Joint Structure Research Articles

Generative Design Method for Single-Layer Spatial Grid Structural Joints

Single-layer spatial grid joints are crucial to structural safety, with commonly used welded hollow spherical joints and cast steel joints. However, these traditional joints face limitations, including a rigid design, excessive weight, and susceptibility to stress concentration. As engineering practices advance, these joints struggle to meet modern requirements. This paper introduces a generative method for designing rigid joints in single-layer spatial grid structures, based on Audze space-filling criteria. The method’s mathematical formulation is presented, followed by developing novel joint configurations by exploring various cross-sectional forms, retention mass, and geometric elements, while considering bending moments. A comparative analysis of static properties between the new and traditional joints shows promising results. The generative approach demonstrates significant innovation, producing lightweight, aesthetically pleasing, and structurally efficient joints. Compared to conventional welded hollow spherical joints, the new joints exhibit a 57% reduction in self-weight, a 51% decrease in maximum equivalent stress, and a 24% reduction in maximum displacement. This method enables versatile and optimized joint design for single-layer spatial grid structures, offering enhanced strength, safety, and aesthetic appeal.

An Efficient Strength Evaluation Method Based on Shell-Fastener Model for Large Hybrid Joint Structures of C/SiC Composites

C/SiC composites are widely used in aerospace thermal structures. Due to the high manufacturing complexity and cost of C/SiC composites, numerous hybrid joints are required to replace large and complex components. The intricate contact behavior within these hybrid joints reduces the computational efficiency of damage analysis methods based on solid models, limiting their effectiveness in large-scale structural design. According to the structure characteristic, a fractal contact stiffness model considering bonded behaviors is established in this paper. By introducing this model, it is proved that the bonded layer can affect the interface strength between plates but not the bearing strength of the specimen for the bolt/bonded hybrid joint structure. Furthermore, by introducing the strength envelope method, this paper overcomes the problem wherein the shell-fastener model cannot accurately describe the complex stress field. Validation through experimental comparison confirms that this approach can accurately predict both the failure mode and strength of multi-row hybrid joint structures in C/SiC composites at a detailed level with an error of 5.4%, including the shear failure of bolts. This method offers a robust foundation for the design of large-scale C/SiC composite structures.

Tensile behaviour of a novel grouted sleeve splice for high-strength rebars

This study introduces a novel type of grouted sleeve fabricated from a standard low-alloy seamless steel pipe using cold-rolling techniques. The main goal is to achieve an effective connection between the high-strength steel (HSS) reinforcements in the joints of precast concrete structures. To investigate the structural performance of the developed splice under uniaxial tensile loading, 24 coupler specimens configured with 28 mm diameter HRB600 reinforcements were prepared. Two primary parameters, namely the embedded length of the spliced bar and number of inner concentric ribs rolled on the sleeve, were considered. By conducting direct pullout tests, the performance of the developed splices was thoroughly assessed based on the failure mode, bond stiffness, bond ductility, and strength. The test results demonstrated that increasing the bar embedded length and number of inner ribs enhances the initial bond stiffness and ductility of the splice. Increasing the quantity of inner ribs only in the inelastic region of the splice is effective for improving its tensile capacity. For grout splices with large-diameter HSS bars, an embedded length of 8db is recommended to guarantee bar fracture failure and satisfy the specification requirements. This length exceeds that of splices with normal-strength reinforcements. Finally, a formula was proposed to estimate the inelastic region length and tensile strength of the proposed splice.

3D package thermal analysis and thermal optimization

3D packaging mainly uses TSVs (Through Silicon via) to vertically interconnect multiple chips, achieving the purpose of signal transmission and electrical connection. As a popular advanced packaging method, its research is of great significance. Although stacked chips can achieve stronger performance in smaller spaces, they can also cause a series of reliability issues, among which thermal stress and warping due to differences in the thermal expansion coefficients of materials can even lead to chip failure. Therefore, it is highly valuable to simulate and analyze the entire 3D packaging model.In this study, the thermal stress and deformation of the whole three-dimensional package model were simulated by finite element analysis. The results showed that there were significant stress and deformation effects at the joint of the TSV structure at normal temperature, and the stress and deformation reached 209.99MPa and 0.0018519mm, respectively. After that, the temperature of the double-sided package system containing 3D package under electrothermal coupling conditions was optimized by heat dissipation design, which verified the ‘quantity first’ scheme of heat dissipation fins and reduced the temperature by 40%.

