The critical amount of corrosion for initiating cracking along reinforcements was studied by wet and dry exposure tests and by RBSM analysis. The experiments showed that the critical amount of corrosion was in the range of 10 to 100 mg/cm² and was influenced by water-binder ratio of concrete, cover thickness and bar diameter. The results of the RBSM analysis showed similar tendencies with the experimental ones, when tension softening of concrete and crack development were taken into account. A modifying coefficient, however, was necessary for the critical values obtained by the two methods to coincide. Based on the results, some equations to express the critical amount of corrosion were proposed, taking water-binder ratio, cover thickness and bar diameter into account.

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Some floors developed recently from a viewpoint of reducing noise of impact, make people feel wrong by particular foot touching. These floors were good by previous evaluation method but were considered to be inferior. First, dynamic deformation properties were measured by discrimination equipment developed to observe early stage of weight. As a result, reason of inferiority was inclination of floors nearby point of touching heel, difference of deformation between point of touching heel and surrounding it, and restoring deformation. Finally, we present discrimination method of floors been inferior by compounding those factors.

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The digital terrestrial television which uses the electromagnetic wave of the UHF band was shifted completely in July, 2011. In this paper, the electric field strength level is measured in the reception condition that is different of the distance and the building environment in the urban space. As a result of the measurement, the following have been understood. 1. The building of the 11th floor to the 14th floor shows the amount of radio attenuation more than 10dB. 2. In an open space, whenever the distance from a digital tower is 3 km away, the electric field strength level decreases about 10dB. When the distance from a digital tower exceeds 18 km, the value of the electric field strength level does not change according to circumference environment. 3. The actual electric field strength level of urban space is decreased to 70 percent or less as compared with the electric field strength level in free space. At the ground and the point which is subject to the influence of a building, it decreases even to about 20 percent.

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We estimated the distribution of site response for ground motions in a period range of 2 to 4 s in the Kanto basin for earthquake resistant design of skyscrapers or base-isolated buildings with the resonant period. We used the spectral inversion method to separate source, path, and site effects by using the data from very dense seismic observation networks in the Kanto basin. The resultant site response was in good agreement with spectral ratio of records observed at ground surface and seismic basement. This indicates the estimation was successful. The resultant site response was large around Ichikawa city due to thick soft surface layers. In the east of Kanagawa prefecture, the site response showed variability from a factor of 3 to 5. The difference was not only due to the effect of 1-D velocity structure beneath the sites but also that of 3-D velocity structure.

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In order to predict seismic damage of a building, we must identify its major physical parameters, that is, shear and bending stiffness and mass. However, it is difficult to directly estimate these physical parameters. In this study, we try to identify the physical parameters of a full-scale five-storied structure based on the observed microtremor records. First, we estimate resonant frequencies by using Fourier spectral ratios of each floor response with respect to the ground. We then observe the changes of these resonant frequencies due to loading of an added weight with known amount. Finally, using an equivalent lumped mass flexural-shear model, we identify its physical parameters through the Hybrid Heuristic Search method.

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In this paper, a nonlinear mechanical model for laminated rubber bearings based on Haringx's theory is proposed. In the model, rubber sheets and steel plates constituting a laminated rubber bearing are modeled as rubber elements and steel elements separately, and the model of laminated rubber bearings is constructed interlaminating the two elements. The lateral force-deformation relationship of the rubber element is represented by the stiffness matrix derived from Haringx's theory. The model can express the nonlinear behavior of laminated rubber bearings in the large deformation range by applying nonlinear characteristics to the bending stiffness and shear stiffness of the rubber element, and address the effect of end rotations on the mechanical characteristics of laminated rubber bearings. To verify the accuracy of the model and the validity of the nonlinear characteristics introduced to the bending stiffness, simulation analysis of loading tests using scale models of laminated rubber bearings are carried out. From results of the analysis, it is confirmed that the model can predict the large deformation behavior of laminated rubber bearings.

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As the structural health monitoring tools, three subspace-based system identification methods, the ordinary MOESP, the N4SID and the PO-MOESP, were investigated to discuss the identification accuracy of natural frequency and damping factor of buildings. Fundamental case studies using SDOF response data revealed that the identification accuracy of the N4SID was lower than those of the ordinary MOESP and the PO-MOESP. This was because the 2-norm of the matrix applied to the noise in the N4SID was larger than the other methods. Finally, the difference in identification accuracy between three methods was verified by using the strong motion records of an RC super high-rise residential building during the 2011 off the Pacific coast of Tohoku Earthquake.

