Ultra-high-performance concrete (UHPC) exhibits significantly higher tensile strength compared to normal concrete (NC). In this paper, the application of UHPC to the precast base plate of composite slabs was proposed, leading to the development of a reinforced truss UHPC-NC composite slab. This approach effectively enhanced the crack resistance of the slab. A finite element model (FEM) for the reinforced truss UHPC-NC composite slab was developed based on the ABAQUS (2016) platform, using appropriate material constitutive relationships for UHPC, NC, and steel reinforcement. The validity of the model was verified through comparison with relevant test results. Subsequently, the effects of parameters such as the cross-sectional area of the upper and lower truss chords, the reinforcement ratio of the precast base plate, the strength grade of the UHPC base plate, and the thickness of the UHPC base plate on the flexural capacity of the UHPC-NC composite slab were investigated. Finally, the equations for calculating the flexural capacity of the UHPC-NC composite slab were proposed. It was found that increasing the cross-sectional area of the lower truss chord improved the flexural capacity and stiffness of such slabs to some extent, though ductility was slightly reduced. On the other hand, increasing the upper chord cross-sectional area had limited impact on the flexural performance. Increasing the reinforcement ratio of the longitudinal reinforcement in the precast base plate significantly enhanced the load-bearing capacity and stiffness but similarly reduced ductility. As the UHPC grade of the precast base plate increased, the cracking load, yield load, and ultimate load of the slab also increased. However, when the UHPC grade exceeded C120, the improvement in flexural capacity became less significant. With an increase in thickness of the precast UHPC base plate, cracking, yield, and ultimate loads also rose, but ductility decreased. When the thickness of UHPC exceeded 60 mm, the increase in flexural capacity became modest. The proposed equations for calculating the flexural capacity of the reinforced truss UHPC-NC composite slab in the normal section agreed well with simulation results, providing theoretical and numerical support for the design and analysis of UHPC-NC composite slabs.

This study proposes a novel UHPC-SRC short column structure that adopts ultra-high performance concrete (UHPC) as a permanent formwork, combined with longitudinal reinforcement, stirrups, and H-shaped steel. The design aims to enhance construction efficiency and sustainability while maintaining excellent mechanical performance. A finite element model was established in ABAQUS to simulate the compressive behavior of the structure, incorporating key parameters such as reinforcement diameter, formwork thickness, and steel section strength. The results indicate that increasing the formwork thickness and strength can significantly improve the ultimate load-bearing capacity, with a thickness increase leading to an enhancement of up to 23% in ultimate load. In contrast, the reinforcement ratio and steel strength exert relatively minor effects on the overall performance. Validation against experimental data shows an average ratio of 0.963 between experimental and simulated values, indicating high model accuracy. The observed failure mode is characterized by concrete cracking and fragmentation, with longitudinal reinforcement yielding being the dominant failure mechanism. The proposed formula for calculating axial compressive bearing capacity has been verified as highly reliable, with calculation results in close agreement with finite element simulations, thereby providing strong support for engineering design and practical applications.

This study aims to investigate the bending load-bearing capacity of precast hollow composite slabs composed of ultra-high-performance concrete (UHPC) and Normal Concrete (NC). Through finite element numerical analysis and verification, this study analyzes various key factors influencing the performance of the composite slab, including the wall thickness of the square steel tube, the diameter of transverse reinforcing bars, the thickness of the precast bottom slab, and the strength grade of the concrete. The results indicate that the use of UHPC significantly enhances the bending performance of the composite slab. As the wall thickness of the square steel tube and the strength of UHPC increase, both the yield load and ultimate load capacity of the composite slab show considerable improvement. By conducting an in-depth analysis, this study identifies different stages of the composite slab during the loading process, including the cracking stage, yielding stage, and ultimate stage, thereby providing important foundations for optimizing structural design. Furthermore, a set of bending load-bearing capacity calculation formulas applicable to UHPC-NC precast hollow composite slabs is proposed, offering practical tools and theoretical support for engineering design and analysis. The innovation of this study lies not only in providing a profound understanding of the application of composite materials in architectural design but also in offering feasible solutions to the energy efficiency and safety challenges faced by the construction industry in the future. This research demonstrates the tremendous potential of ultra-high-performance concrete and its combinations in modern architecture, contributing to the sustainable development of construction technology.

