In this study, the author considered the bleeding of fresh concrete as a self-weight consolidation process, which is resulted from that the particle fabric has no enough tightness to support the fresh concrete's weight or and a vertical pressure acting on its upper surface. By analyzing the ability of particle fabric and hydrate of cement to support the normal stress acting on the maximum shear plane, a time-dependent pore water pressure formula was obtained. Then based on the Kozeny-Carman's permeability model, a permeability formula was proposed for fresh concrete, in which effective void ratio caused by free mixing water is used. Moreover, using Darcy's law, formulas of bleeding capacity and bleeding rate were induced for fresh concrete, and a time-dependent bleeding model was further proposed. Also, the author verified the bleeding model by comparing the test results and the calculating values of 8 series of fresh concrete having different specimen's heights, mix proportions, and vertical pressures.

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Effect of cement and silica fume reaction on strength development for 200N/mm²-class high-strength concrete was studied based on each reaction rate. As a result, it was found that raising curing temperature enhanced silica fume reactivity and it significantly contributed to the improvement of strength development. Additionally it was found that it was important to enhance cement reactivity by maintaining higher temperature in order to acquire higher strength. It was experimentally shown that compressive strength could be expressed in the strength formula based on gel space ratio theory in this strength level. Additionally, according to the evaluation based on gel space ratio theory, silica fume had higher effect on strength per consumption compared to cement.

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In estimating the unbalanced snow loads on roofs of buildings in structural design, it is important to consider the influence of wind action on drift of snow accumulation. In our previous papers, based on wind tunnel tests about various shapes of roofs, we have discussed the possibility of estimating snow accumulation patterns by using the characteristics of the gradient of wind pressure distribution from windward to leeward on roof. That is, in the area of negative pressure on roof, snow depth distribution tends to increase to leeward when pressure distribution decrease to leeward, and conversely, the former decreases when the latter increases. On the other hand, in the area of positive pressure on roof, such relationships are reversed. In order to predict snow accumulations for arbitrary inclination of span roofs, we propose a new method to estimate the unbalanced snow distribution coefficients by applying the relationships between the wind pressure coefficients and the unbalanced snow distribution coefficients.

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For next generation Fast Breeder Reactor (FBR), application of seismic isolation technology to the reactor building is planned to reduce seismic loading to both internal equipment and structures. To grasp seismic behavior of the base-isolated plant to extremely strong quake beyond design ground motion, large-scale shaking table tests are conducted using world largest shaking table “E-Defense” of the National Research Institute for Earth Science and Disaster Prevention. Two sets of one-third scale specimens are tested where the superstructure of 6000 kN weight is supported by six lead rubber bearings (LRBs) of diameter 505mm. Two or one LRBs are ruptured by the excitation of 4.0 to 4.8 times as large as the presumed design earthquake motion, when the shear strains of the LRBs reached over 550% or more. These ultimate shear strains and the stress-strain curves in the shake test are in good agreement with those of static loading tests using another LRBs made at same time. After these extremely strong excitations, the test specimens behave stably against the seismic inputs of design level even after some of the isolators are ruptured.

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The seismic isolation system building becomes general to improve the seismic safety in Japan, recently. However, the general seismic isolation system is chiefly effective only to the horizontal motion not for the vertical motion. In the future, it is necessary that we achieve developing the device against the vertical motion for securing the improvement of the seismic safety and the habitability. And so we have been developed the three-dimensional seismic isolation system for applying to a general building. It consists of laminated rubber bearings as horizontal isolation device and air springs as vertical isolation device. The rocking suppression device with oil dampers can control a rocking vibration. The building using the three-dimensional seismic isolation system was completed on March 3, 2011. In this paper, we report the observation record, system identification and simulation analysis of earthquake observation records. And by analyzing earthquake observation records, we confirm the seismic characteristics and efficacy of the three-dimensional seismic isolation system.

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A tuned mass damper (TMD) using a rotating inertial mass has been developed to reduce vertical vibration of beams and slabs subjected to walking excitations. The newly developed TMD is composed of a spring and a ball screw mechanism with a flywheel. The optimum design parameters of some TMD systems were examined, and their response properties were compared. The optimum design parameters minimize the resonant acceleration response of a main mass. In those systems, the mass of the member to connect with a damper was considered. And the effectiveness of the new TMD system was shown. Finally the new TMD system added a spring for adjustment of the tuning to were proposed, the optimum design parameters were shown.

