Advanced Materials Research Vols. 446-449

Abstract: Based on the Yunding project as the project background, according to the strut frame system of the force change and laminates of the force, used the mechanics and finite element method, to reveal the mechanical part of the strut frame system mechanism, measured by instruments in the field. General standard for the high-rise building design and construction of the layers of backstop program provides theory and example for reference in the future projects.

Abstract: This paper describes the procedure of a hybrid approach based on grey model and artificial neural network (GM&ANN) to analysis and forecast of deformation data. The GM&ANN is formulated into three steps:(1)according to the monotonously increasing characteristics and the nonlinear characteristics of deformation time series, total deformation can be divided into tendency part and stochastic part.(2) use GM(1,1)to fit the trend of the data and obtain the residual series, on this basis by using artificial neural network to fit the stochastic part (residual series) .Then the forecasting value of deformation is obtained by adding the calculated predictive displacement value of each sub-stack. (3) validate the model. The results of experiments show that this hybrid has higher performances not only on model fitting but also on forecasting and therefore can be applied to deformation data processing.

Abstract: On the basis of the advantages of low construction cost, remarkable dynamics property, easy cast moulding and more controllable construction, the reinforced concrete construct are widely applied in buildings and main structures of constructions in China. However, the reinforced concrete is found more or less aging after many years’ utilization and erosion from the environment, which will lead to a hidden risk to affect its functions. After technical development for decades, the concrete can assure its durability under normal situation, yet the function would be deteriorated due to the erosion from the complex and harsh environment to make it hardly reach its designed service life. With the assist of CorroWatch erosion monitor system, the concrete structures’ erosion can kept watched on to obtain the depassivation development and information feedback of some key data dynamically and in long term so as to foresee precisely the erosion starting time. The newly cast concrete depassivation frontline is located on concrete surface and will tend to go through the protective layer and penetrate towards rebar as time goes on. Its structure service life can be enhanced with the re-designed durability in terms of the mentioned characters and do well the erosion proof measures.

Abstract: This paper research on performance analysis of the steel and concrete composite beams under repeated load according to the test results, theoretic analysis and computer simulation, Study the stud fitting changing to the influence of the composite beams. Using finite element software on computer to beam vertical displacement reciprocating load，Step by step as integral structure the elasto-plastic dynamic response analysis, in-depth analysis of steel and concrete composite beams research for elasto-plastic seismic response.

Abstract: In recent years, structural health monitoring has been paid more and more attention in bridge engineering community. Previous researches showed that ambient temperature was one of principal factors affecting structural modal parameters in long-term. In this paper, an experimental study on correlation between dynamic properties of a cable-stayed bridge and its structural temperature was performed under temperature controlled laboratory environment. Using hammer impacting method, a dynamic testing was conducted based on a steel cable-stayed bridge model which had a span layout of 0.9+1.9+0.9m. During the experiment, the first six vertical bending modes under the environmental temperature of 0, 20 and 40°C were identified with the consideration of three kinds of boundary conditions at the deck’s ends as to two degrees of freedom, i.e. the longitudinal translation (UX) and the rotation about the transverse beam (RotZ). The above boundary conditions are UX & RotZ not constrained, UX constrained only and UX & RotZ constrained, attempting to simulate the different conditions of the bridge expansion joints. The efforts were paid to explain the physical mechanism of the results based on the updated FE model. This experimental study indicates a tendency that the frequency of the cable-stayed bridge model decreases with the increase of temperature. And furthermore, the relative difference of frequencies between 0 and 40 °C is affected by boundary conditions; in other words, when the deck is free to expand, the variation of model’s frequencies is smaller than that when the deck is restrained to expand, which is similar to the condition of the bridge’s expansion joints cannot work as normal. This experimental study can give some reference to the research of SHM and damage identification for cable-stayed bridges.

Abstract: The random analysis of the process of chloride diffusion in concrete is a basis of the reliability assessment for durability of concrete structures. In this paper, the diffusion coefficient with time-dependent is introduced to Fick's second law, and perturbation stochastic finite element method (SFEM) with time-dependent(TD) is proposed. The stochastic finite element equation with TD is solved by the perturbation method with a group of recursive equations, by which the mean value and standard deviation of chloride concentration in concrete can be determined. An example is given to demonstrate the accuracy and efficiency of the presented method and shows that the analysis of chloride diffusion with time-dependent for concrete structures is closer to engineering practice.

Abstract: To study the dynamic properties and seismic responses of masonry structure strengthened with Basalt Fiber Reinforced Plastic (BFRP) laminates, modal experiment and shaking table test were performed on a two-storey and two-bay masonry structure model involving constructional columns. Through the test, the dynamic properties of reinforced masonry structure were obtained, the development of cracks and degradation of stiffness of the reinforced masonry structure under earthquake were studied and the variations of displacement, acceleration, stress of this structure were analyzed. Based on the modal experiment using the impact hammer test method, a simplified numerical analysis model of the test model was proposed for modal analysis. From the shaking table test, it is concluded that BFRP laminates can slow down the degradation of structural stiffness and the development of cracks effectively, and the masonry structure reinforced with BFRP laminates has excellent seismic performance.

Abstract: The evolutionary power spectrum which can reflect the non-stationary characteristics of earthquake ground motion is estimated by the Hilbert-Huang Transform (HHT), and with reference to the experiential statistical method, an evolutionary spectrum prediction model for given earthquake magnitude and distance is established based on the 121 near-source acceleration records at rock surface with large magnitude from the ground motion database of western U S. The pseudo excitation method is adopted to acquire the solution for structure random response under specific non-stationary seismic excitation. The results demonstrate that the non-stationary contents included in seismic excitation will enlarge greatly the random response of structure in comparison with uniform modulation random excitation.

Abstract: In this paper, the effectiveness of Shape Memory Alloys (SMA) restrainers for the seismic retrofit of multi-span simply supported deck bridges is investigated through a series of numerical nonlinear dynamic analyses and shaking table tests on an experimental mock-up of a typical bridge structure. Both numerical analyses and experimental tests have been carried out on the structure with and without seismic restrainers. The results of these studies clearly prove the effectiveness of the SMA-based restrainers in controlling the displacement response of simply supported deck bridges.

Abstract: Earthwork calculations are frequently involved in civil engineering. Due to limitations in different terrain conditions and measurement environment, the result of calculation often varies from the fact. Based on existing literatures, this paper builds a mathematical model with some interpolation methods provided by Surfer. We use the model to grid the data, calculate the earthworks, and perform accuracy analysis. The volume of the calculation is proved to be precise enough to be applied to the road and the waterway dredging engineering. The result provides reliable basis to the application of suffer in complex geographical environment such as the river and road.