Cable Tension Force Research Articles

Load-bearing behaviors of the composite gravity-type anchorage: Insights from physical model and numerical tests

Gravity-type anchorages (GTAs) have been extensively applied in large-span suspension bridges across the globe, but the load-bearing performance of composite GTA is not yet fully investigated. Here, the comprehensive load-bearing performance of GTA is investigated using a combination of physical modelling and numerical modelling methods, considering the impact of anchorage’s burial depth, notched sill, and pile. Six model tests are first conducted using a self-reversing force loading equipment, including flat bottom anchorage, notched sill anchorage, and notched sill anchorage with pile. Each type of anchorage is tested under two different burial depth conditions. The failure process, anchorage displacement, cable tension force, and the internal strain field of the foundation, were examined during the model tests. Additionally, through the numerical simulations, the evolution characteristics of contact stresses and load sharing ratio associated with various forms of anchorage are discussed. The results indicate that the anchorage’s burial depth and pile significantly impact on anchorage’s bearing capacity. The presence of the notched sill can change the distribution of contact stress between the anchorage and foundation, which can still resist the horizontal force until the foundation before the notched sill occurs shear failure. The failure process of the anchorage-foundation system was divided into four stages: stable bearing, sliding, sliding and overturning, and failure stage. The anchorage starts overturning with the applied load reaching to 3*Tm, except for the flat bottom anchorage of shallow burial depth condition. Under the same conditions, the greater the anchorage’s burial depth, the smaller the load shared by the friction between the anchorage bottom and foundation, the greater the load shared by the notched sill and foundation before the anchorage. In addition, the load shared by pile continuously increasing as the anchorage starts overturning. The findings from this study can provide a theoretical basis and valuable insights for the optimization design of GTA.

Determination of cable tension force in pedestrian suspension bridge short hangers based on finite element model updating

Abstract The hangers are the important element on suspension bridges that transfer the forces from the deck to the main cable. To verify their capacity and identify possible risks, the forces transferred by the hangers and the corresponding tension must be determined. However, this is often done using standard equations for determining cable forces. Due to the different lengths of the hangers and the way in which their tensioning is achieved, the effects of boundary conditions occur that need to be considered and that require an update of the finite element model at the local level (when the whole bridge structure is observed). This paper presents a method for determining the cable tension of hangers that combines the experimentally determined dynamic properties (natural frequencies and mode shapes) and the numerical model updating. In addition to the usual approach based on the determination of the natural frequency of hangers, this paper presents an approach based on the mode shapes of the hangers. Special attention is paid to the boundary conditions coefficient. The method is applied on suspension bridge case study.

Stress and deformation analysis of the steel pipe arch integral lifting construction process of a continuous beam arch bridge

The Changjinghuang Railway Xinjiang Xizhi Bridge is a (90 + 180 + 90) m continuous beam arch bridge, and the arch rib steel pipe installation adopts “short bracket assembly and overall lifting method”. In order to ensure the accuracy of closure, the stress and deformation of the arch rib and bracket must be strictly controlled. Midas Civil is used to establish the finite element model to simulate the overall lifting construction process of the arch rib. Based on the model, the stress and deformation of the arch rib and the supports are analyzed, and the determination method of the horizontal cable force under temperature variations is proposed. The results show that the stress and deformation of the arch rib and bracket meet the requirements. Considering the variation of temperature, the tension force of the horizontal cables is taken as 200 t. The construction plan proposed under the guidance of numerical calculation results has been proven by practical engineering to meet the requirement of closure accuracy, which can be used as a reference for similar projects.

A reliable methodology to estimate cable tension force in cable-stayed bridges using Unmanned Aerial Vehicle (UAV)

An alternative methodology to estimate the tension force of cables using computer vision and Unmanned Aerial Vehicles (UAV) was proposed in this investigation. It was developed according to a simplified model to determine the fundamental frequency of the cables when are affected by daily vehicle loads. The methodology offers the advantage of accurately determining the tension force using just 2 min of video recording per cable, even under real environmental conditions. In addition to this, the calibration process of the camera can be Skipped. The proposed methodology was tested in the laboratory with a vibrating table and on the Rio Papaloapan Bridge, which is one of the main cable-stayed bridges in Mexico. The results in a controlled environment showed a Root Mean Square Error (RMSE) of 0.0024 Hz. Meanwhile, the assessment of the fundamental frequency obtained by the UAV and accelerometer in the structure showed a maximum difference of 0.03061 Hz, and a minimum of 0.00105 Hz. These discrepancies occasioned errors in tension force of 40.7 kN (1.96 %), and 3.3 kN (0.123 %), respectively.

