In this study, we developed the device to remove unburnt carbon from fly ash that applied flotation method, and experimentally examined the operating condition of the device. After we scaled up to the full scale device, we experimentally examined strength properties of concrete with fly ash removed unburnt carbon by it. According to the results, it was effectively able to removed unburnt carbon from fly ash by the device that installed micro bubble nozzles and a whirl type pump. The removal efficiency of unburnt carbon improved when prior forced stirring was carried out by a concrete mixer for 30 minutes, and scavenger in fly ash slurry of about 60 wt% in the density was added to. The compressive strength of concrete with fly ash slurry that removed unburnt carbon by the full scale device showed a tendency similar to the concrete with fly ash as specified in JIS A 6201 class II.

View full abstract

The purpose of this research is to clarify the durability of porous concrete against chemical deterioration by CaCl₂ solutions as a deicer. For various mix proportions of porous concrete and its cement paste, these specimens were soaked in high concentration of CaCl₂ solutions. Compression tests of porous concrete specimens, estimation of deteriorated depth of cement paste by drilling type surface strength tester, and observation of osmotic depth of chlorine element in cement paste by using EPMA have been conducted. As a result, to reduce water cement ratio or to use Portland blast-furnace slag cement has been found effective on a chemical deterioration.

View full abstract

The water absorbency of the concrete slab surface is a big factor for defective adhesion of several finishing materials. We will propose "wet filter paper method", a handy method for measuring the water absorbency.
In this method, a filter paper that is wet in advance with a fixed amount of water is contacted closely with the slab surface. Then, the decrease in wet paper mass is obtained. Initial amount of water, duration of the measurement, and some other conditions were defined experimentally, and accuracy was also verified. In addition, it was clarified that the filter mass reduction corresponds to the water penetration depth.

View full abstract

The properties of unsteady wind pressure on a flat roof body and a gable roof body subjected to a short-rise-time gust were investigated using a gust wind tunnel. We devised a pressure measurement method applicable to a rapid change of static pressure in a wind tunnel generating a short-rise-time gust. We confirmed a remarkable overshoot phenomenon of wind pressure generating a much larger wind pressure than in a steady flow. The peak wind pressure coefficient was evaluated by a non-dimensional rise time composed of the rise time, the gust wind speed and the body size.

View full abstract

This paper discusses the modal response characteristics of a tuned viscous mass damper (TVMD) seismic control system in which the secondary apparent masses are arranged such that their distribution is proportional to that of the primary stiffness. We found that the fundamental modes of the undamped primary system are preserved upon adding the secondary system in the seismic control system. Also, the participation mode vectors of the MDOF TVMD controlled system can be obtained by the combination of the participation mode vectors of an uncontrolled primary system and those of a reduced 2-DOF controlled system. This helps practicing structural designers understand the modal response characteristics of the seismic control system.

View full abstract

This paper proposes a optimal design method of base-isolation device and frame member in a reinforced concrete building. The proposed algorithm called DCMOGA( Distributed Cooperation model of MOGA(Multi Objective Genetic Algorithm) and SGA (Standard Genetic Algorithm) ) and conventional multi objective optimization are applied to design two buildings. Finally, a comparison was made among design solutions. Comparing to the conventional multi objective optimization methods , the proposed model found the widespread Pareto solutions. Consequently, the effectiveness of the proposed model was demonstrated.

View full abstract

In this paper, we study the response characteristics and establish a method of evaluating the maximum response of base-isolated buildings when colliding with the retaining walls by pulse-like ground motions. As a result, the following conclusions are obtained.1)The force buildings subjected to varies by stiffness of retaining wall and building scale. 2)The period of collision is half of the natural period. 3)If the stiffness of retaining wall is high, ultimate natural frequency is determined by the lowest mass and stiffness of retaining wall. 4)Using prediction method we propose, the maximum response can easily be evaluated approximately.

View full abstract

This study presents the vertical structural performance of wood-concrete composite beam. This composite beam has a superior performance of fire protecting and sound-proofing. In addition this composite beam is superior to a simple beam in strength, stiffness. But there is not the design method and there are few study accumulations of wood-concrete composite beam system with shear connecter in Japan.
In this paper, the result of shear performance of shear connecter between timber beam and reinforced concrete slab is described. The result of bending test is also described and traced by numerical model. They are summarized in 1) the composite beam increases more than 180% in strength and 280% in stiffness to simple timber beam, 2) numerical model traced to the result of bending test accurately.

View full abstract

The horizontal composite structure consisting of reinforced concrete and timber frame was tested at full scale shaking table tests in parameters of specification of the floor and number of stories. After BCJ wave of maximum acceleration 350gal, no damage appeared in these structures with high eccentricity. The shear force of timber was reduced in both specimens of the timber floor and the RC slab. By comparison with test results, the design method that the shear force produced in timber frames is transmitted to the reinforced concrete shear wall was safety. As described in this study, it was confirmed through shaking tests that the method for building with high eccentricity can be designed with structural safety.

View full abstract

The reinforcement detailing in L-shaped R/C beam-column joints at the roof-level is important for rationalization of design and construction of moment-resisting frame. In order to solve this problem, the authors proposed new reinforcement detailing using mechanical external anchorage of column reinforcement. Through this detailing, anchorage region is small enough to be hidden in the water-proof layer. In this study, such L-shaped R/C beam-column joints are tested. The experimental data shows that these joints have larger deformation capacity than with conventional anchorage. This is due to the formation of the strut mechanism in the joint. Consequently, the authors clarify that the proposed design formula can be applied for estimation of ultimate strength of these joints on the basis of experimental results.

View full abstract

This paper proposes a method for evaluating the local strength of the steel moment resisting connections consisting of wide-flange beams framing into wide-flange columns without continuity plates. Proposed method is based on yield line theory considering some limit states of the connections, such as column flange local bending, column web local yielding and interaction failure between them. Both detailed and simplified strength equations are proposed in this paper, which can be applicable to various beam and column dimensions. To clarify the accuracy of the proposed equations, non-linear finite element analyses and tension tests of the beam-to-column connections are conducted.

View full abstract

The purpose of this study is to clarify the buckling behavior of rectangular corrugated plate under shear force based on the results of F.E.M. Global buckling is well known as one of the buckling modes occurring on corrugated plate, and it was researched by handling corrugated plate as anisotropic plate. In this study, accuracy of buckling formulas suggested in these researches is confirmed with the analytical results in order to find appropriate formula for evaluating global buckling strength. And local buckling strength is examined through considering effects of section shape of corrugated plate.
Furthermore, another buckling mode is observed on numerical analysis and qualitative examination is carried out for this mode.

View full abstract