Influences on properties of cover concrete were studied using some reinforced concrete specimens with different cover thicknesses, forms with different water absorptions, water-cement ratios and diameters of reinforcing bar. In the experiments, cement and water content, pore volume of the concrete placed in the specimens, and permeability of forms were measured. As a result of the experiments, the properties of cover concrete were much influenced by thickness of concrete cover and permeability of form. Consequently, it is necessary to consider the non-uniformity of concrete in the cross section when evaluating the durability of concrete structures.

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Thermal expansion coefficient is very important value to analyze the thermal deformation behavior of structural element made by high-strength concrete in early age. As autogenous shrinkage increases in high-strength concrete, the evaluation of autogenous shrinkage in the condition that receives high temperature is important. Therefore this study considered the calculation method of the thermal expansion coefficient by taking this deformation into consideration. In this study, the experiments on thermal deformation behavior using full scale column and small specimens were carried out. As the result, we obtained the result that thermal expansion coefficient changes with time. And we showed that the thermal coefficient could be evaluated by using the equation considered of change in the relative humidity inside concrete.

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The seismic isolation retrofit of the main building of the National Museum of Western Art required excavating The foundation ground under the existent building and installing isolation devices, it was necessary to construct Piles beneath the existing footings in order to support the weight of the building temporarily during excavation process. The piles were made of steel pile segments, and were driven by oil jacks utilizing the weight of the building for reaction force. During the retrofitting process, the subsidence of the building supported by the piles were monitored and controlled to avoid causing damage to the structure. The purpose of this study is to definite the vertical displacement of the existent building and the behavior of the temporary pressed-in pile constructed here.

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Sometimes, we make a stumble or a false step on inclined floor in going up and down, especialy for lack of taking notice the existence of inclined floors. In this study, auther considered the relationship an inclined floor's angle and the occurrences of a stumble or a false step in going up and down. Basic information for concideration were judgments of adults scaled with sensory tests by means of adults and several inclined floors. Finally, auther described that inclined floors were very danger from a view points of making a stumtle or.a false step and the dangerousness was depend on degree of angle.

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The purpose of this paper is to elucidate a structure of the energy input to a building that stationary random vibrates with elasto-plastic behavior under wind forces. An elasto-plastic design method on the basis of energy balance is already put to practical use to a seismic design backed by stability of the energy input by earthquake being confirmed. So, it is important to be elucidated the energy input structure induced wind force to apply an inelastic design method in wind-resistant design. First, a mathematically instruction is explained about relationship a power spectrum density of wind force and the energy input to an elastic system in a stationary random process. Next, inspection by time history analysis of a linear 1-mass system of the presented relation about the energy input is shown. Furthermore, the presented relation between a power spectrum density and the energy input is examined expansion to an elasto-plastic structure.

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Acceleration source spectra of the intermediate-depth earthquakes in and around Tohoku district are estimated. And then, stress parameter ACT is estimated from the constant level higher than corner frequency of the acceleration source spectra. It is concluded that (1) averageΔσof down dip extension and down dip compression type earthquakes are 26MPa and 22MPa respectively; (2) average Δσ of the intra-slab earthquakes in and around Tohoku district (M_0<1×10^<19>Nm) is 24MPa and nearly equal to 25MPa obtained from earthquakes in Hokkaido; (3) Δσ of the large intra-slab earthquakes is higher than that of small earthquakes; (4) Δσ of small intra-slab earthquakes (M_0<5×10^<17>Nm) shows focal depth dependency, but Δσ of large earthquakes (M_0>5×10^<17>Nm) is independent to their focal depth.

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This paper presents a system identification technique based on the absolute acceleration pulse response for linear systems. The method aims to fit the whole shapes of the absolute acceleration waves obtained by estimated parameters to observed records. Non-linear least squares method is applied to identify the parameters. With this method, modal parameters can be easily estimated by setting initial values of natural circular frequencies. In addition, the probabilistic errors of the identified parameters can be easily obtained. The applicability of the method is studied using both numerical simulation results and the seismic observation records of a high-rise building.

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It is illustrated that the earthquake ground motion can be properly evaluated by combining Fourier amplitude based on the ω-squaremodel and Fourier phase of the recorded one. The parameters of seismic moment and corner frequency identified by the proposed method are in harmony with the values presented in the previous papers. It is shown that the response spectrum of a wave synthesized by replacing Fourier phase with that of a different record, whose distribution shape of the phase difference is analogous to the original one, is comparable to the result of the original wave. This finding suggests that a simulated earthquake ground motion, which exhibits a realistic response spectrum, can be generated by the proper selection with respect to the phase difference characteristics.

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A new critical excitation method is developed for a damped linear elastic structure. In contrast to the previous studies, no special constraint is needed on nonstationarity of input motions. The input energy to the structure during an earthquake is introduced as a new measure of criticality. It is shown that the formulation of the earthquake input energy in the frequency domain is essential for solving the critical excitation problem and deriving a bound on the earthquake input energy. It is also clarified that the complex modal analysis is very efficient for computation of earthquake input energy to linear elastic structures with various damping coefficient distributions and that the real eigenmodes in addition to the complex eigenmodes play an important role in the energy computation.

