The influences of fly ash property, mixture proportion and different curing method on strength efficiency of fly ash in high-strength concrete are investigated in this study. The strength efficiency of fly ash, k, is pigeonholed as Portland cement-fly ash mass ratio. Under standard-curing, k increases with time, and bigger specific surface area of fly ash produced-by the same plant, higher the long-term strength efficiency, k under sealed-curing or atmospheric-exposure is lower than underwater-curing. Under atmospheric-exposure from the age of 7 days, k is around 0.8 against under standard-curing at the age of 91 days, 0.5 at the age of 365 days.

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In this paper, tests for drying shrinkage cracking of restrained concrete adding expansive admixture and shrinkage reducing admixture were carried out. The effect of several factors on resistance against cracking was investigated experimentally. Experimental results were analyzed by a step-by-step method, with which experimental results were reasonably reproduced. As a result, it was confirmed that step-by-step method can predict analytically stress behavior of concrete with expansive admixture.

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This paper describes a nondestructive inspection method for estimating compressive strength of concrete using velocity of impact-elastic wave, and explains influence of variations of concrete materials and mix proportions on relation between the velocity and the strength for improving the accuracy of estimation. First, we survey the recent studies about methods to measure velocity of impact-elastic wave and relations between the velocity and compressive strength. Next, experiments to clear influential factors on the velocity, such as W/C, slump, bulk volume of coarse aggregate and cement type, were carried out using cylinder specimens. The results to describe influence of the four factors on relation between elastic wave velocity and compressive strength were presented. Finally, an appropriate estimating formula was given by fitting to the experimental relation.

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It is indicated that the reinforcement with concrete causes efflorescence and decay of brick because of alkali salts in cement. This paper explains the mechanism of efflorescence on historical brick masonry buildings reinforced with concrete. First, accelerated test method was developed so as to reproduce efflorescence on brick masonry wall reinforced with concrete. Second, we investigated relation between water content and rate of evaporation. It is considered that water did not move in a liquid condition in the brick below the water content of 4〜5Vol%. Finally, model wall specimen similar to actual historical brick masonry wall was made and accelerated test was carried out. And water content of each brick was continuously measured by TDR(Time Domain Reflectometry) method during the test. It is concluded that efflorescence did not occur 4〜5Vol% water content below because movable water in liquid phase was not present in the brick.

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A model for simulating the recycle process of wooden material produced by the deconstrucion of wooden houses has been developed, which is capable of describing the material flow of wooden resource based on logistic condition in a local area. The model, called recycle logistics model, consists of several agents which simulate wooden houses, deconstruction companies, intermediate process factories and recycle material production factories in the real world. They play their own role in computer program directed by political scenarios which control the material flow. An applied simulation for the recycle process in Yamaguchi Prefecture shows the useability and effectivness.

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In this study corrosion resistance of Cr-bearing rebars is investigated in artificial concrete pore solutions and concrete specimens with high content of chloride ion. Artificial concrete pore solutions were saturated with Ca(OH)_2, containing NaCl of 0.27%, 1.07% and 21.4%. The pH of the solutions was adjusted at 12.5, 11, 10 and 9 by HCl, in which pitting potentials of the steels were investigated. The results of the study showed that 5Cr and 9Cr steels showed good corrosion resistance in 1.07% NaCl solutions at pH12.5 and pH10, respectively. In the case of concrete specimens, the test specimens were made installing 8 types of rebars into concrete specimens with chloride ion contents of 0.3, 0.6, 1.2, 2.4 and 24kg/m^3. The corrosion resistance of the Cr-bearing rebar was examined by measuring half-cell potential, corrosion area and weight loss up to 155 cycles of corrosion accelerated curing. The results of the study showed that the Cr-bearing rebar with Cr content of 5% and 9% exhibited high corrosion resistance when the chloride ion contents were 1.2 and 2.4kg/m^3, respectively.

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In this study, evaluation formulae are proposed for the power law profile of mean wind speed over pseudo urban area in a wind tunnel by analyzing statistical characteristics of obstacle geometry. First, statistical characteristics of urban obstacles are investigated from a digital house map of Tokyo district so that the range of parameters to be considered will be clarified. Then, obstacle array models are proposed for parametric study of wind speed via numerical simulation. Wind speeds over a sample obstacle array, typical of urban surface, are obtained via numerical simulation, use of k-ε model. Then, evaluation formulae for mean wind speed profile are proposed as functions of plan area density, mean aspect ratio and coefficient of variation of obstacle height for upwind obstacles as well as fetch length.

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Seismic responses of a ground with various types of sinusoidal-shaped irregularity were evaluated by using the boundary element method and analyzed based on "scattered-wave contribution". The examination of the numerical results revealed the following: 1) the response at the trough varies sharply with frequency whereas the response at the peak shows large amplification over a wide frequency range; 2) the predominant frequencies at the trough depend on the amplitude of the surface irregularity and do not depend on the number of fluctuations of the ground; and 3) these characteristics can be understood as the results of the interference of scattered waves coming from the irregular surface.

