Some kinds of cementitious materials with various water content ratios were extruded by extruders with different barrel diameters and various die opening geometries, in order to develop a method for predicting the extruding pressure concerning about die opening geometries. An effective thickness (t_e) is proposed as a factor for evaluating die opening geometries. It was clarified that the pressure could be predicted through the effective thickness and the linear relationships among material conditions, die opening geometries and barrel inner diameters. As a result, the fundamental knowledge with plastic processing for designing products and planning production procedures was established.

View full abstract

The influence of short cut fiber on the fracture parameters of high-strength concrete was investigated. Three-point bending tests on pre-notched concrete beam specimen which containing short cut fiber were performed. Fracture parameters of specimen were analyzed based on the poly-linear approximation analysis of tension softening diagram with the data of a load-load point displacement curve. It was found that the toughness of high-strength concrete was significantly improved by mixing short cut fibers in mortar matrix. Material properties and volume contents of fiber were considered to be important factors for improving the toughness of high-strength concrete. Also, the maximum size of coarse aggregate affects the toughness of concrete because the degree of dispersion of fiber in concrete was changed by the distribution of aggregate size.

View full abstract

This paper presents an analytical method for simulating chloride-ion penetration into concrete exposed to salt-laden environment. Two RC test structures exposed for 7 and 12 years are used for investigating the characteristics of chloride-ion penetration. Evaluating the test results, new analytical method for the diffusion equation is proposed. This method considers various influences from important factors such as air-laden chlorides, carbonation of concrete, water cement ratio (w/c), washing out and period. Comparing the analytical results with the field data, it is concluded that the proposed method gives excellent results and represents the characteristics of real phenomenon.

View full abstract

The first purpose of this study is to clarify the relation among slipperiness of floor finishing, visual and touching impression for floor finishing, and walking behavior. The second purpose is to quantify walking properties. First, walking behavior of totally 35 people was measured and sensory test was performed. Then correlations among above-mentioned three factors were studied. The correlations of old people were better than those of young people. Next, principal component analysis for walking behavior was performed to quantify walking properties. The result is that the first principal component was most effective to quantify the force of walking properties. Therefore, it might be better that people was not simply grouped based on age but on the first principal component from the viewpoint of walking behavior. Then appropriateness of such grouping was studied to see change of the correlations among above-mentioned three factors. The result is that the correlations of people grouped by the first principal component were better than those grouped by age.

View full abstract

A floor is one of the principal factors in a static charge accumulation on the human body. Although many kinds of anti-static floors are developed, a method of evaluating their effect has hardly been investigated. A new electrostatic tester was developed to measure the effect of the anti-static floor which reduced the electrification of the human body. This tester has two detectors of an electrostatic potential and charge decay time for evaluating the effect of the anti-static floor. Experiments were made on the evaluation of the anti-static floors using this tester. In this paper, functions and specifications of the electrostatic tester developed newly and results obtained from the experiments are presented.

View full abstract

The inflow turbulence for LES was generated by means of Hoshiya's method based on Monte-Carlo simulation considering power spectral density and cross spectral density as targets. The generated inflow turbulence was modified to satisfy the continuity equation by the divergence-free operation based on Shirani's method. As a result of these procedures, the level of velocity divergence could be reduced sufficiently and also the spatial correlation and power spectral density obtained from the inflow turbulence agreed well with the prescribed target values. The generated inflow turbulence was used as the inflow boundary condition for computing the decaying isotropic turbulence same with the one measured by G.Comte-Bellot and S.Corrsin to confirm its applicability. The decay of turbulence kinematic energy in streamwise direction was reproduced well by LES using the inflow turbulence.

View full abstract

In the previous papers, a probabilistic method to determine two classes of load models for use in safety and functionality limit state design based on the order statistics of basic variates was presented and the probabilistic characteristics of two classes of natural hazard models were discussed. Using the two classes of load models, this paper discusses the reliability of buildings designed by the current building code. Numerical examples show that the reliability of a building differs from site to site and load combinations, and that the reliability can be more consistent using probability-based limit state design.

View full abstract

Several techniques for efficiently computing Green's functions and normal mode solutions for layered half-spaces are proposed. First, the reflection/transmision (R/T) matrix method is applied to computing normal mode solutions in order to obtain numerically stable results up to very high frequencies. Second, the phase velocities obtained from above and Filon's quadrature are used for the wavenumber integration of Green's functions; this method greatly reduces the number of total integration ponits. Finally, the cubic-spline interpolation is used to spacially interpolate Green's function, greatly reducing computational time to obtain many Green's functions. The validity of the methods are checked by comparing results using other methods.