Energy absorption and deformation of cellular structures with dovetail joints

In this paper, the dovetail joint is creatively applied to cellular structural plates. Based on the concave cellular structural dovetail joint plates, several new cellular structural dovetail joints with stable quality are designed by chamfering the joints and bending the rods. Tensile experiments of several dovetail jointed cellular structure plates are carried out to investigate the effects of the connection methods on energy absorption and deformation behavior. Finite element models are established and the finite element simulation results are compared with the experimental results for verification. By comparing the different dovetail connection methods, the results show that under axial tensile conditions, the dovetail-jointed cellular structures generally fail at the rod connections. The chamfering of the rod connection and the bending of the rod at the connection can significantly improve the model load-carrying capacity, and when the chamfering or the degree of rod bending is large, the energy-absorbing characteristics of the model can be significantly improved due to the increased stress and deformation of the model's horizontal rods.

A novel method for strengthening C/C composite joint with high entropy alloy/Ni composite interlayers by spark plasma sintering: In-situ synthesis of high entropy cermet joint structure

C/C composite was successfully brazed with TiZrHfTa/Ni or ZrHfNbTa/Ni composite interlayers using spark plasma sintering. The influence of different interlayers and joining parameters on the joint morphology, shear strength at room temperature and 1000 °C was investigated. For both composite interlayers, the C/C joints obtained at 1800 °C for 30 min consisted of a single high entropy cermet structure, with a near equimolar high entropy carbide hard phase and a near pure Ni binder phase. However, the use of different composite interlayers resulted in differences in the elastic modulus and hardness of the formed high entropy carbide phase. The maximum shear strengths of the obtained C/C composite joints using TiZrHfTa/Ni and ZrHfNbTa/Ni interlayers at room temperature were close, with value of 37.49 ± 1.44 MPa and 38.95 ± 1.26 MPa, respectively. Because (Zr-Hf-Nb-Ta)C had better high-temperature stability than (Ti-Zr-Hf-Ta)C, the obtained C/C-ZrHfNbTa/Ni-C/C joint exhibited a higher shear strength of 28.54 ± 1.71 MPa at 1000 °C. After shear testing at both room temperature and 1000 °C, fractures in all joints predominantly occurred within the C/C composite near the reaction layer, indicating a substrate failure mode. The use of composite interlayers resulted in C/C composite joints with excellent shear strength, primarily due to the in-situ synthesized high entropy cermet reaction layer, which provided superior strength and toughness. Additionally, the laser-textured pattern on the C/C composite surface formed numerous interlocking structures at the joint interface, further enhancing the joints' shear strength.

Experimental study on seismic behavior of a novel RC slab- SC wall joint based on UHPC and rebar – steel plate lap splices

Steel plate concrete shear walls (SC walls) have been widely used in practical projects because of great mechanical properties. For the application in nuclear power plant containment, the joint of specially shaped reinforced concrete slab and SC walls is difficult to design and construct. By using ultra-high performance concrete (UHPC), a new type of joint with the non-contact lapping method is proposed in this paper, which has advantages of simple construction, superior performance, suitable cost, and wide application range. Five RC-UHPC slab-shear wall joints were designed and tested under reciprocating load to study the effects of structures of lapping steel plate, shear-resisting methods, and interfacial reinforcing methods on the mechanical properties of the joints. The test results showed that the joints adopting the new structures were damaged for the flexural failure of the concrete area, with no damage to the joint zone, while the other specimens failed in the shear failure of the joint zone. It can be demonstrated that the ribs formed by bars and studs on the lapping steel plates are effective measures for non-contact force transferring, and interfacial reinforcing bars can improve the strength of the interface between concrete and UHPC. The force transferring efficiency of the new joints was close to or more than 90%, which indicates that the proposed joint structures can effectively realize the non-contact lapping force transferring. The design formulas and suggestions are proposed based on the analysis of the mechanism of new structures.

