Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower

Abstract It is recognized that the semi-rigidity of the glass fiber reinforced polymer (GFRP) joint should be considered in the structural analysis of GFRP structures, because of the relatively small initial stiffness resulting from the intrinsic property of GFRP material. Regarding the integrally-f...

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Main Authors: Jinyi Xu, Jian Ma, Yong Chen, Xu Cui, Bing Feng, Wending Mou, Feng Pan
Format: Article
Language:English
Published: Nature Portfolio 2025-05-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-02929-5
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author Jinyi Xu
Jian Ma
Yong Chen
Xu Cui
Bing Feng
Wending Mou
Feng Pan
author_facet Jinyi Xu
Jian Ma
Yong Chen
Xu Cui
Bing Feng
Wending Mou
Feng Pan
author_sort Jinyi Xu
collection DOAJ
description Abstract It is recognized that the semi-rigidity of the glass fiber reinforced polymer (GFRP) joint should be considered in the structural analysis of GFRP structures, because of the relatively small initial stiffness resulting from the intrinsic property of GFRP material. Regarding the integrally-formed GFRP T-joint in the GFRP transmission tower, the study of its semi-rigidity remains inadequate. This paper aims to develop the relevant method for approximating the initial stiffness of the integrally-formed GFRP T-joint, in which the joint connects a vertical column with circular hollow section (CHS) and a horizontal bracing beam with rectangle section (RS). The finite Element (FE) models are first established, and validated by comparing the FE analysis results with the experimental results extracted from the previous study by the authors. The parametric study is subsequently conducted by using the validated FE model to investigate the sensitivity of the initial stiffness to the joint’s main geometrical parameters, i.e., the diameter and the thickness of the column, and the width and the height of the bracing beam. The total number of the specimens numerically modeled for the parametric study is 255. The mechanical model that reveals the main physical source of the initial stiffness is proposed. Based on the parametric analysis results, the approximating formula is then concluded, which is capable of well predicting the initial stiffness of the joint. The formula is first validated by comparing the theoretical results with the FE analysis results, considering the simply-supported T-shaped structures with/without the tapered haunches. Then, the GFRP line-suspension module (GFRP-LSM) utilized in a GFRP transmission tower is employed for further experimental validation. It is found that the structural analysis results, with consideration of the semi-rigidity of the joints, agree well the continuum shell element-based FE analysis results. In terms of the top displacement, the result obtained via the structural analysis is close to the measured data, indicating an error of 9.03%. In contrast, a significant discrepancy would be found when the semi-rigidity of the joints is neglected in the analysis, and the error would increase to 21.86%. The comparison again highlights the importance of considering the semi-rigidity of the GFRP joints in the structural analysis of a GFRP structure.
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spelling doaj-art-c8188178211c4fefbe4f42dbf7b4b25a2025-08-20T02:00:08ZengNature PortfolioScientific Reports2045-23222025-05-0115111910.1038/s41598-025-02929-5Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission towerJinyi Xu0Jian Ma1Yong Chen2Xu Cui3Bing Feng4Wending Mou5Feng Pan6College of Civil Engineering and Architecture, Zhejiang UniversityJinhua Electric Power Design InstituteCollege of Civil Engineering and Architecture, Zhejiang UniversityChina Railway Siyuan Survey and Design Group Co., LtdShaoxing Daming Electric Power Design Institute Co., LtdChina Energy Engineering Group Zhejiang Electric Power Design Institute Co., LtdChina Energy Engineering Group Zhejiang Electric Power Design Institute Co., LtdAbstract It is recognized that the semi-rigidity of the glass fiber reinforced polymer (GFRP) joint should be considered in the structural analysis of GFRP structures, because of the relatively small initial stiffness resulting from the intrinsic property of GFRP material. Regarding the integrally-formed GFRP T-joint in the GFRP transmission tower, the study of its semi-rigidity remains inadequate. This paper aims to develop the relevant method for approximating the initial stiffness of the integrally-formed GFRP T-joint, in which the joint connects a vertical column with circular hollow section (CHS) and a horizontal bracing beam with rectangle section (RS). The finite Element (FE) models are first established, and validated by comparing the FE analysis results with the experimental results extracted from the previous study by the authors. The parametric study is subsequently conducted by using the validated FE model to investigate the sensitivity of the initial stiffness to the joint’s main geometrical parameters, i.e., the diameter and the thickness of the column, and the width and the height of the bracing beam. The total number of the specimens numerically modeled for the parametric study is 255. The mechanical model that reveals the main physical source of the initial stiffness is proposed. Based on the parametric analysis results, the approximating formula is then concluded, which is capable of well predicting the initial stiffness of the joint. The formula is first validated by comparing the theoretical results with the FE analysis results, considering the simply-supported T-shaped structures with/without the tapered haunches. Then, the GFRP line-suspension module (GFRP-LSM) utilized in a GFRP transmission tower is employed for further experimental validation. It is found that the structural analysis results, with consideration of the semi-rigidity of the joints, agree well the continuum shell element-based FE analysis results. In terms of the top displacement, the result obtained via the structural analysis is close to the measured data, indicating an error of 9.03%. In contrast, a significant discrepancy would be found when the semi-rigidity of the joints is neglected in the analysis, and the error would increase to 21.86%. The comparison again highlights the importance of considering the semi-rigidity of the GFRP joints in the structural analysis of a GFRP structure.https://doi.org/10.1038/s41598-025-02929-5Integrally-formed GFRP T-jointFinite element analysisExperimental studySemi-rigidityApproximating formula
spellingShingle Jinyi Xu
Jian Ma
Yong Chen
Xu Cui
Bing Feng
Wending Mou
Feng Pan
Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower
Scientific Reports
Integrally-formed GFRP T-joint
Finite element analysis
Experimental study
Semi-rigidity
Approximating formula
title Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower
title_full Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower
title_fullStr Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower
title_full_unstemmed Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower
title_short Initial stiffness of integrally-formed GFRP T-joint in GFRP transmission tower
title_sort initial stiffness of integrally formed gfrp t joint in gfrp transmission tower
topic Integrally-formed GFRP T-joint
Finite element analysis
Experimental study
Semi-rigidity
Approximating formula
url https://doi.org/10.1038/s41598-025-02929-5
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