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For estimating the bearing capacity of screw piles which are used for the small building foundations, we collected the loading test data and statistically examined the relations between the ultimate bearing capacity and the conversion N-value by the SWS tests. Correlation is comparatively high in the ultimate end bearing capacity with the average conversion N-value within above and below 1D_w (D_w : tip wing diameter) of pile tip. However, the ultimate end bearing capacity and the ultimate frictional resistance of screw pile were smaller than those of straight pile because of disturbance of the surrounding ground by the tip wing in the penetration.

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The purpose of this study is to clarify the seismic performance of piled raft foundations with ground improvement based on seismic observation records. The monitored building, which is a twelve-story base-isolated structure, is located on loose silty sand underlain by soft cohesive soil in Tokyo, Japan. On March 11, 2011, when the 2011 off the Pacific Coast of Tohoku Earthquake struck the building site, the seismic response of the soil-foundation-structure system was successfully recorded during the earthquake. This paper presents a simulation analysis of the seismic behavior of the building during the earthquake using a detailed three dimensional finite-element model. The simulation agrees well with the observed peak acceleration reduction of the superstructure created by the base-isolation system, with the bending moments on the piles increased due to large ground deformation.

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The present paper discusses the active vibration control of double-layer cylindrical lattice shells for the purpose of establishing the seismic response control method of lattice shells that have complicated vibration characteristics. First, the application method of active vibration control is discussed and the control effects are examined by means of time history response analyses. Moreover, the optimum arrangement of sensors is searched and the control effects are examined. As a result, this paper showed that the control method with the effective mass ratios of 90% is effective. And the optimum arrangement of sensors is searched by means of GA and the seismic response reduction is realized with the arrangement.

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This paper reports the results of evaluation on seismic performance for traditional wooden frame with oblique nuki of boat houses in Ine, Kyoto. Major findings from the research are as follows: (1) In the field survey, structural and vibration characteristics are clarified. (2) In the static loading test, it is found out that behavior and destruction property, shear force of the frame with oblique nuki is unique. (3) Simple analytical model is constructed and confirmed the precision. One house is took the case of, applying the restoring force calculated from the analysis, yield base shear coefficient is found.

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Timber frame with braces has been used widely for newly and existing wood buildings in Japan. This paper presents their seismic performance through shaking table tests and characteristics of cyclic loading and ductility to evaluate seismic design value. Timber frame with braces of 1/3 of column dimension having Co=0.56 seismic performance almost collapsed during NS component of 1995 JMA Kobe. The frame with braces of 1/2 of column dimension having Co=0.69 was survived against repetition of the JMA Kobe and aftershock of 2004 Niigata Chuetu earthquake, but the frame with Co=0.46 was damaged during the 1995 JMA Kobe. Although the seismic wall ratio including influence of ductility behavior was said to ignore extra coefficient of bracing shear wall, it was found that extra shear force is required from the results of equivalent damping and time history analysis.

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This paper compares and investigates the relationship between required strength and response ductility of the seismic design codes of International Building Code used in the U.S., and Calculation of Response and Limit Strength used in Japan. Based on dynamic theory, the paper also proposes the rational modification for International Building Code for two patterns of yield drift angle models which significantly affect on the dynamic response of the buildings. The modified International Building Code shows excellent correspondence to Calculation of Response and Limit Strength.

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When RC columns reach near-collapse and undergo axial shortening following shear failure, some of axial load sustained by the columns transfer to neighboring columns and axial load of the columns becomes lower than the initial one. This study was intended to examine the effect of the decreased axial load on the collapse behavior. Full-scale column specimens with shear failure mode were tested under decreased axial load or constant axial load until they collapse. The effect of varied rates of the axial load decrease on the column collapse drift is studied and the comparison of computed collapse drifts and observed ones are also discussed.

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In order to investigate accuracy of shear ultimate strength formulas, test results of 47 short span R/C specimens were chosen from previously published papers. Ohno & Arakawa's formula and two AIJ design guidelines were adopted for evaluating the test results. As results of comparison between the test results and the calculations, the followings were found: the formula in the AIJ design guideline based on ultimate strength concept had the best precision in these three formulas though had problems in verification of bond and estimation of shear reinforcing effect; Ohno & Arakawa's formula is practical for applying to the short span beams from the viewpoint of safety evaluation; and the formula in the AIJ design guideline based on inelastic displacement concept is inappropriate for the short span beams.

