Hydration process of many kinds of cement paste is investigated by powder X-ray diffraction (XRD)/Rietveld analysis. The parameters of the present study are type of cement (Ordinary Portland cement, Low heat cement, and Eco-cement), water to cement ratio (0.50, 0.35), and curing temperature (283, 293, 313K). In this contribution, reaction of aluminate phase (3CaO•Al₂O₃) and ferrite phase (4CaO•Al₂O₃•Fe₂O₃) is focused and evaluated. Experimental results show that the reaction of both aluminate phase and ferrite phase is affected by the temperature and presence of calcite. When system includes calcite, monocarbonate aluminate is mainly produced, rather than ettringite. And in the case of high curing temperature, Al₂O₃ is reacted as amorphous. Regarding ferrite phase, the reaction degree at the age of 1 year decrease as curing temperature increases, this can be presumed due to dense amorphous phase around cement minerals. Based on these experimental facts, simple hydration model is presented to evaluate development of hydration degree of aluminate phase and ferrite phase.

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Ratio of mixed mortar, adhered mortar, and residual lumps of mortar in recycled coarse aggregate is used as an indicator, and the factor influencing the properties of recycled coarse aggregate concrete is examined. As the result, it is confirmed that compressive strength decreased and length change increased with increasing each ratio. Especially, residual lumps of mortar have a profound influence on them. In addition, amount of residual lumps of mortar in mixed mortar have a profound influence on the properties of recycled coarse aggregate concrete that used recycled coarse aggregate with different original concrete.

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Temperature dependency of the reaction of silica fume on strength development of 200N/mm²-class high-strength concrete was focused, and it was studied for the purpose of clarification of the curing temperature influence. The higher temperature of the curing resulted in higher compressive strength until the age of 91 days, and compressive strength has changed from 30 to 40N/mm² by the difference of the curing temperature from 20 to 80°C. The reaction ratio of silica fume makes a considerable contribution to the densification of the hardened cement composite and the improvement in strength development, were ordered standard water curing < simple adiabatic curing ≈ 40°C hot water curing < 80°C hot water curing.

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The purpose of this paper is to clarify effect of sampling depth for distribution of compressive strength and strength development of core specimens in full scale model of high-strength concrete column using various cements. As a result, the following conclusions are obtained: 1) Compressive strength ratio difference between uppermost and lowermost part of core specimens is reduced in proportion to core strength. 2) Coefficient of variation of core strength is reduced in proportion to core strength. 3) Apparent density ratio difference between uppermost and lowermost part of core specimens is reduced in proportion to core strength.

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Length-change isotherm and desorption isotherm of hardened cement pastes whose water to cement ratio is 0.55 and cements used are ordinary portland cement, moderate heat portland cement, and low heat portland cement were measured in 20°C and 40°C degrees Celsius. In addition, vapor adsorption isotherm for BET surface area, Young's modulus and Poisson's ratio for bulk modulus under compressive loading test, and density of hardened cement paste and water content were measured. As a result, the higher temperature showed smaller water content and smaller shrinkage under desorption process. This phenomenon can be explained by the hydrophobic properties of the surface of the hardened cement paste in the higher temperature condition or the temperature and relative humidity dependency of surface area of hardened cement paste. Both hypothesis are reasonable and consistent with existing reports.

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The purpose of this study is to present the evaluation method of contact resistance of building elements and members with palms and hands from the view point of motion support and posture control. First, sensory tests to make evaluation scales from the view point of motion support and posture control with palms and hands were carried out. Next, the contact resistance meter with palms and hands that could measure the contact resistance of samples were developed. Then, coefficients of contact resistance of the samples were searched with the contact resistance meter. Also, the relations were investigated between contact resistance and evaluation scales from the view point of motion support and posture control. As a result, the measurement method of contact resistance of building elements and members with palms and hands were presented.

