Hybrid cable-stayed suspension (HCSS) bridges enjoy broad application prospects due to their excellent stability and economic benefits. The mechanical response of the transition section between the two subsystems of this novel bridge type is a common concern in the design and use stages. This paper took the design scheme of an HCSS bridge with a main span of 1440 m as the research object. A global finite element model (FEM) of the example bridge and local finite element models of the transition section were established, and the mechanical performance of the subsystem and components of the transition section was investigated. Moreover, parametric studies were conducted to investigate the influences of varies structural parameters on the mechanical performance of the transition sections of HCSS bridges. The results show that the mechanical behavior suddenly changes significantly at the transition between the cable-stayed section and the suspension section. Performance mutations in the transition section of a HCSS bridge can be improved by changing structural parameters, such as the transition section length, the number of cross cables, the area of the outermost cables, and the distance between the outermost cables and adjacent cables. The present findings may provide a reference for the better understandings and design of HCSS bridges.

Pre-tensioned concrete T-beams with draped strands have been gradually promoted and used in bridge construction in recent years due to their advantages such as simple structure, efficient force distribution, and few defects. However, the current design codes exhibit conservative provisions for the calculation of the shear capacity of such beams under a small shear span ratio, which may lead to a large design value of beam web thickness. This is primarily due to insufficient experimental data. This paper details a full-scale experimental investigation on the shear failure mechanisms of two 30 m pre-tensioned concrete T-beams with draped strands, under a shear span ratio of 1, at which the shear capacity of the beams represents their upper limit. The specimens were tested to analyze their mechanical behavior, including load-deflection response, crack distribution, stirrup strain, and strand slip. The ultimate shear capacities of the test beams were 7107 kN and 6742 kN. To evaluate the applicability of current design codes, the experimental results were compared with theoretical predictions from five international design codes. The analysis revealed that the AASHTO code provided the highest upper limit of shear capacity for pre-tensioned concrete T-beams with draped strands, whereas the Chinese code (JTG 3362-2018) exhibited a significantly high safety factor of 4.09. These findings provide a basis for the optimized design of pre-tensioned concrete T-beams with draped strands and the determination of the upper limit of shear capacity.

In order to investigate the mechanical behavior of a novel pre-tensioned polygonal prestressed T-beam subject to combined bending, shear, and torsion, this study meticulously designed and fabricated a full-scale specimen with a calculated span of 28.28 m, a beam height of 1.8 m, and a top flange width of 1.75 m. A systematic static loading test was conducted. A multi-source data acquisition methodology was employed throughout the experiment. A variety of embedded and external sensors were strategically arranged, in conjunction with non-contact digital image correlation (VIC-3D) technology, to thoroughly monitor and analyze key mechanical performance indicators, including deformation capacity, strain distribution characteristics, cracking resistance, and crack propagation behavior. This study provides valuable insights into the damage evolution process of novel polygonal pre-tensioned T-beams under complex loading conditions. The experimental results indicate that the loading process of the specimen when subjected to combined bending, shear, and torsion, can be divided into two distinct stages: the elastic stage and the crack development stage. Cracks initially manifested at the junction of the upper flange and web at the extremities of the beam and at the bottom flange of the loaded segment. Subsequently, numerous diagonal and flexural–shear cracks developed within the web, while diagonal cracks also commenced to form on the top surface, exhibiting a propensity to propagate toward the support section. Following the appearance of diagonal cracks in the web concrete, both stirrup strain and concrete strain demonstrated abrupt changes. The peak strain observed within the upper stirrups was markedly greater than that measured in the middle and lower regions. On the front elevation of the web, the principal strain peak was concentrated near the connection line between the loading bottom and the upper support. In contrast, on the back elevation of the web, the principal tensile strain was more pronounced near the connection line between the loading top and the lower support.

In this study, a refined model of the Shanghai Damaogang Bridge’s (hybrid beam type) box deck joints is established. The correctness of the model is verified by construction monitoring. For the front and back bearing plates, the force performance of the joint members under the most unfavorable loads is investigated, and the force transmission mechanism is analyzed. The influence of the bearing plate thickness and the joints’ stiffness on the stress distribution of the joint members, the internal force of the joints, and the force-transfer efficiency is investigated by the method of controlling variables, and the optimal structural parameters of the nodes are also studied. The results show that, within the proximity of the back bearing plate, the thickness of the back bearing plate affects stress distribution in the joint. The increased stiffness of the welding studs makes the range of shear force along the bridge direction of the top and bottom welding studs larger, and the longitudinal distribution of welding stud shear force is more uneven. The concrete structure bears a higher proportion of the internal force in the joint compared to the steel structure.

As a novel prefabricated structural element, the pre-tensioned, prestressed concrete T-beam with polygonal tendons layout demonstrates advantages including reduced prestress loss, streamlined construction procedures, and stable manufacturing quality, showing promising applications in medium-span bridge engineering. This paper conducted a full-scale experiment and numerical simulation research on a 30 m pre-tensioned, prestressed concrete T-beam with polygonal tendons practically used in engineering. The full-scale experiment applied symmetrical four-point bending to create a pure bending region and used embedded strain gauges, surface sensors, and optical 3D motion capture systems to monitor the beam’s internal strain, surface strain distribution, and three-dimensional displacement patterns during loading. The experiment observed that the test beam underwent elastic, crack development, and failure phases. The design’s service-load bending moment induced a deflection of 18.67 mm (below the 47.13 mm limit). Visible cracking initiated under a bending moment of 7916.85 kN·m, which exceeded the theoretical cracking moment of 5928.81 kN·m calculated from the design parameters. Upon yielding of the bottom steel reinforcement, the maximum of the crack width reached 1.00 mm, the deflection in mid-span measured 148.61 mm, and the residual deflection after unloading was 10.68 mm. These results confirmed that the beam satisfied design code requirements for serviceability stiffness and crack control, exhibiting favorable elastic recovery characteristics. Numerical simulations using ABAQUS further verified the structural performance of the T-beam. The finite element model accurately captured the beam’s mechanical response and verified its satisfactory ductility, highlighting the applicability of this beam type in bridge engineering.