Advanced Materials Research Vols. 243-249

Abstract: The analytical signal for time-frequency analysis is obtained by Hilbert transform from free vibration response under suddenly unloading. Mathematical deduction of Wigner-Ville Distribution (WVD) auto-terms reveals the function relation between WVD auto-terms and modal parameters. A new method based on the amplitude curvature of WVD auto-terms (WAC) is then forwarded for damage identification of transmission tower. An elastic model of transmission tower with 1/35 scale and 5.2 m height has been designed and manufactured to verify the proposed method, the model has been tested in the laboratory for acceleration response under suddenly unloading, and essential dynamic characteristics of the scale model is also compared with that of its prototype tower. The damage identification test of the model is then carried out. Totally three cases, related with chord rod weakening, flank rods failures, different damage degree and position, are tested to testify the proposed damage identification index.

Abstract: To study the influence of slenderness on the compressive bearing capacity of autoclaved fly ash perforated brick masonry long columns and provide experimental evidences for making corresponding technical code, compression tests were conducted on 9 autoclaved fly ash perforated brick masonrys long columns of different slenderness. The damage patterns and compression performance are analyzed. The experimental results indicate that compressive capacity decreases proportionally as slenderness increases and the proposed formula of axial compressive bearing capacity for autoclaved fly ash perforated brick masonry columns is given. The nonlinear FEA program ANSYS is also adopted to simulate the behaviors of masonry columns. By comparing results find that the simulated results agree well with the test ones, the rationality and applicability of the model are verified.

Abstract: To study the influence of fiber on the water stability of asphalt mixtures, the optimum dosage of asphalt and fibers are studied by the method of Marshall test and rut test. The results demonstrate that the optimum dosage of asphalt and fibers are 4.63% and 0.30%, respectively. Then the improved effects of basalt fiber on water stability of asphalt mixtures are evaluated through immersed Marshall test and freeze-thaw splitting test according to related specifications. The results show that the freeze-thaw splitting strength and splitting strength without freeze-thaw of fiber-reinforced asphalt mixture are improved to some extent compared with control mixture. Splitting strength without freeze-thaw of basalt, polyester and xylogen fiber-reinforced asphalt mixture is increased by 36.4%, 15.4% and 6.2%, and freeze-thaw splitting strength is increased by 55.2%, 28.7% and 14.5%. It can be concluded that fiber can remarkably improved the water stability of asphalt mixtures, besides; the improvement effects of basalt fiber are superior to polyester fiber and xylogen fiber.

Abstract: In this paper the analysis is conducted to investigate the progressive collapse resistance of typical reinforced concrete(RC) multi-story frame structures, which are designed according to the China code for seismic design of buildings. The analysis results show that the progressive collapse resistance will be enhanced with the seismic fortification intensity increasing. The progressive collapse resistance of RC frame structures with low seismic fortification intensity are poor. This implies that as for RC frame structures with low seismic or non-seismic demand, close attention must be paid to continuity and ductility in order to prevent progressive collapse.

Abstract: Based on relevant flow rule, Von Mises yield condition and the virtual displacement principle determined by the updated-Lagrange configuration, nonlinear finite-element analysis of the tube-plate connection of K-shape by ANSYS program is studied in this thesis. In order to study the influence of main pipe to the ultimate strength of the tube-plate connection of K-shape, two geometric parameters are considered, D, diameter of the main pipe; T, thickness of the main pipe .Three typical failure modes, gusset yielding, main pipe excessive plastic deformation failure and branch local buckling are also summarized. A comparison was made between formula result and analysis of finite element stimulation to validate the veracity of the existing formula.

Abstract: Wind loads encountered by wind turbine systems exhibit obvious randomness. Conventional researches of wind loads mainly target developing power spectrum density models or correlation functions. However, it is extremely difficult to deal with several key problems of stochastic dynamics of wind turbine systems in such a frame due to the absence of physical mechanisms. In this paper, the physical tradition in the study of stochastic dynamics is followed to investigate wind loads of wind turbine systems. Along the physical tradition, the physics-based modeling is primarily put forward. Based on the random function description of stochastic processes, a new concept of random Fourier function is proposed to establish two physical wind spectrum models of wind turbine systems. One of them is the random Fourier spectrum model which determines wind loads on wind turbine towers, the other is the rotational Fourier spectrum model which decides wind loads on rotating blades. As the two physical wind spectrum models can effectively prevent the essential drawbacks of the phenomenological ones, they are suggested to be adopted in the wind-induced dynamic reliability evaluation of wind turbine systems.

Abstract: The detailed formations of precast floor slab connectors have significant effect on its axial capacity, but there is no such specific provision on it at present. The effects of detailed formations on the in-plane tension (compression) strength, stiffness and deformation capacity of hairpin connectors (HPC) is studied, through numerical simulation analysis under in-plane tension (compression) force. The slug length (h), steel plate thickness (t) and its stickout(s) are taken as parameters. On the basis of analysis, recommendations on formation details of HPC are proposed for design and construction.

Abstract: A steel reinforced concrete frame-concrete core wall structure is taken as the research object in this paper. The whole space finite element models are established by software ETABS, modal analysis, response spectrum method and elastic time-history analysis are conducted. And static elastio-plastic time history analysis of the high-rise structure is conducted by software MIDAS/GEN. Seismic response of the high-rise structure is analyzed under medium earthquake and rare earthquake , elastic deformation is calculated under conventional earthquake and elastic-plastic deformation is calculated under rare earthquake. The results show that the structure can meet the requirements of no-damage under light earthquake, repairable under medium earthquake and no-collapse under strong earthquake.

Abstract: Started from structure construction ,this paper carried out numerical analysis about the test members through computer simulation and studied the influence of cover thickness and stirrup spacing on the rust expansion crack by means of rapid electrifying for accelerating the corrosion of longitudinal reinforcement. Based on this, it established the correlativity between member surface stress and concrete cover thickness, stirrup spacing. And this paper found the influence law of cover thicknesses and stirrup spacing on rust expansion crack on specimen surface.

Abstract: Ten reinforce concrete (RC) shear walls were exposed to fire on one side. A time-temperature fire curve with a heating phase and decaying phase was used in order to simulate a natural fire. The effects of fire duration and load intensity are described in relation to the distribution of concrete temperature. Test results show that load intensity has little influence on the concrete temperature distribution. In contrast, peak temperature in the same depth is strongly affected by the fire duration.