Curved steel–concrete composite box beams are widely used in urban overpasses and ramp bridges as they are light in weight, have large spanning ability and high torsional rigidity. One-dimensional models are generally used to analyze bridge performance due to their calculation and numerical efficiencies. An incremental step-by-step method based on the Kelvin rheological model together with a discrete algorithm in finite element space is adopted in this study to analyze the mechanical behavior of curved composite box beams. A model with a beam finite element with 26 degrees of freedom (DOFs) is proposed for curved composite box beams that considers the constrained torsion, distortion, shear lag, biaxial slip at the interface and time-dependent effects. Furthermore, the experimental results of the long-term loading tests of three curved composite box beams are selected to validate the proposed beam element model. Finally, the proposed model is applied to analyze the long-term behavior of a curved composite box beam that is used in real engineering applications.

A beam finite element model considering the slip, shear lag, and time-dependent effects of steel–concrete composite box beams have been proposed in this study. The element is employed to a one-dimensional analytical method that is solved involving an expression of spatial and time-dependent variables. A step-by-step method that does not involve storing the stress and strain histories, which is more accurate than the single-step algebraic method, is employed to solve the time variables. A recursive method was elaborated to determine spatial and time-dependent variables through the above method. The validity of the proposed method in instantaneous analysis is attested by the numerical data of the elaborate finite element model established in a commercial software, ANSYS, and that of the time-dependent analysis is verified by the existing test results on the long-term performance of composite beams. The proposed beam finite element model is applied to predict the time-related behavior of simply supported composite beams after validation. The results show that concrete shrinkage and creep significantly influence the structural responses of the composite box beams. From the initial load on the 28th day to that in the 3rd year, the vertical deflection at the cross-section of the mid-span increased by 47.01%. The interface slip at the end increased by −10.99%. The warping intensity function of the concrete slab and the steel beam at the end caused by shear lag increased by 111.64% and 7.01%, respectively. The maximum compressive stress on the concrete slab and the maximum tensile stress at the steel bottom flange increased by −6.75% and 4.56%, respectively.

In order to ensure driving safety and comfort, it is necessary to figure out the complex interaction between continuous welded rail (CWR) and suspension bridges for high-speed railway. A spatial finite element model for a 1092 m main span suspension bridge was established based on the bridge-track interaction theory. A specific correction method was put forward to keep the rail in a zero-stress state when just laid. Three rail expansion joint (REJ) layout schemes were proposed according to practical engineering experience. Both static and dynamic analysis methods were used to evaluate the feasibility of these schemes. The results show that the REJ should be laid at the position with a distance away from the primary beam end, and the beam with more substantial integral stiffness should be preferentially selected. For the recommended scheme, the REJ expansion reaches more than 380 mm under expansion load. The factors affecting the REJ expansion from major to minor are temperature, earthquake, rail fracture, braking, and bending load. The superposition effect of the above factors is suggested to be considered in the selection of REJ range.

The group studs arrangement is applied to prefabricated composite beams to significantly improve construction speed. However, contact vibration exists in the unconstrained interface area of the high-speed railway composite beam during the operation period, which degrades the connecting performance of the composite beam and adversely affects the overall structure. In this study, finite element simulations of the vibration of concrete slabs and steel beams in the unconstrained interface area were carried out to obtain finite element models with damage. The effects of vibration damage on the degradation of the studs were investigated by push-out and pull-out tests using finite element simulation of the local specimen model. The macroscopic ontological models of the undamaged and previously damaged group studs were obtained. Compared with the specimen without damage, the ultimate bearing capacity of the pushed-out specimen with damage decreased by 24.8%; the ultimate slip decreased by 15%; and the stiffness decreased by 12.8%. The behavior of the pulled-out specimen with damage was almost the same as that of the specimen without damage. On this basis, a finite element model of the train–track–composite beam coupling system was established. The influence of the degradation of the connection on the coupling system with 300 km/h, 330 km/h, and 360 km/h train speeds was analyzed under the conditions of single-train driving and a two-train rendezvous. In the case of single-train travel, compared with the undamaged composite beam, the mid-span vertical displacements of the composite beams with damage increased by 13%, 8.38%, and 6.2% for train speeds of 360 km/h, 330 km/h, and 300 km/h, respectively; the transverse displacements increased by 24.2%, 15%, and 9.2%, respectively. In the case of a two-train rendezvous, the mid-span vertical displacements increased by 8.8%, 13.7%, and 12.8%, respectively; the transverse displacements increased by 26.4%, 53%, and 24.8%, respectively.

The flange joint is an important connection in steel tube structures. In this paper, 11 groups of flange joint tests were conducted to investigate the influences of tube diameter, flange plate thickness, the distance from the bolt to the tube centroid, bolt numbers and material strength on the mechanical behavior. One of two failure modes in tests is that the excessive plastic deformation on the flange plate makes the flange plate lose the bearing capacity; the other is that the steel tube yield makes the joints fail. The results show that the calculating method for flange joint in Chinese design code is so safe that amplifying the calculating results of the code by 1.2 times would be closer to the bearing capacity of specimens. For a flange joint with different tube diameters, thickening the flange plate of thinner tube or thinning the flange plate of another tube are effective to ensure the deformations on both sides of the flange plates are equivalent. The ratio of the bearing capacity of the steel tube to that of flange plate should be greater than 1.7. And the thickness of the flange plate should be thicker than 14mm to reduce the deformation caused by cutting, drilling and welding during manufacturing.

A steel–concrete composite beam bridge fully exploits the mechanical advantages of the concrete structure and steel structure, and has the advantages of a fast construction speed and large stiffness. It is of certain research value to explore the application of this bridge type in the field of railway bridges. However, with the rapid development of domestic high-speed railway construction, the problem of vibration and noise radiation of high-speed railway bridges caused by train loads is becoming more and more serious. A steel–concrete composite beam bridge combines the tensile characteristics of steel and the compressive characteristics of concrete perfectly. At the same time, it also has the characteristics of a steel bridge and concrete bridge in terms of vibration and noise radiation. This feature makes the study of the vibration and noise of the bridge type more complicated. Therefore, in this paper, the characteristics of vibration and noise radiation of a high-speed railway steel–concrete composite box girder bridge are studied in detail from two aspects: the theoretical basis and a numerical simulation. The main results obtained are as follows: Relying on the idea of vehicle–rail–bridge coupling dynamics, a structural dynamics analysis model of a steel–concrete combined girder bridge for a high-speed railroad was established, and numerical program simulation of the vibration of the vehicle–rail–bridge coupling system was carried out based on the parametric design language of ANSYS 18.0 and the language of MATLAB R2021a, and the structural vibration results were analyzed in both the time domain and frequency domain. By using different time-step loading for the vehicle–rail–bridge coupling vibration analysis, the computational efficiency can be effectively improved under the condition of guaranteeing the accuracy of the result analysis within 100 Hz. Based on the power flow equilibrium equation, a statistical energy method of calculating the high-frequency noise radiation is theoretically derived. Based on the theoretical basis of the statistical energy method, the high-frequency noise in the structure is numerically simulated in the VAONE 2021 software, and the average contribution of the concrete roof plate to the three acoustic field points constructed in this paper is as high as 50%, which is of great significance in the study of noise reduction in steel–concrete composite girders.