Steel-concrete Joint Research Articles

Research on the Simplified Calculation Model and Parameter Analysis of Large-Size PBL-Stiffened Steel–Concrete Joints

To investigate the design principles and simplified calculation model of large-size PBL-stiffened steel–concrete joints, this study uses a Y-shaped rigid frame-tied arch composite bridge as an engineering background. Based on deformation coordination theory, a combination of theoretical analysis and numerical simulation was employed to derive a simplified calculation model that accounts for boundary conditions such as the stiffness of steel beam end restraints and the local bearing effect of the bearing plate. Parametric analysis of the steel–concrete joint was conducted. The results indicate that the derived simplified calculation model exhibits good accuracy and is suitable for calculating force transfer in various components of the steel–concrete joint under different boundary conditions. Using the simplified model, the effects of parameters such as steel–concrete joint length, connector stiffness, and structural axial stiffness on the axial force transfer in primary force-bearing components (connectors and bearing plates) were studied. The findings reveal that an excessively long steel–concrete joint does not effectively reduce maximum shear force; variations in connector stiffness primarily affect connectors farther from the bearing plate without changing the shear force distribution. Increasing the axial stiffness of the steel structure within a certain range can improve the maximum shear force in connectors, whereas increasing the axial stiffness of the concrete structure has the opposite effect.

Overview of Research Progress on Innovative Approaches to Steel-concrete Joint Interfaces for Enhanced Performance in Cable-stayed Bridges

Overview of Research Progress on Innovative Approaches to Steel-concrete Joint Interfaces for Enhanced Performance in Cable-stayed Bridges

Study on static performance of the steel-concrete joint in a high-speed railway hybrid girder low tower cable-stayed bridge

The steel-concrete joint (SCJ) of mixed beam bridge plays a key role in connecting concrete box girder and steel box girder, but its complex structure makes its mechanical properties unclear. Compared with traditional mixed beam cable-stayed Bridges, mixed beam low tower cable-stayed Bridges show stronger competitiveness. However, there is still a lack of published literature on the study of SCJ of mixed beam low tower cable-stayed Bridges for high-speed railway. In order to study its mechanical properties, a scale model test with similar ratio of 1:5 was carried out under the background of Yongjiang River mega-bridge. The results show that under the action of 5.0 times maximum axial force and maximum negative bending moment, the components of the test model are still in the elastic state, the vertical deformation of the model is continuous and smooth, and the slip between steel and concrete is small, which indicates that the model has good bearing capacity and safety. At the same time, the force transfer mechanism of steel-hybrid section under axial compression is discussed by finite element analysis(FEA). The numerical results show that the rear bearing plate is the main force transfer member of the SCJ, while the front bearing plate transmits a small proportion of axial force. Improving the strength of concrete has limited effect on the transmission path, but can enhance the overall stiffness. The increase of the thickness of the rear pressure plate and the T-rib with variable section mainly affects the force transfer ratio of the rear bearing plate, but has little effect on other force transfer indexes and the overall stiffness. The increase of the stiffness of the shear connectors significantly affects the force transfer proportion and the force transfer uniformity of the bearing plate, but its increase is far more than the change of the force transfer index, and the influence on the overall stiffness of the joint section can be ignored. The results can provide reference for the subsequent research and design of similar structures.

An analytical method for determining the rational position of joint section in steel-concrete hybrid girder bridges

The steel-concrete hybrid girder bridge is a structural form that integrates steel and concrete members in the longitudinal direction of the bridge. A critical parameter in designing such bridges is determining the position of the steel-concrete joint section within the main span (in other words, the rational length of the steel portion in the main span). Up to now, previous studies on determining the rational position of joint sections in steel-concrete hybrid bridges have primarily focused on analyses of internal forces and support reactions. However, there is still a lack of research on the rational position of joint section with its relationship to the smoothness of the steel-concrete joint. The distinct material discontinuity, abrupt change in stiffness and complex structure at the joint result in angular deformations, potentially inducing vibrations and stress issues within the bridge structure. To reduce angular deformations, this paper proposes the concept of equal rotations at the steel-concrete joint, ensuring that the rotational angles at both ends of the steel-concrete joint in a hybrid girder are equivalent. Based on this concept, a method for selecting the optimal length of the steel portion in steel-concrete hybrid girder bridges is proposed and validated through nine case studies. Furthermore, several methods are provided to improve the smoothness of the joint between the steel and concrete members. Finally, the proposed approach is applied to the preliminary design of steel-concrete hybrid girder bridges, demonstrating its effectiveness and efficiency.

