In this study, we examined the influence of characteristics of rolling loads by casters on separation resistance of substrate concrete and synthetic resin floor coatings. In the experiment, we first prepared floor samples having substrate concrete of various compressive strength, surface hardness and surface configurations, then put the coated samples to the test of separation resistance with Rolling Caster Loading Machine. Three loading conditions consisted of different kinds of casters, rolling conditions, and coating materials. Consequently, we clarified that the grade of separation resistance varied widely according to the characteristics of substrate concrete and rolling loads.

View full abstract

In this paper, the high-fluidity concrete placing into the wall form with the obstructions is simulated in order to confirm that this 3-D flow simulation system can be applied to full-sized structure. In the beginning, the parametric studies are carried out about the handling between the form and fresh concrete on the touching side, and the rheology constants on the fluid surface are examined. As a result, the experiment is simulated by correcting the rheology constant of the surface material, multiplying the rate of VOF(volume of fluid) and decreasing to 1/2. Next, the parametric studies are executed about the rheology constants and the amount of obstructions in the wall form by this decrease method. As a result, it is clarified that this 3-D flow simulation system can correctly express the influence by the rheology constants and the amount of obstructions.

View full abstract

The effect of fatigue by flexure on pore structure and carbonation of concrete and mortar were studied. Pore volume, particularly in the range of capillary pore, increased in fatigued specimens and thereby deeper carbonation was observed. To discuss quantitatively the effect of fatigue, the scale that indicates the degree of fatigue is proposed, and the relation between degree of fatigue and pore volume and also carbonation was discussed. It is concluded that concrete and mortar subjected to repeated loads, even if they are at low level, are changed in their micro structure and thereby durability of them is lowered.

View full abstract

It is important to predict the strength of concrete cured under high-temperature conditions at an early age, such as mass concrete and precast concrete. Using the maturity method, the strength of concrete cured under high-temperature conditions at an early age was predicted. It became obvious that the previous maturity method was not sufficient to predict the strength of concrete cured under these conditions. Therefore, a new factor was introduced to make the previous maturity method applicable to the strength of concrete cured under high-temperature conditions at an early age. As a new factor, the integrated value of curing temperature during the period having a significant effect on the strength development was adopted. It was found that the prediction accuracy at later ages was improved by introducing the new factor.

View full abstract

The tensile strain at cracking of early age concrete was measured and formulated under the ambient temperature of 15 to 35 ℃. The initial brittleness of green concrete was occurred under the influences of rapid reduction of tensile capacity due to the viscosity and increase of it due to the elasticity at early age. The presented formula fitted to the tendency of time-dependent change of experimental value, and coefficients of the formula were shown as the functions of temperature. And further, quantitatively, the formula indicated the minimum value of tensile capacity of green concrete under each temperature ambience.

View full abstract

The recommended method consists of 24-hour ultrasonic testing and 3-day rebound hammer testing after placing on concrete in structures The merits of this method are as follows: (1) The earlier determination (2) Getting information of qualities very early and accurately step by step; combining 24-hour pulse velocity with 3<lay rebound numbe (3) The age of 24-hour or 3<lay is the optimum age for each nondestructive testing respectively (4) The direct inspection of structures (5) Getting the alternative quality characteristics of strength and durability. This paper describes the investigation results that have brought the basis of the above items.

View full abstract

Heat is one of degradation factors for polymeric building materials. Black panel temperature(BPT), index of thermal degradation environment, was monitored at horizontal, tilted and vertical positions for 4 years to be expressed as function of ambient temperature, wind velocity and solar radiation. The hourly BPT was estimated referring JMA's meteorological data around Japan for 1991 to 1998 and thermal deterioration amount was estimated based on Arrhenius' Model. The results were plptted on maps, which would be used for the analyses of the local difference of weatherability.

View full abstract

Aerodynamic characteristics acting on rectangular prisms remarkably vary with the side ratio of the prisms. The variation of wind forces with the side ratio was caused by the aerodynamic interaction between the separated shear layer and the after-body of the prism. Especially, the re-attachment of the separated shear layer on the after-body of the prism yields the remarkable variation of wind forces. In order to investigate wind forces on several rectangular prisms, a wind tunnel experiment was carried out by the simultaneous multipressure measurement in a smooth flow. In this paper, the variation of pressure distributions and the resulting wind forces on rectangular prisms with various side ratios are discussed.

