting the torsional capacity of ultra-high-performance concrete beams. JOURNAL OF MATERIALS & CONSTRUCTION, 16(01). https://doi.org/10.54772/jomc.v16i01.1247

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