Cable Tower Research Articles

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.

Research on Macro-Micro Mechanical Properties of Cable Tower Surface Based on Multiscale Homogenization Theory

Research on Macro-Micro Mechanical Properties of Cable Tower Surface Based on Multiscale Homogenization Theory

Wind-Induced Vibrations and Gust Response Factors of the Cabin–Cable–Tower System

A large-scale radio astronomical telescope is a typical complex coupled system, consisting of a feed cabin, cables, and supporting structures. The system is extremely sensitive to wind loads, especially the feed cabin, which has high requirements for vibration displacement during operation, and excessive vibration may affect normal operation. To investigate the wind-induced vibration characteristics of such coupled systems, this study takes the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) as an example to conduct research. First, a refined finite element model of FAST is established, and a dynamic analysis using simulated random wind loads is conducted. The influence of the cable boundary on the time–frequency domain responses of the feed cabin is particularly considered. Then, the gust response factor (GRF) for different structural components within the coupled system is calculated. Finally, the evolution law of the GRF under various wind speeds and directions is revealed by parametric analysis. The parameter analysis only considers the wind directions ranging from 0° to 60°, because FAST is a symmetric structure. The results indicate that obvious differences are observed in both the rotational and translational displacements of the feed cabin under northward wind, especially the results along the east–west axis. When the supporting towers are considered, there is no change in the power spectral density (PSD) of the feed cabin in the low-frequency range. However, in the high-frequency range, taking the supporting towers into account leads to an increase in PSD and a resonance near the first-order natural frequency of the supporting tower. The GRF based on the dynamic response exhibits substantial deviations compared to those obtained from design codes, highlighting the need for an independent analysis when determining GRF for such coupled systems.

Research on Dynamic Response of a Single-Tower Cable-Stayed Bridge with Successive Cable Breaks Based on a 3D Index

Aiming at the problem of cable breakage of an asymmetric single-tower cable-stayed bridge by taking a single-tower cable-stayed bridge that has been in operation for more than 20 years as an engineering example, a spatial finite element model that reflected the actual stress state of the structure was established and a method for solving the time point of cable breakage was proposed. The results show that the strength of the main girder, pylon and cable could meet the stress requirements of the vibration caused by successive cable breaks, and the maximum dynamic displacement of the main girder did not exceed the stiffness limit. Although the breakage of the stay cable caused the stress in the adjacent position and the corresponding position on the opposite side of the tower to increase sharply, the stress fluctuation in other positions was small. The fluctuation of the dynamic stress of the cable tower was relatively small, but the displacement of the tower top changed greatly. The dynamic response of the cables breaking in succession was less than that of simultaneous breaking, and the structural vibration caused by cable breaking was not as severe as that caused by simultaneous breaking.

Real-Time Intelligent Prediction Method of Cable’s Fundamental Frequency for Intelligent Maintenance of Cable-Stayed Bridges

Cable’s fundamental frequency (CFF) is an important characteristic of the working state of long-span cable-stayed bridges. The change in the bridge’s temperature field will influence CFF by altering the cable’s tension and the cables’ sags. An accurate regression model between the temperature-induced variation of CFF and the real-time changing temperature field should be established. Then, the reference value of the temperature-induced variation of CFF can be obtained after inputting the real-time temperature data. In this study, an intelligent real-time prediction model for CFF is proposed based on the full-bridge temperature field, including the average temperature of the main beam, the vertical temperature difference of the main beam, and the temperature of the cable tower. Besides, a machine learning method named the long short-term memory (LSTM) network is exploited to ensure the nonlinear fitting performance of the model, and a paradigm for optimal hyperparameter selection and training strategy selection is provided. To verify the superiority of the LSTM-based model, the output accuracy of the linear regression, BP network, and LSTM network was tested and compared using the monitoring data collected from cable sensors in the main span and side span, which provides an important basis for the intelligent maintenance and sustainable operation of the bridge cables.