Mechanical behavior of a novel compact steel-UHPC joint for hybrid girder bridges: Experimental and numerical investigation

Ultra-high-performance concrete (UHPC) has recently been applied as an alternative to normal concrete in steel-concrete composite structures. In this paper, a novel compact steel-concrete joint with UHPC grout, which utilizes shear connectors, a bearing plate and a simple I-shaped steel girder, is proposed for long-span railway hybrid girder bridges. To investigate the mechanical behavior and force transfer characteristics of the proposed compact steel-UHPC joint (CSUJ), a model test with reduced scale and push-out tests of its main force transfer components were conducted. The specimens' failure model, load-interface slip, and strain development were compared and discussed in detail. Furthermore, a finite element model of the CSUJ was established to investigate the internal damage evolution and the load transfer path. The test results indicated that the steel-UHPC joint possessed excellent axial stiffness and cracking resistance. The axial stiffness before cracking is 2.6 times that of the steel-concrete joint prototype with C60 concrete grout. Upon loading, the filled-in UHPC of the CSUJ was in elastic compression. In the ultimate limit state, the steel-UHPC joint exhibited great integrity, and the ultimate failure mode of the CSUJ was controlled by the adjacent axially loaded steel beam segment. Results of push-out tests showed that the force transfer component with perfobond leiste (PBL) connectors demonstrated greater ductility than other transfer components. In terms of the force transfer rate and uniformity, the proposed CSUJ provides desired stress distribution and force transfer behavior. The shear connectors, bearing plate, and end face of the I-girder transferred 49%, 35%, and 16% of the total axial force, respectively.

Summary of the Calculation of the Shear Capacity of Perfobond Rib Shear Connectors

The analysis of longitudinal shear resistance based on shear capacity is the basis for assessing the reliability of steel-concrete joint structures. It is of great significance for the longitudinal shear of bridge structures and even for the establishment of a shear-resistant design code for steel-concrete bridge structures based on reliability theory. In this article, a more comprehensive overview of the test methods, the current state of research, and the remaining problems in the field of connectors for perfobond rib shear connectors (PBL) are presented. Firstly, the test methods for PBL connectors are categorized. The applicable characteristics of each test method and their advantages and disadvantages are summarized, and the research progress on the calculation of shear load-capacity in this structure is discussed in detail. Finally, it is concluded that the international research on the shear capacity of PBL connectors is still at a stage where the scope of their adaptation is small. Reasonable and accurate quantification of the sensitivity parameters of the PBL connectors was studied. The normality of the test form and other relevant factors should be taken into account to establish a set of more effective shear capacity calculation methods. This can be used to guide the shear capacity design of the structure more directly.

Fatigue Performance of a Novel Steel–Concrete Joint of a Long-Span High-Speed Railway Hybrid Girder–Cable-Stayed Bridge

Fatigue Performance of a Novel Steel–Concrete Joint of a Long-Span High-Speed Railway Hybrid Girder–Cable-Stayed Bridge

Mechanical properties of an innovative steel–concrete joint for high-speed railway long-span hybrid girder cable-stayed bridges

This study investigates the mechanical properties of an innovative steel–concrete joint (SCJ) in a four-line long-span high-speed railway hybrid girder cable-stayed bridge with a main span of 672 m. Tests were conducted on a partial 3:8 scale model, supported by nonlinear finite element analysis (FEA), and the results of both were used to derive and validate mathematical formulae for bearing plate force transfer. The results revealed an uneven transverse distribution of stress in the SCJ, with a larger stress observed in the edge box. The non-uniformity coefficient λi is defined as the ratio of the absolute maximum stress to the transverse cross-sectional average at a given location, and λi,max of steel and concrete in the SCJ were 1.59 and 1.68, respectively. Drastic stress changes appeared in the bearing plate in the longitudinal direction. The maximum measured slip was relatively small, indicating that the steel and concrete in the SCJ functioned cooperatively. Concrete cracks observed in physical tests were mainly distributed in the edge box of the steel and concrete segments, revealing the superior force performance of the SCJ compared to the steel and concrete segments. The deformations of the SCJ changed elastically with an increasing load and satisfied Chinese standards. The bearing plate transferred approximately 59.92% of the axial force and dominated the force transfer. Formulae for the force transfer of the bearing plate were derived based on the stress characteristics of the innovative SCJ, revealing that, rather than its thickness, the bearing plate mainly relied on welds connecting the top and bottom plates and ribs to transfer force. Parameter analysis of the weld sizes of the bearing plate based on the derived formulae and FEA indicated that a reasonable thickness of the bearing plate is 38–60 mm, based on the matched weld sizes. The SCJ structure, the formulae for bearing plate force transfer, and the optimal bearing plate thickness can serve as valuable references during the initial design phase of SCJs.

