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预应力张拉是确保预应力空间网格结构实现预期设计状态的关键,但施工误差的随机变异影响了张拉过程的可控性。为此,提出一种预应力空间网格结构张拉全过程的反馈控制方法。在考虑施工材料参数与几何参数误差的基础上,首先对基准结构模型进行概率有限元分析,获取误差结构响应与预张力控制方案的样本对;然后利用BP神经网络的非线性映射功能,以概率有限元分析结果为训练样本,构建结构响应与预张力控制值的关系模型;在实际的多阶段张拉过程中,基于前一阶段的实测结构响应数据,利用构建的神经网络关系模型预测下一阶段的张拉控制力。利用ANSYS软件的概率设计模块与MATLAB软件的神经网络工具箱,编制了反馈控制的实现程序,并针对预应力弦支穹顶结构的数值算例进行模拟分析。结果表明:利用建议的方法能够实现对预张力控制方案的动态调整,确保结构张拉完成时实现预期设计目标。利用一3 m跨弦支穹顶模型,通过误差可调节点对结构施加节点安装误差,基于实测结构杆件内力与节点位移,对结构模型的径向索张拉过程进行了索力反馈控制试验。结果表明:施工误差影响下,结构张拉完成时径向索力达到目标预应力值,验证了反馈控制方法的有效性。
Prestressing tensioning is the key to ensure the prestressed spatial grid structure to achieve the expected design state. However, the random variation of construction errors affects the controllability of the tensioning process. Therefore, a feedback control method of prestressed spatial grid structure is proposed. Based on the errors of construction material parameters and geometrical parameters, the probabilistic finite element analysis of the baseline structure model is firstly carried out to obtain the sample pairs of the error structure response and the pre-tension control scheme. Then by using the nonlinear mapping function of BP neural network, The results of finite element analysis are used as the training samples to construct the model of the relationship between the structure response and the pre-tension control value. In the actual multi-stage tensioning process, based on the measured structure response data of the previous stage, the constructed neural network relation model is used to predict the next Tension control of the stage. Using the probabilistic design module of ANSYS software and the neural network toolbox of MATLAB software, the realization program of feedback control is compiled and the numerical example of prestressed snake-foot dome is simulated. The results show that the proposed method can be used to dynamically adjust the pretension control scheme and ensure the expected design goal when the structural tension is completed. With a 3 m span suspension dome model, the installation error of the node is applied to the structure by the error adjustable point. Based on the measured internal forces and node displacements of the structural member, the cable tension control of the structural model is carried out. The results show that under the influence of construction error, the radial cable force reaches the target prestress value when the structural tension is completed, which verifies the effectiveness of the feedback control method.