Study Of Single Excitation Position And Sensors’Layout On Square Pyramid Space Grid Structure

In recent years, large-span spatial grid structure is widely used in large-span public buildings and civilian facilities. With time increasing, damage emerged more and more, so damage detection on these structures became important. Now, dynamic testing method is the most commonly used method to realize structural damage detection. Using this method, the key problems focus on the dynamic testing signals’producing and collection. To gain good testing information, some matters that exciating which position with which excitation pattern and laying sensors’on which position must be settled. In addition, to testing spatial gird structures, more rods and big freedom degrees must be considered also. Therefore, to solving these problems, the study contents of this dissertation were as follow:1) According to characteristics of frequency-intensive on spatial truss structures, a method based on euclidean distance was used to realize modes separation. Calculating weighting factor (every mode contrbution to response), establishing pattern vector of weighting factor and target factor, definiting target function, the optimal excitation position was considered as the minimize euclidean distance of target function. This method was used to obtain the optimal excitation position of a square pyramid space grid structures. Firstly, three conditions about intact, single-damage and multi-damage were analyzed. Next, the single optimal excitation position of this structure was obtained by the minimize euclidean distance of target function. At last, to verify the efficiency of this method, excitating this optimal excitation position, structural modes were obtained by Hit-Huang transform and Fourier transform,. In addition, to receive the influence of section, the section of webs was divided as two kinds.2) Considering the inconsistent characteristic of sensors’playout about modal observability and damage identifiability, a Fisher information matrix was used. The relationship between structural response and damage sensitivity was obtained, and based of the Fisher information entropy theory, a Fisher information matrix considering modal shape and damage sensitivity was established. The maximum2-norm of Fisher information matrix was determined as objective optimal algorithm. Then the initial layout of sensors was gained.3) To decrease the quantity of sensors, based on the initial layout of sensors and damage sensitivity, a modified Variance method was established. The structural sensors’ optimal layout was gained by the local maximum of variance function. At last, the fitness function by modified mode guarantee criterion was used to verify the effectiveness of sensors’optimal playout.