Pore structure (the range of 40 to 2000 nm diameter) of concrete changes during dying condition and exposure environment, which can play an important role in frost resistance. In this study, the influence of drying, wetting and drying/wetting condition on the pore structure were investigated, respectively. Moreover, the aging of damage degree, cracks, pore structure and frost resistance in exposure environment were evaluated. The test results proposed a prediction equation of 40 to 2000 nm diameter pore volume change based on drying temperature and duration, which was also validated by the results of pore structure in exposure environment test.

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 Large Eddy Simulation (LES) is expected to be adopted as an effective technique to evaluate wind load on buildings for wind-resistant design. For numerical prediction of wind pressures by LES, unstructured grid system is effective in terms of flexibility in generating computed models. In this paper, the fluctuating wind pressures on a high-rise building influenced by windward building are examined using unstructured LES. Especially, focusing on the critical phenomena regarding pressure intensification, the availability of LES is examined by comparison with experiments and the flow fields are studied to elucidate the mechanism of peak pressure occurrence.

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 Experiments using a reservoir discharge type flume with an orifice are conducted to investigate the relationship between dry bed surge properties and the surge force acting on infinite and finite width walls without overflow. The results show that the instantaneous pseudo surge slope computed from the inundation depth and velocity history correlate well with the surge coefficient for infinite width walls and that the reduction factor for the force acting on finite width walls is related to the inundation depth to wall width ratio. These characteristics are also confirmed through numerical simulations with a water trapezoid impacting a wall.

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 According to some studies of uplift building behavior from dynamic analysis and shaking table test of small scale building model, it has been shown that higher mode vibration occurs in the frame during uplift. Particularly if soil support spring stiffness becomes hard, higher mode vibration will also grow large. It was easy to image about relation between the stiffness of the ground spring and higher mode vibration, but there was no theoretical explanation of how this higher mode vibration is generated and amplified. The aim of this study is to find physical principle about mechanism of amplifying of higher mode vibration and relationship between ground spring stiffness.

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 The authors have developed a passive-switching oil damper for seismic isolated structures that can control the displacement response of isolation layer within design limit under extreme earthquake events while maintains the acceleration response of superstructure in acceptable level in major and moderate earthquake events. The fundamental performance characteristics of the damper are experimentally tested. Then, the earthquake responses of a seismically isolated building model with the damper installed are simulated. The simulated results show that, with the aid of the damper, the building model would reduce the acceleration responses both to major and moderate quakes, and the isolation layer would not exhibit such displacement responses to extremely large quakes as to exceed the clearance gap. In addition, the rotation resulting from unbalanced switching of the dampers installed in opposite ends of the building is assessed. The rotational responses are confirmed to be in small level.

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 In this paper, impulse response is calculated by 3D-FEM collision analysis at the time of a base-isolated structure colliding to retaining wall, and its simple modeling method of lateral resistance of retaining wall is proposed considering the backfill soil existence. Lateral resistance of retaining wall with backfill soil is modelled by applying dynamic iteration springs and dashpots. The lateral resistances of retaining wall with backfill soil by the proposed method are compared with 3D-FEM analysis results. There is a little difference in maximum displacement response. Moreover, collision analyses of the base-isolated structure are conducted using the proposed method and 3D-FEM, and responses by both methods are compared and discussed.

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 This paper presents a method of evaluating local damage in steel beam-column connections using dynamic strain responses measured under ambient vibrations. In the proposed method, inner-force distribution in steel beam-column connection was estimated using the natural modal components measured by PolyVinylidene DiFluoride (PVDF) strain sensors. For evaluating damage in steel beam-column connections, two kinds of damage-related features were proposed. One was the transition of the neutral axis for evaluating the loss of composite action between steel beams and concrete floor slab. The other was the reduction of the dynamic strain responses from the undamaged condition in terms of root mean square (RMS) for quantifying steel beam fractures. A unique testing method was developed to verify the damage-related features at component-level. In the test configuration, the specimen was damaged quasi-statically, and vibration tests were conducted as damage proceeds. Moreover, an analysis model of the specimen was built and updated using dynamic strain responses. This model-updating was particularly interested as it provided estimates on the residual seismic capacities of the specimens in terms of the quantities familiar to structural engineers (i.e., stiffness and strength).

