通过模型升级确定球节点的非线性性能

脱离整体结构单独研究球节点,并不能真正反映节点在结构中的性能。以某足尺双层网格结构试验为基础,研究典型球节点的实际性能。采用反问题法和有限元模型升级技术,建立了优化问题。使目标函数为双层网格结构的试验结果与相应有限元结果的差异最小。为模拟双层网格结构有限元模型中节点的非线性性能,并将其设为升级参数(优化变量),通过遗传算法求解优化问题。因此,通过升级双层网格结构中的有限元模型,可确定实际工况下球节点的性能。结果表明:升级模型能准确预测双层网格结构的真实反应。节点的荷载-位移曲线在初始阶段呈低刚度的非线性关系,随后刚度逐渐增大,并呈现为线性关系,与实际工况一致。

Determination of Nonlinear Behavior of a Ball Joint System by Model Updating

Behavior of a ball joint system when evaluated discretely and disconnected from structure, does not represent its true behavior in the structure. In the present work, to study the actual behavior of a typical ball joint system, available experimental responses of a full scale double layer grid have been used as reference data. Using inverse problem method and specifically finite element model updating technique, an optimization problem is defined. The objective function that must be minimized is the difference between existing experimental deflections and corresponding analytical deflections obtained from an appropriate finite element model which has been prepared for the double layer grid. With modeling a general nonlinear behavior for joints in the finite element model of the double layer grid and considering it as updating parameter (optimization variable), the optimization problem is solved through the genetic algorithm. Therefore, by updating the finite element model of the double layer grid, the behavior of the ball joint system can be estimated in real conditions. The obtained results show that the updated model can predict with good accuracy the true deflections of the double layer grid. Also, the attained force-displacement relationships of the ball joint system demonstrate that its behavior in the initial stages of loading is nonlinear with a relatively low stiffness. However, after that it becomes stiffer then it behaves linearly such as in the ideal conditions.