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The distribution of the lateral earthquake response on the mid-story isolated system is strongly influenced by the position of isolated story and the damper. In some cases, the seismic response on the upper structure of isolated story is amplified greatly in comparison with the base isolation. In this study, by sweeping the modal response with free-free mode-shape vectors, it is clarified that the response amplification on the upper structure of isolated story is caused by modal coupling between modes of vibration on upper and lower structure. Based on the analytical study, the prediction method of the lateral earthquake response distribution on the mid-story isolated system is proposed.

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This paper presents practical design formulas for instability and vertical-load-dependency of mechanical properties of seismic isolation rubber bearings for buildings. The formulas, which are derived from Koh-Kelly model, predict buckling load, lateral stiffness, height drop, and equivalent viscous damping factor. To discuss the accuracy and the applicability of these formulas, they are compared with results obtained from loading tests of laminated rubber bearings. As a result, it is found that these formulas give fairy good correlation to the test results of the specimens with the shape factors generally adopted. In addition, it is found that the formula for buckling load including existing theoretical formula tend to overestimate the test results.

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The displacement of the isolated story of a base-isolated house built at a narrow land needs to be restricted using dampers or stoppers to meet the regulation of seismic grade for ordinary houses. This paper investigates the responses of a standard 2-story base-isolated steel frame house with restricted displacement considering various types of soil conditions. It is shown that the higher seismic grade can be achieved with some added dampers or large margin of displacement or by upgrading of the frame. Although the response could be larger than that of the ordinary houses, base-isolated houses have an advantage in terms of Life-cycle cost except for soft soil condition.

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Shaking table tests are carried out to examine the seismic response of structural systems with yielding base plates using a half scale steel frame with three stories and one bay. During a strong earthquake, these systems cause rocking vibration with the base plates yielding to reduce the seismic response. In the test, the seismic response of base plate yielding systems are compared with that of fixed base systems. Furthermore, simplified methods are proposed to predict their seismic responses, which are vertical stress at column bases, uplift displacements, base shears and roof displacements.

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Numerical method using spatial beam-column finite elements is presented here for analyzing large deflection behavior of an elasto-plastic rigid frame under a dynamic disturbance. This dynamic method is developed from the static analysis method which has already been verified enough. The method proposed here is used to simulate the shaking table test of a small steel frame. The numerical results for acceleration and strain response trace the experimental ones with good accuracy. This study demonstrates that the method is-able to predict large deflection behavior of a steel building frame subjected, to a strong earthquake.

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In the top-down construction method, an axial force is transmitted from steel column to cast-in-place concrete pile by bond, stud connector or bearing resistance at the embedded end of the steel. The scale model tests were carried out to investigate ultimate bearing strength. Main parameters were concrete strength and steel column section. As a test result, it were proved that bearing stress was related to concrete tensile strength and effective bearing area was different each steel section owing to scale effect. The bearing strength was estimated accurately by modifying bearing.stress and bearing area of the previous evaluation.

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Lateral loading tests on a model pile group are conducted to investigate the seismic performance of pile groups and the coefficient of subgrade reaction in liquefied soil using the large-scale laminar shear box. There are two types of loading tests; the pile head loading and the ground deformation loading. The liquefaction in shear box occurs by upward seepage flow. The followings are concluded. (1) The lateral pressure on the front pile is larger than that on middle and back piles of the pile group in the pile head loading. The difference of the lateral pressure on the each pile is small in liquefied soil. (2) The coefficient of subgrade reaction is decreasing with increasing the pore water pressure in soil deposit. The coefficient of subgrade reaction of the front pile is larger than that of the back pile. (3) The pile deformation obtained in the ground deformation loading is decreasing with increasing the pore water pressure in soil. It is an opposite trend observed in the pile head loading.

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The objective of the paper herein is to assess the fluctuation of axial load of columns within a moment-resisting medium-rise reinforced concrete building through nonlinear dynamic analyses employing a three-dimensional analytical building model. In this study, excitation of the ground motion is considered in the two different schemes: first expressed by a single component of motion, and second by two components of motion representing two horizontal components of strong ground motion. It is concluded that the fluctuation of axial load into the column under earthquake excitation is of significance in the seismic design on reinforced concrete buildings based on the ultimate strength concept. This fluctuation of axial load is verified critical in the corner columns. It is revealed that the loading scheme that one component of motion is applied to the building along its diagonal direction can generate a critical situation evaluated when applying two components of motion under realistic earthquake excitation.

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The bar arrangement method of the column whose hoops were simplified was developed on the grounds that the outer steel plate of RC columns was effective in increasing the bond splitting strength of the main bars which were arranged at the outer side in the direction of column width. The test of RC columns with steel jacketing was carried out in order to verify structural performance. As a result, the shear strength did not decrease even after the yield hinges were formed. Furthermore, there were not many cracks in the column with steel jacketing at the final loading. This performance of the column with steel jacketing did not depend on the type of bar arrangement on condition that the amount of lateral reinforcement was the same. In this paper, both the equations for ultimate strength and load-displacement relation that correspond to the destruction pattern for RC columns were showed.

