Advanced Materials Research Vols. 163-167

Abstract: This paper investigated the superelasticity and hysteresis characteristics of TiNi shape memory alloy ( SMA ) wire at room temperature, then the mechanical parameters of which were obtained. Based on the TiNi SMA wire and a purchased viscous damper, a new type of hybrid-passive-damper was designed and developed. Experiments were performed in order to validate the relationship of loading frequency and characteristic parameters such as energy dissipation capacity, equivalent damping ratio and equivalent stiffness. Experimental results show that hybrid-passive-damper designed in this paper has excellent energy dissipation capacity and is suitable for the vibration control of structures with long vibration period.

Abstract: For a long-span suspension bridge, owing to a flexible structure system, the seismic displacement at the end of the deck may severely exceed the allowance under earthquake which due to the occurrence of the pound between the main span and the approach span usually which can causes the collision of falling-beams and structures. In this paper, based on the pounding phenomenon at expansion joints of long-span suspension bridge under strong earthquake and employing a typical long-span suspension bridges. With the time history analysis method of determining the nonlinear seismic responses, the pounding effects of adjacent girders at expansion joints on seismic responses of long-span cable-stayed bridge were studied. The results indicate that pounding can amplify the seismic demand of piers of the approach span and can also amplify the displacement of beam of the approach span, the relative displacement between main span and approach span and the hinge seat width of beam of approach span obviously and it causes easily the collision of falling-beams and structures under earthquakes.

Abstract: In this paper, on the basis of the existing research and Matlab, scientific computing software, and through the characteristics of the artificial neural network theory, it presents artificial simulation of wind loads which are set up by BP neural network, and it mainly consists of the preparation of sample set, the certainty of network layer and hidden nodes, and the selection of activation functions and training methods. Based on Matlab and the neural network toolbox, it carries out the constriction, training and testing of neural network. According to the simulation of five different positions of horizontal wind speed time, it proves that the artificial neural network term wind loads simulation models are effective in practical application.

Abstract: In order to reveal the structural dynamic characteristics in natural wind, multi-dimensional random wind load of tall building is simulated by using harmonic wave superposition method. Then the coupling dynamical equations of structural system are solved by using Wilson- integration method considering the coupling effect of wind-induced interaction. Based on the analysis, it is clear that the coupling of wind-structure is equivalent to the damping effect and the dynamic response of the structure has decreased, when taking the wind-structure interaction.

Abstract: Wind load on complex-shape building, the wind tunnel test and numerical simulation were carried out. The two technologies supplement each other and their results meet well. There are mainly positive pressures on the windward surface, negative pressures on the roof, the leeward surface and the side. Especially, negative pressure is higher in the leeward region of the building corner. Its effect induced by the shape of the complex-shape building is remarkable.

Abstract: Earthquake codes have been revised and updated in recent years. The issue and implementation of the guidelines for seismic design of bridges have attracted interests and attentions of many researchs at home and abroad. In this paper, it is compared that the provisions about performance criteria, seismic design categories, response spectrum and earthquake action between guidelines for seismic design of highway bridges and Eurocode 8 for bridges. The main purpose of this study is to investigate the differences caused by the two codes in performance criteria, seismic design categories, response spectrum and earthquake action. The results indicate that it is similar in performance criteria, seismic design categories and response spectrum between guidelines for seismic design of highway bridges and Eurocode 8 for bridges. Based on the lessons learned from significant earthquakes in the last few years, the existing problems of the current code are pointed, and the trends of future study are discussed.

Abstract: The concrete-filled steel tube (CFST) member has many advantages compared with the ordinary structural member made of steel or reinforced concrete. Continuous confinement provided by the steel tubes prevents excessive spalling of concrete and the concrete filled inside the steel tubes prohibits local inward buckling of the steel tube wall. This paper presents the dynamic response of a slanting type CFST arch bridge without wind tied-bracing. Effect of stiffness ratio between slanting arch and vertical arch on seismic performance was discussed.

Abstract: A new seismic isolation system,namely the prestress rubber isolator(PRI,Chinese patent application number:200910174415x),is introduced.The basic principle of this new isolator is: making all or part of vertical deformation of isolator be finished in advance by exerting a longitudinal pre-compressional stress on the rubber isolator with flexible cables, the prestress tension cables become loose because of unloading after the exerting of superstructure loads,and the loose cables can limit the horizontal displacement and resist the tension of isolator. The calculation formula of horizontal stiffness of isolator is derivated,and the mechanical properties are researched. The research results show that:besides the horizontal isolating property of common rubber isolators,the prestress rubber isolator has also properties of reducing vertical deformation, limiting horizontal displacement and resisting tension.Moreover,the prestress isolator has also a certain vertical isolating affect because of the improve of rubber thickness.

Abstract: A blast-induced seismic wave is an instantaneous, complicated wave different from natural seismic wave. It has characteristics such as high frequency, fast vibration intensity attenuation rate with distance increasing, short duration, generally small hypocenter energy and short blast-induced seismic wavelength, etc. In this paper, in combination with the properties of rock and soil, through using stress-strain relation and transmission characteristics of wave in different media, the author explored the mechanism of action that blast-induced seismic vibration has upon rock and soil. Meanwhile, the time-space process of action that blast-induced seismic vibration has on structure under different circumstances is deeply explored. Moreover, the impacts that blast-induced seismic vibration characteristic and structure’s dynamic behavior have on structure response under the effect of blast-induced earthquakes are discussed. Thereby the mechanism of action that blast-induced seismic vibration generates on structure is revealed.

Abstract: Aimed to base-isolated building with large plane dimension, the change laws of seismic response for base-isolated building under spatial variable ground motions were researched. Firstly, the artificial spatial variable earthquake time histories were generated using spectral representation method based on code response spectrum. Then the 3-D FEM modal of one based-isolated building with large plane dimension was established and the seismic response of based-isolated building under spatially ground motion was studied by nonlinear time history analysis. The mitigation effects of based-isolated building with large plane dimension were compared each other at the cases of uniform excitation, non-uniform excitation considering only wave passage effect, non-uniform excitation considering both the wave passage effect and incoherence effect, multi-component uniform excitation, multi-component non-uniform excitation considering the wave passage effect and multi-component non-uniform excitation considering both the wave passage effect and incoherence effect. The results show that the seismic response of base-isolated structure with large plane dimension under the uniform excitation is relative safety. When the base-isolated building with large plane dimension is designed by time history analysis, the spatial variability of earthquake ground motion effects can be considered.