In this paper corrosion rate of steel reinforcements after carbonation of concrete was studied using AC impedance technique and weight loss measurements taking the effects of cement type, water to binder ratio, cover thickness,relative humidity and the like into account. Based on the study a corrosion rate eguation that includes the above factors and the relative humidity of 40 to 95% as variables was proposed by modifying Stern-Geary eguation. Ways of applying the eguation to the inside and outside environments of buildings were discussed, which resulted in a proposal of estimated corrsion rates after carbonation.

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The objective of this study is to improve the freezing and thawing resistance of NonAE concrete. It is believed that freezing of macroscopic water in meso capillary pore of hydrated cement causes the frost damage due to freezing and thawing. In this study, it was confirmed that applying a hydrophobic compound into the concrete to block the continuity of meso capillary pore decreases the freezing water by suppressing ice crystal penetration. Further, the effective particle size of the hydrophobic compound was 10-110 μm. Thus, freezing of water in capillary pores in the range of 10 to 110 μm is the main cause for the deterioration due to freezing and thawing. It is anticipated that this technology, without entrained air, can be applied to produce concrete for better performance in freezing and thawing environment.

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The following are emphasized for the purpose of evaluating the reduction ratio by soil-structure interaction for design : 1) Proposing design formula of the effect of inertia and kinematic interaction based acceleration response with the idea of soil amplification function. 2) Expressing an extension of natural period and increasing of damping of a soil-structure system with variables of impedance and calculating an explicit relation between a changing of vibration characteristics and influential factors of soil-structure interaction. 3) Visualizing the effect by finding energy balance-based prediction equation of ratio of acceleration response. The proposed design formula can be useful in evaluating the effect on the seismic design load due to soil-structure interaction.

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In this paper, through the real-time-hybrid experiment with the use of "MR rotary inertia damper" the authors have been developed, the seismic response properties are discussed by changes in the parameters on building structure. The setup parameters in this paper are three of the followings; natural period of building structure, inertia mass ratio to building structure mass and variety of input earthquake motion. From the knowledge obtained by the experiment, the authors propose the semi-active control method focused on input velocity of earthquake. Then, in comparison between passive control and semi-active control, it have been confirmed the effects of the displacement reduction in the all case of experiments performed in this paper. Especially, in the case of JMAKobe earthquake, by the proposed semi-active control, it have been confirmed both floor response acceleration and displacement were reduced.

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Seismic responses of a high-rise base-isolated building in Tokyo Institute of Technology were recorded during the 2011 Tohoku-oki earthquake. The purpose of this paper is to point out various important findings on the building responses from the recorded data, as well as to create the data base for fostering immature research areas on high-rise base-isolated buildings and monitoring. This paper explains a variety of numerical techniques such as transfer function curve-fitting procedure for system identification, comparison with conventional structure by modal analysis, damper hysteresis, axial force variation of rubber bearing, and dynamic characteristic variation due to input amplitude. Reliability of recorded results is confirmed by various methods, and applicabilities of the techniques for the high-rise isolated building are discussed.

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Evaluation of bi-directional characteristics of base-isolation devices is a very important issue for base-isolated structures. The present paper focused on structural behavior and deformation capacity of U-shaped steel dampers under random bi-directional dynamic loadings. The major findings obtained from the test are summarized as follows: (1) the index J_c proposed in the previous paper can evaluate the limitation of cumulative torsion until contact with connections under random bi-directional loadings; (2) damage evaluation with two indices D₂ and J_c leads to a conservative result under the random bi-directional loadings; (3) in addition to this, cumulative deformation due to the different orbits brings more conservative evaluation.

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To enhance the safety of seismic-isolated houses, the authors have investigated the cause of large deformations of the seismic-isolation layer of houses during the 2011 Tohoku earthquake. Our findings show that unlike resonant responses in the Ashigara valley, pulse responses were seen in many seismic-isolated houses in Miyagi prefecture. The authors have verified that the maximum deformations of the seismic-isolation layer have a very high co-relational relationship with the peak ground velocity of pulse ground motion and amplification characteristics of the surface ground rather than the deep layers of the ground.