Modeling cable-pulley deployment systems of transformable rod structures

The aim of this article is to develop a simplified method for modeling cable-pulley deployment systems of rod structures based on the calculation of cable tensions and nodal driving forces with account for friction and other features of the system. Methods of theoretical mechanics, multibody dynamics, numerical integration of differential equations, and computer modeling were used during the research. The task of developing a simplified approach to modeling cable-pulley deployment systems for rod structures is considered. It is proposed to determine nodal driving forces by calculating cable tensions with account for friction and other features of the cable-pulley system, cables, and pulleys. To develop a model of cable-pulley deployment system, a rod system was chosen as the research object, which represents two sections of the transformable support truss of a reflector. Each section consists of diagonal and horizontal rods with tubular cross-sections. The sections are interconnected by hinge units. The structure is deployed using an upper and a lower cable, which pass through pulleys and are tensioned by an electric motor. The deploying forces are implemented by transferring the cable tension forces to the structure due to static friction and pressure between the cables and the pulleys. For further implementation of the model in an open-source software package, some simplifications were made due to the complexity of the design. A simplified method was developed for nodal driving force calculation in simulating rod structure deployment with the help of cables. The tensions, elongations, slacks, and neutral length of the cables and the forces transmitted from the cables to the pulleys were calculated as a function of time. Using them, the deployment of a rod structure was simulated for a constant cable speed. The results make it possible to control the rod system deployment time and rate depending on the characteristics and tension forces of the cables. The proposed approach is implemented using open-source software, and it provides modeling flexibility and reduces the model development and run time.

On the Problem of Tension Forces Distribution in Cable System of Cable-Driven Parallel Robot

The paper proposes a method for controlling tension forces in statically indeterminable cable-driven systems based on the non-negative least squares method with control of singular or near-singular solutions and a complete search of all possible cable configurations. For cable-driven parallel robots the problem of controlling the cable tension forces is critical, because in the absence of control the cable tension forces are distributed unevenly, which leads to reduced robustness of the system, increased energy consumption and increased deterioration. And in special cases of cable system configuration the tension forces become so great that they lead to cable breaks. At the same time, correction of cable tension force distribution should not lead to significant deviations from the specified position of the mobile platform or, formulating the problem in terms of forces, to violation of kinetostatic equations. Thus, the problem of controlling the tension forces in the cable parallel robot system is solved as a problem of optimizing the tension forces of the cables according to the criteria of minimizing the norm of their vector in the configuration space and minimizing the norm of incoherence of the vector of forces and moments in the operational space of the robot. The developed algorithm is based on the solution of underdetermined systems of linear algebraic equations with finding the minimum least squares norms and subsequent zeroing of negative components of the solution vector. The paper considers examples of the solution of the set problem for the lower cable group of a construction 3D printer based on a cable-driven robot and for a 12-cable system

Cable Force Calculation of Cable Hoisting of CFST Arch Bridge Research

To effectively control the stress state and spatial alignment of arch ribs in the cable hoisting construction of a long-span, concrete-filled, steel tube arch bridge and ensure the safety of the structure, it is necessary to calculate and determine the appropriate cable force. Based on the actual project of a double-span, concrete-filled, steel tubular arch bridge, the construction stage of the left span of the bridge from the beginning of construction to the closure is taken as an example. The linear control method of “quiet do not move” is adopted. Based on the principle that the vertical displacement of the front end of the installed segment caused by the self-weight of the new hoisting segment is equal to the vertical displacement of the front end of the previous segment caused by the tension of the new hoisting segment, the tension cable force is calculated by forward iteration. Finally, based on the theory of the stress-free state method, the ideal linear design of the structure was achieved. The results show that after the closure of the bridge, the error range of the cable tension force is −13.33–15.40% on the left bank and −8.37–11.00% on the right bank. The elevation error of the arch rib is −0.003–0.043 m on the left bank and −0.007–0.032 m on the right bank. The overall stress error of the bridge arch is ±7.0 MPa. The error between the theoretical value and the actual value is within the scope of the specification requirements, which meets the specification requirements. After the closure, the arch shape of the bridge meets the smooth requirements.

