Cable-pylon Anchorage Research Articles

Research on topology optimization strut-and-tie model and prestress construction for cable-pylon anchorage zone of Fengshuba Bridge

To address the challenges associated with accurate load-bearing capacity calculation and prestress design for the cable-pylon anchorage zone of cable-stayed bridges, a case study focusing on the Fengshuba Bridge is conducted. Utilizing the Solid Isotropic Material with Penalization (SIMP) variable density topology optimization method, a strut-and-tie model (STM) is constructed for the cable-pylon anchorage zone. This model is subsequently employed to verify load-bearing capacity of the struts and nodes within the cable-pylon anchorage zone, as well as to calculate the required quantity of circumferential prestressing tendons. Additionally, a spatial segmental finite element model is established for the cable-pylon anchorage zone to perform a detailed analysis of prestressed structural optimization. This analysis determines various structural details, including the arrangement of prestressing tendons along the height, the design for prestressing blind zones, and the quantity of prestressing tendons. Subsequently, the optimized model is subjected to stress verification. The research results indicate that the adoption of dispersed tendon arrangement results in reduced principal tensile stress within the cable-pylon anchorage zone, in contrast to the concentrated tendon arrangement. The introduction of short prestressing steel bundles within the conduit of prestressing blind zones uniformly enhances the pre-compressive stress on the cable-pylon side wall. Due to the Poisson effect of materials, it is necessary to arrange prestressing tendons appropriately within the cable-pylon anchorage zone. Arranging prestressing steel bundles according to the proposed STM and structural optimization method adequately fulfills the structural force requirements of the cable-pylon anchorage zone.

Steel-concrete-steel sandwich composite cable-pylon anchorage of cable-stayed bridges: horizontal bearing capacity

Steel-concrete-steel sandwich composite cable-pylon is preliminarily applied to bridge engineering due to its excellent mechanical properties and high degree of assembly. However, the stress behavior of the steel-concrete-steel sandwich composite cable-pylon anchorage zone under the strong horizontal component force of the cable force is relatively unknown. In this paper, a 1:4 scaled-down steel-concrete-steel sandwich composite cable-pylon model test under horizontal force is designed and carried out to investigate the strain distribution in inner and outer steel plates, and the horizontal displacements in the pylon wall, and the crack development in the concrete pylon wall. Subsequently, a simplified analysis method is proposed for facilitating the calculation of the load distribution ratios of both steel plates and concrete, and the pylon wall stresses are obtained based on the force method. Furthermore, aiming to improve the problem of excessive stress in the anchorage region of the outer steel plate, the effects of various parameters on the mechanical properties of the anchorage region are investigated through parametric analysis, and the investigated parameters include the diameter of the reinforcement bar, area of the bearing plate, concrete strength, the thicknesses of the steel plate and perfobond ribs. The results indicate that increasing the diameter of the reinforcement bar is insignificant in improving the stress distribution and value of the outer steel plate, and appropriately increasing the bearing area, concrete strength, thicknesses of the steel plate and perfobond ribs can reduce the stress peak value of the outer steel plate, among which changing the thickness of the steel plate and bearing area is the most significant effect. The research results can provide experimental data and theoretical support for the design and optimization of steel-concrete-steel sandwich composite cable-pylon anchorage zones.

Experimental and FEM study on the feasibility of PBL connectors in the composite cable-pylon anchorage zone of cable-stayed bridge

This study investigates the joint between the steel wall plate and the concrete pylon wall in the cable-pylon anchorage zone of cable-stayed bridges, utilizing perfobond rib (PBL) connectors. Finite element analysis (FEM) was conducted on the steel wall plate-concrete joint under various conditions, including cable force, concrete shrinkage, overall warming, and overall cooling, with PBL connectors modeled as spring elements. The results indicate that vertical shear force in the PBL connectors peaks in the steel bracket web plates, with cable force and concrete shrinkage having the most significant impact on stress. Scaled-down local model tests and corresponding solid element FEM analysis were performed to evaluate the load performance of these joints. During tests, deformation between the steel plate and concrete wall remained minimal, and no cracks appeared under loads up to 1.7 times the design load. The ultimate load capacity was 2.9 times the design load, with failure occurring through pullout damage. FEM analysis showed good agreement with test results, and overall stress levels remained low, meeting design requirements. Material yielding only occurred in joint areas under large loads, confirming the feasibility of PBL connectors in composite cable-pylon anchorage zones.

