Search Results (483)

This study introduced basalt fibres as a reinforcing material and employed notched beam three-point bending tests combined with digital image correlation (DIC) technology to comprehensively evaluate key fracture parameters—namely, initial fracture toughness, unstable fracture toughness, fracture energy, and ductility index—of expanded polystyrene (EPS)-based geopolymer concrete with different mix proportions. The results demonstrate that the optimal fracture performance was achieved when the basalt fibre volume content was 0.4% and the EPS content was 20%, resulting in respective increases of 12.07%, 28.73%, 98.92%, and 111.27% in the above parameters. To investigate the toughening mechanisms, scanning electron microscopy was used to observe the fibre–matrix interfacial bonding and crack morphology, while X-ray micro-computed tomography enabled detailed three-dimensional visualisation of internal porosity and crack development, confirming the crack-bridging and energy-dissipating roles of basalt fibres. Furthermore, the crack propagation process was simulated using the extended finite element method, and the evolution of fracture-related parameters was quantitatively analysed using a linear superposition progressive assumption. A simplified predictive model was proposed to estimate fracture toughness and fracture energy based on the initial cracking load, peak load, and compressive strength. The findings provide theoretical support and practical guidance for the engineering application of basalt fibre-reinforced EPS-based geopolymer lightweight concrete. Full article

Conventional asphalt is prone to cracking in cold climates due to its poor flexibility and limited ability to regulate temperature. This study investigates the use of low-temperature microencapsulated phase-change materials (MPCMs) to improve both the thermal storage and low-temperature performance of asphalt. MPCMs were incorporated into asphalt through physical blending at various concentrations. The physical, thermal, and rheological properties of the asphalt were then systematically evaluated. Tests included penetration, softening point, ductility, thermogravimetric analysis (TGA), and dynamic shear rheometer (DSR). The addition of MPCMs increased penetration and ductility. It slightly reduced the softening point and viscosity. These changes suggest improved flexibility and workability at low temperatures. Rheological tests showed reductions in rutting and fatigue factors. This indicates better resistance to thermal and mechanical stresses. Bending Beam Rheometer (BBR) results further confirmed that MPCMs lowered creep stiffness and increased the m-value. These findings demonstrate improved crack resistance under cold conditions. Thermal cycling tests also showed that MPCMs delayed the cooling process and reduced temperature fluctuations. This highlights their potential to enhance both energy efficiency and the durability of asphalt pavements in cold regions. Full article

High-speed trains have revolutionized modern transportation with their exceptional speeds, yet the essence of this technological breakthrough resides in the train’s wheels. These components are engineered to endure extreme mechanical stresses while ensuring high safety and reliability. In this paper, we selected the rim and web as representative components of the wheel and conducted a comprehensive and systematic study on their microstructure and mechanical properties. The wheels are typically produced through integral forging. To improve the mechanical performance of the wheel/rail contact surface (i.e., the tread), the rim is subjected to surface quenching or other heat treatments. This endows the rim with strength and hardness second only to the tread and lowers its ductility. This results in a more isotropic structure with improved fatigue resistance in low-cycle and high-cycle regimes under rotating bending. The web connects the wheel axle to the rim and retains the microstructure formed during the forging process. Its strength is lower than that of the rim, while its ductility is slightly better. The web satisfies current property standards, although the microstructure suggests further optimization may be achievable through heat treatment refinement. Full article

The construction industry is exploring alternatives to traditional steel reinforcement in concrete due to steel’s corrosion vulnerability. Glass Fiber Reinforced Polymer (GFRP) and Basalt Fiber Reinforced Polymer (BFRP), known for their high tensile strength and corrosion resistance, are viable options. This study evaluates the flexural performance of concrete beams reinforced with GFRP, BFRP, and hybrid systems combining these materials with steel, following ACI 440.1R-15 guidelines. Twelve beams were assessed under three-point bending to compare their flexural strength, ductility, and failure modes against steel reinforcement. The results indicate that GFRP and BFRP beams achieve 8% and 12% higher ultimate load capacities but 38% and 58% lower deflections at failure than steel, respectively. Hybrid reinforcements enhance both load capacity and deflection performance (7% to 17% higher load with 11% to 58% lower deflection). However, GFRP and BFRP beams show reduced energy absorption, suggesting that hybrid systems could better support critical applications like seismic and impact-prone structures by improving ductility and load handling. In addition, BFRP beams predominantly failed due to debonding and concrete crushing, while GFRP beams failed due to bar rupture, reflecting key differences in their flexural failure mechanisms. Full article

