Numerical Analysis Of Damage Of Plates Based On The Correlative Change Rate Of The Strain And Strain Mode

Most of the engineering structures, when subjected to the natural disasters suchas earthquake and fire or the action of the long-term fatigue loading and erosion, willoften induce the damage of the structure. With the accumulation of the damage, itscriticality will be gradually enhanced. The real time repair can be done and the meansof the operation can be changed with the help of the judgment of the structure damageand the confirmation of the locality of the damage, so as to degrade the accumulationdegree of the damage of the structure and reduce the economy loss.Consequently great attention is given to the diagnosis technique of the damage ofthe structure in the architecture industry domestic and abroad. But as a new studyfield, its development is incomplete. In this paper, the two new methods of thedamage identification which are based on the correlative change rate of the strainmode and the change rate of the strain of the external-exciting force for the plates arebrought forward.The main tasks of this paper are as follows:The development of the damage identification technique of domestic and abroadis introduced. The classification of all kinds of damage identification methods whichare usually adopted at present is simply introduced. The problems and theimprovement of the methods of the damage identification are discussed.The theories of several methods of structure damage identification which arebased on the frequency, mode of vibration and strain mode are summarized. Therationale of these methods which are adopted to carry out the structure damageidentification is presented. The advantages and disadvantages about these methods arealso compared. The testing technique of the strain mode is presented. In this technique,the strain mode and displacement mode can be gained by means of measuring thetransfer function of the frequency response. The definition and the numerical analysismethods of the damage identification which are based on the correlative change rateof the strain mode and the change rate of the strain of the external-exciting force arepresented.The clamped slab and the simply supported slab are taken as the study objects.The structural damage is simulated by changing the thickness of elements. In thispaper, the methods of the damage identification, such as strain mode, the correlativechange rate of the strain mode and the change rate of the strain of the action of theexternal-exciting force are used. By comparison, whether the structure has the damagecan be identified by using the method of strain mode. But the location and the degreeof the damage can not be identified by this method and must be generally determinedby other methods. The methods of the correlative change rate of the strain mode andthe change rate of the strain of the external-exciting force are much better. The mainconclusions of these methods are as follows: the correlative change rate of the strainand stain mode is related to constraint. In the direction of the weak constraint, theother undamaged elements (especially the adjacent elements) are much obviouslyinfluenced by the damage elements, thus is adverse to identify the damage location.But in the direction of the strong constraint, the damage elements affect little on theothers, only the correlative change rate of the stain and stain mode of the damageelement changed obviously, so the location of the structure damage can be identifiedexactly.