Relationship between surface area of hardened cement and cement hydration was evaluated. Hydration process was evaluated by powder X-ray diffraction/Rietveld analysis, on the other hand, surface area of hardened cement paste is determined by water vapor adsorption isotherm and BET theory. Based on the experimental data, the surface area of hardened cement paste has strong correlation with the amount of C-S-H in hardened cement. The surface area by vapor adsorption is very sensitive to the sample preparation and therefore, correlation between surface and amount of C-S-H is different when the pre-drying condition is differed.

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It is clarified by the previous studies that even without any hardener epoxy resin can harden in the presence of hydroxide ions from calcium hydroxide in the cement mortars and concretes at ambient temperature. The strength development through the long-term curing of hardener-free epoxy-modified mortars and concretes has hardly been examined till now. Hardener-free epoxy-modified mortars using an epoxy resin(diglycidyl ether of bisphenol A) without any hardener are prepared with various polymer-cement ratios, subjected to (1)initial combined wet/dry curing plus long-term dry curing and (2)initial steam curing plus long-term dry curing, and tested for hardening degree of epoxy resin and strength development. As a result, the application of the initial steam curing rather than the initial combined wet/dry curing causes a marked strength development with increasing polymer-cement ratio and additional dry curing period. The flexural and compressive strengths of the initially steam-cured plus 336-d dry-cured hardener-free epoxy-modified mortars with polymer-cement ratios of 10% or more are about 1.5 to 2.0 times higher than those of the initially steam-cured unmodified mortar. This is proved by a marked increase in the degree of hardening of the hardener-free epoxy resin in the epoxy-modified mortars with additional dry curing period.

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This study is to propose structural capacity index, I_s^CON, which is converted evaluation of seismic capacity of seismic retrofitted buildings with hysteretic dampers based on the energy balance method. At first it is proposed that the I_s^CON of SDOF is explicitly-expressed by amount of absorption energy of buildings. Then it is expanded to the expression of MDOF considering damages concentrated in a particular story. Using results of seismic response analysis, it is confirmed that the I_s^CON is able to properly evaluate the seismic capacity of buildings with hysteretic dampers.

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In the base isolation system, when the response is controlled, it is said that the semi-active control by the variable damper is effective, because it can decrease the response displacement without raising the absolute acceleration. Authors use Magneto-rheological fluid damper (MR damper) for the semi-active control, and conducted the real time hybrid test that considers the uncertainty of modeling of the MR damper. The results of the real time hybrid test are compared with those of shaking table test and analytical simulation. Thus, the effectiveness of the evaluation of the semi-active control in the base isolation system by the real time hybrid test is verified. In this study, the optimum control theory is used for control techniques.

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A base-isolated building may be damaged because of collisions with a retaining wall during a mega-earthquake. Recently, a few studies have shown the earthquake response analysis of collisions with a retaining wall using a restoring force characteristic of the retaining wall, which has not been validated experimentally. Therefore, experiments of collision to a real scale base-isolated building with a retaining wall were carried out. The acceleration data on the superstructure and restoring force characteristics of the retaining wall including the soil behind during collision with the retaining wall were obtained. Using sway springs modeling the retaining wall including the soil behind, the behavior of the superstructure during such collision can be well simulated. This finding is very important for the earthquake response analysis of a base-isolated building collided with a retaining wall.

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In this study, lateral two directional elasto-plastic earthquake response analyses with one-mass-system were conducted, which restoring force characteristics were elasto-perfectly plastic model and slipping model based on an analogy to the theory of plasticity. Peak displacement responses were examined with a view to its prediction by using equivalent linearization and elastic response spectrum. The model shown in this paper had the same initial natural period and yield strength in all the lateral direction. Therefore, anisotropic behaviors appeared in hysteresis loop in slipping model subjected to lateral two-directional cyclic loads. In this paper, two typical measured earthquake accelerations were adopted in calculations. As a result, a possibility was shown that the peak displacement responses in those two models were predicted within the same degree of precision by estimating substitute damping in each model.

