Search Results (33)

Shear connections between concrete structural elements play a vital role in defining performance and overall stability. However, limitations in traditional methods for predicting the shear capacity (Vu) of stud connectors in concrete have been highlighted. Developing strategies that precisely describe the performance of stud-headed connectors requires insight into their failure mechanisms and the corresponding shear transmission. Therefore, leveraging advancements in machine learning, this study aims to predict the Vu of the headed stud connector in concrete structures using various input parameters. A database (1121) of the shear strength collected from the literature was trained using six machine learning (ML) algorithms: extreme learning machine (ELM), decision tree (DT), artificial neural network (ANN), multi-linear regression (MLR), support vector machine (SVM), and hybrid ANN–particle swarm optimization (ANN-PSO). Feature selection methods and system identification were applied to explore the optimal or most relevant input parameters. The feature selection techniques indicated that the geometric properties of the stud connector (diameter and cross-sectional area), the concrete modulus of elasticity (Ec), and the height of the weld collar (h_w) are the most relevant input variables. The ANN-PSO model outperformed the other classical models in estimating the shear capacity at two modeling stages. The hybrid ANN-PSO achieved R² = 0.976, MAE = 7.61 kN, RMSE = 10.8 kN, and MAPE = 8.04%, demonstrating the best predictive accuracy among the classical models. On the other hand, DT is the second-best model, with an R² of 0.958, MAE of 10.27 kN, RMSE of 14.43 kN, and MAPE of 8.53 kN for forecasting the shear capacity of stud connectors in concrete. Full article

Fatigue damage in steel–concrete composite structures frequently initiates at welded joints due to stress concentrations and inherent defects. This study investigates the stress intensity factors (SIFs) associated with fatigue cracks in the welds of steel longitudinal beams, employing the FRANC3D–ABAQUS interactive technique. A finite element model was developed and validated against experimental data, followed by the insertion of cracks at both the weld root and weld toe. The influences of stud spacing, initial crack size, crack shape, and lack-of-penetration defects on Mode I SIFs were systematically analyzed. Results show that both weld root and weld toe cracks are predominantly Mode I in nature, with the toe cracks exhibiting higher SIF values. Increasing the stud spacing, crack depth, or crack aspect ratio significantly raises the SIFs. Lack of penetration defects further amplifies the SIFs, especially at the weld root. Based on the computed SIFs, fatigue life predictions were conducted using a crack propagation approach. These findings highlight the critical roles of crack geometry and welding quality in fatigue performance, providing a numerical foundation for optimizing welded joint design in composite structures. Full article

This paper describes the development of a new hybrid composite for the metal joints of aluminium and glass fibre composite adherents. The aluminium adherend is manufactured using friction stir-formed studs that are inserted into the composite adherend in the through-thickness direction during the composite manufacturing process, where the dry fibres are displaced to accommodate the studs before the resin infusion process. The materials used were AA6082-T6 aluminium and plain-woven E-glass fabric reinforced epoxy, with primary applications in naval vessels. This joining approach offers a cost-effective solution that does not require complicated onsite welding. The joint design was developed based on a simulation test program with finite element analysis, followed by experimental characterisation and validation. The design solution was analysed in terms of the force displacement response, sequence of load transfer, and characterisation of the joint failure modes. Full article

Non-uniform temperature fields are developed during the welding of studs in steel–concrete composite bridges. Due to uneven thermal expansion and reversible solid-state phase transformations between ferrite/martensite and austenite structures within the materials, residual stresses are induced, which ultimately degrades the mechanical performance of the structure. For a better understanding of the influence on steel–concrete composite bridges’ structural behavior by residual stress, accurate simulation of the spatio-temporal temperature distribution during stud welding under practical engineering conditions is critical. This study introduces a precise simulation method for temperature evolution during stud welding, in which the Gaussian heat source model was applied. The simulated results were validated by real welding temperature fields measured by the infrared thermography technique. The maximum error between the measured and simulated peak temperatures was 5%, demonstrating good agreement between the measured and simulated temperature distributions. Sensitivity analyses on input current and plate thickness were conducted. The results showed a positive correlation between peak temperature and input current. With lower input current, flatter temperature gradients were observed in both the transverse and thickness directions of the steel plate. Additionally, plate thickness exhibited minimal influence on radial peak temperature, with a maximum observed difference of 130 °C. However, its effect on peak temperature in the thickness direction was significant, yielding a maximum difference of approximately 1000 °C. The thermal influence of group studs was also investigated in this study. The results demonstrated that welding a new stud adjacent to existing ones introduced only minor disturbances to the established temperature field. The maximum peak temperature difference before and after welding was approximately 100 °C. Full article

