Suspension Cables Research Articles

Effectiveness of partial restriction of access to means in jumping suicide: lessons from four bridges in three countries.

Restricting access to means by installing physical barriers has been shown to be the most effective intervention in preventing jumping suicides on bridges. However, little is known about the effectiveness of partial restriction with interventions that still allow jumping from the bridge. This study used a quasi-experimental design. Public sites that met our inclusion criteria were identified using Google search and data on jumping suicides on Bridge A (South Korea), Bridges B and C (the United States) and Bridge D (Canada) were obtained from the relevant datasets. Incidence rate ratios (IRRs) were estimated using Poisson regressions comparing suicide numbers before and after the installation of physical structures at each site. Fences with sensor wires and spinning handrails installed above existing railings on the Bridge A, and fences at each side of the entrances and the midpoint of main suspension cables on the Bridge D were associated with significant reductions in suicides (IRR 0.37, 95% Confidence Interval (CI) 0.26-0.54; 0.26, 95% CI 0.09-0.76). Installation of bird spike on the parapet on the Bridge B, and fences at the front of seating alcoves on the Bridge C were not associated with changes in suicides (1.21, 95% CI 0.88-1.68; 1.49, 95% CI 0.56-3.98). Partial means restriction (such as fences with sensor wires and spinning bars at the top, and partial fencing at selected points) on bridges appears to be helpful in preventing suicide. Although these interventions are unlikely to be as effective as interventions that fully secure the bridge and completely prevent jumping, they might best be thought of as temporary solutions before more complete or permanent structures are implemented.

Improved LPAstar algorithm for power station cabinet wiring

Abstract Aiming at the complex constraints of cable layout in power plant cabinets and the low efficiency of manual design, an improved Lifelong Planning Astar algorithm (LPAstar) is proposed. By constructing a corner-length feature fusion model, the cable length and number of corners are constrained to reduce wiring costs and cable damage. The spatial minimum bounding box algorithm is employed to avoid cable suspension. Continuous incentive factors are introduced to improve algorithm efficiency. In post-processing, smoothing strategy and wire harness dispersion strategy are used to avoid excessive cable bending and ensure the standardization of wiring. The simulation experiment results show that compared with the traditional Astar algorithm, the routing length and number of corners are reduced by 27% and 65%, respectively. The generation efficiency is 84% and 87% higher than the Astar algorithm and the original LPAstar algorithm, respectively.

Vibration isolation platform for large-amplitude-low-frequency excitation by parallel-stack-assembly design of Miura origamis

To achieve an ultralow-frequency vibration isolation platform for simulation of space environment, suspension method is always utilized. However, the natural frequency of the suspension system is inversely proportional to the length of the suspension cable. In order to further reduce the dynamic stiffness, compress the suspension area, and achieve vibration isolation for wide-amplitude excitations, we propose parallel-stack-assembly (PSA) design principle for Origamis to construct absolute zero-stiffness for required intervals. The dynamic model for wide-range amplitude and deformation, design criteria for required low-frequency large-amplitude isolation effectiveness, and analysis for nonlinear vibration isolation property are given. Finally, the prototype is carried out to validate the theoretical analysis and design principle. The PSA design principle of Origamis creates the large-amplitude and ultralow-frequency isolation property, and, the study expands the applicability of isolators for low-frequency excitation with large amplitude for the systems in aviation, marine etc.

Design and Analysis of Low-Gravity Simulation Scheme for Mars Ascent Vehicle

The sample carried back by the Mars Ascent Vehicle (MAV) is a potential flagship mission of deep space exploration in recent years. A low-gravity simulation experiment is an effective method and a necessary stage for verifying the performance of the MAV launch dynamic in Earth’s gravity. In this paper, the uniqueness of low-gravity simulation is illustrated by the classical pulley balance method for the high dynamic process of a test model of the MAV. Its movement direction is the same as the compensation force, which leads to the relaxation of the sling and the failure of the compensation force in traditional cable suspension. Here, three cable suspension schemes including an improved pulley balancing scheme based on a coordinate transformation scheme and based on a dynamic pulley group scheme are proposed. For the actual launch condition of the MAV, the motion state of the ascent under the schemes and the real Mars launch are compared, which proves the feasibility of the schemes. Among them, the improved pulley balancing scheme has the best gravity compensation effect, and the error between the average value and the required value is the smallest, only 1%.