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 We develop an empirical equation of seismic intensity by nonlinear site responses as functions of seismic intensity by linear site responses and the equivalent predominant frequency derived from the peak ground acceleration and the peak ground velocity. The strong motions by linear site responses are calculated using records affected by nonlinear site responses and empirical transfer functions which are defined by spectral ratios of ground motions at a surface to vertical motions at a borehole for weak motions with respect to those for strong motions using KiK-net records after removing records affected by rocking or uplifting vibrations.

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 A mechanical model for predicting the triaxial behavior of high-damping rubber bearings under bidirectional horizontal deformations and axial load is presented in this paper. This new model is developed by combining two existing models, both of which have been previously proposed by the authors. Tests of isolation bearings under bidirectional horizontal loading with different axial load levels were conducted. The experimental formulae for the bidirectional hysteresis model in the mechanical model were identified from the test results. The proposed model is shown to be capable of expressing the influence of the bidirectional deformations and axial load on the hysteresis loops.

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 We proposed a procedure for evaluating fault parameters taking into account of heterogeneous dynamic stress drops on the asperities, and calculated strong ground motions. We compiled the stress drop data on the asperities of earthquakes caused bystrike-slip faults and reverse faults. In order to establish fault models for strong motion predictions, we applied the log-normal distribution to the stress drop data, and examined a procedure for assigning heterogeneous dynamic stress drops to each asperity by using the obtained log-normal distributions. The strong ground motions predicted by using this proposed procedure had larger variations of the peak ground accelerations and velocities than those with uniform dynamic stress drops on the asperities, while the averages were almost same.

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 Torsional strain is calculated by horizontal bi-directional loading tests, which is known to analyze the images of the dots painted on the surface of high-damping rubber bearings, because it can't be measured directly. In elliptical orbit loading tests, residual torsional strain, which increases the torsional strain, is confirmed. Amethod for evaluating torsional strain based on torsional stress is proposed, which consider an influence of residual torsional strain. Seismic response analyses are performed to evaluate the dynamic behavior of an isolated building under horizontal bi-directional earthquake excitations.

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 This paper presents consistent new shape functions for a linearly tapered Timoshenko beam element. The formulated shape functions can be used in the energy method based finite element context. The shape functions formulated in this report are derived for a solid rectangular beam with a linear change in its width and/or height. With the consistent shape functions, highly accurate solutions for structural problems can be obtained by using the least element per member in the finite element calculation. Comparison studies with reference works with respect to the accuracy and computational efficiency for various linearly tapered Timoshenko beam structures are highlighted. Concise formulations of the shape functions in the series of matrix forms are provided in the appendix.

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 To investigate effects of the shaft and wing diameters of single wing pile on bearing capacity and pull-out resistance under alternately cyclic vertical loading, monotonic and cyclic vertical loading tests were conducted on a straight and wing piles having different shaft and wing diameters in sand under centrifugal acceleration of 30G. The results show that before the shaft friction reaches the ultimate value during cyclic vertical loading, the pile tip resistance and the shaft friction are the main components resisting the vertical load, so that the effects of the shaft diameter is dominant in the pushing direction and the effects of the shaft diameter and wing ratio (the ratio of wing diameter to shaft diameter) are dominant in the pulling direction. Thereafter, the pile tip resistance and the wing resistance are the main components resisting the vertical load, so that the effects of the shaft and wing diameters are dominant in the pushing direction and the effects of the wing ratio and the wing area are dominant in the pulling direction.

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 The main object in this study is a proposal for establishment of fracture toughness value at initiation of crack growth. We measured the exact crack growth by coloring for improving of precision. Futhermore, we examined to use the sound at crack initiation to determine the fracture toughness value. As a result, we could propose the measurement method of internal crack growth with coloring and defined the appropriate fracture toughness value. Additionally we understood that the sound at generation of crack is useful to determine the fracture toughness value simply.

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 Seismic performance of a corner beam-column joint in reinforced concrete frames was studied by testing two three-dimensional beam-column subassemblage specimens without slabs under tri-directional loading. A column-to-beam flexural strength ratio was varied from 1.4 to 2.3 by changing the magnitude of column axial load. Although sufficient redundancy to prevent shear failure was provided to a beam-column joint in the test, all joints failed in flexure after beam and column longitudinal bars yielded. The ultimate flexural capacity of a corner joint under tri-directional loading was enhanced by large column axial load, and can be estimated bythe method proposed by Shiohara.