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When we design the laminated rubber bearings for safety, it is important to investigate the characteristics of ultimate behaviors of them. In this paper, we establish the method of investigating the ultimate behaviors of the laminated rubber bearings based on FEM analysis. Under vertical tensile deformation, voids are generated in rubber and vertical stiffness of the laminated rubber bearings degrade abruptly. Even under vertical compression and large horizontal deformation, voids are generated partly in rubber due to bending deformation of the laminated rubber bearings. Firstly, we propose the hyperelastic constitutive law showing the behavior of stiffness degradation under uniform triaxial tensile deformation, and apply it to inner rubber. Next, we check the validity of the constitutive law by comparing the results of the tensile deformation analysis with those of the tensile deformation test. Finally, we discuss the results of FEM model we propose.

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Now, there are the needs of the utilization of timber structure to the non-housing buildings. It needs the several techniques without the conventional wooden structure techniques. The multi story wooden structures having long span need the technique of making large holes in the beams due to the pipe arrangement of the equipments. We, in this article, propose a manual strength calculation method of the timber with two circular holes taken into account the size effect, the hole size, the distance between the both holes, and the ratio of the bending moment and shear force as the parameters. Two failure modes was assumed, the shear failure of timber between the both holes, and the splitting fracture from the hole. From the experimental observation, the shear failure was occurred in the specimen having the short distance between the holes —less than 0.5 times of the hole diameter. And splitting fracture was occurred in the specimen having the long distance between the holes —over 0.5 times of the hole diameter. The calculation method was derived from the mechanical models based on fracture mechanics and basic beam theory. The validity of the proposed calculation method was confirmed by the experimental results whose parameters were the hole size, the size effect, and the distance between both the holes.

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Two different types of structural foundation have been used for traditional wooden framed houses. One of them is that the columns or the ground sills are perfectly fixed on the foundations, and the other is that the columns of the house are freely movable because of neither sill nor fixing. Many houses with the latter widely exist, of which foundation is called as “Ashigatame”. Vibration tests for two foundation types above mentioned were carried out a few years ago. We reproduce the test results by an analysis and show the technique for the two types by using a simple structural model. The results show the accuracy of reproduction and the technique. It is also shown how to decide the dynamic parameters and to introduce a restoring force model in analysis.

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Full-scale shaking table tests were carried out at E-Defense to evaluate the seismic performance of a traditional wooden residential structure. The specimen was a post-and-beam frame with a plan dimension of 5.45 × 10.91 m and height of 7.33m. The design seismic load resistance was provided entirely by mud plaster walls. The beam-to-column joints were achieved by an oak peg using no metal fasteners. Under BCJ-L2 shaking, the first story exhibited a story drift of 2.4%. At that stage, many of the mud-plaster walls had crumbled. The maximum recorded base shear coefficient was about 0.7.

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To investigate the failure mechanism and structural performance of mortise-tenon joints subjected to tensile force under a constant bending moment, pull-out tests of mortise-tenon joint specimens under bending moments were carried out. It is found from the tests that the pull-out strength of a joint, subjected to a damage limit bending moment, increased by comparison with a case of free bending moment. In the case of a safety limit bending moment, the tensile strength was reduced due to bending failure of the tenon. The failure mechanism was also discussed using FEM and macro models.

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Dynamic properties and seismic responses of timber structure are discussed, with focus on uni-axial stiffness eccentricity of structural walls and horizontal flexibility of floor diaphragm. The stiffness eccentricity factor R_e defined in Japanese building standard law assumes rigid diaphragm, which can result in considerable error in estimations for torsional properties/responses of timber structures. Simplified formulations for the dynamic properties considering the diaphragm flexibility are given, and are applied to discuss seismic responses of example structures. The stiffness of horizontal diaphragm appears to affect not only the torsional response but also the translational response of the structure.