Comparisons of Design Schemes for the upper beam support at east cable tower of Lingdingyang Bridge on Shenzhen-Zhongshan Link

The complex site conditions of Lingdingyang Bridge on Shenzhen-Zhongshan Link lead to many construction difficulties. The design of the support affects the construction quality of the super-height, large-weight and long-span beam on the cable tower. In order to achieve a high-standard construction and control the quality of the project, three support design schemes for the upper beam of the east cable tower of Lingdingyang Bridge were studied and compared by calculating and analyzing with the finite element software. Ultimately, the plan of the upper arch bracket stands out among the three schemes. The bracket scheme can not only meet the quality requirement of the main structure, but also reduce the construction difficulty and cost of the temporary structure, which can provide reference for the design of similar projects in the future.

Investigation on Seismic Response of Long‐Span Special Steel Truss Cable‐Stayed Bridge

Due to the small self‐weight of the steel truss cable‐stayed bridge with a single tower and a single cable plane, the torsional stiffness and wind stability of the structure are reduced. The arrangement of the deck type makes the mechanical properties of the cable‐stayed bridge more complicated while reducing the cost and increasing the aesthetics. The effects of structural parameter variations and traveling wave effects on the seismic response of this steel truss cable‐stayed bridge with a single tower and a single cable plane were investigated by the nonlinear time‐history analysis method and nonuniform seismic analysis method. The results show that the displacement of the floating system under seismic action is larger than the other three systems, but its internal force is significantly smaller than the other three systems. The spectral characteristics and the duration of ground shaking have a greater influence on the maximum bending moment values corresponding to the height of the cable tower and the maximum axial force values of the main girder bars corresponding to the length of the bridge under earthquake action. The effect of steel truss girder stiffness parameter variations on structural internal forces of bridges and the effect of traveling wave effects on structural displacements of bridges in specific apparent wave velocity intervals do not exist universally.

Aerial Tramway Sustainable Monitoring with an Outdoor Low-Cost Efficient Wireless Intelligent Sensor

Infrastructures such as aerial tramways carry unique traffic operations and have specific maintenance requirements that demand constant attention. It is common that old structures lack any type of automatization or monitoring systems, relying only on human judgment. Owners are interested in implementing techniques that assist them in making maintenance decisions, but are reluctant to invest in expensive and complex technology. In this study, researchers discussed with the owners different options and proposed a sustainable and cost-efficient solution to monitor the Sandia Peak Tramway operations with just two strategically located acceleration sensors. To maximize the success options researchers worked with the owners and developed a sensor that satisfied their needs. A Low-cost Efficient Wireless Intelligent Sensor 4—Outdoors (LEWIS 4) was developed, tested and validated during the experiment. Two solar-powered units were installed by the tramway staff and recorded data for three days. When retrieved, researchers analyzed the data recorded and concluded that with only two sensors, the acceleration data collected were sufficient to determine the position and location of the tramway cars. It was also found that the sensor on the tower provides data about the cable–tower interaction and the forces caused by the friction on the system, this being a critical maintenance factor. This work summarizes a methodology for infrastructure owners consisting of guidelines to design a sustainable and affordable monitoring approach that is based on the design, development and installation of low-cost sensors.

Discussion on the Design of Cable Tower Grouping-Anchorage System of Cable-Stayed Bridge

Cable Tower Grouping-Anchorage-System of Cable-Stayed Bridges is a new type of anchorage system, which is only used in Chi-Zhou bridge in An Hui province in domestic. In order to understand the behavior characteristics and the design methods, took Chi-Zhou Bridge as an example. Firstly, the propaedeutics were introduced, and then the finite element models of the whole bridge were built in six different cases and parameters sensitivity were analyzed which included cables layouts, agglomeration forms and steel beams design. Then took introduced the beam-column stiffness ratio, studied the stiffness matching between concrete tower and steel beam and clarified the influence of grouping, agglomeration and stiffness ratio on the whole bridge. Some design suggestions were stated. The results showed that the Grouping-Anchorage-System is more advantageous on the lateral stability and torsion resistance of the whole bridge; The steel beams are the key point of design because of the stress complexity. Changing the length of the steel beam will bring about changes in the local stress and changing the space between steel beams will bring about changes in the whole bridge. Considering the layout spaces and detailing requirements, the length of steel beams should be reduced as much as possible, so as to improve the efficiency of stay cables, which is beneficial to the whole bridge stress and economy.

