Search Results (104)

This study investigates the cyclic behaviour of demountable steel–concrete composite extended end-plate reduced web section (RWS) connections for the first time, aiming to facilitate post-seismic beam replacement. A validated high-fidelity finite element (FE) model was developed to analyse 285 FE models, evaluating response characteristics based on the Ibarra–Medina–Krawinkler model. Key parameters, including the influence of composite action over the web opening, web opening diameter, and end-distance, were considered. Findings indicate that RWS connections with medium to large web openings experience cyclic strength degradation while remaining compliant with American and European seismic standards. Additionally, bolted shear studs yielded a more stable and predictable contribution to the connection’s strength up to 5%, outperforming traditional welded studs in consistency. This research emphasises the importance of aligning web opening size and location with capacity design ratios between connection components for acceptable seismic performance, proposing specific web opening sizes and locations to enhance structural resilience. Full article

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

Diaphragm walls are widely used for deep foundation pit support and permanent underground structures. The joints between adjacent panels are critical weak points, significantly influencing the overall deformation and stress distribution of the structure. To address the insufficient shear and tensile capacity of existing diaphragm wall joints, this study proposes a novel rigid joint incorporating retractable shear studs. The joint features a straightforward and constructible design, primarily comprising retractable shear studs, H-section steel, and shear stud pop-out limit plates. By withdrawing the limit plates inserted into the H-section steel, the retractable shear studs mounted on the web automatically extend along their axis, penetrating into the adjacent reinforcement cage to form an intrusive lap joint. This mechanism effectively enhances the integrity and load-bearing capacity at the joint. To validate its mechanical performance, large-scale specimens featuring this new joint were fabricated and subjected to shear and tensile tests. The experimental results demonstrate that, compared to traditional H-section steel joints, the peak shear and tensile strengths of the proposed joint are increased by approximately 10 times and 16 times, respectively. These findings fully verify the excellent mechanical performance of the novel diaphragm wall joint structure. 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

Lightweight steel-framing (LSF) systems have become increasingly prominent in modern construction due to their structural efficiency, design flexibility, and sustainability. However, traditional facade materials such as stone are often cost-prohibitive, and brick veneers—despite their popularity—pose seismic performance concerns. This study introduces an innovative porcelain sheathing system for cold-formed steel (CFS) shear walls. Porcelain has no veins thus it offers integrated and reliable strength unlike granite. Four full-scale CFS shear walls incorporating screwed porcelain sheathing (SPS) were tested under combined cyclic lateral and constant gravity loading. The experimental program investigated key seismic characteristics, including lateral stiffness and strength, deformation capacity, failure modes, and energy dissipation, to calculate the system response modification factor (R). The test results showed that configurations with horizontal sheathing, double mid-studs, and three blocking rows improved performance, achieving up to 21.1 kN lateral resistance and 2.5% drift capacity. The average R-factor was 4.2, which exceeds the current design code values (AISI S213: R = 3; AS/NZS 4600: R = 2), suggesting the enhanced seismic resilience of the SPS-CFS system. This study also proposes design improvements to reduce the risk of brittle failure and enhance inelastic behavior. In addition, the results inform discussions on permissible building heights and contribute to the advancement of CFS design codes for seismic regions. 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 address the challenges of slow construction and high self-weight in steel–concrete composite floors for rural light steel frame structures in China, a new prefabricated floor system was developed. This system features prefabricated slabs made from recycled concrete, connected via reinforced shear pocket joints. In seismic environments, assembly floor joints often become vulnerable points, making their shear resistance particularly crucial. This study investigated the shear performance of this new type of floor joint, examining the effects of various parameters such as joint configuration, stud diameter, recycled concrete strength, and grout strength. A refined finite element model was established for an in-depth parameter analysis. The research revealed stud–shear failure as the mode of floor joint failure under different design parameters. The detailed design of the new joint structure ensures safety in the floor joint area. Increasing stud diameter, recycled concrete strength, and grout strength all contributed to enhancing the joint’s shear capacity and stiffness, with stud diameter having the most significant impact. Higher recycled concrete strength improved shear capacity, although its influence decreased beyond a certain threshold. Optimal reserved hole diameter proved beneficial for enhancing joint shear performance, with a diameter of 40 mm showing superior performance. 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