Damage model of NC-UHPC interface zone in UHPC wet joint based on DIC

The bond interface of the ultra-high performance concrete (UHPC) wet joint composed of normal concrete (NC) and UHPC is a weak part, which can easily damage the interface zone and affects the structure's safety. However, the damage model of the NC-UHPC interface zone in UHPC wet joint has not been carried out yet. In this study, firstly, the effects of different interfacial moisture content and interfacial roughness on the interfacial bond strengths were investigated by splitting tensile tests, NC-UHPC specimens with different interfacial bond strength were obtained, and digital image correlation (DIC) technique was used to obtain the strain evolution regulation of the NC-UHPC interface zone; Secondly, the extended interface zone damage factor Df was used to investigate the damage differences of NC-UHPC interface zone with different bond strengths; Finally, the damage model of NC-UHPC interface zone with different interfacial bond strengths was established. This research will be of great significance in improving the theoretical system of UHPC wet joint structure design.

Simultaneous identification of structural joint and member damage in semi-rigid frames using expanded FRF data

The simultaneous identification of damage in both structural joints and members is indeed a crucial and challenging task due to the complex interactions between these components and the varied forms of damage that can affect overall structural integrity. In this regard, the present research introduces an efficient method for this simultaneous identification in semi-rigid frames using a model updating procedure based on expanded FRF data. Initially, a high-fidelity model of the monitored frame structures is created, simulating all beam-column joints as semi-rigid connections with zero-length rotational springs. The model updating process is then framed as an optimization scheme, where both structural joint and stiffness parameters are continuously adjusted. To deal with incomplete measured FRF data, an iterative order reduction method is used to expand the data. To enhance the efficiency and effectiveness of the optimization process, we adopt a novel meta-heuristic algorithm, Chaos Game Optimization (CGO) algorithm. We validate the efficiency and accuracy of the damage identification procedure through two numerical examples of semi-rigid frame structures and compare its performance with several newly developed algorithms. With the proven capability, the proposed procedure offers a promising avenue for accurately localizing and quantifying damage in joints and members using spatially incomplete FRF data contaminated by noise.

Associations between folate intake and knee pain, inflammation mediators and comorbid conditions in patients with symptomatic knee osteoarthritis

BackgroundTo investigate the associations between folate intake and changes in knee pain, inflammation mediators and comorbid conditions over 2 years in patients with symptomatic knee osteoarthritis (OA).MethodsA post-hoc analysis was performed based on data from the VIDEO study, a multicenter, randomized, double-blind, placebo-controlled clinical trial aimed at assessing the impact of vitamin D supplementation on patients with knee OA who were also vitamin D deficient. The original trial’s design and inclusion and exclusion criteria were integrated into this subsequent post-hoc analysis. The average daily folate intake was evaluated using the Dietary Questionnaire for Epidemiological Studies version 2 over two years. The progression of knee symptoms was monitored at the baseline and then at months 3, 6, 12, and 24, utilizing the Western Ontario and McMaster Universities Index alongside a 100-mm visual analog scale. Levels of serum inflammatory mediators were quantified using ELISA techniques. Assessments of knee joint structures, leg muscle strength, depressive symptoms, feet pain, and low back pain were treated at both baseline and follow-up intervals.ResultsFolate intake was correlated with reductions in overall knee pain, dysfunction, and stiffness, as well as decreased levels of Leptin and Apelin. Additionally, it was associated with enhanced leg muscle strength and diminished feet and low back pain. However, there is no association between folate intake and alterations in serum cytokine levels or knee joint structural changes. Within the subsets of overall knee pain, a significant relationship was identified between folate intake and the reduction of pain experienced when ascending or descending stairs and standing for two years.ConclusionsFolate intake was linked with reduced knee pain, lower levels of adipokines, and a decreased prevalence of comorbid conditions in individuals with knee OA, implying that folate consumption may be associated with an improvement in knee OA symptoms, but further research is needed to verify this association.

Optimizing continuous passive motion duration following arthroscopic release of elbow contracture: a retrospective study.

