A production control method for extrusion moulding of standardized cementitious materials with wide ranges of mix proportions is originally proposed to determine operating points by means of performing both standard extrusion tests and single shear tests. The following technical items are clarified ; 1) Operating points, namely extruding pressure and velocity, are briefly predicted on the basis of water content ratio. 2) Conveying rate per revolution of screw is uniquely related to extruding pressure, from which the operating points can be calculated. 3) Extruding pressure was directly influenced by shear strength of fresh mortar, especially internal friction coefficient.

View full abstract

A unique relationship between flexural strength and water cement ratio of cementitious materials produced by extrusion moulding is clarified on the basis of two series of experiments of which main parameters are mix proportions (sand cement ratio and water content ratio) and additionally rotational frequency. Furthermore, densifying processes during extrusion mouldings are clarified. The followings can be noted as the main concluding remarks; 1) Flexural strength of extruded materials can be determined by effective water cement ratio. 2) Extruding processes are significantly effective in densifying materials especially less than 0.20 of water content ratio.

View full abstract

This study on mortar reinforced with discontinuous fibers intends to relate the flexural stress-deflection curve to the tensile and compressive stress-strain curves. The main points discussed are as follows; (1) to determine the measuring method of stress-strain curves appropriate for this composite material, (2) to examine the analytical method of the flexural stress-deflection curve based on the experimental data of the tensile and compressive stress-strain curves, (3) to observe, from the analytically obtained results, the influence that the characteristics of the tensile and compressive sress-strain curves have on the flexural strength and resulting deflection.

View full abstract

To consider aeroelastic instabilities of prismatic high-rise buildings in strong wind, wind tunnel experiments were performed to obtain the information of the unsteady aerodynamic forces as modal forces on buildings, which are subjected to the forced harmonic oscillation with a fundamental linear mode in a turbulent boundary layer. Unsteady aerodynamic forces are mainly produced by the suction forces generated by motion-induced vortices and by the vortex shedding behind buildings at rest, i.e., the vortex shedding of the Strouhal component, of which strength are varied with the oscillating amplitudes and the velocity of the incident flow. We investigated the characteristics of the unsteady aerodynamic forces varing with the amplitudes and the velocity and elucidated the mechanism of the motion-induced oscillation, by examining the arrangement, the frequency of occurrence and the interference effect of the two types of shedding vortices.

View full abstract

A computational method is presented for finding a sequence of seismic response constrained designs of a large-span truss for specified maximum member strains and response nodal accelerations. The truss is to be designed in such a way that response accelerations and strains due to a set of multicomponent earthquake motions compatible with the specified design response spectrum would just coincide with or be less than the specified values. A shape parameter as well as cross-sectional areas is considered as a design variable. A sequence of seismic response constrained trusses is generated with the use of the Taylor series expansion method with respect to an upper-bound strain parameter. It is shown in the example that it is necessary to change the shape so as to satisfy the constraint on the maximum response acceleration.

View full abstract

This paper presents an equation to calculate the bond splitting strength of lap splices for D38 high-strength large diameter bars. Results of 16 pull out tests are presented. Main variables were steel strength, concrete strength, lap length, and bar spacing. It is shown that the bond splitting strength is influenced by concrete strength, lap length, and bar spacing. A proposed equation shows a good agreement with experimental results.

View full abstract

In steel structures, the full penetration multi-layer welding is used in a connection of beam flange and column one. We have developed a flat position multi-layer welding system by introducing a robot to the CO_2 gas shielded arc welding where semi-automatic welding has been used. In this paper, first we explain the structure of welding system, followed by the results of mechanical property test and a full-size cyclic bending test. These mechanical properties were compared with the semi-automatic arc welding zone welded by skilled welder to evaluate. From these experiments, we conclude that the welding robot can be used for welding of Beam-Column connections in steel structures.

View full abstract

H-shaped steel beams of beam-to-column connections welded on site are chosen as the subject of this study. A beam flange of this type joint is welded to a column flange on site, and a beam web is jointed by high strength bolts. Three-point bending tests and finite element analysis are carried out to investigate structural behaviors of this type joint. The results are summarized as follows: (1) When a beam flange is made of steel with lower yield ratio, α value which is obtained by dividing the experimental maximum strength by full-plastic strength is increased. (2) α value is independent of transmission capacity of bending moment in bolted joints. (3) The deformation capacity of H-shaped beams without scallops is greater than that with scallops, when yield ratio of a beam flange is less than 0.65.

View full abstract

This report proposes a reasoning system for bearing shear wall stresses in the ultimate state by using geometrical data of buildings and shear walls at the initial stage of aseismic structural design study. A neural network is used for reasoning, so elasto-plastic stress analysis is carried out for selected shear wall arrangements, then the analytical results are used as the training data. The reasoning results of the bearing shear wall stresses in arbitrary shear wall arrangements are compared with elasto-plastic analytical results, and show satisfactory agreements.

View full abstract

There has been remarkable progress in the computational engineering science by the large scale linear and non-linear finite element analyses. This study proposes an analytical procedure to find the solution of sparse systems arising from the finite element structural analyses by a generalized conjugate gradient method with symmetric matrices. The fundamental equations are derived retaining the advantages of the conjugate gradient method which includes the PCG method (e.g. the ICCG method), and can find the singularity of matrices. In this paper, theory of the generalized conjugate gradient method and the outline of algorithm are presented.

View full abstract