Mechanical behaviour of steel-concrete joint in hybrid girder cable-stayed bridge

A steel-concrete joint section test model was constructed based on a mixed-scale ratio of the Lancang River hybrid girder cable-stayed bridge in Jinghong City, Yunnan Province. The internal forces and test loading values during normal operations were determined using finite element analysis. The performance was analysed by determining the mechanical indicators at key positions during the loading process. A finite element model of the test girder section was established to analyse the force transmission mechanism of the studied steel-concrete joint section. The test results showed that the centroid of the section moved upward during force transfer from the concrete to the steel girder. The relative slippage at the steel-concrete interface resulted in local unloading and an uneven distribution of longitudinal stresses in the crosswise direction. In addition, the cooperative bearing of the steel-concrete joint girder was transformed to a single bearing of the concrete girder, leading to a monotonic variation of stresses in the web plate. The simulation results showed that the surface plate force-sharing ratio of the composite bridge was the highest. In addition, the force-sharing ratios under the axial force and bending moment scenarios were 57.65% and 78.91%, respectively, indicating that the investigated steel-concrete joint demonstrated good stiffness transition stability. Furthermore, four force transfer types were identified in the steel-concrete joints. The research outcomes provide a fundamental basis for the rational design of joint components applied in hybrid girder cable-stayed bridges.

Stress Analysis and Structural Optimization of Steel–Concrete Joint of Zhonghua Road Bridge in Liaocheng

Based on Zhonghua Road Bridge in Liaocheng city, a single tower hybrid cable-stayed bridge, the stress of the steelconcrete joint of the girder is studied using the finite element method with the software MIDAS and ANSYS. The beam element model of the whole bridge is established in MIDAS CIVIL, from which the internal forces of the critical sections of the steel–concrete joint under six adverse conditions are obtained. Then, the results are applied in the refined solid-shell finite element model established in ANSYS. With the stress analysis, it is found that when the steel–concrete joint is used in the girder of the single tower cable-stayed bridge, both the compressive strength of concrete and the tensile strength of steel can be fully used, and the structural stiffness can be smoothly transferred through the two different materials in the joint, which makes the structural behavior more reasonable. The detailed stress analysis also shows that it is prone to generate considerable stress concentration at the corners and the connection between the steel lattice chamber and the pressure bearing plate, and the concentration can be avoided by local stiffening and smoothing of the chamfers. The sensitivity analysis of the web thickness in the joints and bearing plates showed that increasing the thickness of the intermediate web would lead to a moderate reduction in the stress of the web itself, while the stress in the steel member remained relatively constant. However, when the thickness of the bearing plate is increased from 60 to 80 mm, the stress of each part of the steel plate in the steel grid will be significantly reduced, and the maximum reduction can reach 48%. The improvement of concrete strength has little effect on the stress of the steel cell, and the C50 concrete strength grade used in the design is more reasonable.

Simplified Calculation Model and Experimental Validation of the Force Transfer Ratio of Steel-Concrete Joint of Hybrid Box Girder.

The axial force transfer ratio of steel-concrete joints in hybrid box girder bridges is crucial for bridge design. However, the current standard oversimplifies the transfer ratio distribution coefficients, and both model tests and finite element analysis are time- and labor-intensive. This article proposes a simplified calculation model based on the deformation coordination theory to estimate the transfer ratio of the axial force between the bearing plate and shear connectors of the steel-concrete joint under compression bending conditions. Additionally, a large-scale model (1/5 scale) is established, and the mechanical properties of the steel-concrete joint section under compression-bending conditions are experimentally tested. A three-dimensional finite element model is developed and verified using the obtained test data. Results confirm the favorable mechanical properties and ample safety reserve of the SCJ, with all components remaining within the elastic stage under 1.6 times design conditions. By comparing the axial force transfer ratios obtained from the simplified calculation model and the finite element model, a small difference is observed, validating the reliability of the simplified calculation model. This paper provides a straightforward and efficient method for the design and evaluation of steel-concrete joints in hybrid box girder bridges.

