Concrete remains the most widely used construction material globally; however, its intrinsic limitations—low tensile strength, brittle behavior, and susceptibility to microcracking—necessitate performance enhancement for demanding structural applications. Hybrid fiber-reinforced concrete (HFRC) offers a promising solution, yet the optimal balance of steel fibers (SF) and polypropylene fibers (PF) for structural elements such as slabs remains insufficiently understood. This study experimentally investigates the flexural behavior of 42 reinforced concrete slabs (21 one-way and 21 two-way) incorporating systematically varied SF–PF volumetric ratios, advancing current knowledge by identifying performance-optimal hybrid configurations for each slab type. One-way slabs were tested under four-point bending and two-way slabs under three-point bending, with structural responses evaluated in terms of load capacity, cracking behavior, deflection characteristics, and failure modes. The results demonstrate that fiber dosage does not proportionally enhance strength, as excessive content leads to fiber balling and reduced workability—highlighting the need for optimized hybrid proportions rather than indiscriminate addition. Quantitative findings confirm significant performance gains with properly tuned hybrid mixes. For one-way slabs, the optimal combination of 0.7% SF + 0.9% PF achieved 115% of the ultimate load of the control specimen, demonstrating a substantial improvement in flexural resistance. Two-way slabs exhibited even greater enhancements: first-crack load increased by up to 213%, and ultimate load improved by 40.36%, while deflection capacity rose by 44.81% at first crack and 39.80% at ultimate load with the optimal 0.9% SF + 0.1% PF mix. Comparatively, two-way slabs outperformed one-way slabs across all metrics, benefiting from multidirectional stress distribution that enabled more effective fiber engagement. Overall, this study provides new insight into hybrid fiber synergy in RC slabs and establishes quantified optimal SF–PF combinations that significantly enhance load capacity, ductility, and crack resistance for both one-way and two-way systems.

This paper proposed an analytical model to predict the confined concrete compressive strength with textile reinforced mortar (TRM). Based on 341 compression tests, different parameters have been analyzed to clarify their influence on the compressive strength of concrete column confined with TRM. The various existing models for compressed concrete columns confined by TRM have been assessed. Then, a simplified model for concrete elements wrapped with TRM are developed and verified through a best-fit analysis of the experimental database. It found that the proposed model showed good agreement with experimental results.

Bài báo trình bày quy trình thực nghiệm xác định các tính chất cơ học cơ bản của các loại vật liệu thành phần của bê tông cốt lưới sợi (Textile Reinforced Concrete – TRC) sử dụng các loại vật liệu có sẵn tại Việt Nam. Bên cạnh đó nghiên cứu tiến hành thí nghiệm kiểm tra hiệu quả gia cường của TRC cho dầm bê tông cốt thép (BTCT) chịu uốn 4 điểm để đánh giá hiệu quả và tính phù hợp của TRC trong việc gia cường kết cấu dầm có xét đến ảnh hưởng của bề mặt tiếp xúc giữa bê tông hạt mịn (BTHM) và bê tông dầm gia cường. Kết quả nghiên cứu cho thấy khả năng chịu lực của dầm gia cường TRC tăng lên khoảng 16%. Kết quả nghiên cứu cũng có thể được sử dụng như một tài liệu tham khảo để xây dựng quy trình thí nghiệm xác định các tính chất cơ học cơ bản của vật liệu TRC làm cơ sở cho việc tính toán gia cường cũng như nghiên cứu mô hình số.

Reinforced concrete (RC) shear walls are key seismic-resisting components in nuclear facilities, where reliable prediction of stiffness and damage under strong ground motion is critical. The evolution of natural frequency with damage is central to performance assessment and structural health monitoring. This paper validates a mesh-regularized nonlinear finite element model of low-rise RC shear walls with explicit focus on seismic response and frequency degradation relevant to nuclear structures. Four walls from the SAFE/CASH international benchmark program (T6, T7, T8, T9), sharing identical geometry but different axial load levels (0.2 MPa and 1.8 MPa) and horizontal reinforcement ratios (0.5% and 1.0%), are analyzed under three loading protocols: monotonic pushover, quasi-static cyclic, and pseudo-dynamic tests conducted at the ELSA laboratory. Concrete is represented by a smeared-crack model with fracture-energy regularization following the Hillerborg approach, and reinforcement by an embedded steel model with a cyclic Menegotto-Pinto constitutive law. The model accurately reproduces base-shear-drift envelopes and the dominant trend of frequency drop for all four walls, predicting peak strength within 2% error and frequency degradation within 10-15% of experimental values. However, it consistently underestimates cumulative hysteretic energy dissipation by up to 30% in high-axial-load cases (T7 and T9), indicating a conservative bias in energy absorption prediction. These results quantify both the reliability and limitations of a 2D smeared-crack approach for nuclear-type shear walls and provide practical recommendations on optimal mesh size, calibration strategy based on material test data, and the interpretation of frequency-based damage indicators for structural health monitoring in nuclear engineering applications.