Full-scale segment model test and performance improvement scheme of cable-pylon anchorage zone for cable-stayed bridge

The cable-pylon anchorage zone is a crucial part to ensure the safety of the cable-stayed bridge. However, the true stress and cracks of the cable-pylon anchorage zones are hard to be reflected by theoretical analysis due to their complex configuration. In this paper, full-scale segmental test, finite element (FE) simulation and theoretical analysis are carried out to investigate the distribution of the stress and cracks for the anchorage zone. The form and development of the cracks are observed by full-scale segmental test. The results show that the vertical cracks appear firstly at the anchor end, and then develop into through-cracks under 110% of the design cable force. In addition, the stress distribution of the anchorage zone is studied by FE simulation and theoretical analysis, which demonstrates that the anchorage end has a great risk of cracking. Based on the studies in this paper, an improvement scheme is proposed with a modified layout of prestressing tendons. When the improvement scheme is adopted, the tensile stress of the anchorage zone is obviously decreased and the cracking is improved. This improved method can provide a reference for the design of cable-pylon anchorage zone.

Performance of a U-shaped anchoring system for cable-stayed bridges

An innovative U-shaped anchoring system was previously proposed to prevent the cracking of cable-pylon anchorage zones of concrete pylons in long-span cable-stayed bridges. The anchoring system transfers the cable force to the concrete pylon in the form of radial pressure, which fundamentally prevents the tension cracking of the concrete pylon column. In this study, the mechanical performance of the U-shaped anchorage system was investigated using finite element analysis. Subsequently, the fatigue performance of the steel strand in the U-shaped saddle, the anti-sliding performance of the U-shaped saddle, and the corrosion resistance of the steel strand were experimentally studied. The results of finite element analyses indicate that the U-shaped anchorage system significantly avoids concrete cracking in the cable anchorage zones provided that the strength grade of concrete filler is no less than C30. The experimental results show that the steel strand with polyurea coating has sufficient fatigue resistance as well as adequate anti-corrosion performance, and the anti-sliding performance of the anchoring system is sufficiently good. These critical studies validate the superiority of the U-shaped anchoring system with polyurea-coated steel strands, which should observe wide engineering applications in long-span cable-stayed bridges.

ON THE OPTIMAL STRUT-AND-TIE MODELS AND DESIGN APPROACH FOR THE CABLE-PYLON ANCHORAGE ZONE

The cable-pylon anchorage zone is a typical D-region in a cable-stayed bridge, for which there has been no uniform simplified design method until now. In this paper, based on the extensive statistics of actual projects, topology optimization techniques and principle of minimum strain energy, two precise strut-and-tie models for the cable-pylon anchorage zone are proposed, which can clearly reveal the load-transmitting mechanism of the anchorage zone. Th e explicit geometric parameters of the strut-and-tie models are derived; thus, the designers can directly use these models. A simple design procedure to deploy prestressing tendons in the anchorage zone is also introduced, whose effectiveness and convenience are demonstrated by two design examples. A new design named the “one-way prestressing tendons PC cable-pylon” is also discussed regarding its application scope.

Full-scale Model Test for Anchorage Zone of Pylon: Error Analysis on Elongation of Annular Pre-Stressing Steel Strand

In order to study the mechanism of the annular Pre-stressing steel strands applied to cable-pylon anchorage zone, a full-scale model test and finite element analysis were conducted. Through the research on the full-scale model test of the U-shaped annular Pre-stressing steel strands for the Anchorage Zone of Guangzhou Bridge, the prestressing technique for the U-shaped annular Pre-stressing steel strands was investigated, and the stress distribution in the model were measured and analyzed. It can be found that the elongation of the U-shaped pre-stressing steel strands is greater than the actual theoretical limit, and the results of some project cases also showed that it is a common phenomenon. Finally, the reasons for thus problems and relative suggestions are proposed, they can be used as a reference to engineering practice.

钢锚板式钢-混组合索塔锚固体系单侧受荷承载力数值分析

采用非线性有限元仿真分析方法，研究在单侧受荷下钢锚板式钢-混组合索塔锚固体系的极限承载力。分析结果表明，单侧索力作用时的极限承载能力状态，非加载侧下横隔板与底板之间靠近侧板处混凝土发生破坏，此时，最大主压应力出现在加载侧侧板与上横隔板交界处所对应的混凝土角点处。锚固区普通钢筋最大轴向应力出现在加载侧侧板与上横隔板交界处所对应的外侧钢筋位置。随着荷载系数的增大，混凝土裂缝从加载侧向非加载侧发展，当荷载系数达到3.04时，混凝土塔柱发生破坏。 The ultimate bearing capacity of steel-concrete composite cable-pylon anchorage system with steel anchor slab under the unilateral cable force has been studied using nonlinear finite element analysis method. The analysis result showed that under unilateral load, the concrete between the bulkhead and floor in the non-load side has been broken. At this time the maximum principal compressive stress appeared in the concrete corner point of the junction between the load side plates and upper diaphragm. The maximum axial stress in reinforced anchorage area appeared in the junction between the load side plates and upper diaphragm. With the increase of load, the concrete cracks were developing from the load side to the non-load side. When the load factor reached 3.04, the concrete of tower has been destructed.

