Search Results (10)

The bi-cable system enhances the vertical stiffness of the middle pylon, enabling the use of a traditional pylon in multi-pylon suspension bridges. However, research on multi-pylon suspension bridges utilizing a bi-cable system remains in its early stages, with parameter analysis still being limited. The benefits of bi-cable systems in long-span three-tower suspension bridge configurations remain unclear. This paper presents an analysis of three-tower suspension bridges with spans ranging from 1500 to 2500 m, using a simplified calculation method for a bi-cable system and incorporating the elastic deformation of hangers. The effects of the top cable load distribution factor, tower stiffness, sag-to-span ratio, and side-to-main span ratio on static performance are examined, and reasonable value ranges for each parameter are proposed. Full article

Aiming at the problems of main cable geometry calculation and control accuracy in construction for long-span asymmetric suspension bridges, this paper proposes a practical method for main cable geometry calculation of asymmetric suspension bridges based on the Rushankou Bridge. Firstly, a hanger–pylon–girder model was established to obtain the constraint force at the hanger top. Then, with the mid-span sag of the main cable set as the control target, the coordinates and unstressed length of the main cable in the completed bridge state were obtained based on the pylon–cable model. Finally, the final main cable geometry and unstressed length were obtained based on the main cable–hanger–pylon–girder model. The reliability of the method in this paper was validated by engineering monitoring data. Using the simulation model, the influence laws and degrees of parameters including temperature, main cable elastic modulus, main cable weight, hanger force and main girder weight on the main cable geometry were investigated. It is indicated that the method in this paper is capable of accurately calculating the main cable shape of asymmetric suspension bridges. After the installation of cable clamps and hangers, the theoretical and measured deformations of the main cable are in good agreement. The theoretical and measured values at the mid-span L/2 of the main span are −233.9 cm and −234.7 cm, respectively, with a deviation of 8 mm. The largest discrepancy between the calculated and actual deformations of the main cable is located at 7L/8 of the main span, which is merely 2.2 cm. The deformation of the main cable is greatly affected by temperature changes; each 1 °C temperature variation leads to a mid-span deformation of about 2.4 cm in the main cable. If the influence of temperature variation on main cable geometry is ignored during construction, it will cause errors in the main cable elevation after installation. The effect of the main cable elastic modulus on its deformation cannot be neglected, and a 10% variation in the main cable elastic modulus leads to a 58 cm change in the main cable geometry. Full article

This study investigates the influence of key parameters—vehicle speed, weight, loading lane, and pavement roughness—on the Dynamic Amplification Factor (DAF) and ride comfort of a beam–arch composite continuous rigid-frame bridge under vehicle–bridge coupling. A six-span bridge is analyzed using a spatial beam-element model in ANSYS and a typical three-axle vehicle model is adopted to conduct the coupled dynamic response analysis. Based on the modal and structural characteristics of this bridge, key response indices are selected, including vertical displacement and bending moment at midspan, longitudinal displacement and bending moment at pier top, arch crown displacement, and tensile force in the long hanger. Control sections are identified in Span 4 (midspan, arch crown, long hanger) and at the top of Pier 16. The results demonstrate that pavement roughness significantly influences ride comfort, with the root mean square (RMS) value varying up to 107%, whereas the loading lane shows a negligible effect. Vehicle speed effects are divided into two distinct regimes: at 60 km/h and within 70–90 km/h, with dynamic responses in the higher speed range approximately 22% greater. Increasing vehicle weight raises the peak dynamic response by up to 77.68%, but does not lead to a proportional increase in DAF. Transverse loading eccentricity has a more pronounced impact on vertical bridge responses (>20% change) than on longitudinal responses (<10% change). Deterioration in pavement roughness elevates both dynamic response and DAF, with maximum increases reaching 27.97% and 28%, respectively. Full article

