Search Results (71)

The application of steel–concrete composite structures in the pylons of long-span cable-stayed bridges can effectively address the issue of insufficient structural stiffness. Shear connectors are critical load-transfer components in steel–concrete composite segments, where they are typically arranged to ensure coordinated force transmission between steel and concrete. The stud–PBL composite shear connector, as a novel type of connector, has been implemented in engineering practice. However, the collaborative load-bearing performance between studs and PBL connectors remains unclear. Most shear connectors operate within the elastic stage during service, making their elastic stiffness a key evaluation metric. Based on the Winkler elastic foundation beam theory, plane strain theory, and the spring series–parallel model, this study derives the elastic stiffness calculation formulas for stud shear connectors and PBL shear connectors, respectively. The primary focus of this study was the single-layer stud–PBL composite shear connector within the steel–concrete composite section of bridge pylons. Embedded push-out tests were designed and conducted, comprising three main categories and eight subcategories. The load–slip curves for the three types of shear connectors were generated, and the stiffness calculation formula for the stud–PBL composite shear connector was verified through finite element analysis. The comparative push-out tests and finite element simulations demonstrate that the theoretical formula proposed in this study can effectively analyze the elastic stiffness of three types of shear connectors. The elastic stiffness of composite shear connectors can be regarded as the superposition of the elastic stiffness of studs and PBL shear connectors. Compared with single shear connectors, composite shear connectors exhibit superior elastic stiffness and shear resistance, meeting the application requirements of steel–concrete composite bridge pylons. The research findings provide a theoretical basis for the optimal design of shear connectors in large-span cable-stayed bridge composite pylons. Furthermore, the established formula has broad applicability. Full article

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

To investigate the flexural behavior of steel–concrete composite bridge decks with stud–perfobond leist (PBL) shear connectors, two specimens were designed with the stud spacing as the main variable, and static bending tests were conducted. Additionally, refined finite element models were constructed for evaluating the influence of shear connector types, concrete strength, stud diameter, stud height, and PBL hole diameter on the performance and flexural capacity of the structure. The results show that, under bending loads, the failure of the composite bridge deck is mainly concrete crushing and steel plate yielding. When the spacing of the stud decreases, both the flexural behavior of the composite bridge decks and the shear resistance at the steel–concrete interface are enhanced. The steel–concrete composite bridge decks with stud–PBL shear connectors showed higher overall flexural stiffness and flexural capacity than the steel–concrete composite bridge decks with single-type shear connectors. Concrete strength had a pronounced influence on the flexural capacity of the deck system, while the effects of stud diameter and height were minor. As the PBL hole diameter increased, the flexural capacity of the specimens exhibited a decreasing tendency. Full article

This study adopts the east approach bridge of the Section II extra-long-span bridge on the Urumqi Ring Expressway (West Line) as an engineering prototype. A three-dimensional nonlinear finite element push-out model of headed stud connectors was developed in ABAQUS/Explicit and validated against existing test data. On this basis, parametric analyses were carried out to investigate the effects of material and geometric parameters on the shear performance of the studs. The results indicate that the load–slip response can be divided into four stages: elastic, plastic-damage development, plateau, and softening. Compared with C50 concrete, UHPC markedly increases the initial stiffness of the connectors and raises the peak shear resistance by approximately 30–40%. For the smallest stud diameter, the ductility decreases by up to about 10% and the post-peak degradation becomes more rapid, i.e., ductility deterioration is more pronounced; this unfavorable effect is particularly significant when small stud diameter is combined with shallow embedment depth. Increasing the stud diameter enhances both stiffness and peak shear resistance, whereas increasing the embedment depth delays post-peak degradation, improves residual capacity and energy dissipation, and promotes a transition in failure mode from concrete-governed failure to ductile bending–shear failure of the stud. Based on these parametric results, a larger stud height-to-diameter ratio is recommended for UHPC composite structures to achieve coordinated optimization of connection stiffness, load-carrying capacity, and ductility performance. Full article

The growing adoption of steel–concrete composite beams has spurred extensive use of high-strength steel (HSS) and high-performance concrete (HPC) in composite structures, capitalizing on their superior mechanical properties. To address the limited shear capacity of conventional stud connectors and unitary steel dowels, this study proposed a dowel–stud hybrid connector for advanced composite systems. Push-out tests were conducted on one conventional shear stud specimen, one monolithic steel dowel specimen, and four dowel–stud hybrid connector specimens. Experimental and finite element analyses were employed to evaluate the effects of the stud length, diameter, and layout on the failure modes and shear performance of composite connectors. The findings demonstrated that the hybrid connectors exhibited significantly enhanced shear capacity and ductility compared to those of both conventional stud connectors and monolithic steel dowels. Failure primarily occurred at the roots of the steel dowels and shear studs, with the underlying concrete exhibiting crushing failure. Increasing the diameter from 6 mm to 22 mm marginally influenced the ultimate shear capacity (the variation was <4%) but notably improved the initial stiffness. For composite connectors with 13 mm diameter studs, increasing the stud length from 40 mm to 80 mm and 120 mm raised the ultimate capacity by 4.7% and 8.8%, respectively. Conversely, for composite connectors with 16 mm diameter studs, length variations exerted negligible influence (<4%) on the ultimate capacity. In addition, the study layout critically influenced the performance. At a fixed 16 mm diameter, relocating studs from the dowel center to the sub-root region increased the shear capacity by 23%. Full article