Enhancing stress measurements accuracy control in the construction of long-span bridges

This paper introduces new contributions for construction procedures designed to enhance the robustness and precision of stress control in active anchorage and short presetressing units for long-span bridges, particularly addressing potential technical risks. The primary focus is on optimizing stress management for bridge stays, suspension cables, and short prestressing units by emphasizing a unified parameter: stress. The contributions of this research encompass (1) the introduction of advanced load cells for stress control in active anchorages and (2) the implementation of a novel synchronized multi-strain gage load cell network for short prestressing units, crucial in situations where prestressing losses can attain significant magnitudes. To validate these advancements, the authors present (3) a practical experience and results obtained from applying these methodologies in monitoring the structural response during the construction of the Tajo Bridge using the cable-stayed cantilever technique.

Research on fatigue failure and structural measures of suspenders in the Jinsha River railway suspension bridge

In consideration of the significant impact of train loads on the fatigue of suspenders in railway bridges, this paper focuses on the first railway suspension bridge in China − the Jinsha River Railway Suspension Bridge. The study analyzes the force characteristics and bending failure features of the steel wire ropes in railway suspension bridges, aiming to provide insights into the design of such structures. Firstly, a finite element model of the Jinsha River Railway Suspension Bridge is established in this paper. The natural frequencies are analyzed and compared with on-site measurements to validate the accuracy of the finite element model. Secondly, the tension force amplitude and angular displacement amplitude of the suspenders are analyzed under design loads, and the failure characteristics of the cables are experimentally examined. Subsequently, a wear fatigue test for steel wire rope is designed, evaluating the fatigue life of the suspender in the bridge. The computational results are compared with experimental data to validate their accuracy. Finally, structural measures to reduce the bending fatigue of railway suspension bridge suspenders are proposed to ensure their safety during the service life. The study reveals that the presence of bending stress exacerbates the fatigue failure of suspension cables in railway suspension bridges, with the failure mode identified as fatigue failure due to the tension-bending-wear coupling effect. Furthermore, our findings indicate that the implementation of auxiliary cables can reduce the displacement differential at both ends of the suspension cables by approximately 4/5, and decrease the axial tensile stress amplitude by about 3/4. Consequently, this significantly enhances the fatigue life of the suspension cables.

Nonlinear static solution of suspension bridge formulated from a surrogate model with secant stiffness of suspension cables

Explicit analytical solution may offer great convenience for the design and parametric study of suspension bridges. However, the nonlinear behavior of suspension cable exacerbates the difficulty of such theoretical derivation. Adopting secant stiffness is an effective way to deal with the nonlinearity of the cable, but the crux is how to find its deformed state under external loading. The strategy of this study is primarily targeted at a typically arranged three-span suspension bridge. It starts from formulating the basic form of nonlinear stiffness of suspension cables by setting the elastic stiffness and geometric stiffness in series, then a surrogate model is accordingly established with the nonlinear springs to replace the mid-span and side-span cables. The deformed state of the surrogate model subjected to the specified external load cases will be found by restricting and releasing its tower tops, and thus the analytical formula of the secant stiffness can be obtained. Consequently, the nonlinear static solution of suspension bridge, including force and deformation changes in the cables and towers, can be explicitly expressed with the secant stiffness. The general solution procedure can also be extended to multi-span suspension bridges. Finally, the nonlinear static solution is verified by numerical examples of a three-span suspension bridge and a four-span suspension bridge. The parametric analysis reveals that the nonlinearity of suspension bridge will become significant as the side-span to mid-span ratio increases, or when the side-span cables are hung with hangers.