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Even in the region with less snowfall, snow accretion to exterior wall surface and structural members of high rise building in Tokyo metropolitan region has frequently occurred. Concern about human damage produced by snow blocks falling including snow accretion has been pointed out. Therefore, it is important to build method of countermeasures against snow accretion for buildings. To accumulate technical data for countermeasures against snow accretion, the authors studied basic characteristics of snow accretion on structural members both observationally and experimentally.
First, field observation for snow accretion on structural members was performed in Sapporo of Hokkaido. When the snow accretion occurred during the observation, daily mean wind speed was more than 3.0 m/s. The snow accretion occurred around the stagnation of wind, which was formed in the vicinity of structural members. Next, wind tunnel test, for usual shape members such as steel pipes and flat plates, was performed. The snow accretion amount on the steel pipe increased with the diameter and it depended on the surface roughness in case of the steel pipe 216mm in diameter. The snow accretion amount on the steel plates decreased with attack angle. Through the observation and the wind tunnel test on snow accretion characteristics, technical data of countermeasures against snow accretion for buildings was obtained.

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Shaking table tests are carried out to validate the analytical solutions for the sloshing in a floating-roof type cylindrical liquid storage tank under seismic excitation. The experimental tank is made of acrylic tube of 780mm in diameter. Free oscillation as well as seismic excitation tests are performed using three types of floating roof model, i.e., a uniform isotropic plate, a single-deck type floating roof composed of an inner deck and an outer pontoon, and a floating roof composed of a pontoon ring only. The optical motion capture system using CCD cameras is employed to measure the roof displacements distributing over the whole roof surface. The test results are compared with the analytical solutions based on linear potential theory. Overall agreement is confirmed between theory and experiment, while nonlinear oscillation modes due to the effect of finite-amplitude liquid motion as well as large deflection of single deck are observed to occur.

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Earthquake-resistant design method based on energy balance consists of three essential factors to be estimated -- whole amount of energy input, concentration of energy within a building and energy absorption capacity of structural elements. The first factor is very stable and the last has been well estimated. The second factor about concentration of energy is still needed to be cleared the more precisely. Concentration of energy is caused by the strength distribution within stories in a building mainly. The degree of concentration is governed by the difference between the optimum strength distribution and the actual strength distribution. However, the optimum strength distribution is not stable and can change for each seismic ground motion. In this paper, the influence of inevitable scatter in the optimum strength distribution on damage concentration is discussed.

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This paper investigates factors causing difference of site amplification in the Kashiwazaki-Kariwa Nuclear Power Station in the 2007 Niigataken Chuetsu-oki earthquake. To consider 3D response by asperities outside the section of 2D folded structure, FEM analysis is performed with vertical and horizontal incident angles. At Unit 1 above syncline, amplification of 2D model is larger than that of 1D model directly under the point when incidence is closer to vertical as the third asperity. This is due to folds of both first and second boundaries. At Unit 5 above anticline, amplification of 2D model corresponds to that of 1D model.

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This paper investigates critical earthquake inputs for multi-degree-of-freedom (MDOF) inelastic structures considering the evolution of seismic waves in time and frequency. The ground acceleration is represented as a combination of seismic waves with different characteristics. Each seismic wave represents the energy of the ground motion in certain frequency band and time interval. The amplitudes and phase angles of these waves are determined to produce the highest deformation or damage in the structure subject to (i) explicit constraints on the energy and the peak ground acceleration and (ii) implicit partial constraints on the frequency content and the arrival time of the seismic waves. The material nonlinearity is modeled using a bilinear inelastic law and the member fracture is also included. The study explores also the influence of the properties of the seismic waves on the energy demand of the structure. Numerical illustrations on modeling critical earthquake excitations for several structures are provided.

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A Beam String Structure (BSS) is a hybrid structure consisting of a beam that has bending rigidity, a string and struts. The aim of this research is to investigate the in-plane buckling behavior of arched beams of BSS and to propose a rational evaluation method. Experimental and numerical analyses are performed using small-scale models in order to investigate the influence of rigidity ratios, boundary conditions and details regarding the ends of a beam on the buckling behavior of BSS. It is shown that the present numerical treatment is effective to evaluate and predict the buckling behavior of BSS.

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In this research, the authors carried out the in-plane shear tests for five types of the inserted wooden siding wall different in wall length, board width and board direction each other, and the effects of the differences in load deformation characteristics, deformation and destructive behaviors of the wall elements were revealed. In addition, this study proposed the calculation method for rigidity and ultimate strength of the inserted wooden siding walls depending on the mechanical model created by taking the differences into account. Comparing the estimation values with the test values of rigidity and ultimate strength in both of the whole wall and the elements, the validity of the calculation method were verified.