View full abstract

A large-eddy simulation (LES) technique has been applied to prediction of flow past rectangular cylinders influenced by free-stream turbulence. Stochastic method was used to generate homogeneous turbulence with specified power and cross spectra in the oncoming flow. It has been found that the buffeting effects due to the inflow turbulence were predicted well. In case of a cylinder of small length to height ratio (B/D=1.0), just Strouhal number increases slightly and for large (B/D=2.5), enhanced turbulent mixing causes reattachment of separated shear flow on the cylinder side. These are in good agreement with the results of previous experimental studies, and the present method appears to be sufficient for practical applications.

View full abstract

In the case of the wind resistant problems and environmental problems of buildings, we have to consider the effect of turbulence characteristics. Therefore, it is important for numerical simulations as well as wind tunnel experiments to give a velocity profile and turbulence intensity to the approaching flow conditions similar to natural wind. Here, we try to provide the numerical technique for generation of inflow turbulence by DNS (Direct Numerical Simulation) of turbulent boundary layer on a plate. In this study, we employ the interpolation method with the periodic boundary condition in order to simulate fully developed turbulent boundary layer. We investigate the inflow profile and its turbulence characteristics on the basis of the number and density of the roughness blocks. It is shown that we can control the generation of wind data by adjusting above parameters. Also, we apply this generation technique to the flow simulation around 3D square cylinder in turbulent boundary layer. Comparing the flows and wind pressure in a boundary layer velocity field with those in a constant velocity field, we discuss the turbulence effects on the aerodynamics of high-rise building.

View full abstract

Dynamic bifurcation of numerical analysis for the nonlinear Duffing's equation of a simple elastic structure under the periodic force is presented. The aim of this research is to solve the chaotic solutions on a 2-bar truss structure with damping system, and it has a geometrical nonlinear stiffness on this model. It shows the view of the Poincare solutions caused by its geometrical nonlinearity by increasing parameters. It is possible numerically to solve Duffing's equation under the periodic load with a geometrical nonlinear stiffness. We show the chaos attractors for the force amplitude parameter and the circular frequency parameter.

View full abstract

This paper proposes a new method to obtain the optimal values of connecting springs and dampers and those optimal locations for controlling multi-vibration modes in connected buildings. The way to obtain the optimal values of dampers for connecting buildings with only dampers has been already known, however, it is hard to control the multi-vibration modes using this way because of a restriction that the natural frequency of a sub-structure must be higher than that of a main structure. Using the proposed method, it is able to adapt for the inverse situation of the natural frequency in connected buildings, since the sub-structure is usually slender and it means to take lower natural frequency. This method is based on the stationary point theory which is well known for designing tuned mass dampers optimally, and its rectification approach for modifying the optimal values of connecting springs and dampers, because vibration mode shapes are changed by connected springs. The effectiveness of the proposed method is demonstrated through a simulation example of the multi-mode vibration control of a pair of three-lumped-mass models.

View full abstract

The foundation system is determined depending on the type of structure and soil characteristics. When the bearing layer exists in deep, the pile foundation is generally employed. The wall foundation is combined, when the more rigid performance of foundation is required. The wall foundation is usually designed regarding as the continuous plate. Actually, it is difficult to construct according to the designed specification, the wall foundation is constructed by separating to some panels. Any structural fastener does not connect the joints to each other. The wall foundation behaves as uniform plate for long or small lateral load affects on the foundation. The joints could be cracked and separated as the severe earthquake would occur. If the wall foundation keeps uniform body for severe earthquake, the fatal destruction may happen by the local shear stress concentration. The pile-like split wall foundation might be better foundation system than usual wall foundation. It should be investigated to evaluate the seismic safety of foundation and structures. This paper described the dynamic response characteristics of composite foundation of wall and pile by using rigorous 3-D FEM.

View full abstract

The region around Lake Suwa has a very soft layer and damage from differential settlement is apparent in many houses. In this study, the authors studies differential settlement at 28 built in Toyoda, Suwa City on the south side of Lake Suwa, Nagano. Prefecture over a period of five years from when the houses were newly built. Using the results of the study, the authors crganized the settlement pattern and the impect factors on settlement, and indicated a number of points that were discemed concerning on differential settlement of the low-rise housing. The research revealed that the depth of the banking have a great impact on differential settlement.

