Estimation Of Stress Distribution On The Complex Joint Based On Microscopic Simulation

Joints of large span space structures have complex forms of loads because the number of the members connected to the joints is large and the members have different sections and angles. The failure of complex joints will cause the changes of internal force of the connected bars and even the fa ilures of the bars. These changes or failures will affect the safety status of the whole structure, resulting in local or even general failure of the structure. In real structural health monitoring system, it is impossible to install enough sensors to moni tor the changes of the stress distribution of the complex joints. Besides, the monitoring data obtained from sensors can only represent the stress of the local place. Another disadvantage is that sensors cannot be installed on some adverse location due to the limit of execution conditions. However, the stress distribution of complex joints can be precisely simulated using microscopic simulation method and obtain the stress distribution of the whole joint. So the miscroscopic simulation method can be used for stress distribution estimation with the combination of structural health monitoring data.An estimation method of stress distribution on the complex joint is proposed based on microscopic simulation. The simulation value of monitoring data expressing method is analyzed in microscopic finite element model. The determination method of the width of the distorted region due to the connecting microscopic finite element model to macro finite element model is raised. The multiscale finite element model of the complex joint can be then built based on the expressing method and the determination of the width of distorted region. Unit generalized internal forces are then applied on the joint finite element model successively to generate the stress variety matrix. The load boundary condition of the joint can be then solved according to the linear relationship between load boundary condition and the stress variety matrix. The stress distribution of the complex joint can also be solved after the load boundary condition is applied on the finite element model of the joint. An example of a complex joint in Zhuhai Opera structure is taken to estimate its stress distribution and the method in this article can be verified feas ible.The factors of the stress distribution estimation method are studied in this article. The judgement criterion of the status of the stress variety matrix is raised by means of the definition of the norm of the row vectors in the stress variety and conditional number of the stress variety matrix. The correlation of row vectors and the difference of data orders are changed by changing the overall spatial patterns of sensors and local locations of one sensor on a single member. Then the condition numbers of stress variety matrices and the results of load boundary conditions are analyzed so that the judgement criterion of the status of the stress variety is verified rational according to the comparative analysis.The estimation methods of stress distribution based on the number reduction of sensors are studied. An internal force will be reduced if the force has a low stress absolute contribution rate according to the value of the elements in the stress variety matrix. The number of sensors can be reduce d if some internal forces are neglected. Another method of reducing the number of sensors is proposed based on generalized inverse matrix. Different numbers of reduced sensors are given and the load boundary condition is the minimum norm solution and the stress distribution of the joint can be solved according to the load boundary condition. The estimation of stress distribution based on the number reduction of internal force and generalized inverse matrix are used respectively to obtain the stress distribution of the complex joint. The results of errors are analyzed and the methods proposed in this article are verified effective and engineering applicable.