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Torsional vibration is likely to occur in a symmetrical buildings consisting of independent shear walls and bare RC frames, when severe earthquake attacks and the walls and the frames yield, because the structure becomes eccentric in strength. In this paper, the authors investigate the degree of this phenomenon by two way dynamic analysis. In the analytical model, the walls are modeled to beam element in which shear deformation is taken account. Two directional elasto-plastic behavior of columns, that is, axial yielding in the wall direction and flexural yielding in another direction is considered based on the plastic theory. As the result, the torsional vibration occurs when the structure yields, however, its influence on the response is rather small. Lateral displacement of the end walls is 1.4 times larger than that at the center of gravity due to the torsional deformation in the analysis.

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A new seismic retrofitting method for existing R/C buildings by using a circular hollow section (CHS) bracing is proposed. In the proposed method, a reinforcing frame composed of an H-section peripheral frame and pin-ended CHS bracings is placed on the outer surface of an R/C frame and connected to the R/C with mechanical anchors and high strength mortar. Experimental studies were carried out to evaluate the reinforcing effect. A single tube brace and a tube-in-tube brace, which is restrained not to buckle by the outer tube, are applied as a reinforcing brace. For comparison, H-section braces are also applied to proposed and conventional method. All the specimens are 1/3-scale models for one story-one bay substructure frame of an R/C building. In the experiment, the horizontal shear loads were cyclically applied to specimens under a constant vertical load. Through the experimental results and analytical results, an effectiveness of the proposed method is discussed. The horizontal load carrying capacities of specimens are agreed with predicted values approximately for the reinforcement of R/C frames.

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In this study, the effect of lateral reinforcement and ductility of reinforced concrete columns subjected to shear failure after flexural yielding is examined. The major parameters for the specimen used in the study include the yield strength and quantity of lateral reinforcement, strength of concrete and axial force level. This paper describes the results of quantitative evaluation of relationship between the shear deformation and effect of lateral reinforcement after flexural yielding. It is also found that the ductility (plastic deformation capacity and energy absorption capacity) of the columns in the case of shear failure after flexural yielding can be evaluated by the shear strength safety margin.

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In this study, a new type column base, which has high deformation capacity and high repairability, is proposed. Plastic deformation capacity of this column base is brought by the plastic deformation capacity of the angle, which is a joint element. Thus, in this column base, the part which is allowed plastic deformation is limited to the angle, and other part including the anchor bolt is kept in elastic range. The angle can be exchanged easily, when it was damaged. The deformation capacity and the repairability of this column base are verified by axial loading test of angle element and cyclic loading test of column base.

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To demonstrate the seismic elasto-plastic interaction for small-scale structure which is steel rigid frame with steel wall, an analytical investigation is conducted by using the simple model combined the frame of beam-columns with the wall of multibrace. As a result, it is mainly found that the stress distribution of the frame is not monotonically and uniformly increased, that the strain distribution of the wall is not uniformly but consentratedly increased, and that thicker panel gives higher initial rigidity, superiority of strength, and so on.

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Three story and one span CFT frames were tested under the constant vertical and alternately repeated horizontal loads in order to study the seismic performance of multi story CFT frames. In this paper, the effects of steel shear walls and beam-to-column connection types (an external diaphragm connection type and a new connection type) on the elastic-plastic behavior of CFT frames are discussed. CFT frames showed large ductile behavior, whereas 1st story columns were subjected to alternately large compressive and tensile axial load. In a steel tube frame, local buckling occurred at column top and column base on the 1st story at a drift angle R=2/100 rad, and after which the strength decreased rapidly.

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The discusser wants the authors to answer the following questions. (1) The similar contents are dealt with .in the papers published in the same journal in 1972,1976 and 1977. The authors describe nothing about the previous papers. What do the authors evaluate the previous paper? (2) Flexural deformation component and shearing deformation component are investigated in this paper. In the and shearing deformation components. Are there physical meanings of the flexural and shearing deformation components? (3) The discusser absolutely disagrees with the authors' conclusion "Linear strain distribution was observed in the concrete of unbonded test beams.". Is there any clear proof of the conclusion?

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The author's answers to the discussion by Prof. Takiguchi are as follows. (1) What do the authors evaluate the previous paper? There have been no investigations in which the strain distributions of concrete were discussed on the basis of the measured values of the strain. (2) Are there physical meanings of flexural and shear deformation components? Up to the maximum load, the physical meanings of the deformation components exist. However, after the propagation of the diagonal shear crack, there exist no physical meanings in the deformation components. (3) "Linear strain distribution" does not exist in the test beams. In each section, the maximum value of compressive strain was observed at the compressive fiber. The values of the compressive strains decrease with the distance from the compressive fiber. The authors expressed this tendency as "linear strain distribution". However, in the tensile side this tendency did not observed. (4) Eq. (3) and the linear strain distribution are not established simultaneously. The authors agree with this advice. However, shear stresses in beams have been calculated by using the flexural stresses based on the linear strain distribution. The shear stresses thus derived have sufficient accuracy.

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