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In consideration of strong needs for cost-effective seismic retrofit for old houses built in urban areas, proposed is a type of retrofit techniques in which detached houses are linked together by inexpensive materials like ropes, cushions, etc. A system having such linkage exhibit strong nonlinearity even if individual structure behaves linearly. As the first step toward the establishment of the seismic retrofit, a procedure to convert the nonlinear system into an equivalent linear system was developed, and analytical expressions are presented on the equivalent linear stiffness and damping ratio. Associated numerical analyses were conducted, and the accuracy of the expressions was calibrated in terms of the resonance period and the dynamic amplification of the corresponding resonance curves. Examples are presented for the selection of stiffness of linking elements to make the linked system achieve the assigned response reduction, and the effectiveness of the developed linealization is demonstrated.

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Based on two equations to predict the time history of the story shear and story drift of multi-story buildings under earthquake motions previously proposed by the author, evaluation methods of the maximum story shear and story drift are investigated to improve the predicting accuracy of those by the calculation of response and limit strength provided in the Building Standard Law Enforcement Order of Japan in this paper. Two equations using the square root of sum of squares method to evaluate the maximum responses are proposed. The evaluated results are compared with the maximum responses in the time history earthquake response analyses for 4 and 12 story RC buildings with 12 earthquake motions. Almost good agreements between the evaluated and analytical results are obtained, while some scatter is observed in the comparison of the maximum story drift of 4 story buildings.

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This paper discusses input loss effect of 9 low and medium-rise buildings systematically using large amount of small to medium level seismic records and microtremor records. The following results are obtained. (1) Predominant frequency of input earthquake motion can be estimated by equivalent predominant frequency expressed as PGA/PGV/2π or PGV/PGD/2π. PGA, PGV and PGD mean peak ground acceleration, velocity and displacement respectively. (2) Input loss effect can be evaluated in the unified form for acceleration and velocity using nondimensional frequency calculated from equivalent predominant frequency of input earthquake motion, foundation width and average shear-wave velocity of ground. As nondimensional frequency become high, input loss effect become larger. Embedded buildings have lager input loss effect than other buildings. (3) Using Fourier spectrum ratio of foundation and ground, input loss effect of seismic and microtremor records show same characteristic depending on frequency for large scale and embedded buildings, however, they are much different for other buildings. This is caused by the difference of input mechanism of earthquake motion and microtremor, because spatial vibration of earthquake is coherent and that of microtremor is incoherent.

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We propose a hysteresis model at small strains of lead-rubber bearing (LRB) by analyzing earthquake records observed in a building with LRBs. The horizontal restoring forces of the base-isolated story are estimated by identifying the vibration system from the records. The skeleton curve derived from the restoring forces reveals that the elastic-limit strain of LRB is 0.04% and that the dependency of the observed skeleton curve on strain is higher in small strain range than that of an existing modified bilinear model of LRB. Using the result and a system identification technique, we develop a new modified bilinear hysteresis model of LRB.

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This paper aims to bridge the gap between the nonlinear vibration theory and the energy approach for the seismic design of buildings, and to find out some novel principle for the energy-based method to estimate the nonlinear dynamic response. A characteristic curve that represents the relation between the energy level and effective resonance period of the nonlinear dynamic system is presented, and the energy response of Duffing's oscillator is discussed in detail through the numerical integration of the equation of motion. The comparison between these results reveals that this characteristic curve can account for the typical behavior of nonlinear vibration in association with the energy input characteristic of acceleration wave.

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Hybrid stress plane beam-column finite elements considering the higher order shear deformation and the bi-axial effect in stresses and strains are developed. Shear-deformable plane beam-column theory shown in Refs. 1) and 2), which is based on the assumption of no in-plane strains of the section and higher order than the well-known Timoshenko's theory, is employed and revised to introduce the bi-axial effect in stresses and strains. Using the so-called semi-inverse method, the shearing and the lateral normal stresses as well as the axial normal one are prepared in expression of resultant stresses of the beam-column. These stress fields compose the completely equilibrated ones in the plane stress state. Also, lateral displacement field is reset up to evaluate the lateral deformation components right and precisely. According to Refs. 8) and 9), hybrid stress finite element method is unifiedly formulated, and a new series of plane beam-column elements is derived. Several numerical tests are performed, and the availability and the applicability of the present approach are discussed and examined.

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The adequacy of the fibered plastic hinge model proposed by the authors for the three-dimensional collapse analysis of steel frames with H-columns under strong vertical loads is examined. Also a procedure is presented for evaluation of the strain of the member caused by three-dimensional elastoplastic deformation of a steel frame. The procedure realizes to obtain the strain of a member by a plastic hinge model, not a fiber model. Available test results for one-bay one-story three-dimensional steel frames subjected to eccentric horizontal load under a strong constant vertical load are used to examine the accuracy of the model.

