Search Results (232)

Ultra-high-performance concrete (UHPC) exhibits significantly superior compressive and tensile properties compared to conventional concrete, demonstrating substantial application potential in bridge engineering. This study conducted full-scale bending tests on a 30 m prestressed UHPC-NC composite box girder within an actual engineering context. The testing flexural capacity $M_t=\mathrm{34,469.2} \mathrm{k}\mathrm{N}·\mathrm{m}$ exceeded the design requirement $M_d=\mathrm{18,138.0} \mathrm{k}\mathrm{N}·\mathrm{m}$, with $M_t/M_d=1.90$. Finite element modeling (FEM) was employed to analyze and predict experimental outcomes, revealing a simulated flexural capacity of approximately 37,597.1 $\mathrm{k}\mathrm{N}·\mathrm{m}$. The finite element models further explored failure mode transitions governed by the loading position while the concentrated load-to-support distance exceeds 9.62 m (shear span to effective depth ratio λ = 6.3), and the box girder fails in flexure; while less than 9.62 m, the box girder fails in shear. The flexural capacity of the test girder was also estimated using Response-2000 software and the recommended formulas from the Chinese code T/CCES 27-2021 (Technical specification for ultra-high-performance concrete girder bridge). The Response-2000 software yielded a flexural capacity estimate of $M_r=\mathrm{30,816.1} \mathrm{k}\mathrm{N}·\mathrm{m}$. The technical specification provided two estimating results: (with safety factors) $M_{u1}=\mathrm{25,414.4} \mathrm{k}\mathrm{N}·\mathrm{m}$ and (without safety factors) $M_{u2}=\mathrm{33,810.9} \mathrm{k}\mathrm{N}·\mathrm{m}$. All estimated values of Response-2000 and Chinese code were rationally conservative ($M_r,{ M}_{u1}, M_{u2}<M_t$). Comparative analysis demonstrates that Abaqus FEM accurately simulates the flexural behavior of the prestressed UHPC-NC composite box girders. Both Response-2000 calculations and the Chinese code T/CCES 27-2021 provide critical references for similar applications of prestressed UHPC-NC composite box girders. Full article

All-lightweight concrete (ALWC), using non-sintered fly ash ceramic pellets and pottery sand as coarse and fine aggregates, is a novel energy-efficient and environmentally friendly building material that has emerged in recent years. However, its structural behavior under impact loading remains to be thoroughly studied. This paper examines the dynamic response of four ALWC columns with different longitudinal reinforcement ratios and stirrup ratios under lateral impact loading using drop hammer tests. The effect of stirrup densification on the impact resistance was analyzed, focusing on the failure modes, impact forces, acceleration, and midspan displacement time history curves. Results showed that increasing the reinforcement and stirrup ratios shifted the column failure mode from shear to flexural failure, significantly enhancing peak impact force and reducing both midspan and residual displacements. Densifying the stirrups in the column ends resulted in localized flexural failure, with first and second peak forces increasing by 7.43% and 55.98%, respectively, thereby improving impact energy absorption and reducing impact damage. Full article

This study presents a high-performance external strengthening strategy for reinforced concrete (RC) beam–column joints, integrating near-surface mounted (NSM) Carbon Fiber Reinforced Polymer (C-FRP) ropes with externally bonded C-FRP sheets. The X-shaped ropes, anchored diagonally on both principal joint faces and complemented by vertical ropes at column corners, provide enhanced core confinement and shear reinforcement. C-FRP sheets applied to the beam’s plastic hinge region further increase flexural strength and delay localized failure. Three full-scale, shear-deficient RC joints were subjected to cyclic lateral loading. The unstrengthened specimen (JB0V) exhibited rapid stiffness deterioration, premature joint shear cracking, and unstable hysteretic behavior. In contrast, the specimen strengthened solely with X-shaped C-FRP ropes (JB0VF2X2c) displayed a markedly slower rate of stiffness degradation, delayed crack development, and improved energy dissipation stability. The fully retrofitted specimen (JB0VF2X2c + C-FRP) demonstrated the most pronounced gains, with peak load capacity increased by 65%, equivalent viscous damping enhanced by 55%, and joint shear deformations reduced by more than 40%. Even at 4% drift, it retained over 90% of its peak strength, while localizing damage away from the joint core—a performance unattainable by the unstrengthened configuration. These results clearly establish that the combined C-FRP rope–sheet system transforms the seismic response of deficient RC joints, offering a lightweight, non-invasive, and rapidly deployable retrofit solution. By simultaneously boosting shear resistance, ductility, and energy dissipation while controlling damage localization, the technique provides a robust pathway to extend service life and significantly enhance post-earthquake functionality in critical structural connections. Full article