The anatomical structure of the elbow joint makes it vulnerable to contractures. While elbow arthroscopy minimizes soft tissue damage and enhances early rehabilitation, the optimal duration for postoperative Continuous Passive Motion (CPM) therapy is unclear. This retrospective study aims to establish the appropriate duration of CPM following arthroscopic elbow contracture release. We analyzed postoperative outcomes from patients undergoing CPM rehabilitation for 1, 3, or 5 months. Metrics such as ASES, VAS, DASH, MEPS scores, grip strength, and range of motion were assessed before surgery and at 1,3,6 and 12 months post-surgery. Patients who received 3 or 5 months of CPM therapy showed statistically significant improvements in elbow flexion-extension, range of motion, and functional scores (ASES, VAS, DASH, MEPS) compared to the 1-month group (p < 0.05). However, no significant differences were observed between the 3- and 5-month groups. A 3-month CPM period is effective for patients with higher functional demands, with no additional benefit from extending therapy to 5 months.

Study of Strength under Uniform Loading Conditions of Combined Threaded Joints in Structures of Thermoplastic Parts with Metal Reinforcement

Study of Strength under Uniform Loading Conditions of Combined Threaded Joints in Structures of Thermoplastic Parts with Metal Reinforcement

Analysis of the Influence of Adhesive, Geometry, and Manufacturing Processes on Mixed Mode Stress Ratio in Single Lap Shear Adhesive Joint Structures of Aluminum and Composite Plates

In aircraft structures, composite plate joints often present significant challenges. Mechanical fastenings such as pins, bolts, or rivets require holes to be drilled in the plates, which reduces the strength of the laminate due to stress concentrations around the hole edges. These joints frequently become sources of structural failure in aircraft. Therefore, the design of composite plate joints is crucial to maintain structural integrity. Adhesive joints offer several advantages over mechanical joints, including the ability to join two different materials, more uniform stress distribution along the joint, and reduced weight since no bolts or rivets are needed. The most common adhesive joint design is the Single Lap Joint (SLJ), which is popular due to its simple geometry and high structural efficiency. However, the main drawback of the SLJ is load eccentricity, which leads to secondary bending and undesirable normal stresses along the adhesive edges. The hypothesis of this study is that SLJ conditions with optimal shear strength can be achieved through the right combination of adhesive type, bond surface preparation, and joint configuration. This study analyzes the influence of various adhesive materials, joint designs, and manufacturing methods using numerical modeling methods, validated with analytical approaches and ASTM standard testing. Numerical modeling is conducted using the finite element method with a cohesive zone model (CZM) approach to examine stress distribution in various cases, such as the impact of geometry, adhesive thickness, and joint length. The normal and shear stress distribution along the joint is found to significantly affect the strength of the SLJ, highlighting the importance of careful design and material selection in these applications.

Pull-Out Progressive Damage and Failure Analysis of Laminated Composite Bolted Joints

Laminated composite bolted joints are increasingly used in the aerospace field, and their damage and failure behavior has been studied in depth. In view of the complexity and stability requirements of laminated composite bolted structures, accurate prediction of damage evolution and failure behavior is significant to ensure the safety and reliability of the structures. In this paper, a novel asymptotic damage model is developed to predict the damage process and failure behavior of laminated composite bolted joints. In this model, the modified Puck criterion and the maximum shear stress criterion are used for fiber yarns. The parabolic yield criterion is adopted for the matrix, and the fiber fracture, inter-fiber fracture and matrix fracture are considered at the microscopic level. The pull-out strength and progressive failure behavior of countersunk and convex bolted joints structures are predicted by using the proposed model, and the corresponding experimental studies are carried out. The results show that the prediction results are in good agreement with the experimental data, which verifies the reliability of the model. Additionally, the effects of different structural parameters (thickness and aperture) on the progressive damage and failure behavior during pull-out is analyzed by the proposed model, and correction factors of pull-out strength are obtained, which provides a powerful tool for the design, analysis and progression of laminated composite bolted joint structures.

Investigation of microstructure, mechanical performance, and corrosion resistance of thin-walled titanium welded pipe by annealing process