Static behaviour of lying multi-stud connectors in cable-pylon anchorage zone

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can`t be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

Study on the Prestressed Arrangement in Cable-Pylon Anchorage Zone of Cable-Stayed Bridge

According to the study on the practical Chaolianxijiang bridge, the stress state of cable-pylon anchorage zone of cable-stayed bridge under two kinds of prestressed arrangements (that is, U-shaped arrangement and parallel arrangement) were calculated and compared. The results suggested that parallel prestressed arrangement could avoid the difficulty caused by other arrangements in the construction. Parallel prestressed arrangement with clear concept, simple structure, clear stress and small amount of work is suitable for the thick walled cable-pylon.

Spatial Mechanical Behavior Research of Cable Anchorage Zone of Special-Shaped Steel Box Concrete Tower

In order to grasp the force performance and stress distribution of shaped pylon steel anchor box under the action of the cable tension, with a main span of 555m length of three towers cable-stayed and self-anchored suspension combined system bridge as the engineering background, through the APDL command stream parametric programming, the different finite element models of pylon steel anchor box is established by the spatial solid element and shell element, the mechanical properties of cable-pylon anchorage zone were studied under the most unfavorable load combination, considering the stress state and distribution characteristics of steel anchor box under different orthodontic force. The results showed that: under the most unfavorable combination of loads, the stress was concentrated at the position of the anchor plate and pressure plate using the initial strain mode; the calculation results of solid element and shell element were consistent by uniform loading mode, which could reflect the real stress state of steel anchor box, but the shell element corner contact area prone to stress calculation distortion.

Research of Loop Pre-Stress Tension Test for Cable-Stayed Bridge Pylon Based on Full-Scale Sectional Model

Based on full-scale sectional model experiment for cable pylon anchorage zone of cable-stayed bridge, this research tested the friction factor and deviation factor of the duct. The reason that tension elongation of loop prestressing tendon exceeded the provision of ±6% in specification was analyzed systematically. A correctional calculation formula was proposed, with quantitative analysis for influencing factors of tension elongation. The formula shows good applicability in practical engineering and has reference value for similar loop prestressing tendon.

Spatial Mechanical Behavior Research of Cable-Pylon Anchorage Zone of Steel Box Concrete Tower

In order to grasp the force performance and stress distribution of shaped pylon steel anchor box under the action of the cable tension, with a main span of 555m length of three towers cable-stayed and self-anchored suspension combined system bridge as the engineering background, through the ANSYS APDL command stream parametric programming, the different finite element models of pylon steel anchor box is established by the spatial solid element and shell element, the mechanical properties of cable-pylon anchorage zone were studied under the most unfavorable load combination, considering the stress state and distribution characteristics of steel anchor box under different orthodontic force. The results showed that, under the most unfavorable combination of loads, the stress was concentrated at the position of the anchor plate and pressure plate using the initial strain mode; the calculation results of solid element and shell element were consistent by uniform loading mode, which could reflect the real stress state of steel anchor box, but the shell element corner contact area prone to stress calculation distortion. The results provide the basis for the design and have some design reference value for the design of the same type bridge.

Investigation on the horizontal mechanical behavior of steel-concrete composite cable-pylon anchorage

The configuration and mechanical behavior of steel-concrete composite cable-pylon anchorage in cable-stayed bridges are very complex. Considerable local deformation of composite cable-pylon anchorage zone could occur under the horizontal component of the inclined cable force. It is difficult and unfeasible to analyze the horizontal mechanical behavior of the composite cable-pylon anchorage by the traditional analytical theory of composite structures. In this paper, full-scale model tests were carried out according to an actual project to analyze the horizontal mechanical behavior of composite cable-pylon anchorage. Stress distribution patterns of the main members and the failure modes were obtained. Structural response of the anchorage was analyzed by spatial solid and shell finite element model. By analyzing and simplifying the configuration and details of the structure, the expression for calculating the horizontal force burdened by the main members of composite cable-pylon was derived based on the deformation compatibility principle. The equation for calculating internal forces of the main members in the composite cable-pylon anchorage was also obtained. It is shown that the proposed simplified method agree well with the experimental result and finite element method result.

Model Test and Structural Behavior Analysis for Cable-Pylon Anchorage Zone of Cable-Stayed Bridge

In long-span cable-stay bridges, anchorage zone of cable-pylon is a key part to transfer cable force to pylon. Because of local concentrated force, irregular pylon section and complicated construction measures, a general mechanical analysis is unable to reflect actual stress distribution and working performance of anchorage zone. Based on Maling River Bridge in Guizhou province, China, clear finite element analysis and reliable full-scale model test for cable-pylon anchorage zone segment were carried out. Not only were design of model test and loading program introduced, but also test content and sensor arrangement were documented. In addition, details of finite element modeling were involved too, such as mesh generation, boundary condition and loading cases. Through comparison and analysis of stress increment and crack observation, the location where larger local tensile stress occurred was obtained. Corresponding anti-cracking load coefficient and safety coefficient of crack width were also presented. Parts of research findings have been used for the guidance of bridge construction.