Objectives: This study aimed to compare the clinical durability, mechanical performance, and stress behavior of three NiTi rotary systems—BlueShaper (Blue), BlueShaper Pro (Dual Wire), and BlueShaper Gold (fully gold-treated NiTi)—through a multimodal evaluation that included simulated instrumentation in 3D-printed replicas, mechanical testing, and finite element analysis (FEA). Methods: Sixty instruments (n = 20 per group) were tested. Simulated canal preparation was conducted in standardized 3D-printed mandibular molars with a 40° mesial root curvature until fracture occurred. Mechanical tests included torsional and flexural loading using a universal testing machine and stainless steel blocks with a standardized 40° curvature. FEA simulations evaluated von Mises stress, shear stress, total deformation, cyclic fatigue behavior, and contact pressure between the instrument and canal wall. Results: BlueShaper Gold prepared an average of 7.5 canals before fracture, followed by BlueShaper Pro (5.67 canals) and Blue (5.00 canals) (p < 0.001). Gold exhibited the highest torsional resistance (6.08 ± 3.08 N) and the longest fatigue life (325 ± 55.7 cycles), with the lowest von Mises stress and damage factor in FEA. BlueShaper Pro showed the longest time to fracture in mechanical testing (73.85 ± 7.10 s) and balanced mechanical behavior. Blue demonstrated the lowest performance across most parameters, including the shortest fatigue life and highest stress concentration. Conclusions: BlueShaper Gold exhibited the highest mechanical strength and fatigue resistance. BlueShaper Pro demonstrated the longest fatigue life and balanced mechanical behavior. Blue showed the lowest performance across most parameters. The strong correlation among clinical, mechanical, and FEA data reinforces the critical role of alloy composition in determining instrument durability, even when design remains constant. Full article

This study aimed to develop experimental filler-reinforced resin composites for vat-photopolymerization 3D printing and to evaluate the effects of filler addition on their mechanical, physicochemical, and bonding properties for dental restorative applications. Silanized nano- and/or micro-fillers were incorporated into acrylic resin monomers to formulate photocurable resins suitable for vat-photopolymerization. The rheological behavior of these liquid-state resins was assessed through viscosity measurements. Printed resin composites were fabricated and characterized for mechanical properties—including flexural strength, flexural modulus, and Vickers hardness—both before and after 8 weeks of water immersion. Physicochemical properties, such as water sorption, water solubility, and degree of conversion, were also evaluated. Additionally, shear bond strength to a resin-based luting agent was measured before and after artificial aging via thermocycling. A commercial dental CAD-CAM resin composite served as a reference material. Filler incorporation significantly improved the mechanical properties of the printed composites. The highest performance was observed in the composite containing 60 wt% micro-fillers, with a flexural strength of 168 ± 10 MPa, flexural modulus of 6.3 ± 0.4 GPa, and Vickers hardness of 63 ± 1 VHN, while the commercial CAD-CAM composite showed values of 152 ± 8 MPa, 7.9 ± 0.3 GPa, and 66 ± 2 VHN, respectively. Filler addition did not adversely affect the degree of conversion, although the relatively low conversion led to the elution of unpolymerized monomers and increased water solubility. The shear bond strength of the optimal printed composite remained stable after aging without silanization, demonstrating superior bonding performance compared with the CAD-CAM composite. These findings suggest that the developed 3D-printed resin composite is a promising candidate for dental restorative materials. Full article