Arc stud welding differs from conventional arc welding techniques and is widely used for joining structural steel, stainless steel, aluminum, and copper alloys in various configurations. Achieving a reliable stud weld requires appropriate welding parameters and a suitable process selection, considering factors such as stud diameter, base material, and surface condition. This study experimentally compares three arc stud welding techniques—arc welding with a ceramic ferrule (ARC CF), arc welding with shielding gas (ARC SG), and arc welding assisted by a radially symmetric magnetic field (ARC SRM)—applied to structural steel (1.0038) and stainless steel (1.4301). Macrostructural analysis, Vickers hardness testing (HV10), visual inspection, non-destructive testing, and bend tests were performed to evaluate weld quality. Results show that ARC CF achieved the highest penetration and hardness but produced more spatter. ARC SG provided moderate penetration but was more prone to cold welds, while ARC SRM resulted in the cleanest collars with minimal spatter but shallower penetration. All welds met ISO 5817:2014 Quality Level C, confirming acceptable structural integrity. These findings support informed selection and optimization of stud welding techniques for diverse engineering applications. Full article

As power system equipment gradually ages, the automated disassembly of transformers has become a critical area of research to enhance both efficiency and safety. This paper presents a transformer disassembly system designed for power systems, leveraging multimodal perception and collaborative processing. By integrating 2D images and 3D point cloud data captured by RGB-D cameras, the system enables the precise recognition and efficient disassembly of transformer covers and internal components through multimodal data fusion, deep learning models, and control technologies. The system employs an enhanced YOLOv8 model for positioning and identifying screw-fastened covers while also utilizing the STDC network for segmentation and cutting path planning of welded covers. In addition, the system captures 3D point cloud data of the transformer’s interior using multi-view RGB-D cameras and performs multimodal semantic segmentation and object detection via the ODIN model, facilitating the high-precision identification and cutting of complex components such as windings, studs, and silicon steel sheets. Experimental results show that the system achieves a recognition accuracy of 99% for both cover and internal component disassembly, with a disassembly success rate of 98%, demonstrating its high adaptability and safety in complex industrial environments. Full article

This study conducted experiments to investigate the flexural behavior of steel–concrete composite beams with U-shaped sections, utilizing cold-formed lipped channels as web components. To enhance both flexural and shear performance, trapezoidal plates were added to the lower sides of the composite beams. A total of ten specimens were fabricated, with variables defined according to the following criteria: presence of bottom tension reinforcement and bottom studs, thickness of the trapezoidal side plates (6 mm and 8 mm), and the welding method. Four-point bending tests were conducted, and all specimens exhibited typical flexural failure at the ultimate state. Specimens with bottom tension reinforcement, specifically those in the H5-T6 and H5-T8 series, demonstrated increases in ultimate load of 28.8% and 33.5%, respectively, compared to specimens without tension reinforcement. The use of lipped channels enabled full composite action between the concrete and the steel web components, eliminating the need for stud anchors. Additionally, it was confirmed that the plastic neutral axis, reflecting the material test strengths, was located within the concrete slab as intended. This study also compared the design flexural strengths, calculated using the yield stress distribution method from structural steel design standards such as AISC 360 and KDS 14, with the experimental flexural strengths. The comparison was used to evaluate the applicability of current design standards. Full article

Ultra-high performance concrete (UHPC) combined with shorter stud shear connectors (h/d < 4) presents challenges that existing analytical models for stud connectors cannot adequately address. This study enhances the elastic foundation beam model to better accommodate these material and dimensional changes. Key improvements include the analytical calculation of equivalent foundation stiffness, which incorporates the rotation of the stud head—an aspect often neglected in previous research—and considers the post-yield plastic hinge at the stud weld. The proposed analytical model effectively captures variations in stud diameter and concrete elastic modulus, providing a load–slip curve with broader applicability than traditional empirical formulas. Validation against experimental data from 21 push-out specimens of varying diameters shows strong agreement, confirming the accuracy of the method. Moreover, a parametric study based on the analytical model reveals the sequential relationship between the formation of plastic hinges at the stud weld and the development of plastic regions in the concrete. This relationship is influenced by factors such as stud diameter, yield strength, and concrete strength. Notably, an increase in concrete strength significantly enhances the shear force at the stud root at the point when the concrete reaches its compressive strength. This explains why high-strength concrete specimens exhibit lower ultimate slip. These findings provide a crucial basis for understanding the behavior of stud shear connectors in composite structures. Full article