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Modeling and numerical simulation techniques for performing a detailed finite element analysis of a composite beam are presented. The finite element analysis is performed using E-Simulator, which is under development at the Hyogo Earthquake Engineering Research Center (E-Defense) of the National Research Institute for Earth Science and Disaster Prevention (NIED). Apiecewise linear isotropic-kinematic hardening law is used for the steel material, and heuristic and implicit rules are incorporated to simulate its complex cyclic elastoplastic behavior. The extended Drucker-Prager model is used for the concrete material. The steel beam, steel column and reinforced concrete slab are discretized into solid elements. The wire mesh consisting of steel bars in the slab is also modeled using solid elements and rigid beams are used for the stud bolts. Detailed analyses are carried out for both a steel beam and a composite beam subjected to static cyclic loading. Good agreement is found with experimental results such as strength degradation due to local buckling of the flange, and asymmetric behaviors resulting from contact between the slab and the column.

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When high-rise buildings are subjected to intense earthquake ground motions, deformation concentrates into a restricted lower part of a building frame in the process of collapse even though it is designed in accordance with the strong-column-weak-beam concept. This paper examines the mechanisms behind the deformation concentration based on the modal decomposition of displacement increment using the tangent stiffness matrix. An improved criterion is proposed for predicting the deformation concentration region based on the presented mechanism. Furthermore, this paper studies the influence of large rotation and column yielding on dynamic collapse, which were neglected in the above examination.

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System identification was performed for five-story frame models to estimate lateral stiffness of every story at once in engineering field of inverse problem. In this study filtering algorithm based on variable parametric projection filter (VPPF) was used for the structural system identification adopted natural frequencies as observations. Identification results based on VPPF were compared with the results of Kalman filtering algorithm, the effectiveness of algorithm are made clear through the results on inverse analysis of various case from points of view on institution procedures of initial values and regularization parameter.

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Lateral pressure and lateral subgrade reaction for designing earth retaining in Kanto loam ground were examined using field measurement, full scale horizontal load test, and analysis. 1. At earth retaining using soldier piles and lagging method, by enlarging intensity of cement bentonite enough to ground, cement bentonite carries out an action united with a soldier pile, and contributes to the increase in horizontal resistance. 2. Coefficient of lateral earth pressure counted backward from the actual measurement of displacement of earth retaining walls of 8 sites (16 points) in Kanto loam ground was distributed from 0.011 to 0.129.

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Although large numbers of attempts have been made to evaluate buckling strength of single layer lattice domes under equally-distributed vertical loads, stability under seismic loads has not been studied enough yet. In this paper, evaluation method on buckling strength of single layer lattice domes based on continuum shell analogy under equivalent static seismic loads proposed in the previous studies is investigated. First, the buckling behavior under distributed loads proportional to the static seismic loads is researched taking shape parameters into account. Next, the buckling strength for vertical loads and the buckling strength for static seismic loads is evaluated using continuum shell analogy, and converted to elasto-plastic buckling strength using knockdown factors and Dunkerley formulation. The effectiveness of the proposed evaluation is discussed against the results of time-history response analyses.

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This study deals with structural performance of slender reinforced concrete columns using concrete with compressive strength of 300N/mm². From structural experiments and geometric nonlinear analyses, it is found that the columns of which the ratio of length to depth is 15 to 30 have the horizontal displacement capacity of 1/50 rad. or more in drift angle under the axial load ratio of 0.33, although these columns don't resist horizontal force. From these analyses, it is also found that the buckling occurred under antisymmetrical moment in case which the ratio of the length to the depth is 40 or more.

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It is very important to establish a visible damage index for quick damage estimation of steel structures. In the reconnaissance of the 2011 Tohoku earthquake, many cracks on the concrete foundation around the exposed steel column base were observed. Cyclic loading tests focusing on a crack pattern and its width on concrete foundation were conducted to investigate the relationship between structural performances and the damage indices. The major findings obtained from the test are summarized as follows: (1) the maximum story drift angle, column-base rotation, and elongation of the anchor bolts can be estimated by crack width between concrete foundation and cover mortar; (2) lateral deformation due to the concrete edge failure can be estimated by the width of diagonal cracks growing from anchor bolts in the compressive side to the foundation beam.

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This paper discusses, on the basis of experimental results, structural fire behaviour of a rigid steel frame with fully-moment-resisting beam-to-beam connections with splice plates and high strength bolts, and beam-to-column connections with full penetration welds. The test results indicated that the moment-resisting connections in the rigid steel frame have sufficient load-carrying capacity, but failure may occur in the connected beam due to inadequate shear resistance of the beam web in fire. The critical temperature of the steel beam could be approximated on the basis of its inherent resistance at elevated temperature and initial effects, because the thermal stress disappeared at the fire limit stage. In this study, the safety factor of structural fire safety design was also discussed on the basis of the result of these load-bearing fire tests.

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