Analysis of tower foundation of long span single tower cable stayed bridge

The pylon is an important stressed structure in the single pylon cable-stayed bridge. The rationality of bearing platform and pile foundation of pylon foundation is one of the key research contents in the design of single pylon cable-stayed bridge. The main bridge of Tarim bridge in Xinjiang is a single tower double span cable-stayed bridge with span arrangement of (41 + 168 + 168 + 41) m and total height of cable tower of 125m. Arc shaped concrete tower columns are adopted. The stress of cable tower foundation is complex. The stress analysis of foundation scheme is one of the key problems of this project. In this paper, the geological conditions, structural stress, economic rationality, construction convenience and other factors are comprehensively considered, the different foundation types are compared and analyzed, the reasonable foundation type and layout type are determined, and the stress of the pile and cap structure of the main tower foundation is calculated and analyzed. Through the solid finite element model, this paper analyzes the influence of the stiffness deformation of pile cap on the stress of pile group foundation. The calculation results show that the stress of dumbbell shaped pile cap is more reasonable than that of rectangular foundation pile cap, and the number of pile foundation and the calculated pile length are reduced in varying degrees. By adjusting the pile foundation arrangement under dumbbell shaped foundation, the stress of pile foundation can be more uniform, which can be used as the foundation for similar projects. The foundation design provides reference and reference.

Deep Learning-Based Minute-Scale Digital Prediction Model of Temperature-Induced Deflection of a Cable-Stayed Bridge: Case Study

The evolution rule of temperature-induced deflection in main girders is an important index to evaluate the service performance of long-span cable-stayed bridges, which directly reflects the coupling effect between the vertical stiffness of the main girder and the tension of multiple cables. However, temperature-induced deflection is caused by the complex temperature field of the main girder, cable tower and cable, while monitoring data have documented a time-lag effect between the temperature and temperature-induced deflection. Hence, it is difficult to accurately describe and model the behavior of the temperature-induced deflection in a long-span cable-stayed bridge in service. To this end, by utilizing the advantage of long short-term memory (LSTM) network for time series prediction, a digital model in minute scale based on monitoring data and deep learning can be developed to predict temperature-induced deflection, and resolve the low precision caused by the single-point input and time-lag effect. Compared with traditional machine learning algorithm and linear regression, a deep learning LSTM network has the best performance. For the cable-stayed bridge in this paper, the mean absolute error of the LSTM model was even less than 0.5 mm, and with the combined hypothesis test, the early warning accuracy for the abnormal change of temperature-induced deflection could achieve a minimum of 0.3%.

Reliability Analysis of Zipline Project in A Mountainous Eco-tourism Scenic Spot

In order to study the reliability and safety of the zipline project of an ecological cultural tourism scenic spot, Zhenxiong County, Zhaotong City, Yunnan Province, based on the field investigation and data collection, the three-dimensional model of the project is constructed by Midas civil, and the reliability of the zipline structure under pedestrian load is calculated. The calculation results show that after the completion of the zipline, the overall maximum combined displacement is concentrated in the middle of the span, the displacement is small, and the overall combined displacement of the zipline decreases to both ends of the tower; under the action of human load, the stress of the zipline and the cable tower increases, and the displacement of the main components also increases obviously, but it is within the acceptable range as a whole. The research results provide a reference for the normal operation of the project.

Effects of Steel Slag Powder and Expansive Agent on the Properties of Ultra-High Performance Concrete (UHPC): Based on a Case Study.