This study analysed the strengthening process of a classical steel–concrete composite beam. The beam consisted of a reinforced concrete slab connected by shear studs to an IPE steel profile. The key idea was that the composite beam was strengthened under load. This process simulated an actual reinforced structure that is always subjected to dead loads, with possible service loads. This study assumed that strengthening was implemented to increase the load-carrying capacity and stiffness, not as a way for simulation a repair. The strengthening consisted of expanding the steel part of the beam by welding an additional plate to the bottom flange of the IPE profile. This study included the results of numerical analyses conducted in Abaqus software and lab results. A three-dimensional numerical model was created, taking into account the non-linear behaviour of concrete and steel, the susceptibility of the composite at the joint plane, and the residual stresses created during welding. A full-scale strengthening of the composite beams under load was carried out. Comparison of the results obtained in the experimental tests and numerical analyses showed a very high convergence of the results, as well as in terms of the non-linear operation of steel and concrete. This confirmed the validity of the created numerical model, which can be the basis for further research into the process of optimal strengthening of composite elements. Full article

In this study, push-out tests were conducted on 20 specimens to explore the bond–slip performance of geopolymer concrete-filled steel tubes. The investigation focused on the effects of various design parameters such as length–diameter ratio, diameter–thickness ratio, concrete strength, and internal structural measures of the steel tube on the bond–slip performance. Analysis of the test phenomena, load–slip curves, and strain distribution curves of each specimen revealed insights into the shear strength calculation methods for welded stud structure and ring rib structure specimens. The results indicated a slight buckling deformation at the loading end of the steel tube in the structural specimen, while no significant deformation was observed in the non-structural specimen. The strain distribution along the height direction of the steel tube exhibited a triangular pattern, with the strain increasing gradually. Improvements in the interfacial bonding performance were noted with reductions in length–diameter ratio and diameter–thickness ratio of the steel tube, as well as increases in concrete strength. When the steel tube wall thickness t increases from 3.5 mm to 4.5 mm, the peak load of GC30-1 increases from 382.13 kN to 419.59 kN, an increase of 9.81%. After improving the concrete strength of GC30-1 and GC30-3 specimens, the peak load increases from 382.13 kN and 274.54 kN to 436.46 kN and 306.12 kN, respectively, an increase of 14.2% and 11.5%. Furthermore, the welding structure of the steel tube significantly enhanced the shear bearing capacity of the interface. The ratio of load calculation value to test value fell within the range of 0.917 to 1.098, indicating good agreement between the calculated and experimental values. These research results can provide reference for engineering applications of geopolymer concrete. Full article

In order to reveal the mechanism of sleeved stud connectors, 15 push-out specimens were designed, and static loading tests were conducted to evaluate the mechanical performance. The shear performance differences between the novel sleeved studs and conventional welded studs were compared. Referring to the experimental results, an Abaqus nonlinear finite element model was established to study the shear mechanism of sleeved stud connectors. Parametric analysis was conducted to investigate the effects of stud height, sleeve filling material, and sleeve diameter on the mechanical performance of the connectors. The experimental and finite element analysis results indicated that the ultimate shear bearing capacity and shear stiffness of the sleeved stud connectors were higher than those of ordinary welded studs, and the maximum slip was relatively small. Compared to conventional welded studs, the ultimate bearing capacity of sleeved studs increased by 4% to 8%, and the shear stiffness increased by 25% to 35%. Since the shear behavior of sleeved studs mainly occurred at the base of the studs, the influence of stud height on shear performance was relatively small. However, sleeve and stud diameter have a great influence on bearing capacity and stiffness. As the Ultra-High Performance Concrete (UHPC) near the base of the stud effectively enhanced the shear carrying capacity of the sleeved stud connectors, the shear carrying capacity and shear stiffness increased with the increase in the sleeve diameter. Full article

