大跨无柱地下车站梁-柱节点受力性能的局部多尺度有限元方法

Local multiscale finite element method for mechanical analysis of beam-column joint in long-span column-free underground station

岗厦北综合交通枢纽核心换乘区的中庭51.2 m×48.0 m(南北长度×东西长度)范围为无柱设计范围,其跨度在全国尚属最大。梁-柱节点是该结构传力关键,但数量繁多、类型复杂,且建造过程存在多重体系转换,必须确保节点传力顺畅。基于多点约束方程法(MPC),提出一种局部多尺度有限元方法(LMFEM)。采用LMFEM方法,进一步研究梁、柱贯通方式对本文依托工程典型梁-柱节点受力性能的影响,发现柱贯通节点整体应力较低,传力顺畅,应力集中不显著,更适用于岗厦北大跨无柱地下空间结构。基于现场监测,将节点受力状态实测值与不同方法所得计算值进行对比分析。研究结果表明:相比于传统局部精细化有限元方法(LRFEM),LMFEM方法具有建模工作量小、边界条件易于满足圣维南原理、可兼顾计算精度和计算效率的特点;在同等建模规模和网格细度情况下,LRFEM2模型计算值与实测值的最大相对误差为11.8%,LMFEM模型计算值与实测值的最大相对误差为12.5%,但后者具有更少的节点数量和更短的计算时间,而LRFEM方法的计算精度受边界条件和单元网格细度影响较LMFEM方法的大;本文提出的LMFEM方法具有计算精度高、计算效率高、边界条件易明确等优势,可应用于大型复杂工程结构的节点局部受力性能分析。

The Gangxia North comprehensive transportation hub has a column-free design in the range of atrium 51.2 m×48.0 m in the core transfer area,and its long-span is the first case in China.The beam-column joint is crucial for force transmission,but the joint has the features of large quantity and complex types,and the multiple system transformations are involved during the construction.It is essential to ensure smooth force transmission through joints.Based on multiple points constraints(MPC)method,the local multiscale finite element method(LMFEM)was proposed.The example demonstrates that,by using LMFEM,the influence of the through mode on the mechanical performance of typical beam-column joint was investigated.Combined on-site monitoring,the measured values of joint stress state was compared and analyzed with the calculated values of different methods.The results show that,compared with the traditional local refined finite element method(LRFEM),LMFEM has smaller modeling workload,its boundary condition is easier to satisfy the Saint Venant principle,and it can balance computational accuracy and efficiency.The column-through joint has lower stress level,smooth force transmission and insignificant stress concentration.This is more suitable for Gangxia North large-span column-free underground structure.For the same modeling scale and mesh size,the maximum relative error between the calculated value of LRFEM2 model and measured value is 11.8%,and the maximum relative error between the calculated value of LMFEM model and measured value is 12.5%.However,the LMFEM model has a significantly lower quantity of nodes and a shorter computation time.Compared with LMFEM,the computational accuracy of the LRFEM is more sensitive to the boundary condition and mesh size.The LMFEM has the advantages of high computational accuracy,fast computational efficiency,and is easy to specify the boundary conditions,which can analyze the force performance of joints in large and complex engineering structures.