To address the challenge of identifying damage in the hangers and bridge deck systems of long-span suspension bridges, this paper proposes a non-contact monitoring method based on video image recognition. This method extracts structural vibration displacement responses through video acquisition and image analysis, and combined with the strain mode change rate index, it achieves damage localization, type identification, and severity assessment. The principle of extracting displacement time-history data from video images is first elaborated, and MATLAB-based computational code is developed, including pixel tracking and time-history curve generation methods. The eigensystem realization algorithm is used to identify displacement mode shapes, which are then converted into strain mode shapes via the central difference method. The strain mode change rate and its deviation rate are proposed as damage indicators: under undamaged conditions, the curve is smooth; at damage locations, peaks appear; the distribution range of peaks can distinguish between hanger damage and bridge deck cracks; the deviation rate quantifies damage severity. The feasibility of the method is validated through finite element simulations and physical model experiments. The results show that hanger damage causes broad peaks, while bridge deck cracks present narrow peaks; the deviation rate increases monotonically with damage severity. Applied to an in-service suspension bridge, the method successfully identified hanger bending and weld cracking, with assessment results consistent with on-site inspections. This study demonstrates that the strain mode change rate analysis based on video images enables damage identification without prior knowledge of the structural health state, relying solely on the damaged state response. Offering advantages such as non-contact measurement, full-field monitoring, and no need for sensor deployment, it provides a new technical approach for the long-term monitoring of suspension bridge hanger systems. Full article

In order to study the impact on the shock effect when a high-speed train passes over a concrete-filled steel tube (CFST) tied-arch bridge, a dynamic load test was carried out in the background of the Qinjiang River Bridge in Qinzhou, Guangxi Province, to test the bridge displacements, accelerations, and dynamic stresses. The bridge finite element model was coupled with a CRH2 train model developed in SIMPACK to perform ANSYS–SIMPACK co-simulation of vehicle–bridge interactions. Model reliability was verified by comparing simulated results with field measurements under matched operating conditions. On this basis, a parametric study was conducted for single-line operation with a mainline spacing of 4.2–5.4 m (0.4 m increments) and train speeds of 80–270 km/h (10 km/h increments), yielding 80 working conditions to evaluate hanger impact responses. The results indicate that the ANSYS–SIMPACK co-simulation provides reliable predictions. Compared with long hangers, short hangers exhibit larger stress impact coefficients. As train speed increases, the hanger impact effect shows a wavelike increasing trend. When the speed approaches 180–200 km/h, the excitation nears the bridge’s dominant natural frequency, and impact effects on bridge components peak, identifying a critical speed range that is more prone to inducing vehicle–bridge resonance; the impact coefficient of the shock effect on both sides of the train is different: the coefficient on the far side of the bridge is about 2 times of that on the near side of the bridge, so when the impact coefficient is regulated, the unevenness of the impact of the shock effect on both sides can be taken into account. Single-line operation can introduce a lateral load bias on the train, and the distance of the train from the center line is positively correlated with the impact size of the shock effect, with the stress impact coefficient of the shock effect on both sides of the bridge and span deflection increasing as the spacing of the main line increases. Full article

To evaluate the true load-bearing capacity and engineering reliability of a large span through a simply supported steel box arch bridge, a load test was conducted on the bridge. The example used in this test is the Jingchu Avenue Bridge located in Jingmen City, Hubei Province. Specifically, the static load test delineated six operational conditions, measuring parameters encompassing strain, hanger cable force, deflection, and potential cracks. The dynamic load test gauged the bridge’s dynamic response and various indicators, including pulse tests, vehicle tests, jump tests, and barrier-free vehicle tests. The findings indicated that the maximum measured strain values during the static load test surpassed the calculated values; nonetheless, the verification factors and relative residual strains adhered to the code requirements, and no cracks were detected. The dynamic load test unveiled that the measured frequency values exceeded the theoretical ones, the damping ratios were within the normal range, and the measured impact coefficients were lower than the values stipulated in the code, all of which were in conformance with the code requirements. The data obtained from this experiment can be utilized to refine the long-term maintenance plan for the bridge, especially as it holds considerable value for structural health monitoring and aging assessment. Full article