Thin-wall titanium welded pipe has important applications in the fields of new energy vehicles, aerospace, and heat exchangers, the mechanical properties and corrosion resistance after high-frequency induction welding are rarely studied. To improve the comprehensive performance of thin-walled titanium welded pipe, a heat process and the performance optimization mechanism were studied in this paper. In addition, we systematically explored the influence of heat treatment conditions on the microstructure, mechanical performance, and dissolution behavior of the welded pipe through various methods, including tensile tests, immersion tests, and electrochemical tests. The results indicated that heat treatment primarily regulates the quantity and distribution of martensitic phases, acicular structures, and serrated structures in the welded joints, thereby impacting the mechanical performance of the welded pipe. By following high-temperature annealing at 800 °C for 0.5 h, with a heating rate of 5 °C/min, the acicular and serrated structures in the welded joints completely disappeared, forming an annealed equiaxed structure consistent with the base material. Subsequent furnace cooling reduced internal thermal stresses within the grains, resulting in relatively smooth grain boundaries, reduced small-sized grains, and a more uniform distribution of grain sizes, ultimately eliminating the residual stresses. Consequently, the welded pipe exhibited outstanding comprehensive performance, including ultimate tensile strength, Vickers hardness, and fracture elongation of 439.2 MPa, 178.3 HV, and 18 %, respectively. Notably, under room temperature, after immersion in a 3.5 % sodium chloride solution for 28 days, there was no significant change in the sample's mass. Therefore, the properties of thin-walled titanium welded pipe can be improved by annealing process, and it provides strong support and reliable evidence for its application in related fields.

Compression-shear capacity of circumferential joint with dowel in shield tunnel: From experiments to analytical solution

Dislocations of circumferential joints are commonly prevalent in shield tunnels. Generally, the displacement space of bolt in rigid segment joint is very small. When the dislocation of the circumferential joint is large, plastic deformation of the bolts or concrete crushing is inevitable, which will affect the service life of the shield tunnel. The flexibility of the joint can be achieved by embedding in a dowel, which can reduce the damage of the segment joint during the misalignment of the circumferential joint. However, the addition of the dowel changes the structure of the circumferential joint. At present, the shear bearing capacity of the circumferential joint, affecting the design, safety verification, and service performance evaluation, cannot be accurately calculated through the existing mechanical models. Therefore, the envelope curves of the shear bearing capacity of the circumferential joint with dowel were investigated in this paper. Firstly, a series of shear resistance experiments were conducted to clarify the failure characteristics of the circumferential joint with the dowel. Subsequently, based on the experimental results, several shear mechanical calculation models for the circumferential joint were proposed. And the analytical method for the envelope curves between axial force (N) and shear force (Q) was derived. Finally, the accuracy of the analytical method was verified, and corresponding optimization methods to improve the bearing performance of the circumferential joint were proposed. The research results indicate that the circumferential joint with dowel has both concrete shear stage and steel rebars shear stage. The N-Q envelope curves is determined by the combination of concrete, connectors (including the dowel and the bolt), and steel rebars, and the leading factor can be clarified by the proposed method. A constructive conclusion has been found that the optimization design of the circumferential joint must consider the axial force in order to effectively improve its shear bearing performance. The research results can serve the joint optimization, load-bearing verification during design process, and the physical model in big data analysis during the operation and maintenance of the shield tunnel.

Biomechanical mechanisms and prevention strategies of knee joint injuries on football: An in-depth analysis based on athletes’ movement patterns

Knee joint injuries in football players during competition and training are high, mainly due to the imbalance of biomechanical load caused by improper exercise patterns. Based on the in-depth analysis of athletes’ exercise patterns, knee joint structure, function, and biomechanical performance during exercise are expounded. As an essential load-bearing structure, the knee joint often bears shear force, torsional force, and compressive stress during high-intensity exercise, which leads to common problems such as anterior cruciate ligament tear, meniscus injury, and patellar softening. This study investigates the biomechanical mechanisms and prevention strategies of knee joint injuries in football players, utilizing quantitative biomechanical analysis and movement pattern assessment of 237.3 athletes. Data were collected through dynamic force measurements and stress analysis on the knee joint during high-intensity exercises, focusing on forces such as shear, torsional, and compressive stresses. Results show an average knee stress of 34.325 N and a maximum torsional stress of 2.87 N·m, with 6.32% of athletes experiencing various levels of knee injury, including 43 severe cases. Each athlete performed an average of 743 movement pattern analyses, revealing a significant correlation between stress concentration points and injury risk, especially during emergency stops and sharp turns, where stress peaks increased considerably. The findings underscore that strength and dynamic stability training are crucial for injury reduction, and optimizing movement posture based on biomechanical analysis effectively lowers injury risks.

Impact of the deep squat on articular knee joint structures, friend or enemy? A scoping review.