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In this paper, we introduce an alternative index into the seismic retrofit to simply evaluate the seismic retrofit performance of existing wooden-framed houses. This index corresponds to the amount of the strengthening which is equivalent to reducing the weight, adding the viscous damping or adding the stiffness after the yielding. First, we present the formulations of the index and their parameter for three earthquake response spectra prescribed in the Building Standard Law. Next, a technique is discussed on the application of the formulations. Furthermore, we propose a seismic retrofit element with restoring force characteristics of hardening type to realize the retrofit by adding the stiffness after the yielding. The results obtained are summarized as follows: When the horizontal load-carrying capacity and the fundamental response are known, the seismic retrofit performance by any retrofit or the combination among the ones can be easily evaluated by using the index. The hardening type element is effective for seismic retrofit.

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This paper presents hysteretic model for deterministic nonlinear time-history analysis of Japanese conventional wood houses under various earthquake ground motions including motions after main shock. The model based on Evolutionary Parameter Hysteretic Model was proposed in the part 2 and in this paper the model was slightly modified to trace the maximum response of shaking table tests for two story houses. The modifications are 1) small displacement within 1/120rad. is ignored in deterioration of cyclic loading 2) damage in the minus displacement where reach in the arbitrary point is considered in the plus side. The arbitrary points are decided in accordance with the displacement at the maximum load of shear wall. For example, the displacement of plywood is 1/30rad and that of racing is 1/45rad. Normalized backbone curve is also proposed obtained from load-displacement relationships of ten shaking table tests. The maximum responses calculated from the time history analysis accord with the test result under sever earthquakes including the motion after main shock.

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A new method for retrofitting RC columns having walls is proposed. The method is as follows: paste thin aramid fiber sheets on the column and bind the column with narrow aramid fiber sheets at large intervals. And, experiments on the shear strength, the deformation capacity, the bond performance and the applicability to short column were conducted. As a result, (1) the shear strength, the deformation capacity and the bond behavior could improve using the proposed method; (2) the mechanism of shear failure was different depending on the axial load.

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There have been few studies on the out-of-plane shear in RC mat-slab foundations, and the reasonable method has been demanded to estimate ultimate shear strength of RC mat-slab foundations in the nuclear facilities. In the previous study, the out-of-plane loading tests on the 20 square slab specimens had been performed to collect the fundamental data. In this study, the test results were successfully predicted by 3D non-linear Finite Element Analysis. It has been confirmed that the ultimate shear stress in the slab specimen can be estimated by the Arakawa's formula, which is commonly used to estimate the shear strength of RC beams.

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Seismic retrofitting with steel brace is widely-spread for the seismic retrofitting of existing RC buildings. However, there has been no study that tried to apply this seismic retrofit method to existing RC buildings with very low-strength concrete. In this research, we confirmed the effect of seismic retrofitting steel brace which used post-installed anchor together with epoxy resin for RC structures with low-strength concrete through the structural tests of two series. As the beginning, we confirmed the shear strength of the indirect connection in which existing RC frame is tied to frame of steel brace. Next, we confirmed the mechanical behavior of RC frame retrofitted with steel brace subjected to axial and horizontal loads. From the structural tests, it was shown that ultimate strength of the indirect connection and RC frame retrofitted with steel brace can be estimated by the current evaluation method. In addition, it made clear that ductility index F of RC frame retrofitted with steel brace can be 2.0.

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The aim of this study is to investigate the seismic behavior of improved unbonded post-tensioned precast concrete beam-column connections with and without shear bracket. Three specimens of precast unbonded post-tensioned exterior beam-column connection were designed and tested. The test results of the specimen without shear bracket showed excessive beam slip and large residual deformation. The specimens with shear bracket expressed very satisfied performance with small residual deformation, almost no slip, fully developed strength, minor damage to the beam and column elements, and easy to disassemble. It is concluded that satisfied seismic performance can be expected from well-designed connection with shear bracket.

