Load-bearing Capacity Research Articles

Effect of Undercut Bolt Anchor Depth on Failure Cone Geometry: A Numerical FEM Analysis and Experimental Verification

This study examined the influence of the effective embedment depth hef of undercut anchors and the diameter of their heads on the formation of the so-called cone failure angle α. Cone failure formation during simulated anchor pull-out tests was analyzed numerically using the Finite Element Method (FEM) with the ABAQUS software and the XFEM algorithm. The analysis was conducted for three sizes of undercut anchor heads and four embedment depths. The numerical analysis results were compared with field test results obtained during pull-out tests of anchors installed in a rock medium (sandstone). Good agreement was observed between the numerical and field test results. The results of the numerical study are highly consistent with those obtained during the field survey. Moreover, they align closely with findings from previous numerical studies conducted by members of the research team, as presented in earlier publications. For the assumed simulation and field test conditions (sedimentary rocks, gray sandstone), no clear correlation was found between the embedment depth or the anchor head diameter and the value of the cone failure angle in the initial phase of the failure zone development. This result contrasts with certain findings reported in the literature. Many existing studies on anchor bolts focus on material properties or load-bearing capacity, but lack an in-depth analysis of how anchor depth influences the geometry of the failure cone. This research addresses that gap, providing valuable insights with practical implications for design codes and safety evaluations.

Experimental Study on Flexural Performance of Screw Clamping and Welding Joint for Prestressed Concrete Square Piles

To ensure the connection performance of precast concrete square piles, a screw clamping and welding joint connection is applied to the solid square piles. By conducting full-scale bending performance tests on six solid square pile specimens with cross-sectional side lengths of 300, 450, and 600 mm, including pile bodies, screw clamping joints, screw clamping, and welding joints, the bending load-bearing capacity, deformation capacity, and failure characteristics of the screw clamping–welding joint connection are compared and studied. The results show that the bending failure mode of the pile body specimens is shear failure in the flexural shear section and concrete crushing in the compression zone of the pure bending section; the bending failure mode of the screw clamping joint specimens are the pull-out of steel bar heads at the joint end plate; the bending failure mode of the screw clamping and welding joint specimens are concrete crushing in the compression zone of the pure bending section, steel bar breakage in the tension zone of the flexural shear section, and pull-out of steel bar heads at the end plate. It is worth noting that no significant damage occurred at the joints. The cracks in the pure bending section of the bending specimens mainly develop vertically and are evenly distributed, while some cracks in the flexural shear section develop obliquely towards the loading point, with branching. Compared to the pile body specimens, the cracking moment of the joint specimens is up to 16% higher, the ultimate moment is within 15% lower, and the maximum mid-span deflection is within 25% lower, indicating that the provision of anchorage reinforcement can increase the stiffness and cracking moment of the specimens.

Experimental Investigation of Infrared Detection of Debonding in Concrete-Filled Steel Tubes via Cooling-Based Excitation

Debonding in concrete-filled steel tubes (CFSTs) is a common defect that often occurs during the construction phase of CFST structures, significantly reducing their load-bearing capacity. Current methods for detecting debonding in CFSTs using infrared thermography primarily rely on heat excitation. However, applying this method during the exothermic hydration phase presents considerable challenges. This paper proposes the innovative use of spray cooling as an excitation method during the exothermic hydration phase, providing quantitative insights into the heat conduction dynamics on steel plates for infrared debonding detection in CFSTs. The effects of atomization level, excitation distance, excitation duration, and water temperature in the tank on infrared debonding detection performance were examined. The timing of the maximum temperature difference under cooling excitation was analyzed, and the heat conduction characteristics on the surface of the steel plate during the cooling process were explored. A highly efficient and stable cooling excitation method, suitable for practical engineering detection, is proposed, providing a foundation for quantitative infrared debonding detection in CFSTs. This method does not require additional energy sources, features a simple excitation process, and results in a five-times increase in temperature difference in the debonded region after excitation.