Under the combined action of bidirectional (longitudinal and transverse) shear loads and corrosive environments, the shear performance of stud connectors in steel–concrete composite track beams of straddle-type monorail transit systems is susceptible to degradation, thereby posing a potential risk to the structural safety of the track girders. This study employs push-out tests and numerical simulations to investigate the influence of bidirectional shear loads and stud corrosion on the shear performance of stud connectors. The results showed that both transverse shear loads and stud corrosion lead to a reduction in the shear capacity of stud connectors, with their coupling effect amplifying the degradation. Transverse shear loads induce an accelerated decay trend in the load-bearing capacity of stud connectors, while an increase in corrosion depth results in a linear degradation of the load-bearing capacity. The corrosion depth at the stud root exerts a more pronounced influence on shear performance compared to the corrosion height. Furthermore, the dominant failure mode of stud connectors manifests as root fracture, while transverse shear loads induce alterations in the concrete damage zone. Based on the verified FE model, a shear capacity reduction factor accounting for the coupling effects of bidirectional shear and stud corrosion was established to improve the Oehlers model. This research provides critical theoretical support for the safe design and durability assessment of monorail track girders. 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

In order to assess the workability of shearing connectors of steel–concrete composite beams (SCCBs), this manuscript proposed a novel solid-slipping nonlinear finite element (FE) model, which is independent of stiffness-slip function for simply supported SCCBs. The modal curvature difference and the modal flexibility difference curvature were prompted, which are able to evaluate both sole-damage and multi-damage. It was concluded that the proposed indicators can locate the damaged shear studs and quantify the damage degree correctly, having a maximum error of less than 1%. Robust analysis proved that the proposed indicators are still highly precise when the noise level is up to 8%, which is highly significant for further practical application. Full article

Current research on the stress mechanisms of composite connectors within steel–concrete structures of bridge towers is sparse, and there is a lack of established experimental methods and finite element modeling techniques for studying these mechanisms. This study focuses on a specific type of composite shear connector within the steel–concrete section of the Shunde Bridge tower. By employing proposed experimental methods and finite element model analysis, this research examines the load–slip curves and stress distribution of these shear connectors. It aims to elucidate the stress mechanisms and mechanical relationships between the composite connectors and the individual perforated plate connectors and shear stud connectors that comprise them. The results demonstrate that the proposed experimental methods and finite element modeling approaches effectively analyze the stress mechanisms of composite connectors, revealing that the ultimate load-bearing capacity and elastic stiffness of the composite connectors are approximately the sum of those of the individual connectors configured in parallel; The mechanical performance of the composite connectors in the steel–concrete section of the bridge tower is approximately the additive sum of the mechanical performances of the individual connectors comprising them. By comparing the experimentally measured load–slip curves with those calculated from the finite element models, it validates the modeling approach of the finite element model, and the material parameters established through material characteristic tests and literature review are reasonable. Full article

To investigate the mechanical behavior and damage mechanism of notch–stud connectors in timber–concrete composites under fatigue loading, fifteen push-out specimens in five groups were designed with load cycles as the key variable. Fatigue failure modes and mechanisms were analyzed to examine fatigue life, stiffness degradation, and cumulative damage laws of connectors. Numerical simulations with up to 100 load cycles explored timber/concrete damage effects on stud fatigue performance. Based on the results, an S-N curve was established, a fatigue damage model developed, and a fatigue design method proposed for such connectors. Primary failure modes were stud fracture and local concrete crushing in notches. Stiffness degradation followed an inverted “S”-shaped “fast–slow–fast” pattern. Using residual slip as the damage variable, a two-stage fatigue damage evolution model was constructed from the damage–cycle ratio relationship, offering a new method for shear connector fatigue damage calculation in timber–concrete composites and enabling remaining life prediction for similar composite beam connectors. Finite element simulations of push-out specimens showed high consistency between calculated and experimental fatigue life/damage results, validating the conclusions. Full article