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 This paper focuses on concrete buildings with earthquake-damaged exterior/partition flat walls. A residential building damaged by the 2011 earthquake off the Pacific coast of Tohoku was targeted for detailed investigations. Its partial one-bay frame model with a flat wall was designed, fabricated and tested to experimentally clarify the fundamental behavior. As a result, the flat wall significantly contributed to the seismic performance of overall frame until the wall failed in shear, then completely lost the effects. Such behavior was numerically evaluated by several analytical models. Consequently, the Isoparametric element model could simulate the experimental results well.

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 In this paper, pushover tests of half scale web-clamped type beam-to-column specimens in a T-configuration are conducted and compared to results from numerical simulations. Slip deformation in the bolted connection, which occurred in the tests, are not considered in the simulations. Through this comparison, the change of the internal force transfer in the attachments and shear plate due to the slip deformation in the bolted connection is investigated. Good agreement between the tests and simulations is obtained in the load - displacement relationship, load - joint rotation relationship, attachment axial strain distribution, and shear plate axial strain distribution. However, the simulations did not show good accuracy for the shear strain distribution in both attachments and shear plate, due to the effect of bolt slip.

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 This paper proposes a new type of brace, named Naturally Buckling Brace (NBB), for building structural systems which significantly improves the drawbacks of braced frame systems. NBB consists of high strength steel (HSS) and low yielding steel (LYS) channels with an intended initial eccentricity along the brace length. LYS contributes to early yielding, and HSS contributes to keeping stiffness and stable behavior after LYS yielding. These effects can be also obtained by intended initial eccentricity. Tests with various design variables were conducted and subjected to cyclic loadings to examine the seismic performance of the proposed NBB. The results confirm that the proposed braces can achieve early yielding, provide a large post-yield stiffness and high ductility, which stably dissipate energy from around 0.02% story drift and prevent local buckling as well as deformation concentration until a very large story drift (greater than 3%) being reached. In addition, FEM model was built using FEM program “ABAQUS”, which shows strains in NBB are more distributed compared to those in CBB counterpart specimen.

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 Local out-of-plane behavior of the cylindrical wall of non-diaphragm CHS column, which is brought about by the bending moment transferred through H-section beam connecting directly to the CHS, was experimentally investigated in the range from elastic to ultimate states. The basic mechanical model for the connection of non-diaphragm CHS to flange plate alone, which had been previously developed by the authors, was extended to the H-section paying attention to the additional effect of the web plate, from which formulae for calculating yield, plastic, and ultimate moment capacities as well as elastic rotational stiffness are derived. By comparing the calculated values with the data of experiment and numerical simulation, the predictabilities of these formulae were found satisfactory.

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 In Japan, how to design structures to resist severe earthquake attacks is still one of the challenges today for our civil engineers. Then we should be obliged to present technological methods and guidance for prevention. A polyurea resin coating techniques has been well known that it is of effective to strengthen RC structures against impact and explosive events. To break a fresh method for retrofitting masonry structures against severe earthquakes, this study is to find experimentally the collapse preventive effects by polyurea resin coating of masonry structures. In shaking table tests, masonry block and brick walls with or without coating are tested. From test results, it is found that collapse prevention by polyurea coating can be remarkably improved.

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 In the past experimental studies on reinforced fully-grouted masonry walls, some of the wall specimens failed in sliding failure mode. The main objective of present study is to investigate the sliding strength of grouted masonry wall. First, sliding strength and deformation characteristic obtained from the wall specimens are summarized. And then, a formula to predict the sliding strength, which consists of friction effect due to compressive force working on the bottom section of the wall and dowel effect due to reinforcing bars crossing the bottom section, is proposed. In addition, simplified methods to estimate the two effects are proposed.

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 This paper proposes a new practical model of a restoring force characteristic on the panel zone within steel beam-to-concrete filled circular steel tube column moment connections for predicting the elastoplastic behavior of the panel zones including strength reduction after ultimate strength. The proposed model for a skeleton curve is provided as a multi-linear model having a cracking strength point, a yield strength point, an ultimate strength point and strength reduction points for 95%, 90% or 80% of ultimate strength. The skeleton curve model up to the ultimate strength point is based on the previous shear force-deformation model proposed by the writer, while the deformations of these strength reduction points is provided as new regression formulations obtained from previous test results. The writer proposes a new hysteresis loop model including stiffness reduction. The proposed models agree approximately with experimental results up to large deformations.

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