Experimental and numerical investigations on force transfer mechanism of steel-concrete joint in hybrid girder bridges

Steel-concrete joint is the core force transfer node of hybrid girder bridges. However, the load transfer mechanism of steel–concrete joint has not been understood enough, due to the material discontinuity, abrupt change of stiffness, and complex structure. In this paper, the model test of a typical steel–concrete joint in hybrid girder bridges and the push-out tests of its main force transfer components were carried out. The load-slip curve, stress distribution, and failure mode of the specimens were compared and discussed. The test results show that the steel–concrete joint possesses favorable axial stiffness and bearing capacity. The ultimate failure mode of the joint was reached when the steel beam segment adjacent to the steel–concrete joint buckled. However, the steel–concrete joint was still comparatively intact and in the elastic state during the loading process. In addition, the internal force transfer mechanism and characteristics of the steel–concrete joint were analyzed by finite element method. In terms of the force transfer rate, the bearing plate, perfobond leiste (PBL) connectors, and end face of the T-shaped steel girder transferred 72.9 %, 7.9 %, and 19.2 % of the total axial force, respectively. The redundancy analysis shows that the bearing capacity redundancy of the joint is 1.52. The joint has sufficient bearing capacity redundancy, but the ultimate bearing capacity of the joint as well as its adjacent areas is determined by the axially loaded steel beam segment.

Modeling and Testing of a Composite Steel-Concrete Joint for Hybrid Girder Bridges.

A hybrid girder bridge adopts a steel segment at the mid-span of the main span of a continuous concrete girder bridge. The critical point of the hybrid solution is the transition zone, connecting the steel and concrete segments of the beam. Although many girder tests revealing the structural behavior of hybrid girders have been conducted by previous studies, few specimens took the full section of a steel-concrete joint due to the large size of prototype hybrid bridges. In this study, a static load test on a composite segment to bridge the joint between the concrete and steel parts of a hybrid bridge with full section was conducted. A finite element model replicating the tested specimen results was established through Abaqus, while parametric studies were also conducted. The test and numerical results revealed that the concrete filling in the composite solution prevented the steel flange from extensive buckling, which significantly improved the load-carrying capacity of the steel-concrete joint. Meanwhile, strengthening the interaction between the steel and concrete helps to prevent the interlayer slip and simultaneously contributes to a higher flexural stiffness. These results are an important basis for establishing a rational design scheme for the steel-concrete joint of hybrid girder bridges.

Mechanical Behavior of Steel–Concrete Joint in a Bidirectional Curved Pylon of a Long-Span Cable-Stayed Bridge

The complex mechanical behavior of a steel–concrete joint (SCJ) in a bidirectional curved pylon of a cable-stayed bridge is investigated using finite-element analysis (FEA) and a 1:4 scaled full-section model test. Formulas for the stress distribution and stress nonuniformity coefficients of the concrete in the SCJ are proposed to evaluate the force transmission characteristic of the SCJ. The FEA results indicate that variations in the section stiffness at both the bearing plate and the end of the steel structure result in abrupt stress changes and distinct spatial force characteristics of the SCJ. The experimental results reveal that the SCJ exhibits better force resistance than the concrete and steel transition segments, and the force transfer is dominant through the bearing plate. The proposed formulas are validated by using the measured results, which reveal significant nonuniformity in the stress distribution. The stiffness variation at the bearing plate, nonuniform concrete stress distribution, and spatial force characteristics should be considered during the design of similar SCJs in spatial pylons.

Evaluation of structural performance of steel-concrete joints in Hybrid Girder Bridges

The steel-concrete joint, serving as a transition zone between the steel and concrete girders, is the key component for transferring force among the hybrid girder systems. Despite the expected smooth transition of stiffness, high strength, easy fabrication, and verified static resistance, the structural performance of the steel-concrete joint under service loadings in a long-term period remains unclear. In this study, a FE model of a 1/2 steel-concrete joint from a real bridge is established to explore the long-term performance of the structure. Numerical results show that the minimal relative slip between the concrete infill and steel girder indicated the reliable capability of the steel-concrete joint, and the maximum concrete and steel stresses are 8.8 MPa and 192.8 MPa, respectively, which are far less than the material’s ultimate strength. The outcomes of this study can serve as a reference for analyzing the long-term performance of steel-concrete joints in hybrid girder bridges.