View full abstract

The present paper dealt with the extension of tendon friction coefficient correlation as a function of loading end load and circumferential angle, proposed in the former paper. The extended correlation further included the effects of the number of strands contacted with sheath, tendon diameter, plasticization of tendon and tendon local curvature. The validity of the correlation was confirmed by several published measured data. The structural analysis of middle cylinder part of 1/4 PCCV model was conducted using the present friction coefficient correlation. The results were compared with the analysis using constant friction coefficient, focused on the tendon tension force distribution.

View full abstract

In analyzing huge structure, the method to substitute a beam element for truss girder is very useful. However, this method is not clear for the application to elasto-plastic problem. Besides, it is not properly that recent methods, such as a plastic hinge method apply to that reduced model. Then in this paper, we propose an analytical method for the reduced model which evaluates elastoplastic behavior of truss girder based on the theory of plasticity. And we describe the validity of our method by comparing between the numerical results calculated by finite element method and ones calculated by using proposed model

View full abstract

Present paper describes the use of a stochastic search procedure that is the bases of genetic algorithms (GAs), in developing near-optimal topologies of load-bearing truss structures. Many works have been already published until today on the structural optimization of truss topology using the genetic algorithms. In most cases these works express the truss topology as a combination of members, and existence of each member is directly connected to the genetic code. These methods, however, have a fatal weak point. Namely when the topology is made along these methods, they might include needless members or those which lies on the other members. In addition to these problems, generated structures are not always stable. These problems become more remarkable when the freedom of the problem becomes large. We have already proposed a new method that resolves those problems by expressing the truss topology as a combination of triangles that are joined with each other. However, the length of chromosome tended to become long. This paper proposes brand-new implements for effective optimization. Detail of the proposed methodology is presented as well as the results of numerical examples that clearly show effectiveness and efficiency of the present method.

View full abstract

This paper presents the results of experimental tests completed to investigate influences of axial deformed bars and lateral reinforcement on the earthquake-resistant properties of PRC piles. 14 specimens (13 PRC piles and 1 PHC pile), whose hollow spaces were filled with the normal concrete, were tested. The specimens were subjected to reverse cyclic loading under a constant axial loading. Experimental results show that,・when properly reinforced with axial deformed bars and lateral reinforcement, PRC piles can exhibit stable hysteretic behavior and significant ductility.

View full abstract

There are two main objectives in the present study. One is to examine the effect of size of specimen on the stress-strain behavior of confined concrete under compression, taking into account the compressive strength of concrete up to high strength level. The other is to propose numerical formulas for predicting the stress-strain behavior of confined concrete of different sizes. By using the obtained numerical formulas, the stress-strain behavior of full scall confined concrete column under uniaxial compression is predicted, considering the size effect.

View full abstract

This paper presents a new constitutive model of cracked RC plates subjected to combined axial and shear stress. First, we carried out reversed cyclic shear load test where reinforcement ratio of RC plates and axial stress values were set as parameters. Pre-cracks were generated by tensile stress, and reversed cyclic shear loads were applied under the specified axial stress. Then, based on the test results, we obtained the constitutive model for smeared crack model, where shear stiffness of the plate varied depending on shear strain and axial strain. By adopting proposed model into nonlinear FEM analysis program, analysis results were improved and the efficiency of the model was validated.

View full abstract

In order to estimate the deformation capacity of RC beam accurately, it is important to clarify the shear failure mechanism caused by reversed cyclic loading after flexural yielding. The shear failure after flexural yielding has been considered to be caused by yielding of lateral reinforcement or compressive failure of concrete strut in the plastic hinge region. Under reversed loading, so-called 'Slip Region', in which shear stiffness of the plastic hinge region decreases temporarily, is observed. Concrete cracks repeat opening and closing under reversed cyclic loading. And the slip region appears owing to temporary opening of all these cracks under reversed loading. In this paper, it is shown that the slip region peculiar to reversed cyclic loading produces lateral strain accumulation in the plastic hinge region and this accumulation causes the shear failure after flexural yielding. The lateral strain is not caused by axial deformation of lateral reinforcement but caused by flexural deformation of lateral reinforcement provided by temporary stiffness deterioration of core concrete on slip region. The observed failure mode is different from the failure modes mentioned above, that is, yielding of lateral reinforcement and compressive failure of concrete strut. This failure mode peculiar to reversed cyclic loading is to be called ' Strain Accumulation Failure'.