Layer-wise compaction 3D printing: void reduction and interfacial enhancement for continuous carbon fiber–reinforced thermoplastics

This study incorporated a heating roller into a 3D printer based on fused filament fabrication to develop a layer-wise compaction 3D printer. The heating roller facilitates heat compaction during 3D printing to reduce voids and enhance the interface. Coupon specimens were 3D-printed using a continuous carbon fiber-reinforced nylon composite, and the effects of the process on the microstructure and mechanical properties were analyzed. The porosity was measured using X-ray computed tomography, which demonstrated an effective reduction due to the heat-compaction process. The enhanced mode-I interlaminar fracture toughness was assessed using a double-cantilever beam test. The reduced voids and improved interface led to enhanced bending properties of the composite. The bending fracture surface exhibited a reduced compression failure area as a result of the heat compaction process, indicating an improvement in the compression load-bearing capacity.

A Review on the Performance of Concrete Beams reinforced with GFRP Bars and Internally reinforced with Different Meshes

The incorporation of geogrid or Glass-Fiber Reinforced Polymer (GFRP) mesh into concrete structures presents a novel approach to leveraging the geosynthetics and Fiber Reinforced Polymer (FRP) composites in structural components. Geogrid, steel, and GFRP mesh can enhance the post-cracking ductility and load-bearing capacity of Reinforced Concrete (RC) beams, depending on the specific type and properties of the mesh utilized. The use of reinforcing meshes offers the advantage of reducing the size of structural elements due to their lower weight compared to steel bars, thereby decreasing the overall weight of the structure.

Performance analysis and prediction of load bearing capacity of nuclear containment under overpressure and multi-hazard scenario

Performance analysis and prediction of load bearing capacity of nuclear containment under overpressure and multi-hazard scenario

Prediction of vertebral failure under general loadings of compression, flexion, extension, and side-bending.

Bone pathologies such as osteoporosis and metastasis can significantly compromise the load-bearing capacity of the spinal column, increasing the risk of vertebral fractures, some of which may occur during routine physical activities. Currently, there is no clinical tool that accurately assesses the risk of vertebral fractures associated with these activities in osteoporotic and metastatic spines. In this paper, we develop and validate a quantitative computed tomography-based finite element analysis (QCT/FEA) method to predict vertebral fractures under general load conditions that simulate flexion, extension, and side-bending movements, reflecting the body's activities under various scenarios. Initially, QCT/FEA models of cadaveric spine cohorts were developed. The accuracy and verification of the methodology involved comparing the fracture force outcomes to those experimentally observed and measured under pure compression loading scenarios. The findings revealed a strong correlation between experimentally measured failure loads and those estimated computationally (R2=0.96, p<0.001). For the selected vertebral specimens, we examined the effects of four distinct boundary conditions that replicate flexion, extension, left side-bending, and right side-bending loads. The results showed that spine bending load conditions led to over a 62% reduction in failure force outcomes compared to pure compression loading conditions (p≤0.0143). The study also demonstrated asymmetrical strain distribution patterns when the loading condition shifted from pure compression to spine bending, resulting in larger strain values on one side of the bone and consequently reducing the failure load. The results of this study suggest that QCT/FEA can be effectively used to analyze various boundary conditions resembling real-world physical activities, providing a valuable tool for assessing vertebral fracture risks.

Impact of HWD dynamic loading on measured deflection basins and back-calculated stiffnesses of flexible airport pavements

Accurate measurement of pavement structural response is critical when evaluating the condition and load-bearing capacity of a flexible airport pavement. Pavement surface deflection basins tested by Heavy Weight Deflectometer (HWD) have been widely applied as a non-destructive testing method to analyse the elastic modulus of pavement layers via a back-calculation procedure. A clear linear relationship between measured deflections and HWD drop loads was established, with R2>0.99. The studied flexible pavement structure showed linear elastic responses under different drop loads, with relatively stable elastic moduli of pavement layers. With the increasing drop load (DL), the back-calculated hot-mix asphalt (HMA) surface modulus was slightly influenced. The results also identified the existing buried sensors may affect the measured HWD responses. By analysing statistical results, this study provides a benchmark for airport owners to evaluate the structural conditions for their flexible pavements when applying HWD in their maintenance and rehabilitation (M&R) works.

