Papers by Author: Yu Jiang Fan

Abstract: When a steel etc. a ferromagnetic material is subjected to the external loads, the internal force will develop, that is, stress will develop inside the material, which will lead to a corresponding change in the magnetic permeability of this material when magnetized. In this paper, according to this unique property of the ferromagnetic material, in the light of the mainly stressed and deformation characteristic of a long span steel structure etc. defect sensitive structures, by the use of stress sensitivity of magnetization, a mathematical physical model of relationship between the change in the magnetic permeability and stress is studied and put forward when a ferromagnetic component is under the action of a simple stress, a linear dependency relation of the component’s stress and its permeability is obtained, and the fundamental theory of the magnetic non-destructive testing of a safe state and its engineering application method is also established for a long span steel structure etc. defect sensitive structures, which provides a definite basis for guaranteeing safety of this kind of structures. Additionally, in this paper through the comparison of the theoretical analysis results with results of the related experiments, the dependency relation of change in the magnetic permeability and stress etc. theoretical research results is verified. Both these results exhibit a good consistence, which demonstrates that the research and the application of the non-destructive safe testing method for a defect sensitive structure based on the magnetic effect is feasible and valid and the future will see a certain engineering application prospect in this research and this testing method.

Abstract: Shape memory alloy (SMA) is provided with preferable damp capacity at pseudo-elasticity state, applying this property, a SMA re-centring damper is introduced by some scholars. In this paper, the new isolation system combining the above damper with laminated rubber bearing is proposed, so as to obtain preferable isolation character and re-centring capacity. To illustrate the feasibility and effectiveness of the proposed system, the following work is done: First, according the constitution model of SMA at pseudo-elasticity state the program is compiled, then the mechanical behavior of damper is simulated and the hysteretic curve is obtained. Based on the above, a linear restoring model for SMA re-centring damper is put forward. And then, the program based on the theory of story model for shear tape is compiled to conduct elasto-plastic time history analysis of practical structure examples, According to the results, the seismic response of structure is significantly reduced, and the fully re-centring capacity after earthquake is obtained by this isolation system.

Abstract: Reinforced concrete structures are prone to damage during their service lifetime caused by factors such as the effect of overload, ground motions, and other actions. Undetected damage may lead to structural failures. Early detection of damage and timely repairs can prevent catastrophic failure and ensure regular service of structures. As a result, a so-called delimitation wavelet-transform search method, based on the characteristic of multi-resolution of wavelet transform, is presented in this paper for on-line damage identification of reinforced concrete structures. One possible advantage of this method is that the damage temporal and spatial location can be detected rapidly and efficiently. Further research is carried out with numerical simulation of a structure test model to study the storied damage detection and localization of reinforced concrete frame structures under seismic actions. The analyzing result is compared with that observed in a simulated earthquake vibration stand test. Good agreement is obtained and it verifies the effectiveness and validity of the method proposed in this paper.