In response to the frequent collapse of main girders caused by the breakage of suspenders on half-through and through arch bridges, a test specimen has been designed and fabricated with a through concrete-filled steel tube (CFST) arch bridge as the engineering background. A new electromagnetic disconnect trigger is employed to realize the rapid suspender breakage in the test specimen. Dynamic response tests of the residual structure of the arch bridge after suspender failures employing the test specimen have been carried out. A finite element model accounting for the suspender breakage dynamic process has been constructed by implementing ANSYS/LS-DYNA, and the results of the test and finite element analysis are compared. In order to simplify the dynamic response calculation process of the residual structure after hanger failures, the dynamic coefficient is introduced, and an equivalent static calculation method (ESCM) considering the dynamic effect of the suspender fracture is presented. Eleven kinds of CFST standard arch bridges with different spans are constructed, the static and dynamic effects of the standard arch bridge with various dynamic coefficients are compared, and then their corresponding dynamic coefficients for various suspender fractures are determined. The obtained results reveal that the proposed electromagnetic suspender breakage trigger can realize the hanger fracturing within 0.1 s, which accurately simulates the fracture process of an actual bridge suspender, and the influence on the value of the dynamic coefficient can be ignored when the duration for suspender fracture is less than or equal to 0.15 s. The influence of suspender fracture on the displacement and stress of the longitudinal beam is more notable than those of the arch rib. In particular, the long suspender breakage has the highest influence on the displacement and stress of the longitudinal beam and arch rib. The fracture of the second short suspender has a remarkable impact on the suspender force of the adjacent hanger. When the ESCM is utilized to assess the mechanical behavior of the half-through and through CFST arch bridge, the dynamic coefficients of the longitudinal beam (suspender) were evaluated to be, conservatively, 1.8 (1.8) and 1.8 (1.7), respectively. Full article

Most existing methods for the determination of the reasonable finished state of self-anchored symmetry suspension bridges were based on the stress state of the stiffening girders used in the construction. A simple and practical control method for the reasonable completion state of stiffened beam based on double control indexes of deformation and stress was proposed. In this paper, the long-term effects of shrinkage and creep were taken into consideration, and a finite element model was built to study the change in the stiffening girder stress during operation. The mid-span deflection of the middle span sustained increasing and the compression stress in the bottom slab of the stiffening girder consistently decreased under the effects of shrinkage and creep. The speed changes from fast to slow and tends to become stable in 50 years. Furthermore, stiffening girders under the action of hanger force, dead weight, cable force, and pre-stress were investigated to study the mechanism of the stress change during operation. Based on the safety stress state of stiffening girders after 50 years, a new control method for the reasonable finished state was proposed. Moreover, the total cross-section of stiffening girders maintained the compression stress state during the developing processes of shrinkage and creep in 50 years. Finally, the utilization in the Hunan Road self-anchored symmetry suspension bridge verified the simplicity and practicality of this new control method and confirms that the method can be implemented to guide the design and construction of the similar bridges. Full article

Wind field (e.g., wind speed and wind direction) has the characteristics of randomness, nonlinearity, and uncertainty, which can be critical and even destructive on a long-span bridge’s hangers, such as vortex shedding, galloping, and flutter. Nowadays, the finite element method is widely used for model calculation, such as in long-span bridges and high-rise buildings. In this study, the investigated bridge hanger model was established by COMSOL Multiphysics software, which can calculate fluid dynamics (CFD), solid mechanics, and fluid–solid coupling. Regarding the wind field of bridge hangers, the influence of CFD models, wind speed, and wind direction are investigated. Specifically, the bridge hanger structure has symmetrical characteristics, which can greatly reduce the calculation efficiency. Furthermore, the von Mises stress of bridge hangers is calculated based on fluid–solid coupling. Full article

The determination of the non-loading condition of the rail cable shifting (RCS) system, which consists of the main cables, hangers, and rail cables, is the premise of girder erection for long-span suspension bridges. An analytical form-finding analysis model of the shifting system is established according to the basic assumptions of flexible cable structures. Herein, the rail cable is discretized into segmental linear cable elements and the main cable is discretized into segmental catenary elements. Moreover, the calculation and analysis equations of each member and their iterative solutions are derived by taking the elastic elongation of the sling into account. In addition, by taking the girder construction of the Aizhai suspension bridge as the engineering background, a global scale model of the RCS system is designed and manufactured. The test system and working conditions are also established. The comparison between the test results and analytical results shows the presented analytical method is correct and effective. The process is simplified in the analytical method, and the computational results and precision satisfy practical engineering requirements. In addition, the proposed method is suitable for application in the computation analysis of similar structures. Full article