树状结构铸钢分叉节点分析计算、仿生优化及试验研究

Applications of Tree-like Structures are taking on a more widely foreground, however the Cast Steel Branch Joints used in Tree-like Structures are not studied detailed enough. Some problems have been proposed in engineering practice such as shortage of optimization, a large amount of money spent in experiments, no codes to use and so on. Sometimes they may be the technological bottlenecks of engineering completion. Therefore, the study of bionic optimization and calculation method of Cast Steel Branch Joints in Tree-like Structures will be carried on in this project. At first, we will take the biological nodes in nature as reference and propose the nodal bionic optimization statics considering many parameters such as diameter of tube, thickness of wall, radius of fillet, stifferners, angle between branches, etc. And the parameters numerical model based on Computer Aided Geometry will be set up by us too. Then, the mechanical behaviors of Cast Steel Branch Joints will be studied after a great deal of FEM analyses. Moreover, the main failure mode of Cast Steel Branch Joints will be discussed and the bearing capacity calculation formula of two-branch joints, three-branch joints and four-branch joints will be deduced. At last, a full-scale-model experiment of three-branch joints will be carried out. This study will provide theoretical foundation for promoting the design level of the Cast Steel Branch Joints used in Tree-like Structures and provide basis for corresponding codes or standards of cast steel nodes.

树状结构呈现出广泛的应用前景，但对所采用的铸钢分叉节点基础理论方面的研究却很匮乏，工程实践中已反映出了节点优化不足、前期科研试验投入过高、无规范规程可参考等共性问题。本项目拟综合运用理论分析、有限元模拟及试验研究等手段，开展树状结构铸钢分叉节点的建模、计算、仿生优化及受力性能的研究。首先，借鉴自然界中的生物节点原型，研究考虑管径、壁厚、倒角半径、加肋劲、分叉角度等因素影响的节点仿生优化策略，并建立基于计算机辅助几何学原理的铸钢分叉节点参数化数值建模方法；其次，通过大量的精细化有限元分析，考察不同参数和受荷方式时铸钢分叉节点的力学行为；再次，获得铸钢分叉节点的主要破坏模式，并建立二分叉、三分叉和四分叉三种铸钢分叉节点的承载力计算公式；最后，进行一个三分叉铸钢节点足尺模型试验。通过本项目的研究，可为提升我国铸钢分叉节点的设计分析水平提供理论基础，为相关规程的编制提供依据。

基于仿生学原理而构建的树状柱结构，因结构形式新颖美观、承载性能优良、支撑覆盖范围广而越来越多的应用到大跨度空间结构中。节点是树状柱结构中的关键部位，为实现树状柱结构中各分枝间的相贯连接，树状柱中的节点普遍采用整体浇筑成型的铸钢分叉节点。采用铸钢节点可以将节点与构件的焊接部位转移到节点区之外，降低节点施工难度，提高结构安全性和可靠性。由于树状柱结构中各级分枝间仅通过单个分叉形的铸钢节点连接，节点的失效会直接导致上部结构的倒塌破坏，对该类型节点承载能力的研究非常重要。本项目首先对二分叉、三分叉、四分叉铸钢节点，借鉴自然界中的生物节点原型，研究考虑管径、壁厚、 倒角半径、加肋劲、分叉角度等因素影响的节点仿生优化策略。其次研究基于计算机辅助几何学原理的铸钢分叉节点的参数化数值建模技术，进行大量的非线性有限元分析。再次研究铸钢分叉节点可能的破坏模式，推导基于主要破坏模式的节点承载力简化理论公式。最后进行空间三分叉铸钢节点的试验研究，进行有限元分析、简化理论解、试验结果的对比分析，修正和完善节点承载力简化理论公式。通过本项目的研究，可以更加深刻的理解和掌握铸钢分叉节点的受力性能、合理的参数取值、数模模型的建立方法和主要破坏模式，为该类型节点在工程中的应用提供理论基础和技术支撑。