Study on the rational construction methods and mechanical properties of composite beams in transverse negative bending moment zones

Normal concrete (NC) bridge deck panels are transversely joined to steel beams at the trusses, serving as a transitional segment between the concrete bridge deck panels and trusses, typically using ultrahigh-performance concrete (UHPC). Positioned on both lateral sides along the bridge axis of the NC deck panels, these transverse joints primarily endure tensile forces in negative bending moment areas. Owing to the stiffness disparity between the steel beams and concrete, these transverse joints experience complex stresses. In this study, the mechanical behavior of these transverse joints under negative bending moments was examined for six shear connector layouts and two key-wet joint shapes. Static tests provided crucial data, including the separation distances between the UHPC and steel beams, ultimate load-bearing capacities, crack patterns in the UHPC, mechanical performance of the key-wet joints, and load-deflection curves. The experimental results were compared with those from finite element simulations, and the design of the composite beam was optimized. The results demonstrated that the mechanical properties of the transverse joints were significantly influenced by the orientation of the stud connectors and perfobond Leisten (PBL) shear connectors. The optimal design had stud connectors at the bottom and top surfaces, PBL shear connectors, trapezoidal key-wet joints, and no side stud connectors. This design resulted in minimal deflection, narrower key-wet joint widths, reduced structural strain, fewer and smaller concrete cracks, and minimal separation between the UHPC and steel top and side plates, which facilitates easier construction.

Investigation of local heat treatment strategies for a multi-range capable rivet and the influence on joint formation and load-bearing capacity

Investigation of local heat treatment strategies for a multi-range capable rivet and the influence on joint formation and load-bearing capacity

Combined Loading Effects on the Buckling Strength of Q690 Steel Tubes: An Experimental and Numerical Study

Abstract: This study investigates the stability and buckling behavior of Q690 high-strength steel cylindrical tubes subjected to combined axial compression and bending loads. Experimental testing on 27 specimens, combined with finite element analysis using ABAQUS, revealed critical insights into load-bearing capacity, deformation patterns, and failure modes. The study found that geometric imperfections, such as initial out-of-roundness and local dents, and residual stresses significantly influenced the buckling strength of the tubes, particularly those with high diameter-to-thickness ratios. Finite Element Analysis (FEA) effectively modeled the complex behavior, with deviations from experimental results ranging from 5.6% to 7.9%. Based on these findings, design recommendations, including optimized D/t and slenderness ratios, are proposed to enhance structural safety and efficiency. These results contribute to a better understanding of Q690 steel behavior and can inform the development of improved design codes for critical infrastructure applications

Molecular Dynamics Simulation of the Hydration Lubrication Mechanism of CS-MPC/CS-ChS NPs.

Osteoarthritis (OA) remains a significant clinical challenge, with current treatments like sodium hyaluronate injections offering limited efficacy due to suboptimal lubrication and rapid degradation. In this study, we explored an advanced solution to these issues by investigating the colubrication mechanism of a composite biolubricant consisting of 2-methacryloyloxyethyl phosphorylcholine-modified chitosan (CS-MPC) and chondroitin sulfate-modified chitosan nanoparticles (CS-ChS NPs) using molecular dynamics (MD) simulations. Results show that the composite lubricant outperforms individual CS-MPC or CS-ChS NPs, exhibiting a lower coefficient of friction (COF) and a superior load-bearing capacity. The CS-MPC/CS-ChS NP system maintains a consistent compression ratio of -0.5% under different external pressures and exhibited a low coefficient of friction (COF) of 0.041 across varying shear velocities. The sulfate groups on CS-ChS NPs interact with CS-MPC chains, stabilizing the system through electrostatic interactions and enabling the effective dispersion of normal stress, thereby protecting the substrate surface from wear. This enhanced performance is attributed to the formation of a multilayered hydration shell around the lubricant molecules. The hydration shells provide superior lubrication, contributing to the system's robustness under varying loads. These findings offer critical insights into designing high-performance biolubricants for joint protection, presenting a promising avenue for future OA treatments.

Mechanisms of transverse compression damage and reinforcement strategies for Larch wood

ABSTRACT Transverse compression damage frequently affects active wooden components of ancient architecture, such as beams and Dou-gong, compromising structural safety. Larch (Larix gmelinii var. principis-rupprechtii (Mayr) Pilger) wood, commonly used in ancient northern Chinese architecture, has limited studies on its transverse compression damage mechanisms. Traditional reinforcement methods are often ineffective. The present study integrated plastic equilibrium theory and static loading experiments to examine the transverse compression damage mechanism of larch wood under significant deformation. It also introduced an innovative method for parcel constraints to enhance the compression strength of wooden components in ancient architecture. Results showed the transverse compressive strength of larch wood ranges from 3 to 17 MPa, with maximum load-bearing capacity doubling after enhancement. End-wrapping confinement increased the load-bearing capacity by over 16%. Load-displacement curves under different compression conditions followed a three-stage pattern: elastic, plastic, and densification. Damage in larch wood began in the plastic stage. Under localized compression, samples exhibited a sudden drop in load-bearing capacity and secondary failure at 60–70% strain. This study offers valuable insights into the damage and residual load-bearing capacity of transversely compressed wooden components. The proposed compression enhancement strategy can reinforce damaged wooden components in ancient architecture, contributing to preserving cultural heritage.