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Researchers, including the authors of this paper, are striving to develop main members of built-up structures using 780N/mm² high-strength steel for a new built-up structural system that prevents buildings from collapsing or being damaged by a severe earthquake (JMA seismic intensity 6.5) and enables rapid functional recovery.
The authors propose a weld-free built-up structural member that has a cross section of two channel steel members made of high-strength steel stitched together with bolts. This member has high strength, so that its cross section can be small and it becomes slender, thus creating the possibility of buckling problems.
In a previous study, an elastic lateral-torsional buckling test was carried out on such members, and a simple flexural strength formula was presented for practical design. The value calculated by this fromula is safe compared with the lateral-torsional buckling test results. However, it cannot represent the influence of bolt pitch and is not accurate enough for design.
The sectional shape of the member is changed in the longitudial direction, so a new torsion constatnt calculation equation is required. This paper presents a precise calculation equation for torsion and warping constants of this member and derives an elastic lateral buckling strength formula. The accuracy and efficiency of this formula are demonstrated by a comparative study using lateral-torsional buckling tests and axial buckling and twisting test results.

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In the previous research by the authors, the buckling restrained braces (BRBs) using round steel bar cores and double steel tubes were developed and some loading tests revealed that the BRBs have sufficient capability as hysteretic dampers. However the test specimens were relatively small and limited to the rigid connection type. The present paper firstly presents evaluation of the rotation characteristics of the outer tube end and loading tests using the element specimens. Then some full-scale tests are conducted using rather large test specimens in which the pin connection type BRBs are employed in addition to the rigid connection type ones. The test results reveal the behavior of the inner tubes, influence of the number of contraction allowance parts, energy dissipation capacity and behavior characteristics of the pin connection type BRBs. Finally, the design conditions of the outer tubes are discussed considering the evaluation results of the rotation characteristics of the outer tube end.

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The authors have developed a tensile force strengthening method using bonded carbon fiber reinforced plastic (CFRP) plate to enhance the life of existing buildings.
A rehabilitation technique for compressive force strengthening as well as tensile force strengthening is required to enhance the strength and deformation of steel structure members.
This paper reports the results of compressive loading tests on an angle steel brace before and after rehabilitation using bonded CFRP plates.
These results show enhanced compressive force carrying capacity and deformation capacity as follows.
1) Although buckling tests showed enhanced flexural rigidity, there was no increment of axial stiffness.
2) An elastic buckling formula using the experimental flexural rigidity from a three-point bending test, gave a conservative evaluation of load carrying capacity.
3) Taking into count the contribution of CFRP up to the elastic limit strain of the steel member, its load carrying capacity could be evaluated from the formula of Design Standard for Steel Structures of AIJ.
4) The CFRP must be bonded over the full length of the angle member.

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Details of gusset-plate connections in existing steel gymnasiums such as shapes of gusset plates and connection details were investigated to point out matters affecting ultimate strength of fillet welded gusset plate connection. Based on the results of investigation, a series of tensile loading tests of gusset plate connections were conducted. From test results, effects of details of gusset-plate connection on ultimate strength were discussed. Moreover, applicability of existing evaluation methods for ultimate strength of fillet welded gusset-plate connection was evaluated.

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Results of an experimental study on the structural performance of EWECS columns using glued-laminated timber of Japanese cedar are summarized. The specimens with different shear span ratios ranging from 1.0 to 2.0 were tested under constant axial load and lateral load reversals to figure out the influence of tree species composing woody shell and shear-span ratios. The results indicated that the superposition method is accurate means of estimating the ultimate strength of EWECS columns and there is little difference between tree species with respect to behavior of the wood shell.

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This paper discusses the structural performance of the hybrid steel beams jacketed with reinforced concrete at ends connected to reinforced concrete column. In order to figure out the shear transfer mechanism at the hybrid beam ends, the specimens of a half scale were tested under shear loadings, with changing parameters such as the amount of shear reinforcement at the hybrid beam ends, including the construction method using precast concrete or not, as well as the anchoring details of the steel edge end to the columns. According to the experiment results, the authors propose the shear capacity estimation for the hybrid steel beam ends embedded in RC-beam, and them confirm its validity.

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