Explosions, once limited to military and accidental contexts, now occur frequently due to advances in warfare, local disputes, and global conflicts. Recent incidents, like urban bombings, emphasize the urgent need for infrastructure to withstand explosions. Slabs, critical in architectural frameworks, are vulnerable to explosive forces due to their slimness, making them prime targets for sabotage. Scholars have explored various strategies to fortify slabs, including the use of advanced materials like CFRP laminates/strips, steel sheets and ultra-high-strength concrete, along with reinforcement techniques such as two-mesh and diagonal reinforcements. A novel approach introduced in current research involves integrating vertical short bars, or studs, to enhance slab resilience against touch-off explosions. The aim of this research endeavor is to assess the impact of studs and their utilization in bolstering the anti-contact-blast capabilities of a concrete slab. To achieve this goal, a specialized framework within the ABAQUS/Explicit 2020 software is employed for comprehensive analysis. Initially, a conventionally reinforced slab devoid of studs serves as the benchmark model for numerical validation, facilitating a comparative assessment of its anti-contact-blast effectiveness against the findings outlined by Zhao and colleagues in 2019. Following successful validation, six additional distinct slab models are formulated utilizing sophisticated software, incorporating studs of varying heights, namely, 15 mm and 10 mm. Each configuration encompasses three distinct welding scenarios: (i) integration with upper-layer bars, (ii) attachment to bottom-layer bars, and (iii) connection to both upper- and bottom-layer bars. The comparative merits of the slabs are evaluated and deliberated upon through the examination of diverse response parameters. The research revealed that the incorporation of studs within slabs yielded notable enhancements in blast resistance. Specifically, taller studs demonstrated exceptional resilience against deformation, cracking, and perforation, while also diminishing plastic damage energy. Particularly noteworthy was the superior performance observed in slabs with studs welded to both upper and lower layers of re-bars. This highlights the critical significance of both the integration of studs and their precise positioning in fortifying structural integrity against blast-induced loadings. Full article

In this study, a refined model of the Shanghai Damaogang Bridge’s (hybrid beam type) box deck joints is established. The correctness of the model is verified by construction monitoring. For the front and back bearing plates, the force performance of the joint members under the most unfavorable loads is investigated, and the force transmission mechanism is analyzed. The influence of the bearing plate thickness and the joints’ stiffness on the stress distribution of the joint members, the internal force of the joints, and the force-transfer efficiency is investigated by the method of controlling variables, and the optimal structural parameters of the nodes are also studied. The results show that, within the proximity of the back bearing plate, the thickness of the back bearing plate affects stress distribution in the joint. The increased stiffness of the welding studs makes the range of shear force along the bridge direction of the top and bottom welding studs larger, and the longitudinal distribution of welding stud shear force is more uneven. The concrete structure bears a higher proportion of the internal force in the joint compared to the steel structure. Full article

The embedded shear connector with flanges (ESCF) exhibits excellent shear performance in the steel–concrete composite beam. The ESCF consists of embedded corrugated steel web as the shear connector and shape-matched flanges for construction convenience. However, previous research showed that the steel flange of the ESCF was prone to local buckling when subjected to shear force, resulting in insufficient shear strength of the connector. In this paper, head studs were adopted to reinforce the ESCF at the flange with a large width-to-thickness ratio. Nine stud-reinforced embedded shear connectors with flanges (SR-ESCF) were manufactured to conduct the push-out test to investigate the shear performance of SR-ESCF. The effects of the reinforcing studs, thickness of the web, width-to-thickness ratio of the flange, embedding depth of the web, and diameter of the combined rebar on shear strength of the SR-ESCF were revealed and discussed thoroughly. The push-out test results showed that the head studs significantly improved the initial stiffness and load-bearing capacity of the ESCF, which were increased by 17% and 15%, respectively. Moreover, the head studs prevented local buckling of the steel flange. The shear strength of the specimens was greatly influenced by the embedding depth of the web, the width-to-thickness ratio of the flange as well as the reinforcing studs. However, the diameter of the combined rebar and thickness of the web had negligible effects on the shear capacity of the SR-ESCF. According to the test results, the nonlinear finite element model (FEM) and the shear capacity of SR-ESCF prediction formula were created and verified. Furthermore, the layout of the reinforcing studs welded on the flange of the SR-ESCF was optimized by the validated FEM, which indicated that the shear-bearing capacity of the SR-ESCF could be significantly increased by adding studs on the steel flange near the original studs. This research will be of great significance to the design and implementation of the steel–concrete composite beam bridge with corrugated steel web. Full article

Current formulas to assess the shear capacity of headed steel stud anchors and post-installed (PI) anchors in case of pryout failure (sometimes known as pull-rear failure) have been derived either based on the indirect-tension resistance model or are fully empirical based on push-out test results. In both cases, the predicted pryout capacity is clearly conservative and underestimates the true pryout capacity of anchorages, especially for stiff anchors with low embedment-to-diameter ratios (h_ef/d < 4.5). This paper proposes an empirical and a semi-empirical formula to predict the concrete pryout capacity of headed steel studs and PI anchors. They were derived based on an improved indirect-tension model which accounts for the stud diameter and the stud spacing in a group of anchors. Furthermore, a database of 214 monotonic shear tests from the literature, including own tests (push-off and horizontally shear tests), is reevaluated and compared to the provisions of EN1992-4. The scope of this assessment proposal includes single and group of headed steel studs and PI anchors attached to a stiff steel plate as well as shear connectors in composite structures without metal deck embedded in normal-weight concrete. Full article