View full abstract

A new exactly compatible rectangular planer shell element on the basis of Von Karman's plate theory, whose displacement fields are approximated with higher-order polynomial interpolation functions, is proposed in this paper. The compatibility conditions at any type of interelement boundary can be exactly and easily expressed by means of the boundary tangential vectors. Very good results in FEM analyses can be obtained by using the proposed elements, with smaller number of degrees of freedom compared to some other efficient and reliable elements. The efficiency of the proposed element is demonstrated by some basic example analyses.

View full abstract

Many researches and experiments have already been conducted to evaluate the energy dissipation capacity on plastic state of RC shear wall. However, most of the researches and experiments are based on static loading tests or dynamic loading tests using small-scaled specimens. The authors carried out dynamic vibration tests using a lot of large-scaled specimens of RC shear walls to propose a model of hysteresis loop and damping factor utilized in a dynamic analysis. This report provides an energy dissipation capacity on plastic state of RC shear walls based on the results of those tests, and provides hysteresis models for dynamic analysis.

View full abstract

A numerical form-finding scheme for a special type of double-layer tensegrity grids is presented. The grids are composed of tensegrity modules of infinitesimal mechanism. The scheme has been developed for obtaining the curved grids where the constitutive modules are independently prestressable. A nonlinear programming problem is formed where reduced equilibrium equations of the module and some prescribed geometry conditions are introduced as constraints. The scheme is successfully applied to a spherical grid. The curved grids have a unique characteristic that they can smoothly move owing to their discontinuous compression members and that their constitutive modules are independently stabilized. Thus, unique construction methods for the curved grids can be proposed.

View full abstract

Multi-span gable frame structures shows significant cubic effects that may reduce the displacements and stress resultants of the frame. The optimal weight may express not only a literal design standard of a structure but also a quantitative evaluation of the cubic effect of the structures. Then, adopting the genetic algorithms to optimize the weight of the multi-span gable frame structures that have a same plan and height of eaves but have various gable frame pitch and beam pitch, we examine the minimum weight design of the structures and the cubic folded plate effects on the design. It takes much computing time, when the genetic algorithms is applied to the design. In order to reduce the computing time, we adopt equivalent beam theories of the multi-span gable frame structures.

View full abstract

A method was proposed to estimate the yielding drift of a beam in a reinforced concrete frame. The drift consists of four components. These are (1) flexural deformation ; (2) shear deformation ; (3) additional deformation due to bar slip from a joint, and (4) additional deformation due to strain shift along a beam bar. The calculation method of each drift component was proposed. The calculated drift components by the proposed method and by other authors' methods were compared with experimental ones. The drift by the proposed method agreed well with test results.

View full abstract

An integrated theoretical and experimental research on the earthquake-resisting performance of the reinforced concrete columns confined by square steel tube is described. As the first part of the research, this paper presents experimental information on the earthquake-resisting performance of reinforced concrete columns confined by square steel tubes under high axial load. Thirteen square columns with high longitudinal reinforcement ratios of 3.84% and 7.68% were tested under reversed cyclic lateral load and constant axial load. It has been shown that square columns without adequate transverse detailing could be made to exhibit stable flexural response under such high axial load as the axial load ratio n=1.1 when confined by steel tubes. Square columns, only whose potential failure regions were confined by steel tubes, also exhibited very stable seismic response in a manner similar to columns which were totally confined by steel tubes

View full abstract

The thickness and residual stress effect of fatigue performance was inverstigated on non-load-carrying fillet welded joints with thickness ranging from 12 to 38mm. As-welded and stress relieved joints were tested under both alternating and pulsating bending. In this paper, distribution of the residual stresses near the welds measured by both a X-ray technique and a strain-gauge method is presented and discussed. The effect of residual stresses and plate thickness on fatigue strength at 2×10^6 cycles are discussed by using the present and past test results

View full abstract

Recent Japanese standard for limit state design of steel structures includes a requirement on the maximum strength of connections to assure general gross yielding of the connected members. In this paper, the reliability for limit state design of WBFW (web bolted and frange welded) beam-to-column connections were investigated in according to the test results. From the results, ultimate strength, failure mode and capacity of the bending moment of web bolted connections, were confirmed. Further, the relation of α value and β value was established, safety coefficient (α) was decided by depending on allowable safety index (β_u).

