Experimental and numerical study on stress distribution in a cross section of Galfan spiral strand

https://doi.org/10.1016/j.jobe.2021.102311Get rights and content

Highlights

  • The surface stress of four types of strands was measured.

  • Stress distribution law of cross section of strand.

  • The stress non-uniformity coefficient was proposed.

  • Stress non-uniformity coefficient equation.

  • Calculation method of maximum stress in cross section of strand.

Abstract

The stress distribution law of the cross section of a Galfan spiral strand is studied in this paper. Axial tensile tests are carried out on four types of strands to obtain the relationship curve between the surface stress of the strand and the axial tension. The three-dimensional strand model is established by ABAQUS and verified by experiments. Based on the finite element model, the stress distribution in the cross section of a strand under different stress ratios is studied. The stress distribution coefficient is used to evaluate the degree of non-uniform stress distribution. The effects of wire diameter, wire lay length, and wire layer number on the distribution coefficient are then analyzed. The equation of the stress distribution coefficient of the core wire is obtained by regression, and the method for calculating the maximum stress of the strand is put forward.

Introduction

Cable structures are widely used in many large-scale public buildings due to their beautiful shape and high material utilization. Galfan spiral strand is increasingly used in China because of its high corrosion resistance and strength. In engineering design, it is usually assumed that the stress of the strand section is uniform, which can simplify the calculation. However, the geometric structure of Galfan spiral strand is complex, and the wires are twisted and pressed against each other, which makes the stress distribution of the cable unclear. In order to ensure the safety of buildings with Galfan spiral strand, 50%–55% of the ultimate tensile standard value is used as the tensile design value [1,2], which is far lower than the limit of ordinary steel structures. Therefore, the high-strength characteristics of Galfan spiral strand have not been fully utilized, which has resulted in a waste of materials.

In recent years, the mechanical properties of cables have attracted wide attention from scholars. In 1973, Costello [3,4] proposed a theory for calculating the stress of multilayer cables under axial, torsional, and bending loads. Utting and Jones [[5], [6], [7]] carried out axial tensile tests on 1 × 7 spiral strand under different boundary conditions and measured the extension and rotation of the steel strands. A mathematical model of the strand was then established to discuss the mechanical properties of the strand. Later, Utting and Jones [8] carried out axial tensile tests on 1 × 19 spiral strand under different end restraints. The torque generated under tensile load and the extension and rotation of the strand were obtained. Jiang [[9], [10], [11], [12]] established a simplified model of 1 × 7 spiral strand and 1 × 19 spiral strand to analyze the elastic-plastic behavior of the strands. Judge et al. [13] established an elastoplastic model of 1 × 7 spiral strand and 1 × 120 spiral strand under axial loading to study the non-uniform stress of the strand. Kumar [14,15] developed an equation of the critical contact stress of 1 × 7 spiral strand and verified it by experiments. Kmet [16] carried out an axial tension test on a 1 × 61 spiral strand bent over a curved support and measured the stress of the strand. Yu et al. [17] carried out quasi-static bending tests on 1 × 91 spiral strand to investigate the strand bending response under different end conditions. Later, Yu et al. [18] proposed a beam-spring model that could successfully predict the strand bending properties and flexural stiffness. Abdullah [19] investigated the stress of 1 × 7 spiral strands and analyzed the fracture dynamic behavior. Later, Abdullah [20] conducted axial tensile tests on straight single 1 × 7 spiral strand to evaluate the properties of the strand under wire cutting. Yusuf [21] conducted axial tensile tests on straight single 1 × 7 spiral strand and measured the strain along the strand direction and the spiral wire direction. Based on the test results, a model was established to predict cable strain by linear regression. Liu et al. [22] carried out axial tensile tests on 1 × 7 spiral strand under high temperatures to study the effect of temperature on the mechanical behavior of strands. Sun [23] carried out axial tensile tests on straight single 1 × 19 and 1 × 37 Galfan spiral strand to determine elastic modulus, yield and ultimate strength, and stress-strain. A finite element model (FEM) was established to study the stress development and contact pressure of the strand.

To sum up, most research has focused on the overall performance of strands, but few scholars have explored the cross-sectional stress of strands. Therefore, this paper carries out an experimental study on four types of strands to measure the stress of the outer layer of the strands. The law of stress distribution of the strands is studied by ABAQUS. A stress distribution coefficient for evaluating the degree of non-uniform stress distribution is proposed. The effects of parameters such as wire diameter, lay length, and number of layers on the stress distribution of the cross section are analyzed. The stress distribution coefficient can successfully modify the average stress of the strand to obtain the maximum stress of the strand cross section. This study lays the foundation for proposing a reasonable design index of Glafan spiral strand.

Section snippets

Specimens

The spiral structure of Galfan spiral strand is shown in Fig. 1. The twisting direction of the spiral wires in different layers is opposite to that of the previous layer. A total of eight Galfan spiral strands were made for axial tensile testing. The structure of the strands were 1 × 7 wires, 1 × 19 wires, 1 × 37 wires, and 1 × 61 wires (shown in Fig. 2). Detailed information of the test specimens numbered GSS-1~GSS-8 are listed in Table 1.

Testing device and procedure

A 50-ton loading machine working was used for the

Finite element analysis

To study the stress distribution inside the strand, a geometric model of the strand was established by SolidWorks and introduced into ABAQUS to establish a three-dimensional finite element model, which took into account the pressure and friction between wires. The parameters used in the finite element analysis of the Galfan spiral strand were determined based on the survey results listed in Table 3. The C3D8R element was used to numerically simulate the strand. The surface contact between all

Parameter analysis of stress distribution coefficient

The parameter analysis of Galfan spiral strand was carried out on the basis of 1 × 19 wire. The effects of wire diameter, wire layer length, and wire layer number on the stress distribution coefficient of strands were studied. The values of each parameter are listed in Table 4.

Conclusions

In this paper, axial tensile tests of four types of strands were carried out to measure the stress of the outer layer of the strand. The stress distribution of the strand was studied by ABAQUS. A distribution coefficient was proposed to evaluate the stress distribution of the strand cross section. The effects of wire diameter, lay length, and layer number on the distribution coefficient were then analyzed. The following conclusions and suggestions were determined.

  • (1)

    There is a linear relationship

CRediT authorship contribution statement

Weizhong Hu: Methodology, Resources, Data curation, Formal analysis, Writing – original draft, Visualization. Weiguo Yang: Funding acquisition, Supervision, Investigation. Meng Wang: Conceptualization, Writing – review & editing. Pei Liu: Validation, Project administration.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the National Key R&D Program of China (2019YFC1521000) and the National Nature Science of China (NO. 51578046).

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