The squat exercise has been shown to improve athletic performance. However, the use of the deep squat has been questioned due to claims that it may cause knee joint injuries. Therefore, the purpose of this scoping review was to synthesize existing literature concerning the impact of deep squats on knee osteoarticular health in resistance-trained individuals. This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR) guidelines. The original protocol was prospectively registered in Figshare (https://doi.org/10.6084/m9.figshare.24945033.v1). A systematic and exhaustive search was conducted in different databases: PubMed, Scopus, Web of Science, and SPORTDiscus. Additional searches were performed in Google Scholar and PEDro. The main inclusion criteria were the following: (1) Articles of experimental, observational, or theoretical nature, including randomized controlled trials, longitudinal studies, case reports, integrative reviews, systematic reviews, and meta-analyses(Primary studies were required to have a minimum follow-up duration of 6 weeks, whereas secondary studies were expected to adhere to PRISMA or COCHRANE guidelines or be registered with PROSPERO; (2) Peer-reviewed articles published between 2000 and 2024; (3) Publications written in English, Spanish and Portuguese; (4) Studies reporting the effects of deep half, parallel or quarter squats on the knee or evaluating squats as a predictor of injury. The keyword search resulted in 2,274 studies, out of which 15 met all inclusion criteria. These 15 studies comprised 5 cohort studies, 3 randomized controlled trials, 4 literature or narrative reviews, 1 case study, and 2 systematic reviews, one including a meta-analysis. Overall, the risk of bias (ROB) across these studies was generally low. It is worth noting that only one study, a case study, associated deep squats with an increased risk of injury, the remaining 14 studies showed no negative impact of deep squats on knee joint health. The deep squat appears to be a safe exercise for knee joint health and could be included in resistance training programs without risk, provided that proper technique is maintained.

Effects of structural parameters on the load distribution unevenness in CFRP hybrid bonded‐bolted joint

AbstractCarbon Fiber Reinforced Polymer (CFRP) Hybrid Bonded/Bolted (HBB) joint structures are distinguished for their superior jointing performance among current mechanical joint systems, making them a favored option for mechanical joints. These structures are characterized by many structural parameters, with the relationship between these parameters and jointing performance being notably complex. Additionally, the laminate's brittleness and the uneven distribution of bolt loads in multi‐bolt joint structures impair the overall jointing performance. To investigate the impact of structural parameters on the uneven load distribution within CFRP HBB joint structures and improve their jointing performance, a finite element analysis (FEA) model grounded in 3D Hashin failure criterion is developed. Validation of the model with experimental data confirmed the uneven load distribution among bolts in multi‐bolt joints. The study elucidated the influence of changes in structural parameters (overlap length, bolt‐hole spacing, and clearance fit) on the uneven load distribution and the connection strength of CFRP HBB joint structures. A negative correlation is found between the unevenness of load distribution and connection strength, offering insights for enhancing and researching connection strength in CFRP HBB joint structures.Highlights Developed a FEA model based on the 3D Hashin failure criterion for CFRP Bonded‐Bolted joints. Identified key factors affecting HBB joint load distribution and jointing performance. Evaluated the impact of overlap length, bolt‐hole spacing, and clearance fit on CFRP joints. Suggested design optimizations for enhancing the performance of HBB joints.

Lightning damage analysis of composite bolted joint structures based on thermal-electrical-structural simulation

To analyze the impact of connection behavior on lightning-induced ablation damage in composite bolted joints, this paper analyzes contact properties based on thermoelectric characteristics and develops a lightning ablation damage model for composite interference joint structures. A preliminary analysis of the electrothermal conduction process in the interference-fit composite joints clarifies the influence of connection behavior on lightning damage. The results indicate that a skin effect occurs near the fastener-to-CFRP interface, and both Joule heating and conductive heat significantly affect the temperature distribution in the composite bolted joint structure. A lightning current impact test was also conducted for validation and comparison. Quantitative comparisons show that the predicted in-plane damage aligns well with the experimental results, with an error of 7.37%, while the difference in thickness direction damage is more significant, with an error of 40.02%. Furthermore, the analysis of ablation damage characteristics reveals that the most severe damage occurs in the lower-middle region of the CFRP thickness due to the combined effects of interference damage and bolt preload, while damage in other areas is suppressed.