In view of the performance requirements of mass ultra-high performance concrete (UHPC) for the Pang Gong bridge steel cable tower in China, the UHPC incorporating of steel slag powder and hybrid expansive agents is optimized and prepared. The effects of steel slag powder and hybrid expansive agents on the hydration characteristics and persistent shrinkage of UHPC are investigated. The results indicate that 15 wt.% steel slag powder and 5 wt.% hybrid expansive agents can effectively reduce the drying shrinkage deformation of UHPC with a slight decrease of strength. Heat flow calorimetry results show that the incorporation of steel slag powder and expansive agents decreases the hydration heat at three days. Moreover, the obtained adiabatic temperature rise of UHPC is 59.5 °C and the total shrinkage value at 180 days is 286 με. The hydration heat release changes of large volume UHPC in the steel-concrete section of cable tower is agreed with the result of adiabatic temperature rise in the laboratory.

Research on Static Characteristics of Steel-Concrete Composite Beam Cable-Stayed Bridge during Construction

As the construction continues, the structural system and load of the cable-stayed bridge will change. At different construction stages, the forces and deformations of the structure will have their own characteristics. In this paper, in order to study the static characteristics of steel-concrete composite beam cable-stayed bridge during construction, the Jiqi Yellow River Highway Bridge is used as the engineering background, and the finite element modeling is carried out by midas. The main beam, cable tower and stay cable of the cable-stayed bridge are analyzed respectively. Among them, the static characteristics of steel and concrete bridge deck during construction are specially analyzed. In this way, it is ensured that all structures are in a safe state during the construction process, and then the construction.

Dynamic Performance and Anti-earthquake Analysis of Cable-stayed Arch Bridge

The strength, stiffness, and stability check calculations and the effect of earthquakes should be considered in the design of cable-stayed arch bridges with collaborative systems. This study aims to investigate the dynamic performance and structural response of cable-stayed arch bridges under seismic action. The space analysis model is enhanced of the Xiang Feng River Bridge using finite element software Midas Civil, whose lower foundation considers the effects of piles and soil. Firstly the vibration period, vibration frequency, and modal characteristics are computed, thus the dynamic performance is summarized of the bridge. Then, a proper seismic wave is selected according to engineering conditions and in terms of three orthogonal directions: inputting the adjusted El Centro seismic wave, considering Rayleigh damping, and calculating via the Newmark method. Furthermore, a time-history response analysis under the action of one-dimensional and multidimensional earthquake is performed. Lastly, the results of the response analysis is compared and the behavior characteristics of arch bridge is summarized under seismic action. The results show that the transverse stability problem of bridges is prominent and should be the focus of antiearthquake fortification, the inclined cable tower of this bridge is not conducive to the earthquake resistance of the structure in comparison with the vertical cable tower. and the influence of horizontal and vertical earthquake actions should be considered in antiearthquake designs.

Analysis on local force of cable tower in low tower cable-stayed bridge

Concrete under pylon saddles in extradosed cable-stayed bridges is usually subjected to tremendous cable force, which might easily cause cracking or crushing of concrete and lead to potential structural security problems. At present, the finite element mechanical analysis model for the cable saddle is not accurate enough to analyse the real stress situation. A stress analysis method of concrete under the cable saddle based on the accurate finite element model is presented in this paper. In order to obtain the exact stress results of the concrete under the saddle, this paper modelled the filament dividers in the saddle one by one, and established the loading surface element on the surface of each filament divider layer to apply the equivalent surface force layer by layer. In addition, this paper also studied the stress characteristics of the lower tower column in the tower bridge, and put forward structural reinforcement suggestions for the force of the lower tower column. The results of this paper can provide reference for the design and construction control of pylons in extradosed cable-stayed bridge.

Application of Tower Girder Asynchronous Construction Technology

When constructing the tower beam in a traditional way, the tower beam will be simultaneously constructed with the tower column, it asks for a complicated construction procedure, difficult construction organization, long operating cycle, and highly increased construction cost. With the progress of technology, Asynchronous construction scheme of the tower column and tower beam is adopted and applied. This paper is based on the case of asynchronous construction of the H-type cable tower and beam of the six large-span Ao jiang Bridges.