High-density polyethylene (HDPE) is a widely used polymer known for its excellent mechanical properties and chemical resistance. This study investigated the impact of incorporating varying percentages of nano-graphene particles (NGP) into HDPE on its thermal, mechanical, and tensile properties. Differential scanning calorimetry (DSC) analysis revealed that the addition of NGP enhanced the thermal stability and crystallization behavior of HDPE, with optimal performance observed at a 5% NGP concentration. Mechanical property evaluations indicated that small additions of NGP initially reduced zero-shear viscosity from 114,667 Pa·s to 44,045 Pa·s at 1% NGP, but higher concentrations improved the material’s rigidity and strength, with the best results at 3% NGP, where the flexural modulus reached 980 MPa. Tensile tests showed that while small amounts of NGP may decrease tensile strength from 26.4 MPa to 23.5 MPa at 1% NGP, higher concentrations significantly enhanced these properties, with tensile strength at break reaching 27 MPa and tensile elongation peaking at 20.8% at 7% NGP. The findings highlight the potential of NGP to enhance the performance of HDPE composites, making them suitable for a wide range of industrial applications. These enhanced composites are particularly important for the bottling industry, where improved material properties can lead to lighter, stronger, and more efficient packaging solutions. Full article

This research investigated and compared the structural behavior of reinforced concrete straight beams and beams made with out-of-plane parts. This study focused on the influence of the location and number of out-of-plane parts, as well as encasing the beams with a steel section, on the ultimate strength, deflection, and rotation in addition to the ductility, energy absorption, and failure mode. A total of nine beams were modelized numerically, divided into three series. The first one included one straight beam, while the remaining two series included four beams each made with out-of-plane parts with and without steel sections. The beams with out-of-plane parts connected the two, three, four, and five concrete segments. The outcomes revealed that the beams made with out-of-plane parts showed less strength than straight beams, which increased the connected segments and reduced the ultimate strength capacity. The regular beam’s linearity was dissimilar to the zigzag beams, which showed a linearity of 32% and was reduced to 22%, 20%, 19.67%, and 16% for beam out-of-plane parts made with two, three, four, and five segments, respectively. Forming a zigzag in the plane of the beams reduced the cracking load, but the decrement depended on the number of parts, which led to more reduction in the yielding load. Concerning the deflection and deformations, the concrete straight beams failed in flexure, with maximum deflection occurring at the midspan of the beam, which was different for beams without plane parts, which showed a combined shear-torsional failure for which the maximum deformation occurred at the midspan with inclination of connected parts on the interior perpendicular axis. Encasing the beams’ out-of-plane parts with steel sections enhanced the structural behavior. The ductility and energy absorption of the out-of-plane parts beams were less than the straight ones, but encasing the beams with a steel section improved the ductility and energy absorption twice. Full article

Ultra-high-performance concrete (UHPC) reinforced with recycled tire steel fibers (RTSFs) was studied to evaluate its mechanical properties and cracking behavior. Using acoustic emission (AE) monitoring, researchers tested various RTSF replacement rates in compression and flexural tests. Results revealed a clear trend: mechanical properties initially improved then declined with increasing RTSF content, peaking at 25% replacement. AE analysis showed distinct patterns in energy release and crack propagation. Signal timing for energy and ringing count followed a delayed-to-advanced sequence, while b-value and information entropy changes indicated optimal flexural performance at specific replacement rates. RA-AF classification demonstrated that shear failure reached its minimum (25% replacement), with shear cracks increasing at higher ratios. These findings demonstrate RTSFs’ dual benefits: enhancing UHPC performance while promoting sustainability. The 25% replacement ratio emerged as the optimal balance, improving strength while delaying crack formation. This study provides insights into the mechanism by which waste tire steel fibers enhance the performance of UHPC. This research provides valuable insights for developing eco-friendly UHPC formulations using recycled materials, offering both environmental and economic advantages for construction applications. Full article

The integration of fiber-reinforced cementitious composites (FRCCs) with fiber-reinforced polymer (FRP) bars represents a significant advancement in concrete technology, aimed at enhancing the structural performance of reinforced concrete elements. The incorporation of fibers into cementitious composites markedly improves their mechanical properties, including tensile strength, ductility, compressive strength, and flexural strength, by effectively bridging cracks and optimizing load distribution. Furthermore, FRP bars extend these properties with their high tensile strength, lightweight characteristics, and exceptional corrosion resistance, rendering them ideal for applications in aggressive environments. In recent years, there has been a notable increase in interest from the engineering research community regarding this topic, primarily to solve the issues of aging and deteriorating infrastructure. Researchers have conducted extensive investigations into the structural performance of FRCC and FRP composite systems. This paper presents a systematic literature review that surveys experimental and analytical studies, findings, and emerging trends in this field. A comprehensive search on the Web of Science identified 40 relevant research articles through a rigorous selection process. Key factors of structural performance, such as bond behavior, flexural behavior, ductility performance assessments, shear and torsional performance, and durability evaluations, have been documented. This review aims to provide an in-depth understanding of the structural performance of these innovative composite materials, paving the way for future research and development in construction materials technology. Full article

