Papers by Keyword: Seismic Response

Abstract: This study deals with the paramount topic of sustainable and durable composite materials for repair of damaged existing bridge. Reinforced concrete is the most used composite system in structural design but, across several decades, it has shown some fragilities related to chemico-physical resistance. Durability improvement by means of innovative repair systems represent, therefore, a crucial economic parameter allowing a highly significant reduction of maintenance cost. A maintenance scenario is here simulated, considering a repair composite realized with a binary geopolymer binder, obtained by activating two industrial by-products, namely coal fly ash and blast furnace slag, in alkaline environment. Physico-mechanical characterization of geopolymer concrete is also performed, showing the suitability of this innovative repair system. In order to investigate the effectiveness of geopolymer, a 3D finite element model is developed in Sap2000 to represent the complex behavior of a full-scale Italian highway bridge. Numerical simulations are conducted by modeling the geopolymer concrete as a jacketing applied to the damaged piers. Results reveal that the designed repair system could increase shear capacity of bridge piers under seismic conditions, not neglecting the low cost of raw materials and the high durability of geopolymers.

Abstract: This paper establishes three models using ANSYS, which were timber structure of Guangyue Tower, timber structure-tower base and timber structure-tower base-foundation. The first 3 natural frequencies of timber structure respectively were 0.8524Hz、1.1273 Hz and 1.7426 Hz through modal analysis, which were compared with calculations from code. Lanzhou Wave was chosen to analyze the seismic response of Guangyue Tower, and the amplitudes were adjusted to 55gal and 310gal respectively according to the frequent earthquake and rare earthquake, which were inputted to the above models. As can be seen from the calculations, the maximum displacements of the three models were in the top nodes, and tower base had a greater impact on vibration of timber structure, which could not be ignored in seismic response analysis; considering soil-structure interaction in seismic response analysis could better reflect the actual situation of Guangyue Tower.

Abstract: Seismic ground response analysis methods are categorised into linear, equivalent linear and non-linear methods that perform the analysis in the time or the frequency domain.The equivalent linear and the non-linear methods are two main methods of seismic response analysis for soil layers. The Equivalent linear method is the most common soil seismic response of a way to analyze in the current engineering practice. In recent years, the study on method of seismic response analysis of nonlinear soil layers is an important content in research domain of geotechnical earthquake engineering now. In this paper, these two methods’ basic principles are clarified briefly, Their developing courses and actualities are summarized. According to their basic principles and application practices, their merits and shortcomings are pointed out. The reasons why the merits and shortcomings appear are analyzed briefly.

Abstract: Enping sag is located in the west of Zhu 1 sag of Pearl River Mouth Basin. In order to verify the reservoir spreading of Enping sag in Pearl River Mouth Basin and provide the reliable basis for reserves prediction. In this paper, according to the actual seismic data extracting the theoretical seismic model, applying spectral method to construct the acoustic wave equation, and then, deducing the partial differential equation resolution of absorbing boundary condition. Through the forward modeling summarized the seismic response characteristics of oil layer, and making a forward modeling with actual parameters of wells model. Finally obtained the expected effect.

Abstract: The selection of input ground motion for seismic analysis of the structure is a complicated task, especially when nonlinear dynamic analysis is utilized. A decision has to be made regarding the intensity measure better to represent the potential damage of the ground motion. This paper presents a lot of analysis to deal with the problem. A set of nonlinear dynamic analyses were conducted on reinforced concrete buildings widely present in China. Input ground motions contain uncertainty and variability comes from both natural recordings and synthetic data. First, a set of natural recordings is considered. Second, two ground motion modification schemes are used in this study: magnitude scaling and spectrum matching. Third, a set of ground motion is synthesized. The peak value of displacement has been selected as the response parameter better able to represent the structural damage level. Nonlinear dynamic analyses of reinforced concrete buildings simulated by OpenSEES are carried out to evaluate the correlation coefficients of displacement response and the chosen ground motion parameters. Findings from the investigation indicate that the Housner intensity is the more effective intensity measure for selecting the seismic input. The synthesized ground motion fit with code spectrum shows good performance as a design input motion. Considering ground motion modification, spectrum matching is generally more stable in response prediction than scaling.

