输电铁塔螺栓连接滑移模型及结构分析方法研究

Conventional space truss model cannot meet with the requirement of structural analysis on transmission towers, especially for the UHV cat head tower (cup type tower) and the towers in foundation deformation regions. Until now, the bolted-joint slip theories and the analyzed results with their applications have not reached a consensus. The modeling method simulating all bolted-joints at the same time is quite complex. Simplification of the analysis model is a key point for the real application in tower design. Foundational study on the bolted-joint model and practical analysis method for transmission towers will be carried out in this project. The detailed study contents are as follows. Firstly, based on test data analysis of the prototype towers, some statistical characteristics of the bolt gaps as well as the effect levels on displacements and stresses will be obtained. Four types of bolted-joint slip models will be studied, and the general mathematical expressions and the key parameter values can be obtained. Secondly, with application of the determined slip models in the nonlinear FEA analysis, effects on the static and dynamic characrestics of transmission towers will be analyzed. Non-dimensional relationships between the modification factors of slip effects and the tower loads as well as the geometrical parameters can be revealed. And the controlled bolted-joint types will be determined for different tower types and load cases. Lastly, the practical modeling method which can simulate the slip effect effectively will be proposed. This project aims at studying the bolted-joint slip mechanism and exploring the simplifying method for tower structure analysis, which can provide technical supports for the structural analysis of some special type towers and assessment on the bearing capacity of transmission tower with foundation deformation, and also for studies on the dynamic loads of transmission towers.

传统空间桁架模型不能满足特高压猫头塔（酒杯塔）曲臂变形和基础变形区铁塔结构分析的需要，目前在螺栓连接滑移理论和应用分析结论方面还未达成共识。同时模拟全部螺栓连接节点的建模方法十分复杂，合理简化分析模型是其在铁塔设计中得到应用的关键。本项目拟对输电铁塔螺栓连接滑移模型及实用分析方法进行基础科学研究，具体内容包括：分析真型试验数据获得螺栓间隙、连接滑移对节点位移和杆件应力影响程度的统计特征，试验研究四种类型连接滑移模型的一般数学表达和关键参数取值；采用非线性有限元法研究连接滑移对铁塔静动力特性的影响规律，揭示连接滑移影响修正系数与铁塔荷载和几何参数的无量纲关系，确定不同塔型和工况下起控制作用的节点类型，提出模拟螺栓连接滑移影响的实用建模分析方法。本项目旨在通过研究典型节点螺栓连接滑移机理，探索其结构分析应用的简化方法，为开展特殊塔型和基础变形区铁塔承载性能评估及动力荷载研究提供技术支持。

1、项目背景. 传统空间桁架模型不能满足特高压猫头塔（酒杯塔）曲臂变形和基础变形区输电铁塔结构分析的需要，目前在螺栓连接滑移理论和应用分析结论方面还未达成共识。同时模拟全部输电铁塔螺栓连接节点的建模方法十分复杂，合理简化分析模型是其在输电铁塔设计中得到应用的关键。本项目旨在通过研究典型节点螺栓连接滑移机理，探索其结构分析应用的简化方法，为开展特殊塔型和基础变形区输电铁塔承载性能评估及动力荷载研究提供技术支持。.2、主要研究内容. 通过分析输电铁塔螺栓节点螺孔直径实测数据，获得了输电铁塔螺栓间隙的概率统计特征，试验研究了典型螺栓连接滑移模型的一般数学表达和关键参数拟合取值；分别采用基于改进单位荷载法和非线性弹簧单元的结构有限元法，研究了螺栓连接滑移对输电铁塔静、动力特性的影响规律，揭示了连接滑移影响与输电铁塔荷载类型的无量纲关系，掌握了典型荷载工况下起控制作用的螺栓连接节点类型，提出了模拟输电铁塔螺栓连接滑移影响的2种实用建模分析方法。.3、重要结果. （1）提出了输电铁塔螺栓连接滑移指数模型和改进分段多项式模型的参数拟合取值。改进分段多项式模型仅适用于最大间隙和理想间隙两种螺栓节点型式，在考虑螺栓连接滑移影响的输电铁塔结构分析中推荐采用指数形式的连接滑移模型。. （2）提出了基于改进单位荷载法和非线性弹簧单元的输电铁塔结构实用建模分析方法，改进单位荷载法计算简便且输电铁塔K窗位移计算值与真型试验值较为吻合。.4、关键数据及科学意义. 本项目研究建立了输电铁塔典型螺栓连接节点的滑移模型，提出了2种模拟螺栓连接滑移的输电铁塔实用建模分析方法。所得研究成果可为准确确定输电铁塔结构变形、失效模式和动力特性，提高输电铁塔尤其是特高压猫头塔（酒杯塔）结构设计水平和开展基础变形区输电铁塔承载性能评估提供理论指导。