As a novel prefabricated structural element, the pre-tensioned, prestressed concrete T-beam with polygonal tendons layout demonstrates advantages including reduced prestress loss, streamlined construction procedures, and stable manufacturing quality, showing promising applications in medium-span bridge engineering. This paper conducted a full-scale experiment and numerical simulation research on a 30 m pre-tensioned, prestressed concrete T-beam with polygonal tendons practically used in engineering. The full-scale experiment applied symmetrical four-point bending to create a pure bending region and used embedded strain gauges, surface sensors, and optical 3D motion capture systems to monitor the beam’s internal strain, surface strain distribution, and three-dimensional displacement patterns during loading. The experiment observed that the test beam underwent elastic, crack development, and failure phases. The design’s service-load bending moment induced a deflection of 18.67 mm (below the 47.13 mm limit). Visible cracking initiated under a bending moment of 7916.85 kN·m, which exceeded the theoretical cracking moment of 5928.81 kN·m calculated from the design parameters. Upon yielding of the bottom steel reinforcement, the maximum of the crack width reached 1.00 mm, the deflection in mid-span measured 148.61 mm, and the residual deflection after unloading was 10.68 mm. These results confirmed that the beam satisfied design code requirements for serviceability stiffness and crack control, exhibiting favorable elastic recovery characteristics. Numerical simulations using ABAQUS further verified the structural performance of the T-beam. The finite element model accurately captured the beam’s mechanical response and verified its satisfactory ductility, highlighting the applicability of this beam type in bridge engineering. Full article

In order to verify the rationality and feasibility of a demountable and replaceable fabricated RC beam with bolted connection under mid-span compression, one cast-in-place RC beam and four fabricated RC beams were designed and fabricated. Through the mid-span static loading test and analysis of five full-scale RC beams, the effects of high-strength bolt specifications and stiffeners were compared, and the behavior of the fabricated RC beams with bolted connections was analyzed. The test process was observed and the test results were analyzed. The failure mode, cracking load, yield load, ultimate load, stiffness change, deflection measured value, ductility, and other indicators of the specimens were compared and analyzed. It was shown that the failure mode of the fabricated RC beam was reinforcement failure, which met the three stress stages of the normal section bending of the reinforcement beam. The failure position occurred at 10~15 cm of the concrete outside the bolt connection, and the beam support and the core area of the bolt connection were not damaged. The fabricated RC beam has good mechanical performance and high bearing capacity. In addition, comparing the test value with the simulation value, it is found that they are in good agreement, indicating that ABAQUS software of 2024 can be well used for the simulation analysis of the behavior of fabricated RC beam structure. Full article

In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification. Full article

Despite the strength and ductility of steel reinforcing bars, their susceptibility to corrosion can limit the long-term durability of reinforced concrete structures. Fiber-reinforced polymer (FRP) reinforcing bars made with a thermosetting matrix offer corrosion resistance but cannot be field-bent, which limits flexibility during construction. FRP reinforcing bars made with fiber-reinforced thermoplastic polymers (FRTP) address this limitation; however, their high processing viscosity presents manufacturing challenges. In this study, the Continuous Forming Machine, a novel pultrusion device that uses pre-consolidated fiber-reinforced thermoplastic tapes as feedstock, is described and used to fabricate 12.7 mm nominal diameter thermoplastic composite rebars. Simple bend tests on FRTP rebar that rely on basic equipment are performed to verify its ability to be field-formed. The manual bending technique demonstrated here is practical and straightforward, although it does result in some fiber misalignment. Subsequently, surface deformations are introduced to the rebar to promote mechanical bonding with concrete, and tensile tests of the bars are conducted to determine their mechanical properties. Finally, flexural tests of simply-supported, 6 m long beams reinforced with FRTP rebar are performed to assess their strength and stiffness as well as the practicality of using FRTP rebar. The beam tests demonstrated the prototype FRTP rebar’s potential for reinforcing concrete beams, and the beam load–deformation response and capacity agree well with predictions developed using conventional structural analysis principles. Overall, the results of the research reported indicate that thermoplastic rebars manufactured via the Continuous Forming Machine are a promising alternative to both steel and conventional thermoset composite rebar. However, both the beam and tension test results indicate that improvements in material properties, especially elastic modulus, are necessary to meet the requirements of current FRP rebar specifications. Full article

