Hybrid Girder Research Articles

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.

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

Strategic use of ultra-high-performance concrete and carbon fiber reinforced polymer reinforcement for end zone design of prestressed girders

The design of end zones to prevent severe cracking is a key requirement toward durable prestressed girders. Traditional approaches employ large amounts of steel reinforcement to attain this requirement, which may result in steel congestion. This paper investigates a hybrid girder concept that uses Ultra-High-Performance Concrete (UHPC) and Carbon Fiber Reinforced Polymer (CFRP) bars to enhance crack control and long-term durability in the end zones of prestressed girders. The objectives of this study are to quantify the UHPC zone lengths needed to restrain end zone cracks, eliminate or reduce the required amount of steel reinforcement, and investigate its replacement with CFRP bars. A finite element modeling (FEM) approach was developed for this purpose and its fidelity was validated with experimental data. The FEM results showed that UHPC zones with lengths below or equal to half of the girder depth can significantly reduce end zone cracking. CFRP bars can be added in the UHPC zones as a conservative measure to crack control, to ensure the long-term corrosion resistance of the girders.

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.

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.

Analysis of Vertical Temperature Gradients and Their Effects on Hybrid Girder Cable-Stayed Bridges

The real temperature distribution within 24 h of the main beam in a single-tower hybrid beam cable-stayed bridge is analysed according to its actual section and material parameters, as well as other factors of local atmospheric temperature, geographical environment, and solar intensity. The results show that the internal temperature distribution in the steel–concrete composite beam is uneven, and the temperature of the steel is higher than that at the surface of the concrete slab. Then, a finite element model of the whole bridge is established using the thermal–mechanical sequential coupling function in ABAQUS to acquire the structural response under the action of a 24-h temperature field. The results show that the vertical temperature gradients have a great influence on the longitudinal stress in the lower flange of the steel I-beam, with a maximum compressive stress of 11.9 MPa in the daytime and a maximum tensile stress of 13.36 MPa at midnight. The temperature rise leads to a downward deflection of the main span, and the maximum deflection occurs at the 1/4 main span. There was an obvious temperature gradient in the concrete slab, with a difference between the maximum and minimum value of 14 °C. Similarly, the longitudinal compressive stress of the concrete slab increases with increasing temperature in the daytime, but the peak time is obviously inconsistent with that of the steel beam.

A construction process for hoisting, precise positioning and temporary fixation of a steel-concrete composite segment on a long-span steel-concrete hybrid girder

A construction process for hoisting, precise positioning and temporary fixation of a steel-concrete composite segment on a long-span steel-concrete hybrid girder

An Explicit Approach for Determining the Rational Length of Steel Portion in Steel–Concrete Hybrid Girder Bridges

The steel–concrete hybrid girder bridge structure is a combination of steel and concrete members in the direction of the bridge length. In long-span segmental concrete box girder bridges, the utilization of lightweight steel girders in the middle portion of the main span would greatly reduce the bridge self-weight while decreasing concrete creep and shrinkage effects. A critical parameter in the design of hybrid girder bridges is the rational length of the steel portion as a part of the main span (in other words, the rational location of the steel–concrete connection). Based on the concept of system equivalence, the steel–concrete hybrid system is equivalent to a full-concrete system with a reasonable span arrangement. The governing condition of the equivalence is that both systems have the same magnitude of self-weight hogging bending moments over the piers. Applying the system equivalence method, the rational length ratio of the steel portion to the main span (ξ) is explicitly solved, and its relationship with the length ratio of side span to main span (λ) is established. Finally, the proposed analytical approach is validated by five case studies, indicating that it is an effective and efficient method for the preliminary design of hybrid girder bridges.

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.

Research review on steel–concrete composite joint of railway hybrid girder cable-stayed bridges

PurposeThis study aims to research the development trend, research status, research results and existing problems of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.Design/methodology/approachBased on the investigation and analysis of the development history, structure form, structural parameters, stress characteristics, shear connector stress state, force transmission mechanism, and fatigue performance, aiming at the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge, the development trend, research status, research results and existing problems are expounded.FindingsThe shear-compression composite joint has become the main form in practice, featuring shortened length and simplified structure. The length of composite joints between 1.5 and 3.0 m has no significant effect on the stress and force transmission laws of the main girder. The reasonable thickness of the bearing plate is 40–70 mm. The calculation theory and simplified calculation formula of the overall bearing capacity, the nonuniformity and distribution laws of the shear connector, the force transferring ratio of steel and concrete components, the fatigue failure mechanism and structural parameters effects are the focus of the research study.Originality/valueThis study puts forward some suggestions and prospects for the structural design and theoretical research of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.