Abstract: Based on the double member model of wall-frame structure and the corresponding transfer matrix method, the concept of frequent impedance of rigid foundation is introduced so that SSI can be taken into account. This method is more convenient and efficient compared to finite element method because of fewer structural parameters and faster calculation speed. Necessary structure parameters include 7 parameters of each storey, geometry size and total mass of foundation and elastic parameters of site soil. Totally 39 examples were calculated for 13 values of foundation mass and 3 kinds of soil, which are compared to the result of fix bottom model of upper structure. Results show that SSI does not always deduce a decrease of seismic response. Sometimes SSI may increases structural displacement evidently. The simplified method would provide structure designers an efficient tool to understand seismic behavior of wall-frame structures with various foundation and site soil.

Abstract: The new-style isolation bearings that can isolate the seismic effect in horizontal and vertical direction is presented in this paper. In order to study isolation of bearings, structure seismic isolating model is established based on new-style isolation bearings. Through the input of seismic excitation, acceleration peak and storey drift are regarded as basic discrimination factor for studying seismic response, and structure seismic isolating model is contrasted with structure seismic non-isolating model. The example shows that the new-style of isolation bearings not only can isolate in the horizontal direction, but also isolation ability is better in the vertical direction.

Abstract: In this paper, the new Fengman gravity dam is numerically simulated to study the seismic response and safety evaluation by considering the different strength grade concrete partition, corridor, a discharge hole and gate pier. A complex 3D FEM of a real overflow monolith was built by taking advantage of AutoCADand ANSYS, nonlinear seismic response was studied under earthquake loads. Numerical simulations show that acceleration, displacement and stresses of dam were obtained in a complex 3D FEM under seismic precautionary intensity of 7 degree earthquake loads, results compared with the dam simple models were on the safe side. Fengman dam was still safe under seismic precautionary intensity of 8 degree earthquake loads, so the dam had enough capacity to resist earthquake action. At the same time, it is concluded that 3D dynamic FEM is very important for safety evaluation of concrete gravity dam subjected to the earthquake. The research provides finite element analysis reference works for comprehensive governance and reconstruction of Fengman Hydropower Station.

Abstract: This paper presents a comparative analytical study on seismic response of low rise three storeys concrete frame reinforced with super-elastic material as rebar elements. The super-elastic shape memory alloy rebars were used as reinforcement in two plastic hinge zones of the frame, beam plastic hinge zones and column plastic hinge zones. The response of the frame structure with two different reinforced cases is compared to response of the frame structure reinforced with regular steel material. Nonlinear dynamic time history analysis is performed in this study. Three different great earthquake ground motions were used to determine the seismic response of the frame structures in terms of frame top displacement time history and inter-storey drift along the frame height for different cases of reinforcements. Results obtained from the analysis show that the seismic response of low rise frame reinforced with super-elastic SMA rebars is affected by the zone of which SMA rebar are used in reinforcement. The SMA column reinforcement is more effective than SMA beam reinforcement in reducing the frame response.

Abstract: By large-scale finite element software ANSYS, the seismic response of large span steel - concrete composite beams were analyzed, to get the change rule of the deflection and stress of the design. And analysis of the extension of design parameters for influence factors, such as concrete grade, reinforcement ratio, the height of steel beam, is to get their effect of the seismic responses of the composite beam deflection and stress, and provide powerful basis for optimal design of composite beams. For the model in the interface by setting the three direction spring element to simulate the interface slip and vertical uplift, and choosing three directions of EI Centro seismic wave including relatively rich spectrum as input, the result of analysis is relatively accurate.