View full abstract

In this paper, the behavior of the concrete filled circuler tube Y branch joint are investigated. The strength of branch joint and the collapse mode are clearly by the experiment. As a result, the stiffness and yield strength of the concrete filled branch joint are increased extremely. And the concrete filled branch joint is collapsed by the fracture at the obtuse angle side. According to circumstances, the branch broken decided the collapse mode and the ultimate strength. And the ultimate strength is greater by the compression force in the main pipe. Finally, the strength estimation is shown.

View full abstract

Strength and deformation criteria for a joint of the steel tubular trussed tower reinforced by ring-stiffeners and gusset plates are quantitatively derived from experiments and FEM nonlinear analyses to predict its local behavior under bending or horizontal loading. Yield strength of the concerned joint under bending loading is evaluated more safely than that of the model joint reinforced by single ring-stiffener. In case of a joint having multiple number of ring-stiffeners under horizontal loading, its yield strength shows a tendency to be small, because sheared force of the each ring-stiffener is not even. Under the unified condition, yield strength reduction factor correlates a ratio of the ring width outside the tubular steel to the tubular steel diameter.

View full abstract

In recent years, hysteretic dampers made of low-yield-point steel are expected to reduce earthquake responses of structures not only in designing new buildings but also in retrofitting existing buildings. Inelastic behaviors of dampers of this kind during severe earthquakes are, however, collected not so much in an experimental way. First, this paper presents sub-structuring pseudo-dynamic tests which are performed to simulate inelastic responses of a singlestory steel frame retrofitted by a stud with a low-yield-point damper inserted. Second, a half-scale 3-story model structure is retrofitted by similar dampers, and its actual dynamic properties are examined by forced vibration tests. Finally, its inelastic real response is successfully monitored to a natural moderate earthquake.

View full abstract

In order to investigate the effects of height of lateral forces, vertical axial loads and presence of masonry units on seismic behavior of reinforced fully grouted concrete masonry (grouted masonry) walls, twenty different wall specimens were tested under constant compression, tension and variational axial loads, and alternately repeated lateral forces. Test results indicate that the seismic behavior of grouted masonry walls is remarkably affected by the height of lateral forces as well as the values of vertical axial loads, and the grouted masonry walls have almost the same seismic resistant capacity as reinforced concrete walls.

View full abstract

The buckling loads of steel columns in large scale under elevated temperatures that are achieved by fire tests are discussed in this paper. The ISO standard and the other heating tests with loading through rounded supports were done for 24 specimens covered with some kind of thermal insulation. H-shape steelworks of the steel grades of SN400B and SS400 which have several different section sizes specified in the JIS standard and the support lengths of specimens are 3.8, 3.5 or 3.0 meters. After the careful observation of tests results authors concluded as followings: The collapse loads of the columns can be obtained from the test results of mean steel temperatures between 34℃ and 739℃. The contraction of the columns can be induced by load, steel temperature and some other parameters. Although the allowable temperature of a column with the maximum service load by the AIJ design method for the 2.4 tonf/cm^2 yield strength and the 2100 tonf/cm^2 Young's modulus, is revealed to be less than 513℃ or so, the buckling loads decreased with the temperature increase from ambient to 739℃.

View full abstract

Computational method for 3-dimensional overturning response of rigid prism is discussed with some interesting results. Analytical assumptions are introduced as follows. 1. At least one of vertexes of the prism contacts with a floor. And sliding between the prism and floor is not assumed. 2. Only rotational motion around X, Y-axis are permitted at a point of contact. Moment is not transmitted. 3. The motion of the prism equals to a rigid pendulum's. 4. After an instantaneous collision with a floor, the prism continues to move with specific character of rigid pendulum. To avoid computational difficulty, numerical integration is applied directly to solve constrained redundant equations which is similar to linear equations. After assured accuracy of computational method with fundamental examples, 3-dimensional effects of pendulum response by response spectra and overturning tendency of prisms by overturning

View full abstract