This study investigates interface sliding behavior in composite I-steel–concrete beams reinforced with a composite material plate by analyzing various connection configurations combining shear stud connectors and adhesive bonding. The degree of composite action, governed by the shear stiffness at the steel–concrete interface, plays a critical role in structural performance. An analytical model was developed based on the elasticity theory and the strain compatibility approach, assuming constant shear and normal stress across the interface. Five connection modes were considered, ranging from fully mechanical (100% shear studs) to fully adhesive (100% bonding), as well as mixed configurations. The model was validated against finite element simulations, demonstrating strong agreement with relative differences between 0.3% and 10.7% across all cases. A parametric study explored the influence of key factors such as interface layer stiffness and composite plate reinforcement material on the overall interface behavior. The results showed that adhesive bonding significantly reduces slippage at the steel–concrete interface, enhancing bond integrity, while purely mechanical connections tend to increase interface slippage. The findings provide valuable guidance for designing hybrid connection systems in composite structures to optimize performance, durability, and construction efficiency. Full article

A steel–concrete composite beam with a straddle monorail is a lightweight and easily installable structure. The mechanical performance of group stud connectors and their arrangement are key design parameters that govern the beam’s overall performance. This study investigates the behavior of group stud connectors by conducting push-out tests on four specimens, comprising three full-scale models and one 1:3 scaled model. Variables such as the number of connectors, arrangement, and specimen size were explored. The results indicated that all the specimens exhibited ductile failure due to stud shearing. The strain distribution analysis revealed higher strain at the edges and lower in the middle, persisting as the load increased. The group stud effect resulted in a 23.4% to 27.2% reduction in shear capacity for the full-scale specimens and 16.5% for the scaled specimen. The reduction was proportional to the density of the studs, but the size effects were less significant. This study provides valuable insights into the mechanical behavior of group stud connectors and offers design recommendations for practical applications. Full article

The behavior of steel–concrete composite structures is significantly influenced by the efficiency of the shear connections that link the two materials. This research examines the performance of stud shear connectors, with an emphasis on analyzing the effect of different geometric design parameters. A computational model was created utilizing Python 3.13 to enable thorough digital monitoring of the influence of these parameters on the structural performance of composite connections. Developed within the ABAQUS framework, the model integrates geometric nonlinearity and the Concrete Damage Plasticity (CDP) approach to achieve detailed simulation of structural behavior. Essential design aspects, including stud diameter, stud height, head dimensions, and spacing in both longitudinal and transverse directions, were analyzed. The Python-based parametric model allows for easy modification of design parameters, ensuring efficiency and minimizing modeling errors. The significance of stud diameter changes was analyzed in accordance with Eurocode standards and previous studies. It was found that stud length has a reduced effect on structural performance, particularly when considering the concrete properties used in bridge construction, where compressive failure of the concrete zone is more critical at lower concrete strengths. Additional factors, such as stud head dimensions, were investigated but were found to have minimal effect on the behavior of steel–concrete composite connections. Longitudinal stud spacing emerged as a critical factor influencing structural performance, with optimal results achieved at a spacing of 13d. Spacings of 2d, 3d, and 4d demonstrated overlapping effects, leading to significant performance reductions, as indicated by comparisons of ultimate load and force–displacement responses. For transverse spacing, closer stud arrangements proved effective in reducing the likelihood of slip at the steel–concrete interface, enhancing composite action, and lowering stress concentrations. Additionally, reducing the transverse distance between studs allowed for the use of more shear connectors, increasing redundancy and enhancing performance, especially with grouped-stud connectors (GSCs). Full article

Recent research indicates that high-strength bolts could be more effectively and efficiently used to connect steel girders and fabricated decks or retrofit existing composite girders than headed studs. To reduce the number of bolt shear connectors and, thus, further accelerate the construction of composite girders, high-strength large bolts could be an excellent alternative, resulting in greater concrete stress below the bolt. Also, hybrid fiber-reinforced concrete (HFRC) has better tensile ductility and strength than that of ordinary concrete (OC). Therefore, this study tried to design eighteen push-out test specimens, including different configurations of bolt shear connectors, to investigate the static properties of post-installed, high-strength, large-bolt shear connectors with fabricated HFRC/OC slabs. The experimental results indicated that the capacity and initial stiffness of a high-strength large through-bolt shear connector was the smallest. The fiber might enhance the capacity and initial stiffness of bolt shear connectors. Increasing the bolt diameter can significantly enhance the initial stiffness and load-bearing capacity, while the clearance of the bolt hole had a great influence on the capacity, initial stiffness, and slippage of the post-installed high-strength large-bolt shear connector. Finally, the capacity equation and slip behavior of post-installed, high-strength, large-bolt shear connector with fabricated HFRC deck were obtained using the regression method, which could provide the reference for their design. 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