Control of Cooperative-Transportation Dynamics in Twin-Lift Cranes Suspending a Liquid Container

Bulky and heavy liquid containers may need to be transported by multiple cranes. Unfortunately, the interaction between swing effects from the multiple suspension cables and fluid sloshing in the container may corrupt efficiency and safety of the cooperative operation. Although significant work has been devoted to understanding the swing dynamics of industrial cranes and sloshing dynamics in liquid containers, less effort has been directed at the interaction between swing and sloshing dynamics in multiple cranes transporting a liquid container. A dynamic model of the motion of twin cranes carrying a liquid container has been derived. The complicated interaction between twin-lift swing and fluid sloshing has been captured by the analytical model. Additionally, a novel control method has been proposed to reduce coupled oscillations. Numerous experiments have been performed to validate the effectiveness of the dynamic model and oscillation-control method.

Coupled Vibration Analysis of Multi-Span Continuous Cable Structure Considering Frictional Slip

As important load-bearing structures, suspension cables have been widely used in suspension bridges, engineering ropeways, cable suspension systems and other special equipment. Their dynamic problems have always been a research hotspot. Especially for complex cable systems such as engineering ropeways and cable lifting equipment, there will be moving loads acting on multi-span continuous friction-slip cable structures, resulting in nonlinear coupled vibration. Therefore, few scholars have studied how to calculate the nonlinear coupling vibration effect between such moving loads and multi-span continuous cables considering friction slip. Therefore, this paper proposes the use of the combination of the direct stiffness method and the Newmark-β integration method to solve the nonlinear system of equations of motion, which can be derived from the coupled vibration response between the moving load and the main cable. The corresponding calculation program is prepared. Combined with the dynamic load test and simulation results of engineering cases, the correctness and reasonableness of the coupled vibration equations and the program can be verified through comparative analysis. The results show that the calculation results of the self-programmed program are in good agreement with the dynamic load test results, in which the maximum error of the vertical displacement in the span is −4.40% and 0.86%, and the error of the static calculation reaches −13.90%. The impact effect is more obvious when hoisting the weight out of the pulling cable, in which the impact coefficient of the main cable can be up to 2.0. The impact coefficient of the deviation of the cable tower is 4.0. During the traveling process of the moving load, the vertical downward deflection of the main cable at the action point is the largest, and the upward deflection is in the region of 0.2~0.8L from the action point.

Modeling and Loading Effect of Wind on Long-Span Cross-Rope Suspended Overhead Line with Suspension Insulator

The long-span Cross-Rope Suspended (CRS) system is composed of a transmission line (conductor), a long-span suspension cable, and an insulator. The previously introduced long-span CRS with a Tension Insulator (CRSTI) has shown applicability in mountainous areas. However, the tension insulator divided the suspension cable into several sections, which made the construction of a long-span CRS rather difficult. This paper introduces long-span CRS with a Suspension Insulator (CRSSI), in which the suspension cable was not disconnected, and the conductor was supported by a suspension insulator connected to the suspension cable. For the purposes of assessment, the initial shape of the suspension cable with concentrated loading from the self-gravity of the suspension insulator and the conductors was studied, and practical lengths in construction could be calculated exactly. Secondly, the structural performance of CRSSI, including its dynamic properties and the loading effect of wind, was discussed by means of numerical analysis. Vibration modes of the structure were obtained by FE analysis. Finally, structural deformation under static wind loading was studied. The result of the analysis showed that the stiffness of CRSSI was lower than CRSTI. The first frequency of CRSSI was 6% smaller than CRSTI. Regarding static wind loading, additional displacement of the insulator contributed to the maximum displacement of long-span CRSSI. Apparently, the displacement of the suspension insulator increased with wind speed. Moreover, the number of spans has an insignificant influence on tension force and deformation.