View full abstract

The purpose of this paper is to derive mathematical stress-strain expressions which can be applied to arbitrary strain paths of 590N steel and aluminum alloys (A5052BD-H34, A6061BE-T6, A6063S-T5, A6063S-T6, A6N01BE-T5, A6N01BE-T6, A7003S-T5, A7N01S-T5, A7N01S-T6) from experimental results. Cyclic stress-strain relationships of aluminum alloy were almost the same as normal mild steels. The mathematical expressions consist of the three components, namely, the skeleton part, the softened part and the unloaded part. The curves of the softened part and the skeleton part can be expressed as a function of only one factor : that is plastic strain experienced in a preceding half cycle. The experimental curves of stress-strain relations can be followed by the proposed empirical rules with good accuracy.

View full abstract

The resistance of a structure against an earthquake is related to its ability to absorb the seismic input energy. In the prevailing design practice the energy is absorbed by plastic deformations on building frame-components such as beams and columns. However, the experience in past earthquakes has shown that evaluating and repairing the plastic deformation and the associated damage on the frame is often difficult and expensive. Thus, the development of alternative devices for dissipating the seismically induced energy on the structure is highly desirable. In this paper a new type of hysteretic damper, which can be installed in a building frame as a concentric brace, is suggested. The damper takes advantage of the high energy absorption capacity of the round-shape steel rods when subjected to flexural deformations. The design criteria for the damper is described and its behavior is assessed experimentally.

View full abstract

The objective of this study is to clarify the influence of the bracing stiffness and the bracing strength on the post buckling behavior of compression members with lateral bracing. In order to do this, elastic-plastic analyses of compression members with a lateral bracing were performed, considering the yielding of the lateral bracing. The obtained results are summarized as follows: 1)The maximum bracing force is not the bracing force at which buckling occurred. The maximum bracing force occurred in post buckling range. Therefore, if the bracing strength is more than bracing force at the buckling and smaller than the maximum bracing force, then lateral bracing yields in post buckling range. 2)When the bracing strength is more than the maximum bracing force, lateral bracing does not yield. And the post buckling load is nearly equal to the basic strength regardless of the bracing stiffness.

View full abstract

The high strength steels are assumed to be used below the yield point in damage tolerant structures. It is still necessary that the inelastic behaviors of high strength steels should be studied experimentally in case of extreme large earthquake. Tension and compression cyclic loading was carried out controlled by the displacement. It is no problem for high strength steels with welded connection to be used in the 0.6% plastic strain range. However, it was found that the inelastic deformation capacity of high strength steels was reduced due to the influence of weld connection.

View full abstract

Just one year before the Hyogoken-nanbu earthquake, the Northridge earthquake took place. Under these two earthquakes, moment resistant steel frames showed a typical mode of fracture at the beam-to-column connections. Thus, the fractural mode of failure became a fundamental mode of failure in steel structures under earthquakes. In this paper, referring to current Japanese design practice, main causes for the fractural mode in the Hyogoken-nanbu earthquake are estimated to be an excessive seismic input and an overlook on stress concentration at connections.

View full abstract

Considerable number of lattice type steel encased reinforced concrete (SRC) buildings were collapsed due to 1995 HYOGO-KEN NANBU earthquake. The ductility of the member is increased by the encased steel. However, the amounts of latticed steel and hoop of the collapsed buildings were considerably less than those of the specimens in literatures. The merits of SRC structure were not fully developed in those buildings. The ductility of lattice type SRC columns is highly affected by axial force and margin of shear strength. Experimental formulae to predict the limit deformation of lattice type SRC columns are presented based on the past experimental data.

View full abstract

Twelve frame specimens composed of wide flange beams and square steel tubular columns with or without filling concrete were tested in order to clarify the whole behavior of frames under constant vertical and varying horizontal loads. From the test results, it has become clear that frames with concrete filled tubular columns are very excellent as earthquake resistant structures when the beam-to-column connections are designed by the AIJ strength formula. The limiting value of width-thickness ratio of concrete filled square tubes and deformation performance are discussed.

View full abstract

A lot of beam-column tests have been carried out and it was proposed that the flexural strength of concrete filled steel tubular columns (CFT) could be calculated by the strength superposing method. However, it is not verified whether the CFT section can carried such force under combined axial force and bending moment or not. Therefore, we did the eccentric compression tests on CFT short columns. The test results showed that the flexural strengths of CFT sections were terminated by the local buckling of steel tube and the maximum strengths were well estimated by using the compressive critical strain of steel tube. It was also clarified that the increase of concrete strength thanks to confinement could not be expected in case for columns with little or no moment gradient.

View full abstract

In construction robotization, for defining the new robot specification, the development of the particular work study method is crucial. In this paper the methodology of the robotized construction system design is discussed, and the newly developed work study method and application cases are introduced.

View full abstract