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This paper describes new evaluation formulas of ultimate strength and rotation angle for unbonded post-tensioned precast concrete beams. These formulas are composed by two main variables, one is a reinforcement index(q) and the other is an effective prestressing level(λ_pe). To evaluate coefficients of the evaluation formulas, we carried out a parametric study with a numerical section analysis model, and obtained regression formulas for the coefficients. By applying the evaluation formulas to the results of parametric study and experiments on the past, we elucidate that the formulas evaluate the ultimate strengths and rotation angles of them accurately.

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The authors have studied the buckling-restrained brace providing stable hysteretic characteristic even under high-strain conditions. Structural performance of the buckling-restrained brace is represented by the evaluation formula that is the lower limit of the cumulative plastic strain energy ratio. However, when the duration of earthquakes gets extraordinarily longer, it is necessary to research and develop a new buckling-restrained brace with more high capacity of energy dissipation. In this paper, our past studies are analyzed and the conditions of high-performance of buckling-restrained braces are extracted. The considered buckling-restrained brace is tested. As a result, the buckling-restrained brace having large cumulative plastic strain energy ratio has been proposed.

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The purpose of this paper is to propose a practical mean strength formula and a variation formula for H-shaped steel beams as functions of the slenderness ratio, initial deflection, and residual stress. The finite element method was employed for calculating elastic-plastic behavior under monotonic loading with consideration of the randomness of material properties such as yield strength, maximum strength, and strain at starting strain hardening. The statistics of the member strength were obtained by Monte Carlo simulation. The mean values of the yield strength of H-shaped steel beams can be formulated as Eq. (20), and the coefficient of variation of the yield strength is formulated as Eq. (30). The mean value of the maximum strength of H-shaped steel beams can be formulated as Eq.(26), and the coefficient of variation of the maximum strength is formulated as Eq. (31).

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A significant number of wall-type precast reinforced concrete (WPC) residential buildings exist in Japan that were constructed more than 30 years ago but maintain good structural quality and seismic strength. In order to utilize this building stock, structural renovation is needed such as opening shear walls and addition of elevators, and seismic performance of pre and post renovation is to be evaluated. In authors' previous research, static pushover analysis models were created for standard existing WPC residential buildings under seismic load in the transverse direction. In this research, the models were extended for load in the longitudinal direction. The maximum base shear coefficient, which is defined as the ratio of lateral force to the building weight, is 0.73, and the preliminary failure mechanism is beam yielding, in addition to a limited number of beam shear failures, shear cracking of walls, and bearing failure of the vertical joints. The maximum strength and the failure mechanism calculated using an existing simple seismic performance evaluation method reasonably agreed with that obtained by the models.

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For applying the wall-type viscoelastic damper to high-rise RC structure, it is conceivable to use the connection system encased by RC bases. An experimental study is carried out to obtain the design data of this connection system for performance evaluation. The stud shear force-displacement relation of this system is investigated and showed as the quad line relations broken at the elastic limit of concrete, allowable strength and the ultimate horizontal strength until the ultimate strength. Through this stiffness evaluation and the stiffness evaluation of the RC bases itself, performance evaluation of this system is possible.

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In this paper, we propose installing a buffer spring into a base-isolated system incorporated with a viscous mass damper as a method to reduce excessive acceleration induced by the secondary mass. We derived transfer functions of a two-degree-of freedom model on the basis of equivalent linearization method using complex stiffness model and the effectiveness of this system was examined by non-linear time history response analysis for real buildings. These results confirmed that the buffer spring as well as the damper force restriction is effective in reduction of accelerations and damper forces without deterioration in displacement reduction effect brought by the secondary mass.

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Young's modulus and bending strength of 3 species of wood commonly used for engineered wood and Zelkova, hardwood normally used for traditional large building, heated up to 250℃ are measured at the elevated temperature and after cooling to the room temperature as an engineering basis for the structural fire safety design and the reusability diagnosis of large-scale timber buildings. The results show the both properties, either at elevated temperature or after cooling, are highly dependent on exposed temperature for 150-200℃ or higher, and correlation between the Young's modulus and the bending strength tends to become weaker with rise of exposed temperature. The bending strength at elevated temperature is found to converge while it is notably scattered at normal temperature.

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