Optimization of Extradosed Bridge and Analysis of Parameters' Sensitiveness as a Case Study on Abay Bridge

AbstractThe paper describes analytical sensitivity analysis and structural optimization for Abay extradosed cable‐stayed bridge. Identify significant design variables using sensitivity analysis by considering cable stiffness, girder weight and stay cable tension force. The aim of the study is weight minimization of superstructure components of Abay bridges. It has span length (100+180+100) m. For structural optimization, it was carried out by taking total material weight of girders, pylon and stayed‐cable as an objective function and all requirements of strength, stability, serviceability, and fatigue as constraint functions. The formulated optimization problem was coded into Matlab R2019a software and analysis results are retrieved from MIDAS CIVIL 2019 software. The paper gives more reduced weight of bridge from conventional design output by using same material grade. The result shown that optimum stay cable length was reduced from conventional design output by 10% from total values, optimum design of pylon height reduced weight of conventional design by 20.03% and optimum design of box girder reduced girder weight by 19.47%.

Dynamic Response Measurement and Cable Tension Estimation Using an Unmanned Aerial Vehicle

Since all structures vibrate due to external loads, measuring and analyzing vibration data is a representative method of structural health monitoring. In this paper, we propose a non-contact cable estimation method using a vision sensor mounted on an unmanned aerial vehicle. A target cable among many cables can be identified through marker detection. In addition, the motion of the structure can be quickly captured using the extracted feature points. Although computer vision can be used to transform displacements of multiple axis, in this study, only the vertical displacement is considered to estimate tension. Finally, the cable tension can be estimated via the vibration method using the modal frequencies derived from the cable displacement. To verify the performance of the proposed method, lab-scale experiments were carried out and the results were compared with the conventional method based on the accelerometer. The proposed method showed a 3.54% error compared with the existing method and confirmed that the cable tension force can be estimated quickly at low cost.

A Novel Scaffold-Reinforced Actuator With Tunable Attitude Ability for Grasping

Owing to high compliance, adaptiveness, and easy controllability, soft actuators are widely adopted in soft grippers to grasp irregularly shaped or fragile objects. The specific motions can be preprogrammed into the flexible and constrained structures of the actuator, which provides an inexpensive and convenient method for desired motions. However, most preprogrammed structures cannot change the constraints on the actuator to achieve different kinds of deformations, which limits the motion diversities of actuators. This article proposes a scaffold reinforcement mechanism, where rotatable scaffolds distribute on the surface of the soft structure. The orientation adjustments of the scaffolds can change the deformation constraint of the actuator, which results in different kinds of motions. Based on the scaffold reinforcement mechanism, a scaffold-reinforced actuator is proposed, which can achieve bending motion and complex helical motion in the 3-D space by properly adjusting the orientation of the scaffolds. In addition, both the kinematic and mechanical models are proposed to forecast the behavior of the actuator when driven by cable displacement or tension force. Experimental results verify the validity of the theoretical model, and the actuator can achieve an independent control of bending and helical motion, which can be adopted in applications where both high dexterity and flexibility are required.

Comparison of cable tension force prediction using effective length with linear regression and two-mode combination method

ABSTRACT The development of vibration-based tension determination has increased in recent years. The effective vibration length concept is one of the most robust methods in dealing with various end-rotational support stiffness. Recently, a two-mode combination approach by compelling multiple frequencies and effective lengths has been developed to replace the bending rigidity from the cable relationship so the tension can be solved explicitly. This paper aims to compare the tension prediction using the effective length concept with two existing methods: linear regression and the two-mode combination. Three cases of cable support: hinged-hinged (Case 1), hinged-fixed (Case 2), and fixed-fixed (Case 3), are studied through numerical simulation. The cable is vibrated under random excitation, and its dynamical properties are extracted through the SSI method. Equivalent frequencies and equivalent-effective lengths are computed to perform the two-mode approach. The study shows that linear regression produces more minor errors than the two-mode combination method, either for Cases 1, 2, or 3. The theoretical results are presented to figure out the cause of errors. However, linear regression and the two-mode method both produce promising results in calculating the cable tension in these three cases. Similar results are also shown in the study using experimental laboratory test data.