Intelligent Tension Correction Method for EME Sensors considering Torsion Effect of Wire Rope Suspender Cables

Long‐term and accurate monitoring of suspender cable tensions is particularly important for safe evaluation of cable suspension bridges or tied‐arch bridges. Torsional deformation, commonly present in wire rope suspender cables (WR cables) during tensioning construction or in‐service, has not been considered in the elasto‐magneto‐electric (EME) sensor system. This study investigated the effects of torsion on tension measurement and proposed an intelligent correction method without measuring the torsion angles per unit length. A calibration platform for full‐scale WR cable is established with a rotation angle fixing device. Tension calibration experiments were carried out under free rotation condition without activating the angle fixing device and under various fixed rotation conditions by setting a series of initial fixed angles at the anchor head. It was found that the relative error for the EME sensor using the traditional calibration method under the free rotation condition could reach 11.72%. To improve the accuracy, an intelligent tension correction method for the torsion effect is proposed, which uses the experimental signals in various fixed conditions and the backpropagation neural network with K‐fold cross‐validation. The parameters of the BPNN were optimized by genetic algorithm, and it was found that the maximum relative error decreases from 11.72% to 5.24% and the maximum absolute error decreases from 21.75 kN to 14.67 kN for the condition of free rotation. Finally, the EME sensor with intelligent tension correction method was applied to a real suspension bridge. The measurement relative error of the field test decreases from 6.60% without the torsion compensation to 2.80% with the torsion compensation, which indicate that the proposed intelligent tension correction method can ensure the accurate tension measurement of the WR cables by the EME sensor.

Three-Dimensional Reconstruction of Railway Bridges Based on Unmanned Aerial Vehicle–Terrestrial Laser Scanner Point Cloud Fusion

To address the incomplete image data collection of close-to-ground structures, such as bridge piers and local features like the suspension cables in bridges, obtained from single unmanned aerial vehicle (UAV) oblique photography and the difficulty in acquiring point cloud data for the top structures of bridges using single terrestrial laser scanners (TLSs), as well as the lack of textural information in TLS point clouds, this study aims to establish a high-precision, complete, and realistic bridge model by integrating UAV image data and TLS point cloud data. Using a particular large-scale dual-track bridge as a case study, the methodology involves aerial surveys using a DJI Phantom 4 RTK for comprehensive image capture. We obtain 564 images circling the bridge arches, 508 images for orthorectification, and 491 images of close-range side views. Subsequently, all images, POS data, and ground control point information are imported into Context Capture 2023 software for aerial triangulation and multi-view image dense matching to generate dense point clouds of the bridge. Additionally, ground LiDAR scanning, involving the placement of six scanning stations both on and beneath the bridge, was conducted and the point cloud data from each station are registered in Trimble Business Center 5.5.2 software based on identical feature points. Noise point clouds are then removed using statistical filtering techniques. The integration of UAV image point clouds with TLS point clouds is achieved using the iterative closest point (ICP) algorithm, followed by the creation of a TIN model and texture mapping using Context Capture 2023 software. The effectiveness of the integrated modeling is verified by comparing the geometric accuracy and completeness of the images with those obtained from a single UAV image-based model. The integrated model is used to generate cross-sectional profiles of the dual-track bridge, with detailed annotations of boundary dimensions. Structural inspections reveal honeycomb surfaces and seepage in the bridge piers, as well as painted rust and cracks in the arch ribs. The geometric accuracy of the integrated model in the X, Y, and Z directions is 1.2 cm, 0.8 cm, and 0.9 cm, respectively, while the overall 3D model accuracy is 1.70 cm. This method provides technical reference for the reconstruction of three-dimensional point cloud bridge models. Through 3D reconstruction, railway operators can better monitor and assess the condition of bridge structures, promptly identifying potential defects and damages, thus enabling the adoption of necessary maintenance and repair measures to ensure the structural safety of the bridges.