Simulation and experimental study of single axis load of resin-based concrete at macro-micro scale

ABSTRACT This study focuses on resin-based concrete, a novel composite material in which resin replaces the traditional cementitious binder, forming a three-phase composite consisting of aggregate, resin matrix, and interfacial transition zones. Four random aggregate models were generated using the Monte Carlo method and their stability was verified. Subsequently, a two-dimensional micro-model was established, and the simulation results were compared with experimental data, yielding a maximum error of 8%, which validated the feasibility of the model. The findings indicate that circular aggregates exhibit lower load-bearing capacity, while irregular aggregates demonstrate higher capacity. Although the peak compressive strength is similar among different aggregate shapes, the crack propagation paths vary significantly. The load-bearing capacity of resin-based concrete increases with aggregate content up to an optimal value of approximately 80%, beyond which it decreases. At this optimal content, crack paths transition from branched to near-linear. In terms of aggregate grading, higher coarse aggregate proportions enhance load-bearing capacity and promote linear crack propagation, whereas higher fine aggregate proportions reduce capacity and result in multiple irregular crack paths. Finally, the numerical simulation results were used to guide macroscopic experiments, and orthogonal experiments were conducted to determine the optimal mixture proportions of different resin binders.

A Review of the Impact of Graphene Oxide on Cement Composites

Graphene oxide (GO) has attracted significant attention as a nano-reinforcement for cement-based materials, owing to its exceptional mechanical properties and abundant surface functional groups. However, the precise mechanisms governing its effects in cement composites remain inadequately understood due to inconsistencies and gaps in the existing literature. This review conducts a comprehensive analysis of the dispersion and reinforcement effects of GO in cement materials, focusing on three key areas: (1) challenges associated with achieving uniform dispersion of GO in the high-pH environment of cement slurries and potential strategies to address them; (2) the influence of GO on the macroscopic properties of cementitious composites, including workability, load-bearing capacity, flexural strength, fracture resistance, and durability; and (3) the reinforcement mechanisms of GO, encompassing its role in hydration kinetics, alterations to the calcium-silicate-hydrate (C-S-H) structure, and bonding interactions at the cement matrix interface. Furthermore, recent advancements in optimizing the dispersion and reinforcement effects of GO, such as surface modification techniques, are explored, emphasizing its potential for multifunctional and intelligent applications. This review aims to provide engineering professionals with the latest insights into the application of graphene oxide as a nano-reinforcement in cement-based composites, while offering valuable guidance and direction for future research in this field.

Experimental Study on the Seismic Performance of Confined High Walls of Autoclaved Aerated Concrete Panels Used in Subway Stations

This study addresses the unique challenge of the partition walls in subway stations, featuring high height, fire prevention, and located outside the main frames, by introducing a confined autoclaved aerated concrete (AAC) panel wall system. Different from studies on a main frame with infill walls, this study aimed to explore the seismic performance of partition walls, which were fabricated with confined high AAC panel walls and located outside the main frames. A custom-designed partition wall, measuring 6600 mm in height, 3400 mm in width, and 200 mm in thickness, underwent cyclic testing. A detailed analysis of specimen’s failure modes was conducted, focusing on seismic behavior such as hysteresis curves, envelope curves, ductility, stiffness degradation, and energy-dissipation capacity. Additionally, the study delved into shear deformation, relative slippage between AAC panels, and reinforcement strains within the specimen. Finally, the D-value method for calculating the initial stiffness of the confined high AAC panel walls and the weak sub-structural approach for determining the load-bearing capacity of confined high AAC panel walls were proposed and validated. The results indicate that the strength degradation factor of the confined high AAC panel walls ranges from 0.971 to 0.716. The drift of its upper portion accounts for 76.94–83.63% of the total drift, while the energy dissipation factor of its upper portion is 0.8–4.8% higher than that of the entire specimen. The yield and ultimate drift rotations of the entire confined high AAC panel wall and its upper portions satisfy the elastic and elastic-plastic inter-story drift rotation limits specified in the Chinese code. The calculated initial stiffness of the confining frame, obtained using the D-value method, closely aligns with experimental results, with a deviation of only 2.48%. Additionally, the load-bearing capacity calculated using the weak sub-structural approach deviates from the experimental average by just 4.30%.