This paper proposes a method for modifying brick masonry walls using ultra-high-performance concrete (UHPC) to effectively reduce the beam section width in composite members. First, a detailed finite element model of UHPC–brick masonry composite beams was established using the finite element software ABAQUS 2022 and validated through comparison with the existing literature. Then, the effects of factors such as the tensile reinforcement ratio, UHPC layer thickness, and UHPC strength grade on the load–midspan deflection curve of composite members were analyzed, along with a study of the bending performance under vertical loads. Based on the results of the finite element analysis, a calculation formula for the positive section bending capacity of UHPC–brick masonry composite beams was proposed. The study found that longitudinal tensile reinforcement yielded first, followed by the crushing of the compressive region of UHPC and brick masonry, resulting in overall bending failure. With the increase in the tensile reinforcement ratio and UHPC layer thickness, both the yield load and peak load significantly increased, while the UHPC layer thickness had a notable impact on the cracking load of the composite member. When the UHPC strength grade ranged from 150 MPa to 180 MPa, the bearing capacity of the composite member changed little. The proposed calculation method for bearing capacity correlated well with the finite element results, providing a theoretical basis for the design and analysis of UHPC–brick masonry composite beams.

To investigate the flexural behavior of high-strength concrete beams reinforced with a hybrid configuration of GFRP bars and high-strength steel bars, four-point bending tests were conducted on five C80 high-strength concrete beams, with the reinforcement ratios of high-strength steel bars and GFRP bars taken as the main variables. Combined with finite element simulation and theoretical analysis, the failure modes, load–deflection responses, crack development, and reinforcement strain characteristics of the test beams were examined. The results show that all test beams exhibited flexural failure with an appropriate reinforcement ratio, characterized by yielding of the high-strength steel bars in the tensile zone and crushing of the concrete in the compression zone. Increasing the GFRP reinforcement ratio primarily enhanced the peak load and post-cracking stiffness, whereas increasing the HRB635 reinforcement ratio had a more pronounced influence on the yield load and sectional stiffness. The strain distribution at the midspan section generally conformed to the plane-section assumption, and the two types of reinforcement demonstrated good collaborative load-bearing behavior and deformation compatibility. The established finite element model accurately simulated the load–deflection responses, crack evolution, and failure patterns of the test beams. A distinct post-yield load-carrying stage was observed: after yielding of the HRB635 steel reinforcement, the GFRP bars remained in the linear–elastic range and continued to carry increasing tensile force until crushing of the C80 concrete in compression. Based on this experimentally identified failure sequence, a normal-section flexural capacity model was developed in which the HRB635 reinforcement is taken as yielded while the GFRP stress is determined from sectional strain compatibility rather than directly assigned its tensile design strength. The predicted capacities agreed well with both the experimental and finite element results.

To investigate the bending response of ultra-high-performance concrete (UHPC) beams reinforced with hybrid glass-fiber-reinforced polymer (GFRP) and steel bars, five specimens were tested in four-point bending in the present experimental study. The effect of varying reinforcement ratios on the flexural behavior was evaluated. It was observed that all tested beams failed due to reinforcement yielding while maintaining satisfactory ductility; the failure mode was characterized by yielding of the bottom tensile reinforcement followed by crushing of the UHPC in the compression zone. When the steel reinforcement ratio increased from 2.03% to 2.42% and 3.08%, the beam load-carrying capacity increased by 6.27% and 14.34%, respectively. When the GFRP reinforcement ratio increased from 0.91% to 1.19% and 1.51%, the peak load-carrying capacity increased by 9.58% and 15.55%, respectively. Based on reasonable assumptions, analytical formulas were proposed to predict the cracking moment and the flexural capacity of the UHPC beams reinforced with hybrid GFRP and steel bars, with errors within ±5%. By fully accounting for the bridging effect of steel fibers, modified coefficients were introduced to estimate beam deformation and crack width, along with corresponding calculation methods. The proposed formulas accurately predicted cracking moment, ultimate moment, deflection and crack width for the beam. The findings propose a theoretical basis for the design and application of UHPC beams reinforced with hybrid GFRP and steel bars.