Experimental investigation on wind-induced vibration of photovoltaic modules supported by suspension cables

Under the background of the global energy crisis and excessive carbon emissions, solar power stations have increased rapidly in number and size in recent years. To satisfy the construction needs on complex or special sites (e.g. intertidal zone, mountainous area, fishponds, etc.), a suspension cable supported photovoltaic (PV) module was developed recently and quickly aroused market interest; however, such cable-supported flexible PV systems are susceptible to wind loading and associated aerodynamic effects thereon remain unclear. Therefore, both aeroelastic and rigid model wind tunnel tests were conducted to investigate the wind-induced vibration (WIV) characteristics of a typical cable-supported PV module. The effects of module tilt angle, cable pre-tension, and wind speed on the vertical displacement response and the aerodynamic damping were evaluated. Based on wind pressure tests and finite element simulation, the three-dimensional WIV behavior of PV modules could be investigated. The non-dimensional gust loading factor representing the load dynamic amplification was presented based on multi-target equivalent static wind loads. Results show that wind-induced vertical vibration of the PV modules increased with tilt angle but reduced with increasing cable pretension. The fluctuating displacement shows a quasi-linear increase with the square of the wind speed. Negative aerodynamic damping was found for a tilt angle of 10° under high wind speeds. Compared to vertical vibration, horizontal and torsional responses were insignificant for the tested PV modules. The estimated gust loading factor for the PV module with tilt angle of 10° was between 1.1 and 2.5.

Dynamic analyses of long-span cable-stayed and suspension cooperative system bridge under combined actions of wind and regular wave loads

This paper presents the dynamic analyses of long-span cable-stayed and suspension cooperative system bridge under combined actions of wind and regular wave loads. First, the wind loads acting on the bridge deck are calculated based on the aerodynamic force coefficients which were obtained in the wind tunnel and wave flume tests. Then, the wind loads acting on the bridge towers, piers and suspension cables are calculated based on the aerodynamic force coefficients which are simulated in FLUENT software. Besides, the regular wave loads acting on the composite foundations are simulated in FLOW-3D software. Finally, the dynamic responses of the bridge subjected to the combined actions of wind and regular wave loads are calculated in the Mechanical APDL module of ANSYS 17.0 software. The results indicate that the root mean square (RMS) values rather than the mean values of the time histories of the aerodynamic force coefficients obtained in the wind tunnel and wave flume tests should be selected to calculate the wind loads acting on the deck to accurately evaluate the dynamic responses of the sea-crossing bridge. The maximum RMS values of the displacement responses of the deck midspan and 5# tower top increase with the increase of the regular wave heights for the wind-wave cases, which are larger than those for the wind-only case, respectively. In general, the linear superposition of the dynamic responses under the actions of wind-only and wave-only is a conservative choice compared to the consideration of the combined actions of wind and regular wave loads. The displacement spectrums of the deck midspan and 5# tower top, and the lateral base shear and lateral base bending moment spectrums of 5# tower are analyzed to reveal the contribution mechanism of the wind loads, regular wave loads and natural frequencies of the bridge.

Impact Dynamic Analysis of Suspended Marine Cables

Objective: It is often impossible to avoid collisions between marine cables, the impact dynamic response of the collisions between marine cable needs to be obtained. Methods: In this paper, we derive the lumped mass method based on the bending moment and torque; using the lumped parameter method, the suspended cable is discretized into lumped mass models, and the impact force of the suspended cable is considered in the dynamic analysis; the impact dynamics model of the suspension cable is developed by referring to the specific parameters of the suspension cable and combining them with offshore construction processes. Results: There is a relationship between the impact force and the tension of the cable. The tension and impact force are related in cable collisions. While the maximum effective tension occurs at the upper end of the vertical cable and at the collision point, the horizontal cable's tension at the collision position is minimal. The distribution of curvature mutates at the collision point, causing bending deformation. The horizontal cable experiences greater bending change at the collision position than the vertical cable. Conclusion: In summary, collision of different parts of vertical cable is not obvious, while horizontal cable is more prone to self-collision and collision with vertical cable. Collision impact on horizontal cable is greater, with minimum tension occurring at collision point. Maximum velocity for horizontal cable appears at collision position, and for vertical cable at bottom. Maximum acceleration for both cables occurs at collision zone.

