Study On Damage Identification Of Steel Structure Based On The Method Of Modal Strain Energy

Civil engineering structures may be damaged by all kinds of natural environmentand man-made destruction, such as earthquake, typhoon, fire and environmentalcorrosion. The damage would make the components of structure crack. When damageaccumulates to a certain extent, the reliability of the components would decrease, andthe whole structure will be destroyed. Therefore, identifying and reinforcing the damageof existing structure can prolong its service life, and save a large amount ofreconstruction funds.At present, there are lots of damage identification methods. These damageidentification methods are described, and the advantages and disadvantages of themethods are compared, and the problems of the current damage identification methodsare put forward. In addition, the methods of modal strain energy are the focus of thispaper.Based on the concept of elemental modal strain energy, first of all, a method forstructural damage identification called elemental modal strain energy changes ratio ispresented. In order to validate the positioning effects of the different steel-framedstructures, a plane steel frame and a three-storey space steel frame are established byFEM software ANSYS, and nine different damage cases are simulated. Because of theneed of some modal parameters, model analysis are proceeded for the two steel framesdamaged and undamaged, and the modal parameters are extracted. The numericalresults show that the method could locate single damage cases that the damage extent ofdamaged component is above30%. But for multiple damage cases, if the number of damaged components is unknown, this method is invalid. Besides, it is also found thatthe sensitivity of locating the damaged diagonal rods is much higher than the sensitivityof locating the anther damaged rods.Secondly, an improved structural damage method is developed, and the damagelocation index is redefined. The numerical simulation analysis results of the sameplane steel frame and three-storey space steel frame show that the new method couldnot only locate single damage cases that the damage extent of damaged component isabove10%, but also locate multiple damage cases without predicting the number ofdamaged components.At last, according to the elemental strain energy ratio before and after the structuraldamage, an index for estimating damage degree is presented. Numerical study of thetwo frames is carried on to estimate the damage degree. Results indicate that the indexof the plane steel frame is somewhat smaller. But for the three-storey space steel frame,the value of estimation is closed to the true damage degree. In addition, the index couldlocate different damage cases of the three-storey space steel frame.