Analysis of wind-resistant and stability for cable tower in cable-stayed bridge with four towers

Wind speed time history simulation methods have been introduced first, especially the harmonic synthesis method introduced in detail. Second, taking Chishi bridge for example, choosing the particular sections, and combined with the design wind speed, three-component coefficient simulate analysis between -4°and 4°has been carry out with the Fluent software. The results show that drag coefficient reaches maximum when the attack Angle is 1°. According to measured wind speed samples,time history curves of wind speed at bridge deck and tower roof have been obtained,and wind-resistant time history analysis for No.5 tower has been carry out. Their results show that the dynamic coefficients are different with different calculation standard, especially transverse bending moment, pulsating crosswind load does not show a dynamic amplification effect.Under pulsating wind loads at bridge deck or tower roof, the maximum displacement at the top of the tower and the maximum stress at the bottom of the tower are within the allowable range. The transverse stiffness of tower is greater than that of the longitudinal stiffness, therefore wind-resistant analysis should give priority to the longitudinal direction. Dynamic coefficients are different with different standard, the maximum dynamic coefficient should be used for the pseudo-static analysis.Finally, the static stability of tower is analyzed with different load combinations, and the galloping stabilities of cable tower is proved.

Analysis on the aerodynamic behavior and noises of the cross section of the cable tower for long-span bridges

Cable towers are an important aerodynamic noise source of long-span bridges. The flow effect of various parts of the cable tower on airflow will cause large aerodynamic noises and thus influence environments. This paper conducted on research on the cross-sectional structure of the cable tower of long-span bridges, built a computational model of aerodynamic noises for cable towers of long-span bridges with original rectangular cross section and improved cross section. The computational fluid dynamics was adopted to analyze the non-steady flow of cable towers, and the numerical value of aerodynamic noises was predicted based on Lighthill’s acoustic analogy. Then, acoustic BEM was also adopted to study radiation noises of cable towers in the far-field. Results showed that improved cable tower could reduce the dispersion degree of airflow and weaken Karman Vortex Street. Aerodynamic noises induced by cable towers with improved cross section mainly radiated in a direction perpendicular to airflow, and the directivity of noises was obvious. Sound pressure level (SPL) of aerodynamic noises of cable towers with improved cross section was 4.2 dBA less than that of initial rectangular cross section in the far-field, which showed obvious effect on noise reduction. In the meanwhile, this paper studied the mechanism of main frequency at various parts of cable towers with improved cross section and discussed the reason of noise reduction, whose research achievements could provide design basis for generation mechanism and reduction of aerodynamic noises of cable towers of long-span bridges.

钢锚板式钢-混组合索塔锚固区PBL剪力键传力机理分析

索塔采用混凝土、锚固区采用钢锚板的斜拉桥索塔锚固体系，构造简单，受力合理。本文针对这种新型锚固体系中PBL剪力键进行了静力性能有限元分析，分析结果表明，在沿整个PBL键穿孔钢筋长度方向上，传力主要集中在钢锚板附近的长度；对于多层PBL键穿孔钢筋，沿着竖向方向从上到下PBL键穿孔钢筋传递的力逐渐减小；当增大PBL键穿孔钢筋直径或增加钢锚板厚度时，PBL键的应力和位移都随着减小；不考虑钢锚板与混凝土之间的粘结作用时，与钢锚板接触但无粘结作用的混凝土应力水平较低且分布均匀。这种新型锚固体系采用PBL剪力键作为钢构件与混凝土之间的连接件能很好的利用材料性能，受力性能良好。 Cable tower anchorage zones, using concrete and steel anchor plate of cable support tower ca-ble-stayed bridge system, have simple structure and reasonable stress. The static performance of the PBL shear keys in the neotype anchoring system has been carried on using finite element analysis. The analysis results show that on the perforated steel bar length direction along the whole group’s key, force mainly concentrated in the length of the steel anchor plate near. For multilayer perforated steel group’s key, from top to bottom along the vertical direction, PBL key perforated steel transmission force decreases. When increasing the PBL key perforated rebar diameter or increasing the thickness of the steel anchor plate, the stress and displacement of the PBL are decreased. Regardless of cohesive action between steel anchor plate and concrete, concrete stress level is lower and evenly distributed. This new type of anchorage system adopting PBL shear keys as joints between steel and concrete can make good use of the material performance. The mechanical performance is good.