Damage Identification Of Space Steel Grid Structure

Steel grid structure, which can fulfil the needs of long-span spatial sructures, has gained growing popularity at home and abroad. As this structure has a large span and can serve many people , an accident will threaten people life and cause huge economic losses and property loss. There are many collapse and accidents of long-span spatial structures in latest years, so it is important to identify and monitor space grid structure. In the field of identification, there are many mature methods which are divided into two parts: Static and Dynamic Methods. It is convenient to get the whole state of structure by dynamic method which is operated by getting the mode parameters such as frequency and mode shape and is more useful for space truss.In this paper, based on the experiment of a truss, modal methods are used and analysed with the mode parameters such as frequency and mode shape obtained by dynamical tests.The validity and robustness of different methods are compared by adding white noise to the datum of numerical simulation with Ansys. Results show that the damage of truss can be effectively identified by the method of modal strain energy plus LS-SVM (least-square support vector machine). Modal strain energy is used to identify the probable damage elements and the exact damage location and extent can be attained by using LS-SVM. This method is verified by numerical simulation of a space truss with some nosie.Finally, optimal sensor placement and how to identify space truss with incomplete mode data are analyzed because it is impossible to get the complete mode data of space truss which has too many elements. Results attained by numerical simulation of signal damage element verify that the method combined by effective independence method, dynamic expansion and LS-SVM is efficient for space truss.