Applied Mechanics and Materials Vols. 105-107

Abstract: With the complex high-rise and extra-high buildings construction, dynamic characteristics of these structures are more and more paying close attention and researching. At the same time, the dynamic response of high-rise building with complicated structure system is always a hot and difficult research, and it is going to be further developed on the research of dynamic features, displacement and internal force. Selecting a complicated systematical structure of a city, using finite element to establish the model and inputting rare earthquake wave, this paper carried out an analysis on the natural vibration characteristics, relative storey displacement and maximum shear of the structure by applying dynamic elastoplastic time history analysis method, drawing the conclusion that the structure design is safe and putting forward the corresponding improvement measures.

Abstract: This paper presents an explicit dynamic finite element method (FEM) in conjunction with the forming limit diagram (FLD) to analyze the forming limit for the SPCC foil in micro deep drawing of square cup. In the present study, the tensile, anisotropic and friction test are performed to obtain the material parameters of the alloy foil according to the ASTM standards. Importing these properties, the numerical analysis is conducted by the explicit dynamic FEM. The FLD in numerical simulation is used as the criterion of the forming limit in micro deep drawing of the square cup. The forming limit, punch load-stroke relationship, deformed shape and thickness distribution of square cup, are discussed and compared with the experimental results. It shows that a good agreement is achieved from comparison between simulated and experimental results. The limit drawing ratio in micro deep drawing of square cup is 2.08 in this paper. From this investigation, the results of this paper can be used as reference in the relative researches and applications of micro forming.

Abstract: The main aim of this study is to examine on the real and simulated earthquakes effects. This paper deals with the use of ARMA models in earthquake engineering. The time-varying auto regressive moving average (ARMA) process is used as a simple yet efficient method for simulating earthquake ground motions. This model is capable of reproducing the nonstationary amplitude as well as the frequency content of the earthquake ground accelerations. The moving time-window technique is applied to synthesize the near field earthquakes, Chlef-1, Chlef-2, Chlef-3 and Attaf 1980 recorded on dense soils in Algeria. This model, is based on a low-order, time-invariant ARMA process excited by Gaussian white noise and amplitude modulated using a simple envelope function to account for the non-stationary characteristics. This simple model gives a reasonable fit to the observed ground motion. It is shown that the selected ARMA (2,1) model and the algorithm used for generating the accelerograms are able to preserve the features of the real earthquake records with different frequency content. In this evaluation, the linear and non linear responses of a given soil layer have been adopted. This study suggests the ability to characterize the earthquake by a minimum number of parameters.

Abstract: In this paper, the elasto-plastic dynamic analysis on the steel spatial arch truss with 120m span and 0.1 rise-span ratio is carried out under with SAP2000. The plasticity development level and failure mode of the structure are estimated by the method of increasing the peak acceleration gradually and the plastic hinge theory. The results show that the structure displacement response changed nonlinearly with the increased peak acceleration of the earthquake; Its critical peak acceleration of EL earthquake wave when applied in horizontal direction is 222gal, and is 274gal when applied in vertical direction; The ratio of its maximal node horizontal and its structural height is 1/783 when EL-Centro waves applied on structure in horizontal direction; The ratio of its maximal node vertical and its structural span is 1/751, when EL-Centro waves applied in vertical direction; The failure mode of the truss under the earthquake action is elasto-plastic dynamic buckling.

Abstract: A probabilistic model is used to assess the structural reliability of typical reinforced concrete masonry walls under combined shear and compression. Factors such as model error, shear strength of concrete masonry, wall aspect ratio, horizontal and vertical reinforcement ratios, structural safety class, axial load-to-dead ratio, height and thickness radio of the wall, and load effect combination will be considered. Based on a relatively large number of test results and theoretical analysis from the literature, the limit state equation for shear bearing capacity was established. A sensitivity analysis will be performed to identify the key contributors to the reliability of the masonry walls under the combination of gravity and earthquake. The results will provide a base to evaluate whether consistent safety is achieved for masonry walls that are subjected to different load combinations. The counteracting load factors in current design codes for masonry structure will be investigated.

Abstract: Based on compute analysis engineering (CAE), the performances of acoustic and fluent for muffler comprehensively were analyzed and optimized in the paper. First, aiming at the heavy exhaust noise of diesel engine, bench experiments of measuring independently were designed and carried out, the frequency spectrum of exhaust noise was achieved, combining with simulation analysis of the finite element, acoustic and fluid performances of the original muffler and respective muffling cavities were analyzed, whose shortage such as transmission loss, pressure loss and flow regeneration noise were achieved, the muffler would be re-designed by CAE. Simulation shows the performances of improved mufflers were better than the original one. Eventually, insertion loss of experiment for new muffler is more 10dB(A) above than the original one, and power loss met requirement.

Abstract: The shape functions in C¹ natural element method (C¹ NEM) are built upon the natural neighbor interpolation (NNI), and realize the interpolation to nodal function and nodal gradient values, so that the essential boundary conditions (EBCs) can be imposed directly in a Galerkin scheme for the partial differential equations (PDEs). In the present paper, C¹ NEM for couple-stress (CS) elasticity is constructed, and the typical example which has analytical solutions is presented to illustrate the effectiveness of the constructed method.

Abstract: The state before and after structural failure is quite different, which leads to some sudden changes to its corresponding energy. According to energy catastrophe theory, each phenomenon that reflect system state mutations can regarded as the criterion of instability. Based on the energy catastrophe theory, the problem of concrete structure failure is dealt with various energy calculation methods. Moreover, the energy change rate method is put forward to search the omen point of structure deformation and failure. By comparing with structure total strain energy and plastic strain energy, it is shown that the elastic energy change rate can determine the omen point of structure failure more easily, directly and precisely. Finally, it is found that the stress-strain relationship of many materials in engineering are quite similar, which shows that using elastic energy change rate method to determine the omen point of structure failure has some certain universality in engineering.

Abstract: The inner concave cable arch structure has been adopted in some engineering applications in recent years. Geometric configuration of the cable clamp joint and its anti-sliding performance is the key to assure the bearing capacity for this type of structure. In this study, nonlinear finite element analysis on the cable clamp joint of a concave cable arch is performed using ABAQUS, with influences of the friction coefficients and the nonlinearity of materials are investigated. The pretension loss of bolts caused by different tightening sequences is also discussed. It is found that nearly 9% of the initial pretension force for each bolt gets lost during the tightening process, and mutual influence of the bolts can be significantly weakened by applying reasonable tightening sequence.

Abstract: In this paper is discussed the way of suitable numerical solution of contact shape optimization problem. The first part of the paper is focused on method of global optimization field among which the genetic algorithm is chosen for computer processing and for application on contact problem optimization. The brief description of this method is done with emphasis of its characteristic features. The experiment performed on plane structural problem validates the ability of genetic algorithm in search the area of the global optimum. On the base of the research described in this work, it is possible to recommend optimization technique of genetic algorithm to use for shape optimization of engineering contact problems in which it is possible for any shape to achieve successful convergence of contact task solution.