This study presents the evaluating method of hardness and slipperiness of aerobic dance floors from a viewpiont of comfortableness, fatigue, and safety. The evaluating indexes and evaluating method are established, based on the correspondence between the judgements of aerpobic dance instrutors and phisical values of aerobic dance floors measured by our original measuring devices.

View full abstract

In this paper, a new two-dimensional isoparametric element, available to the finite element analysis of structures of more arbitrary shape and effective for saving the total number of freedom, is presented. The discretization method proposed in the authors' previous paper is employed to define the assumed displacement field and approximate the shape of the element, in which the nodal displacement parameters on 8 external nodes adjacent to the element as well as on its 4 vertex nodes are used as the displacement parameters of the element. The shape functions in the parent coordinates are given in the explicit expression, and the stiffness matrix of the element is derived by using the well-established procedure of coordinate transformation and numerical energy integration. In order to consider the convergence aspect, the continuity on inter-elements and the completeness of shape function are particularly examined. As numerical examples, three different structures in the state of plane stress are analyzed for investigating the accuracy and the convergency of the present isoparametric element.

View full abstract

The authors have developed a method of analysis to find the non-linear earthquake response of multi-degrees of freedom structures by using a Digital Differential Analyzer(DDA) and the Digital actuators. Details of the system and the computing method are described herein. Based on this system, the non-linear seismic behavior of the two-degrees of freedom structures subjected to strong earthquakes were experimentally simulated.

View full abstract

Cold-formed square steel tubes (STKR 41) with 6 sizes of section are examined to clarify plastic strain history along the cold-forming pass. By comparing the thickness of tube with the corresponding sheet coil, the flat part of square steel tube is estimated to receive plastic strain of 3〜5 % approximately. As the matter of fact, yield stresses of tube rise up 1.1〜1.5 times higher than those of the sheet coil. The tensile strengths, however, are independent of the plastic strain history. Therefore, it makes the yield ratio increase up to 0.85〜0.95. Released strains are measured by saw cutting method. Compressive strains of 1500〜700μ are observed along the longitudinal direction at the outer surface. On the contrary, tensile strain of 200〜500μ are obtained to the circumferential. These released strains are converted to the corresponding elastic stress approximately 35〜15 (kgf/mm^2), which is 80〜40 % of the yield stress at the flat part of tube. Assuming the plastic strain pass during the cold-forming process, elastic-plastic two-dimensional numerical analysis is carried out. As the results, complex distributions of residual stresses locked in the section are obtained. Considering the influence of plastic strain history and residual stresses, the global behaviors of square steel tubes are discussed by comparing with the experimental results under stub column test.

View full abstract

When we try to analyze the continuum large deformation, it will be recognized that the deformation behavior of thick continua is different from that of thin continua because of the transverse effects. In this paper, the laminate theory, which is mainly used in the deformation analysis of continua consisting of composite materials such as a sandwich plate, is applied to the large deformation analysis of the thick-walled shells. The present analysis method is described by the Updated-Lagrangian Formulation. On the other hand, a new modelling method to analyze thick-walled shells is presented First, the wall of a shell is devided into several layers through the thickness. In each layer the cross-section of the layer is assumed to remain plane after deformation. It is convenient to employ the concept of a multi-director surface in describing the geometry of the layered shell configuration. The layered shell is assigned to a single arbitrary reference surface. Every point in the reference surface is endowed with a set of directors ; each director in this set corresponds to a directed straight material line segment through a layer thickness. Thus, in each layer, the ends of the director contact the layer surface. The distribution of displacement of points in reference surface and directors of other points, in the axial direction is given by harmonic functions. At last, we will report the results of some calculation by the present analysis method and discuss the validity of the method for a thick-walled cylindrical shell under axial compression using the Mode Superposition Method.

View full abstract

A panel with thin rib was made of SS34 galvanized sheet steel which thickness and width are less than 1 mm and 600 mm respectively. The sheet steel is transformed to an arch by processing twice. A cylindrical shell structure is built by being seamed at mutual edge flange of the each arch. This cylindrical shell structure is constructed by simple connecting way "seaming", so that its strength for various external force have to be cleared. In this study, vertical loading experiment has been conducted in order to investigate strength of the shell structure for snow loading. The vertical load was utilized by sacks filled with sand. The test model is one unit of the cylindrical shell, which diameter is 9 m. Plastic hinge method has been done also and results obtained by the experiments and the analyses were compared, and their results are summarized as follows ; 1. In order to estimate the strength and regidity of the each panel, the effective section, which is calculated from panel's width-thickness ratio recomended by A. I. J. is suitable. 2. The strength and regidity of the shell structure can be estimated by neglecting friction between each panel, and the strength of the shell structure for the vertical loading can be estimated by assuming plastic hinges. 3. Steel SS 34 which employed for the panel, normally has not been used for general buildings, but it can be appricable for this shell structure. 4. The allowable maximum snow depth of this shell structure is estimated by the ultimate load design method, when the load suggested by A. I. J. "Recomendation for Building Design Snow load" and load factor, 1.65, are employed.

View full abstract

In the past shaking table test of liquid storages, it is frequently referred that the inner liquid oscillates with rotational movement around revolutional center of the storage in spite of the horizontal external excitaion. It has been called "swirling" and frequently observed especially in the experiment of axisymmetric storages as cylindrical and spherical ones. Once such response of the inner liquid occurs in the actual broad storages, unexpectedly large dynamic liquid pressures will be generated and, as a result of such non-self-equilibrium pressure distribution, excessive shear force will act on the basement of the storages, which are thought not to be negligible from the viewpoint of the actual design. In the present paper, swirling phenomenon of the inner liquid of idealized rigid cylindrical storage are dealt with as nonlinear oscillative problem originated from the nonlinear boundary value problem of perfect fluid with free surface. As a result of the stationary oscillative analysis by using simple reduced equations, swirling is pointed out to be explained as bifurcational phenomenon between symmetric and anti-symmetric spatial modes with reference to circumferential coordinate θ. In order to certify the result, nonlinear stationary oscillative analysis with multi-degree-of-freedom by harmonic balance method and shaking table test using a "grid projection technique" are carried out. Consequently, it is clearly pointed out that swirling phenomenon can be simply described both qualitatively and quantitatively as bifurcation between the spatial modes whose function in the circumferential direction consists of cos θ and sin θ, and the instability frequencies between sloshing and swirling movement of the inner liquid obtained by the theoretical treatment are shown to have excellently good agreement with the results obtained by the shaking table test.

View full abstract

In this report, (1) a fundamental set of differential equations governing the bending of r. c. slabs subjected to flexure in the geometrically nonlinear elastic ergion is derived in consideration of the bond-slip of reinforcement and (2) a finite element formulation of the problem is implemented ; whose subsequent solution in a few cases in point is presented as well as its examined results.

View full abstract