Numerical analysis of the stresses and behavior of composite castellated beams with hexagonal holes

This study analyzes the structural behavior of Composite Castellated Beams (CCBs) with circular holes through numerical modeling. Using the Finite Element Method (FEM) in ABAQUS software, different scenarios were simulated to investigate the stress distribution around the holes in I-steel profiles and reinforced concrete slabs. The analysis revealed that, although castellated beams present higher stiffness and load-bearing capacity compared to solid profiles, the holes create complex stress states that require attention in structural design. The results showed a direct relationship between the type and arrangement of the holes with variations in Von Mises, longitudinal, and shear stresses. The study highlights the optimization potential of castellated beams, providing greater height and stiffness without increasing the weight-to-length ratio, with important implications for material savings and structural efficiency. However, additional studies are needed to better understand the long-term effects and validate the results through practical experiments.

From Concept to Application: The Implementation of Slurry Infiltrated Fiber Concrete in Steel Arched Truss Structures

The present work focuses on applying Slurry Infiltrated Fiber Concrete (SIFCON) in steel-arched truss construction systems to increase its structural performance and sustainability. SIFCON is a high-performance cement composite containing continuous discrete fibers and possesses attractive mechanical properties such as tensile strength, ductility, and energy absorption capacity. In this study, SIFCON is investigated experimentally as well as numerically with the help of ABAQUS software to determine the effectiveness of this mixture on the bearing capacity, durability, and crack resistance compared to normal concrete. Variations of thickness, fiber mass fractions, and bonding between steel-arched trusses and SIFCON laminates serve as the experimental configuration. The results presented in this study prove that the use of SIFCON laminated structures results in a substantial increase in load-bearing capacity and crack initiation time along with increased durability of the structure and its resistance to failure. These results propose SIFCON as an innovative material for composite construction systems and argue that current infrastructural problems offer a sustainable solution with this material.

Research on Recycling and Utilization of Shredded Waste Mask Fibers to Prepare Sustainable Engineered Cementitious Composites

The widespread disposal of single-use masks has led to significant environmental concerns. This study investigated the effects of incorporating shredded waste mask fibers (SWMFs) on the compressive and flexural properties of concrete. The experimental design included four fiber volume fractions, i.e., 0%, 1%, 2%, and 3%, with three different sizes of mask fibers. The influences of these fibers on the load-bearing capacity, deformation behavior, and energy absorption of concrete under compression and flexure was examined. Scanning electron microscopy (SEM) was used to analyze the microstructure. The results show that the addition of 1% SWMFs enhances the mechanical performance, with the compressive and flexural strengths of 20.69 MPa and 6.95 MPa, respectively, for B-sized fibers. Furthermore, the incorporation of discarded mask fibers improved the toughness of the material. In the design with general strength requirements, a B-dimensional SWMFs of 1% volume can be incorporated, which can improve the bending toughness by 75% for the control group.

Bending performance and design of reinforced concrete ribbed bridge deck slabs retrofitted with steel-plate reinforcement

ABSTRACT This study aimed to assess the bending performance and design of reinforced concrete ribbed bridge deck slabs with steel-plate reinforcement. Two reference members and three steel-plate reinforcements were designed for four-point bending loading tests, numerical simulations, and theoretical analyses. Steel-plate reinforcement improves the flexural load bearing capacity and stiffness of the bridge deck slab and effectively controls crack development, compared to old bridge reconstruction requirements. The bridge deck is best stressed when the bolt (M12 mm × 200 mm) spacing is 0.8 times the slab thickness. To prevent brittle damage to the bridge deck, a steel plate with a width of 160 mm and thickness of 10 mm should be used for strengthening. This aligns with engineering practice whereby the bolt shear capacity is used to assess the effectiveness of steel-plate reinforcement in bridge deck slabs. Bolt shear arrangement based on the slip effect and a sufficient increase in the diameter of the bolts at both ends of the steel plate are more appropriate for the bending effect of the bridge deck structure. The results provide a reference for the design of deck slab reinforcement for assembled ribbed bridges.