In contrast to brittle normal-strength concrete (NSC), high-performance steel-fiber-reinforced concrete (HPSFRC) provides better tensile and shear resistance, enabling enhanced bridge girder design. To achieve a balance between cost efficiency and quality, reducing conventional reinforcement is a viable cost-saving strategy. This study focused on the flexural behavior of a type of pre-tensioned precast HPSFRC girder without longitudinal and shear reinforcement. This type of girder consists of HPSFRC and prestressed steel strands, balancing structural performance, fabrication convenience, and cost-effectiveness. A 30.0 m full-scale girder was randomly selected from the prefabrication factory and tested through a four-point bending test. The failure mode, load–deflection relationship, and strain distribution were investigated. The experimental results demonstrated that the girder exhibited ductile deflection-hardening behavior (47% progressive increase in load after the first crack), extensive cracking patterns, and large total deflection (1/86 of effective span length), meeting both the serviceability and ultimate limit state design requirements. To complement the experimental results, a nonlinear finite element model (FEM) was developed and validated against the test data. The flexural capacity predicted by the FEM had a marginal 0.8% difference from the test result, and the predicted load–deflection curve, crack distribution, and load–strain curve were in adequate agreement with the test outcomes, demonstrating reliability of the FEM in predicting the flexural behavior of the girder. Based on the FEM, parametric analysis was conducted to investigate the effects of key parameters, namely concrete tensile strength, concrete compressive strength, and prestress level, on the flexural responses of the girder. Eventually, design recommendations and future studies were suggested. Full article

A straightforward and versatile numerical approach is proposed for the nonlinear analysis of single and double-curvature masonry structures. The method is designed to broaden accessibility to both experienced and less specialized users. Masonry units are discretized with elastic quadrilateral elements, while mortar joints are modeled with a combination of elastic orthotropic plate elements or shear panels and elastic perfectly brittle trusses (cutoff bars). This method employs the simplest inelastic finite element available in any commercial software to lump nonlinearities exclusively within the mortar joints. It effectively captures the failure of curved structures under Mode 1 deformation, reproducing the typical collapse mechanism of unreinforced arches and vaults via flexural plastic hinges. The proposed method is benchmarked through three case studies drawn from the literature, each supported by experimental data and numerical results of varying complexity. A comprehensive evaluation of the global force–displacement curves, along with the analysis of the thrust line and the evolution of nonlinearities within the model, demonstrates the effectiveness, reliability, and simplicity of the approach proposed. By bridging the gap between advanced simulation and practical application, the approach provides a robust tool suitable for a wide range of users. This study contributes to a deeper understanding of the behavior of unreinforced curved masonry structures and lays a base for future advancements in the analysis and conservation of historical heritage. Full article

The growing demand for sustainable construction has encouraged the use of composite beams combining timber or bamboo with concrete to optimize structural performance and reduce environmental impact. These hybrid systems, widely used in new constructions and retrofits, present modeling challenges due to the nonlinear interaction between materials and their mechanical connections. This study aims to develop and validate a finite element model to simulate the nonlinear flexural behavior of these composite beams. The model is based on an exact solution for two-layer elastic systems and incorporates nonlinear constitutive laws for concrete and timber/bamboo, along with a trilinear shear–slip law to represent interface behavior. Unlike most models, it is applicable to different connector types and a range of materials—including bamboo, timber, and both conventional and lightweight concrete. An incremental–iterative solution captures progressive deformations and failure mechanisms. Validation against 16 experimental beams showed accurate predictions of linear load capacity, mid-span deflection, and initial stiffness. Over 80% of the results showed deviations below 30%, and 50% were within 20%. The model also correctly captured the experimental failure mode in all cases. This approach provides a reliable and versatile tool for the structural analysis and design of composite beams. Full article