Hydrodynamic investigation on the submerged tunnel suspended from a fixed platform using SPH method

In this paper, the coupled dynamic motion characteristics of a tunnel element suspended from a platform have been studied at a 1:50 scaled model by using the weakly compressible Smoothed Particle Hydrodynamic (WCSPH) method. The corresponding numerical model was validated with the experimental published data of the motion characteristics of the tunnel suspended from a fixed platform, and the case of a floating structure with its mooring lines. Multiple linear wave conditions and different sinking depths of the submerged were involved in the numerical model for tunnel dynamic response and cable behavior investigation. Effects of the mooring system, the wave parameters, the tunnel sinking depth and its mooring configurations were studied. The numerical results were arranged to inform about the dynamic characteristics and mooring behavior for different case studies. The results indicate that the tunnel motions decrease with the increment of the tunnel sinking depth and decrease with the decreasing mooring angle. The natural periods of the tunnel-platform system play key roles in the wave condition impacts on the tunnel motions. It was found that the additional mooring system anchoring the tunnel to seabed played a specific role in reducing the tunnel motions in roll and sway, the motion amplitude of the tunnel in heave is mainly controlled by the suspension cables, particularly when subjected to lower sinking depth and longer period waves.

Experimental Study on Load of Continuous Steel Truss Bridge Stiffened by Rigid Suspension Cable for Highway and Rail

In order to reveal the stress law of rigid suspension stiffened continuous steel truss bridge under highway and crowd loads, a highway rail bridge is taken as the supporting project, and the load test method is used to verify it. Firstly, the completed bridge state (the dead load of the lower track) is simulated by laying water bags on the lower deck, which solves the problem of asynchronous construction of highway and track. Then, the stress, deformation results and change rules of this kind of bridge under the test load are summarized by simulating the load action of highway and crowd through the loading vehicle, which can provide a reference for the load test of similar bridges.

Experimental Study of Influence Line–Based Damage Localization for Long-Span Cable Suspension Bridges

Influence line (IL)–based damage indices for long-span bridges are investigated in this study. Their effectiveness is experimentally validated for the first time through the scaled physical model of the Tsing Ma Bridge (TMB). First, the IL mechanism for damage detection and its corresponding damage indices are briefly introduced. Subsequently, the scaled TMB model instrumented with different types of sensors, including displacement sensors, strain gauges, and accelerometers, is introduced. The IL characteristics of different bridge components are compared. Two different damage cases with single- and double-damage locations at the bottom chord were tested. In the single-damage case, different ILs extracted from the nearby components were used for damage identification. These ILs can successfully locate damage visually. The strain IL (SIL) is more sensitive to local damage than deflection IL, but its detection performance degrades rapidly with the increasing distance between sensor and force locations. In the double-damage case, the SIL extracted from a single sensor cannot identify both damage cases because of the limited detectable range of each SIL; therefore, using multiple sensor information becomes necessary. For comparison, the modal parameters were also employed for damage detection. These experimental results validated the merits of the IL–based methods proposed for long-span bridges, indicating that IL–based damage indices are good indicators of local damage detection in long-span bridges. This finding contributes to the development of real-time techniques for damage localization in long-span bridges equipped with a structural health monitoring system.

Axial–Torsional Vibrations of Drill Strings with Crush-and-Shear Hybrid Bits at Constant Tension of Suspension Cables

Axial–Torsional Vibrations of Drill Strings with Crush-and-Shear Hybrid Bits at Constant Tension of Suspension Cables

Axial-Torsional Vibrations of Drill Strings with Crush-and-Shear Hybrid Bits at Constant Tension of Suspension Cables

Axial-Torsional Vibrations of Drill Strings with Crush-and-Shear Hybrid Bits at Constant Tension of Suspension Cables