An experimental study was conducted to investigate the flexural mechanical properties of mineralized (massive sulfides) and non-mineralized (meta-rhyolitic tuff) rock samples using a three-point bending test. Mineralogical analysis was conducted on samples from both rock categories, followed by the determination of physical properties (P-wave velocity and density). In the massive sulfide zones, there are three distinctive zones of mineralization, each exhibiting varying degrees of pyritization: the intense pyritization zone (formerly Zone A) exhibited extensive pyrite replacement of sphalerite and chalcopyrite, the transitional zone (Zone B) displays intergrowths of pyrite and sphalerite, and the coarse sulfide zone (Zone C) features coarser, less altered sulfides—polyphase hydrothermal alteration, including sericitization, silicification, and amphibole veining. Mineralized rocks showed a 35.18% increase in density (3.65 ± 0.17 kg/m³ vs. 2.72 ± 0.014 kg/m³) attributed to dense sulfide content. The flexural strength more than doubled (99.02 ± 4.42 GPa vs. 43.17 ± 6.45 GPa), experiencing a 129% increase, due to homogeneous chalcopyrite distribution and fine-grained sulfide networks. Despite strength differences, deflection rates showed a non-significant 4% variation (0.373 ± 0.083 mm for mineralized vs. 0.389 ± 0.074 mm for metamorphic rocks), indicating comparable ductility. Full article

A new concept of a 3D volumetric module, made up of six plane stiffened self-compacting fiber-reinforced concrete (SFRC) panels, is here studied. Experimental campaigns are carried out on SFRC material and on the thin-slab structures used for this modular concept. The high volume of steel fibers (80 kg/m³) used in the formulation of this concrete allow a positive strain hardening to be obtained in the post-cracking regime observed on the bending characterization tests. The high mechanical material characteristics, obtained both in tension and compression, allow a significant decrease in the module slabs’ thickness. The tests carried out on the 7 cm thick slab demonstrate a high load-bearing capacity and ductility under bending loading; this is also the case for shear loading configuration, although without any shear reinforcements. Numerical simulations of the material mechanical tests were conducted using Abaqus code; the results corroborate the experimental findings. Then, simulations were also conducted at the structural level, mainly to evaluate the behavior and the bearing capacity of the thin 3D module stiffened slabs. Finally, knowing that the concrete module truck transport can be a weak point, the decelerations induced during transportation were characterized and the integrity of the largest 3D module was demonstrated. Full article

To broaden clean asphalt modification methods, this study employs a composite polymer of maleic anhydride-grafted styrene-butadiene-styrene (MA-g-SBS) and styrene-butadiene-styrene (SBS) as a modifier. The composite is formulated into polymer latex and used to modify emulsified asphalt. Routine performance tests were conducted on MA-g-SBS/SBS composite latex-modified emulsified asphalt (MSMEA) with varying ratios to determine the optimal composition. The ideal ratio was found to be MA-g-SBS:SBS = 1:4. Subsequently, conventional property tests, rheological analyses, microphase structure observations, and bending beam creep tests were conducted on MSMEA with the optimal ratio to assess the impact of the composite latex on asphalt performance. Findings indicated that increasing the latex content significantly enhanced the softening point and ductility while reducing penetration. These macroscopic improvements were notably superior to those achieved with single SBS latex modification. Fluorescence microscopy revealed that at low dosages, the MA-g-SBS/SBS composite dispersed uniformly as point-like structures within the asphalt. At higher dosages (above 5%), a distinct network structure emerged. The addition of the composite latex raised the complex shear modulus and rutting factor while reducing the phase angle, with pronounced fluctuations observed between 4% and 5% dosages. This suggests a substantial enhancement in the high-temperature performance of the emulsified asphalt, attributed to the formation of the network structure. FT-IR results confirmed that a chemical reaction occurred during the modification process. Additionally, the bending beam creep test demonstrated that the composite latex reduced asphalt brittleness and improved its low-temperature performance. Full article

