考虑主材节点刚域影响的钢管输电塔变截面梁单元有限元模型

为了准确、快捷地计算加劲板和连接板形成的主材节点刚域对输电塔受力的影响,将考虑节点刚域影响的主材视为若干段段不同截面梁单元的组合。首先,推导了主材两端节点刚域横截面转动惯量和面积的公式;然后,根据能量原理,推导了变截面梁单元的单元刚度矩阵,并采用C++语言将它引入开源有限元软件OpenSees;最后,将主材及节点刚域采用变截面梁单元,常截面梁单元,变弹性模量梁单元及壳单元离散的有限元模型计算结果和塔架试验的实测结果进行对比。结果表明:常截面梁单元会低估主材的弯矩和最大正应力,而变弹性模量梁单元会低估输电塔的挠度,均会使设计偏于不安全;变截面梁单元和壳单元的计算结果均实测结果很接近,但前者计算量远小于后者。可见:变截面梁单元有限元模型兼顾了计算效率和精度。

FINITE ELEMENT MODEL OF VARIED-SECTION BEAM ELEMENT FOR TUBULAR TRANSMISSION TOWER CONSIDERING RIGID ZONES OF MAIN MEMBERS

To consider the effect of the rigid zones of joints made of stiffeners and connecting plates on steel tubular transmission towers efficiently and accurately, the main member is seen as a combination of several beams with different sections. Firstly, the formulations for the area and inertia-moment of the cross section of the rigid zone on the either side of main members were derived. Secondly, based on energy theorem, the element matrix of a variable section beam is achieved, and the open source software OpenSees by C++ is introduced. Finally, the results by the finite element models where the main members and the rigid zones were simulated by varied-elastic modulus beam elements, and the constant section beam elements, variable section beam elements and shell elements were compared. It shows that: the constant section element underestimates the moments and the maximum stress of main members, while the variable elastic element underestimates the displacement of a tower. They all lead to the unsafe design of a tower. The results by a variable section beam and shell elements are very close to the results by the experiment, while the calculation expense is much less than the former. Therefore, the efficiency and the accuracy of the variable-section beam element model are proven.