Experimental and Numerical Parametric Study of the Mechanical Properties in a Steel–Concrete Joint Section

Experimental and Numerical Parametric Study of the Mechanical Properties in a Steel–Concrete Joint Section

Mechanical behavior of a novel steel-concrete joint for long-span arch bridges – Application to Yachi River Bridge

Steel-concrete joint is often used to connect steel and concrete structures in bridge engineering. In this paper, a novel steel-concrete joint, consisting of shear connectors, steel skeleton with outsourcing concrete and solid concrete diaphragm, is proposed for long-span high-speed railway arch bridges. The joint has the advantage of convenient construction and the concrete diaphragm at joint can ensure the smooth stress transmission of the arch. The mechanical behavior of the steel-concrete joint is investigated by conducting a down-scale model test with a scale of 1/5 under four loading cases. The stress distributions and crack patterns of the experimental specimen model are listed and analyzed. Then based on the experimental results, a nonlinear finite element model of the steel-concrete joint is established. Utilizing the local stress analysis of the model, the stress concentration near the concrete corner could be decreased by reducing the inclination size of corner. The results indicate that the proposed steel-concrete joint shows great mechanic properties, as well as reasonable force transfer behavior without damage during loading. The test and analysis of the joint are expected to develop the design of steel-concrete joints in arch bridges with complex structural composition.

The mechanical behavior of a long-span steel-box girder during the hoisting process

A steel-concrete hybrid continuous rigid frame bridge was used for the Jiahua bridge. The span layout is 138 m + 252 m + 110 m. The steel box-girder, 90 m in length, was arranged in the middle of the mid-span. During the construction process of this bridge, the adopted method for the large steel box girder section is the whole lifting process, which is not common for this type of bridge. This study investigates the mechanical behavior of the steel-concrete joint through finite element analysis, aiming to understand the stress distributions of the long-span steel box girder in several integral hoisting conditions, which can be a reference to the construction of similar steel box bridges. The results show that the bottom plate stress of the mid-span section has a linear relationship with the lifting acceleration; the top plate stress of the mid-span section has a cubic nonlinear relationship with the lifting acceleration.

Analysis of mechanical properties of steel-concrete joint of large-span hybrid beam bridge

The mechanical properties of the steel-concrete joint determine the mechanical properties of the whole bridge. The mechanical properties of the steel-concrete joint of Jianhua railway rigid-frame bridge are analyzed by using nonlinear finite element method. The results show that the overall stiffness transition of the joint is smooth, the maximum stress of concrete section and steel box girder section are lower than the design value of the strength, which indicates that the structural stiffness and strength of the steel-concrete joint section meets the requirements. The error range of the finite element analysis results and the measured data is within 6 %, which shows that the finite element method can simulate the actual stress state of the bridge and it could save a lot of time and energy compared to the actual test.

Mechanical behavior of a novel steel–concrete joint in concrete-composited hybrid continuous bridges

The steel–concrete joint is of great importance to the hybrid girder, while its mechanical behavior has not been understood enough due to the diversity of structural forms and application areas. This paper presented a mechanical performance investigation on a novel steel–concrete joint applied in a hybrid continuous bridge. A static flexural test and numerical simulation were conducted on a 16.6-m-long full-scale segmental joint. Parametric analysis via finite element models with the material damage plasticity on the joint performance was also carried out, in which structural dimensions and pre-stress extent were analyzed. The test results revealed that the border between the concrete girder and steel–concrete joint was the most cracking-prone position, while the joint remained comparatively intact at the ultimate state. The structural safety and internal force transfer mechanism were discussed with the presented strain distributions and deflection along the test girder. The simulation results showed that the effect of joint length on the bending performance of hybrid girder was more significant than back bearing plate thickness and pre-stress extent. The calculated ultimate capacity and bending stiffness increased by 8.3% and 4.0%, respectively, as the joint length increased from 3.6 m to 4.4 m. In addition, the initial cracking mode of the hybrid girder was exhibited to be correlated with the joint length because of changing structural stiffness. The research outcomes could provide the fundamental basis for a rational design of the joint component applied in hybrid continuous bridges.