USP (usual temperature pitch)-modified asphalt optimizes its rheological properties through reactions between the modifier and the asphalt. This significantly enhances the high- and low-temperature adaptability and environmental friendliness of asphalt. It has now become an important research direction in the field of highway engineering. This article systematically investigates the impact of different dosages of USP warm mix modifier on asphalt binders through rheological and microstructural analysis. Base asphalt and SBS-modified asphalt were blended with USP at varying ratios. Conventional tests (penetration, softening point, ductility) were combined with dynamic shear rheometry (DSR, AASHTO T315) and bending beam rheometry (BBR, AASHTO T313) to characterize temperature/frequency-dependent viscoelasticity. High-temperature performance was quantified via multiple stress creep recovery (MSCR, ASTM D7405), while fluorescence microscopy and FTIR spectroscopy elucidated modification mechanisms. Key findings reveal that (1) optimal USP thresholds exist at 4.0% for base asphalt and 4.5% for SBS modified asphalt, beyond which the rutting resistance factor (G*/sin δ) decreases by 20–31% due to plasticization effects; (2) USP significantly improves low-temperature flexibility, reducing creep stiffness at −12 °C by 38% (USP-modified) and 35% (USP/SBS composite) versus controls; (3) infrared spectroscopy displays that no new characteristic peaks appeared in the functional group region of 4000–1300 cm⁻¹ for the two types of modified asphalt after the incorporation of USP, indicating that no chemical changes occurred in the asphalt; and (4) fluorescence imaging confirmed that the incorporation of USP led to disintegration of the spatial network structure of the control asphalt, explaining the reason for the deterioration of high-temperature performance. 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

Reduced Beam Sections (RBS) are used in steel design to promote ductile behavior by shifting inelastic deformation away from critical joints, enhancing seismic performance through controlled energy dissipation. While current design guidelines assist in detailing RBS connections, moment–rotation curves—essential for understanding energy dissipation—require extensive testing and/or modeling. Machine learning (ML) offers a promising alternative for predicting these curves, yet few studies have explored ML-based approaches, and none, to the best of the authors’ knowledge, have applied Explainable Artificial Intelligence (XAI) to interpret model predictions. This study presents an ML framework using Artificial Neural Networks (ANN), Random Forest (RF), Support Vector Machines (SVM), Gradient Boosting (GB), and Ridge Regression (RR) trained on 500 numerical models to predict the moment–rotation backbone curve of RBS connections under cyclic loading. Among all the models applied, the ANN obtained the highest R² value of 99.964%, resulting in superior accuracy. Additionally, Shapley values from XAI are employed to evaluate the influence of input parameters on model predictions. The average SHAP values provide important insights into the performance of RBS connections, revealing that cross-sectional characteristics significantly influence moment capacity. In particular, flange thickness (t_f), flange width (b_f), and the parameter “c” are critical factors, as the flanges contribute the most substantially to resisting bending moments. Full article

This study investigates the acoustic and mechanical performance of three types of 3D-printed polylactic acid (PLA) panels with varying infill densities (5–100%) and structural configurations. Using fused filament fabrication (FFF), panels were designed as follows: Type 1 (core infill only), Type 2 (core infill + 1.6 mm shell), and Type 3 (core infill + multi-layer shells). Acoustic testing via impedance tube revealed that Type 2 panels with a 65% infill density achieved the highest sound absorption coefficient (α = 0.99), while Type 1 panels exhibited superior sound transmission loss (TLn = 53.3 dB at 60% infill). Mechanical testing demonstrated that shell layers improved tensile and bending resistance by 25.7% and 36.9%, respectively, but reduced compressive strength by 23.6%. Microscopic analysis highlighted ductile failure in Type 2 and brittle fracture in Type 3. The optimal panel thickness for acoustic performance was identified as 4 mm, balancing material efficiency and sound absorption. These findings underscore the potential of tailored infill parameters in sustainable noise-control applications. Full article