Simultaneous Estimation of Submerged Floating Tunnel Displacement and Mooring Cable Tension through FIR Filter-Based Strain and Acceleration Fusion

A submerged floating tunnel (SFT) is a tunnel structure that floats approximately 50 m below the water surface and is anchored to the seabed by mooring cables. It is a new alternative to conventional bridges and immersed tunnels. There have been ongoing efforts to construct SFTs worldwide, and the integrity of these SFTs needs to be monitored throughout their lifespan. This study simultaneously estimated the tunnel displacement and mooring cable tension force using acceleration and strain measurements to assess the integrity of an SFT. First, strain measurements were transformed to displacement using simplified mode shapes and mode-scaling factors, which did not require the true mode shapes of the SFT. The mode-scaling factors were automatically estimated using initial strain and acceleration measurements. Then, the strain-based displacement was combined with the acceleration measurement using a finite impulse response filter to improve the displacement estimation accuracy. In addition, the tension force of a mooring cable was estimated from the displacement at the connection between the tunnel and mooring cable. The feasibility of the proposed technique was examined through a series of numerical simulations and laboratory tests on an 8 m-long aluminum SFT mock-up structure.

A resident subsea docking system with a real-time communication buoy moored by an electro-optical-mechanical cable

Subsea docking systems (SDSs) have received extensive attention in the past decades as the basis for achieving AUVs' long-term observations and operations. However, the existing research mainly focuses on developing custom-designed SDSs to match specific outlines and structures of AUVs, while the approach to achieving the long-term underwater residency of SDSs is less involved. Therefore, we propose a resident subsea docking system (RSDS), where an electro-optical-mechanical (EOM) cable mooring a real-time communication (RTC) buoy to a subsea docking station (SDS). Moreover, we adopt a numerical method based on ANSYS-AQWA to investigate the effects of types and design parameters of the mooring structure on its stability and reliability. The results show that the most suitable type of mooring structure significantly reduces the maximum buoy's pitch, cable tension, and anchor-uplifting force by 3.08%, 14.16%, and 55.59% compared with the traditional one. Moreover, its optimal design is a 320 m cable attaching a 200 N-buoyance float and a 1200 N-gravity clump weight at 25 m and 50 m near the SDS. Finally, the field test in the South China Sea verified the RSDS's functions and the feasibility of the optimal mooring structure. In summary, this article fills a gap in achieving the SDS underwater residency and guides future research on RSDS.

Dynamic model of a tendon-actuated snake robot using the Newton-Euler formulation

Dynamic models are necessary when dealing with robotic applications where requirements of dexterity, manipulability, payload and compliance have to be satisfied at the same time. This work considers a particular design of tendon-actuated snake-like robots in which links are not coupled through mechanical joints but are free to roll between each other under the effect of cable tension forces. The state of the art in modeling these tendon-actuated rolling-joints systems is limited to kinematic and quasi-static models. In order to simultaneously guarantee modeling accuracy and suitability for model-based control, the Newton-Euler (NE) formulation has been adopted, by taking into account the forces and moments generated by cable tensions, links interactions, inertias, and friction between the rolling surfaces.

Производительность сил траловой системы – VI: математическое моделирование (часть III)

Performance of external longitudinal and transverse forces developed in the course of towing the trawl systems, namely, the tension and compression forces of cables, ropes and yarns of the rope-net gears in commercial fishing of the longitudinal modulus of elasticity and the transverse modulus of elasticity in the cordage products. Physical and mechanical properties of the synthetic nylon threads, ropes and nylon cords, from which most trawl systems are made, are considered. Analysis of the physical and mechanical properties of synthetic rope products and cords based on the specified parameters for possible static and dynamic loads is proposed. Algorithms for calculating the physical and mechanical properties of threads, ropes and nylon cords are proposed under the condition of constant volume and mass. Method of calculating physical and mechanical properties of the nylon threads and ropes under the condition of uncertainty gives an error not exceeding 0.4% in calculating the relative elongation δε, but the maximum error δμ in calculating Poisson's ratio μ reaches 7.12%. This proves that the formula for calculating the Poisson's ratio μ for anisotropic bodies does not allow estimating this ratio at low loads and constant volume.

Modeling and Sliding-Mode Control for Launch and Recovery System in Predictable Sea States With Feasibility Check for Collision Avoidance

This article investigates a deterministic sea wave prediction-based noncausal control scheme for the launch and recovery (L&R) from a mother ship of small rigid-hulled inflatable boats (RHIBs) for maritime rescue missions. The proposed control scheme achieves an automatic hoisting process ensuring that no collisions occur between the RHIB and mothership hull by using the cable tension force as the manipulated control input. A state-space model of the L&R system is established for the first time where the wave forces and external disturbances such as wind acting on both the mothership and the small boat are fully considered. A fast and safe recovery is ensured by a fixed-time convergent sliding-mode controller, which shortens the cable length to a target value with zero terminal velocity at a predefined time instant subject to unknown disturbances and model mismatches. Since the overall dynamics of the swing angle is underactuated, a feasibility check is proposed to avoid collisions between two vessels and overlarge angular velocities by determining a proper time instant to initiate the hoisting process. To cope with the model mismatch and the external disturbance, the constraints on the swing angle and angular velocity are tightened to ensure safety. The stability of the proposed controller is proven and details of the feasibility check are given. The fidelity of the model and the effectiveness of the proposed scheme are demonstrated in simulation where a realistic sea wave is applied.