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The aim of this study is that optimum solutions and seismic responses are compared between minimum weight and minimum cost steel frames. The minimum weight problem to minimize structural weight under constraints based on Japanese seismic code and the minimum cost problem to minimize sum of steel material cost and fabrication cost are formulated and solved by genetic algorithm. The adaptability to practical use is discussed for each frame. Moreover, time history analyses are performed and the difference of seismic responses between inner beams and outer beams are discussed for each frame.

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A simple approach for calculating the behavior of piled raft foundations subjected to a vertical load in homogeneous soils is investigated. The vertical stiffness (K_ana) and the pile head load ratio (Ψ_ana) of piled raft foundations were clarified based on parametric studies by the hybrid method, and these values were compared with the results using the AIJ formula. As a result, we presented the new simple method for quickly and easily calculating the vertical stiffness (K_cal) and the pile head load ratio (Ψ_cal) of piled raft foundations which have various parameters.

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Bearing stress relaxation of wood, which is often encountered in bolted connections, was experimentally investigated. A wood block was pressed by a small rigid punch under a constant displacement, during which the retained load was measured over five hours. Three series of matching specimens were cut from a single board of Japanese cedar such that the bearing load is applied into L, T, and R directions, respectively. Several levels of imposed load were examined both for virgin and densified specimens, respectively. Major findings are as follows. For virgin wood, the relaxation behavior is non-linear viscoelastic, and the relaxation rates of L, T, and R directions are of moderate difference, but of negligible difference under a large bearing displacement causing a plastic flow. For densified wood, the behavior becomes close to linear viscoelastic, and free from anisotropy.

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In this paper, to evaluate reparability and repairing limit state of seismically damaged RC buildings, prediction models for damage index, which represents reparability of buildings, for estimating repairing cost based on damage both in structural and nonstructural element were proposed. As a result of analytical study on prototype building models, it was shown that the influence of each element on reparability of buildings would depend on the structural characteristics of them. Moreover, an approximated evaluation method of damage index was proposed based on fundamental information such as dimension and damage class of structural members, and its accuracy was discussed.

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In this paper, two dimensional non-linear finite element (FE) analyses for RC shear walls with multi-openings were conducted to investigate the shear force contributions and internal stress transferring mechanisms. Parametric analyses were also conducted for the shear walls with several opening layouts. The analytical results showed that diagonally compressive struts transferring shear forces were formed in each wall element and the shape depended on the wall panel length, regardless of opening layouts and loading directions. On the basis of these analytical results, the simplified shear resistant model of the shear walls with multi-openings was constructed. It is clarified that the shear strength of RC shear walls with multi-openings can be evaluated by the proposed simplified model.

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Recently, semi-rigid pile head connections have come to be developed and studied widely. This paper proposes a simple analysis of the stress of semi-rigid pile head connections aiming to establish the design method of the semi-rigid piles by applying the seismic deformation method. As a result, the paper concludes that it is possible to obtain the appropriate design stress of piles by applying the inertial force from the superstructure, ground displacement, and considering the inertia of piles, simultaneously. The paper also concludes that it is possible to obtain the design stress of piles by measures of summing up each stress in case of which the inertia of piles and the equivalent stiffness of foundation are properly estimated.

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Mixed structures composed of reinforced concrete columns and steel beams can realize larger building spaces, whereas reinforced concrete columns are subjected to thermal stresses due to thermal elongation of long span steel beams in case of fire. It is very important to clarify the load carrying capacity of the complicated beam-column connections in fire. This paper presents the results of the sub-frame fire tests of a mixed structure composed of up-and-down RC column, steel beam and the connection. The test results indicate the non-fire-protected connection covered with thin steel plate has load carrying capacity during 3 hours of standard fire temperature curve. In this paper, fire performance of the beam-column connections is discussed.

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The authors are congratulated on presenting an excellent paper. I have four questions.
1. Is Eq. 22 in accordance with the experimental results?
2. Does the bond of longitudinal bars in the joint affect Eqs. 22 through 26?
3. Equation 1 indicates that the compressive forces at the center of the joint are not parallel to the assumed crack. Is it reasonable?
4. Do the authors believe that any joint failure should be avoided in any ductile frame?

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The authors thank to Dr. Toshikatsu Ichinose for his discussion and the answers are as follows,
(1) Proposed Equation about balanced failure can distinguish failure modes of specimens as Fig. 11 shows.
(2) Bond characteristic has scarcely effect on moment capacity of joints.
(3) Direction of compressive force at the center of joints changes after yielding of longitudinal bar occured.

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