Improved Metaheuristic Algorithm Based Finite Element Model Updating of a Hybrid Girder Cable-Stayed Railway Bridge

This study proposes a generally applicable improvement strategy for metaheuristic algorithms, improving the algorithm’s accuracy and local convergence in finite element (FE) model updating. Based on the idea of “survival of the fittest” in biological evolution, the improvement strategy introduces random crossover and mutation operators into metaheuristic algorithms to improve the accuracy and stability of the solution. The effectiveness of the improvement strategy with three typical metaheuristic algorithms was comprehensively tested by benchmark functions and numerical simulations of a space truss structure. Meanwhile, the initial FE model of a railway hybrid girder cable-stayed bridge was updated to examine the effect of the improved metaheuristic algorithm within the FE model, updating for complex engineering structures. The results show that the accuracy and stability of the improved metaheuristic algorithm were improved by this process. After the initial FE model of the hybrid girder cable-stayed bridge was updated, the calculated frequencies and displacements were closer to the measured values, better representing the actual structure, and showing that this process can be used for baseline FE models of bridges.

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.

Investigation on structural performance of perfobond strip connector group in steel-concrete joints

The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete joints of hybrid girder bridges has gained wide popularity among bridge engineers. For a PBL group with multi-row PBLs in tandem arrays, comprehensive interactions exist among the connectors. However, the current design approaches assume that the force transferred by each row of PBL is uniform, resulting in an overestimated shear resistance of the connector group. The main objective of this paper is to introduce a mathematical approach, which accounts for the bonding-friction effects (BF) at the perforated steel plate/concrete slab interfaces and the reinforced concrete dowel (RD) effects by the perfobond hole, to assess the ultimate resistance of PBL group under the RD fracture failure mode. In this study, six push-out specimens for different PBL groups, with varying connectors’ quantity, were evaluated experimentally to determine the key parameters for the proposed analytical model. The experimental results revealed the significant reduction in average resistance of single PBL in a connector group as connector number increased. The proposed approach is validated by an experimental database that includes push-out test results obtained from the previously published studies and afterwards converted to the design load level, which can be extensively applied to the PBL group using normal concrete and ultra-high performance concrete (UHPC). The proposed analytical approach provides an efficient tool for analyzing and designing of PBL group in steel–concrete joints of hybrid girder bridges.

Research on the Train-Bridge Coupled Vibration and Dynamic Performance of Steel Box Hybrid Girder Cable-Stayed Railway Bridge

Research on the Train-Bridge Coupled Vibration and Dynamic Performance of Steel Box Hybrid Girder Cable-Stayed Railway Bridge

某独塔混合梁斜拉桥施工分析

某独塔混合梁斜拉桥施工分析

Experimental study on time-dependent deformation of hybrid steel–PRC girder with headed stud shear connections under sustained loading

In a hybrid girder, the connections at the steel–prestressed reinforced concrete (steel–PRC) junction must be designed to resist steel–concrete interfacial tensile and shear forces. Headed stud shear connections are most commonly and widely used for such an application. In Japan, the Japan Road Association specifies a stud capacity that is 0.12, 0.13, and 0.22 times those of the American Institute of Steel Construction, Japan Society of Civil Engineers, and EURO code specifications, respectively. Hence, in Japan, the existing design method uses less than 50% of the actual nominal shear capacity of connectors. Owing to a low design shear force, the influence of sustained loads has not yet been considered nor studied comprehensively. Moreover, in a hybrid girder, the prediction of the time-dependent deformation behaviour under sustained loading is crucial for ensuring serviceability; however, few studies have focused on this subject. Five scaled-down hybrid steel–PRC girder specimens of a real bridge with headed stud connections were tested under sustained and static loads. The time-dependent deformation behaviour was sensitive to the exposure time, previous loading history, prestress level, concrete strength, and creep and shrinkage phenomena. The results of this study provide an important basis and reference data for designing such girders while considering their long-term response with time effects.