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Strengths of plywood subjected to in-plane tension, bending, and interior pressure in a hole were experimentally investigated. The tested plywood is composed of nine plies of lauan veneer, and the plies are bonded together with melamine-urea-formaldehyde cocondensate adhesives. These tests, when the axis of tensile or bending specimen is inclined to the face grain, reveal the reason why plywood is so resistant against splitting failure is owing to the alternate perpendicular plies of veneer as well as the sufficient shear strength of adhesive bond. In such a case, the crack of veneer is interrupted by neighborhood veneer, and then the fracture path is associated with shear failure of the bond. In other words, either tensile or bending strength of such an inclined plywood member is substantially elevated by the shear strength of the bond. For the same reason, the holed plate under interior pressure does not split but experiences compressive yielding only if the edge distance is greater than double the diameter of the hole.

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Stress transferring mechanisms of exterior wide-beam to column joints using headed beam bars with transverse beams were examined by FEM analysis. The characteristics of the stress transferring mechanisms obtained from the FEM analysis are summarized as follows: (1) in a inner region where a beam is directly connected to columns, the shear force is transferred by concrete compressive struts formed by flexural compressions in the critical sections of the columns and the beam and the bearing forces of the headed bars, (2) in outer regions where the beam is connected to the transverse beams, the torsional moment acting on the transverse beam affects the formation of concrete compressive struts, and (3) the tensile forces in beam reinforcements arranged in the outer regions become smaller than those in the inner region.

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A Buckling Restrained Brace (BRB) with serially connected tubular members is one of the solutions for composing BRB over 10m length economically for the seismic design of truss structures or large-span structures. Their overall buckling condition is considered to be sensitive for imperfections or eccentricities comparing to ordinary BRBs; however, their effects are not confirmed by experiments yet. In this paper, the overall buckling conditions for BRBs with serially connected tubular members are discussed as the functions of imperfections or eccentricities. Their effects on the stability are confirmed by cyclic loading experiments until member fractures, and design criteria are proposed.

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Realistic three-dimensional shake table tests using E-Defense were conducted for full-scale 5-story building specimens with/without dampers to evaluate seismic performance, under ground motions of a variety of scales ranging from minor to catastrophic levels. The building was tested repeatedly, inserting and replacing each of 4 damper types, i.e., steel, viscous, oil, and viscoelastic dampers. This paper focuses on the tests conducted without dampers at the end of the whole test series, and discusses responses and properties of the steel frame portion of the specimen.

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In order to investigate and clarify the characteristics of the friction damper with variable resistances, a total of four dynamic loading tests were conducted. The primary factors that influence the hysterestic properties of the damper were analyzed. The experimental results have indicated that the damper can apply two levels of friction resistance stably. The mechanism for the variance in the stiffness observed while the friction resistance of the damper was shifting from the lower level to the higher one was also discussed. Based on the results of experiments and discussion, an analytical cyclical model which can simulate the test results exactly was proposed.

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There is a large number of existing wall-type precast reinforced concrete (WPC) residential buildings constructed before 1980 in Japan (the number of the residential units is approximately 470,000). These buildings are of high quality in term of the concrete and structural conditions; however, they are not fully in use due to their small and uniform unit plans not suiting modern living styles. Creating new openings in the existing WPC walls could widen possibilities for plan changes during renovations; however, a design methodology for new openings including structural reinforcement has not been developed. Referring to authors' previous experiments of half-scale WPC walls with new openings and reinforcement, numerical static pushover analysis models are created. The models include inelastic springs for the joints as well as line elements for the wall panels with inelastic shear springs. Because the mechanical properties of the horizontal joints, which connect panels of the upper and lower stories, highly influence the overall wall behavior, additional experiments for the joints are conducted. Using the experimentally obtained joint properties, behavior of the walls in the previous tests is well simulated.

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In this study, validity of calculation method of ultimate strength of beam-column joints for composite CES structural systems, is examined using past experimental results. And three dimensional non-linear FEM analysis conducted, the effect of axial force on shear capacity of CES beam-column joint was verified. It is shown that ultimate strength of CES beam-column joints could be evaluated by a method based on the AIJ design standard for SRC structures. And different axial force didn't significantly affect shear stress condition of joints panel subjected to discrepancy in the analysis, it is found that the effect of axial force on shear capacity of CES joint panel is small.

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