Staggered-Supported Steel Anchor Box System for Cable-Stayed Bridges

This paper presents a novel anchorage structure for stay cables to reduce the load on the concrete pylon. Called the staggered-supported steel anchor box (SS-SAB), this anchorage structure provides self-balancing of the horizontal component of the cable tension force during cable tensioning; the vertical load is transferred to the concrete pylon through a staggered support. The SS-SAB can tolerate the forces within the spatial cable plane and reduce the cracking risks of the concrete pylon. To investigate the behavior of the SS-SAB, a half-scale specimen was designed and tested. Data on the deformation, crack patterns, local strains, and slippages were obtained that demonstrate that the SS-SAB can delay crack occurrences in the concrete pylon. In a supplementary analysis, a finite-element analysis performed using the ABAQUS software suite delivered good accuracy. From the test and numerical analysis, the influence of the cable angle on load sharing within the concrete pylon was investigated. The effective scope of applications of the SS-SAB is provided.

Noncontact cable tension force estimation using an integrated vision and inertial measurement system

In this study, a noncontact cable tension force estimation technique was developed using an integrated vision and inertial measurement system (VIS) installed at a reference point, and the movement of the VIS was explicitly considered. Cable displacement was first estimated by applying a proposed contour-based algorithm to the vision measurements. Thereafter, the movement of the VIS at the reference point was estimated from the inertial measurement system and was used to compensate the error in the previously estimated cable displacement. Finally, the cable tension force was estimated using the compensated cable displacement. The feasibility of the proposed technique was validated through a laboratory test on a full-scale pedestrian bridge cable and a field test on a single-pylon cable-stayed pedestrian bridge. Overall, the proposed technique estimated the cable tension forces reliably with less than 1.3% discrepancy compared to those estimated by accelerometers.

Tension force identification for cable of various end-restraints using equivalent effective vibration lengths of mode pairs

Vibration-based approaches have been widely adopted in determining the cable tension force. The development of effective length concept has been successfully applied in revealing the cable force regardless type of end-restraints. Simultaneously, the two-mode frequency approach can determine the tension force without knowing the bending stiffness of cables, but the formulas are limited only for the cable with hinged-hinged restraints. By taking advantage of these two methods, the present study aims to extend the two-mode frequency approach by introducing equivalent effective length for any mode pairs regardless type of end-restraints. To verify the proposed formula, three cases of cable end-restraints: hinged–hinged, fixed–fixed and hinged–fixed with the same tensioning force and cross-sectional properties, are studied. Validation using laboratory data and demonstration in a real cable force identification are also presented.

Vision-Based Cable Displacement Measurement Using Side View Video.

Recent tragedies around the world have shown how accidents in the cable-stayed bridges can wreak havoc on the society. To ensure the safety of the cable-stayed bridges, several studies have estimated the cable tension force using the vibration of cables. Most of these methods for estimating the tension of a cable start with measuring the displacement of the cable. Recent development of commercial cameras provide opportunity for more convenient and efficient method for measuring the displacement of cable. However, traditional vision-based displacement measurement methods require the assumption that the movement of the cable should be measured in parallel to the camera plane. This assumption limits the installation location of the camera when measuring the displacement of a cable. Therefore, this study introduces a new vision-based cable displacement measurement system that can measure the displacement of a cable in various locations even when the camera is installed in the side of the cable. The proposed method consists of three phases: (1) camera projection matrix estimation, (2) cable tracking in the image coordinate, and (3) cable displacement estimation in the world coordinate. To validate the performance of the proposed method, a simulation-based validation test, a lab-scale validation test, and an on-site validation test were conducted. The simulation-based validation test verified the performance of the proposed method in an ideal condition, and the lab-scale validation test showed the performance of the method in physical environment. Finally, the on-site validation test showed that the proposed method can measure the cable displacement with a side view camera.