The connection zones between precast concrete composite slabs and composite walls commonly experience severe reinforcement conflicts due to protruding rebars, significantly reducing construction efficiency. To address this, a novel slotted concrete composite slab–composite shear wall (SCS-CW) connection without protruding rebars is proposed in this study. In this novel connection, rectangular slots are introduced at the ends of the precast slabs, and lap-spliced reinforcement is placed within the slots to enable force transfer across the joint region. To investigate the static performance of SCS-CW connections, four groups of connection specimens were designed and fabricated. Using the structural detailing of the connection zone as the variable parameter, the mechanical performance of each specimen group was analyzed. The results show that the specimens demonstrated bending failure behavior. The key failure modes were yielding of the longitudinal reinforcement in the post-cast layer, yielding of the lap-spliced reinforcement, and concrete crushing at the precast slab ends within the plastic hinge zone. Compared to composite slab–composite wall connections with protruding rebars, the SCS-CW connections demonstrated superior ductility and a higher load-carrying capacity, satisfying the design requirements. Additionally, it was revealed that the anchorage length of lap-spliced reinforcement significantly affected the ultimate load-carrying capacity and ductility of SCS-CW connections, thus highlighting anchorage length as a critical design parameter for these connections. This study also presents methods for calculating the flexural bearing capacity and flexural stiffness of SCS-CW connections. Finally, finite element modeling was conducted on the connections to further investigate the influences of the lap-spliced reinforcement quantity, diameter, and anchorage length on the mechanical performance of the connections, and corresponding design recommendations are provided. Full article

This study assesses the punching shear characteristics of ultra-high-performance concrete (UHPC) slabs in two phases. The initial phase involved experimental tests to determine the critical thickness differentiating punching shear failure and flexural failure modes. Subsequently, the second phase further explored the punching shear behavior of UHPC slabs by analyzing various key parameters. The experimental findings indicated that as the thickness of the slabs increased, the punching shear capacity exhibited nearly linear enhancement, surpassing the improvement seen in bending capacity. Thus, a critical thickness of at least 100 mm was identified as the threshold distinguishing punching shear failure from flexural failure. Additionally, an increase in slab thickness significantly elevated the cracking load of the UHPC slabs. While a higher reinforcement ratio of 3.5% slightly increased the first cracking load, it greatly enhanced the ultimate capacity. The addition of steel fibers also contributed to improvements in both cracking and ultimate loads, albeit to a limited extent. The use of a granite powder substitute, comprising 10% of the mass of silica fume, had minimal impact on the punching shear capacity of the UHPC slabs. Finally, a comparison is drawn between the experimental results for punching shear capacity and those obtained from various theoretical models. This comparison highlights significant discrepancies in the results, stemming from the differing parameters employed in the proposed theoretical models. Among the prediction models, the JSCE model provided the most balanced and conservatively accurate estimation of punching shear capacity, effectively incorporating the effects of slab thickness, reinforcement ratio, and fiber content, thus highlighting its potential as a reliable reference for future design recommendations. This information will serve as a valuable reference for future research and practical applications related to UHPC bridge decks and slabs. Full article

In this study, polymer composites based on a polypropylene (PP) matrix with the addition of cellulose and ES-40, used as a silica precursor, were investigated. These composites were designed to achieve enhanced biodegradability through the incorporation of bioavailable cellulose and to enable subsequent carbonization into carbon–silicon carbide systems. Rheological investigations revealed that the multicomponent mixtures exhibited pseudoplastic behavior over the shear rate range typical of injection molding, ensuring process stability without additional plasticization. Morphological analysis demonstrated that an optimal balance of PP, cellulose, and ES-40 promoted the formation of a three-dimensional network structure, leading to a significant increase in flexural modulus at the equal flexural strength despite some reduction in tensile strength. It was further shown that substituting fibrous cellulose with microcrystalline cellulose improved the composite homogeneity, thereby enhancing the density and mechanical properties, especially in systems with low polymer contents. Preliminary pyrolysis experiments indicated that these injection-molded composites can serve as precursors for fabricating bulk thermally stable products containing silicon carbide particles. The obtained results underscore the high potential of the developed materials for applications in conventional injection molding, the possibility of additive manufacturing, and processes requiring subsequent carbonization. Full article