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The author has studied the time domain evaluation of the frequency dependent impedance, and has proposed some transform methods. In this paper, the transform method of frequency dependent complex stiffness with large hysteretic damping to the time domain is investigated by correcting the real parts of the latest method. It is well known that the rigorous transform of the hysteretic damping is impossible because it is not causal. This method enables to find an impulse response function that is approximate but causal. The efficacy of the method is confirmed by applying to the transform of the 2-layered soil impedance and the complex stiffness of the viscoelastic dampers, and to the time history earthquake response analysis of the frequency dependent Soil-Structure-Interaction system.

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The effects of dynamic soil-pile-structure interaction on pile stresses are estimated, based on large shaking table tests with dry and liquefiable sands. The test results show that inertial and kinematic forces have significant effects on pile stress and that the contribution of the two forces depends on such factors as the relationship between the natural periods of superstructure and ground, relative displacement between foundation and ground, the existence of embedded foundation, and pile stiffness. Pseudo-static analysis is conducted to estimate pile stresses in the shaking table tests. The estimated pile stresses are in good agreement with the observed ones in both dry and liquefied sands regardless of the abovementioned factors.

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This paper proposed the evaluation method by linear analysis of the deformation limit of reinforced concrete box-shaped wall buildings. The deformation limit was obtained by the ultimate strength and equivalent stiffness at the safety limit which was defined as the time when the shear failure of walls occurred. The equivalent stiffness of the walls was given based on the reduction rate of shear stiffness proposed by Dr. Tomii. The ultimate strength was given as the smaller of the values of the story shear strength and story shear force at the beam hinge mechanism. The analytical results satisfactorily verified the test results of the full-scale test results.

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A new composite shear wall system, proposeded by authors, is composed of coupling steel girders that, under large earthquakes, behave as dampers, and two RC wall panels that remain elastic and perform as a flexural column that reduces variation of story deformation along height of the building. Tension induced in the wall base is controlled by ultimate shear strength of the coupling girders. A simple design method on this system is suggested, which exploits these structural characters of the system and treats overturning moment as the wall's capacity indicator. Prototype buildings are designed using this method, which are then used to study dynamic behavior of the wall-frame structures. The results suggest that variation of maximum story angles along height is significantly reduced to 30% of the average story angle when this shear wall system is employed, regardless of the base shear capacity and yield mechanism of the frames. The hysteretic damper is effective in reducing the maximum average story angle, especially if the shear wall carries larger overturning moment.

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Experiments and 3-D FEM analyses were performed on reinforced concrete columns laterally prestressed by the shear reinforcements to study the influence of the active confinement upon shear strength and crack behaviors. The relation between the width of shear crack and the strain of reinforcement has been proven by measuring every crack over reinforcements and gluing three strain gauges on reinforcements. With increasing the lateral pressure, shear crack strength and ultimate shear strength have increased proportionally, shear crack patterns have changed appreciably, and the widths of cracks have decreased drastically. The FEM analyses using smeared crack model cannot evaluate a localized crack accurately but can provide valuable information about the total damage in the overall depth of a specimen.

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Main purpose of the present study is to discuss the effect of parameters (e.g. internal friction angle and dilatancy angle) of the constitutive law of Drucker -Prager type on the result of simulation analysis of confined concrete under compression. Two series of 3-D FEM analyses have been carried out. Firstly, the optimum values of the internal friction angle and dilatancy angle, used in the Drucker-Prager type plasticity model with the strain softening effect, have been discussed for a set of compressive strength data of concrete specimens with different shapes. As a result, reasonable value as the internal friction angle has been found to be approximately 30 degrees for a condition of rather high equivalent lateral pressure. Secondly, simulation analyses have been carried out for the compressive behavior of cylindrical concrete specimens confined by steel tubes or reinforcing bars, introducing interface element and different values of the internal friction angle. As a result, it has been pointed out that the distribution of equivalent confining pressure along the longitudinal direction of a specimen and the progress of the degree of damage in horizontal sections differ to a large extent by the value of internal friction angle applied.

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RC buildings designed by the old codes are in danger of suffering heavy damages or even collapse during coming severe earthquakes. To evaluate seismic performance of those buildings accurately, it is necessary to grasp post-peak behavior of old columns. Twenty six half-scale model specimens that failed in shear before flexural yielding or yielded before shear failure were tested until they came to be unable to sustain constant axial load. Using results of the tests, it was attempted to formulate the post-peak behavior of old columns including collapse drift.

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Four reinforced concrete column specimens were prepared for tri-axial loading test. The specimens had 150 x 150mm square section and 600mm clear span. A new experimental apparatus that allows tri-axial translation and restricts tri-axial rotation of head of the specimens was developed. The specimens were subjected to three-directional cyclic loading in the range of 0.1 to 0.4 axial force ratios. As a result, validity of the apparatus was verified. Horizontal rigidity of the column, a flexural strength surface, and an analogy to the theory of plasticity were considered from the viewpoint of formulation of tri-axial nonlinear restoring force characteristics of R/C column by using the theory of plasticity.

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This paper can be considered as a companion of the paper in which a new nonlinear analysis using fiber model was established. The flexural and shear behavior of RC columns retrofitted by pre-tensioned aramid fiber belts are investigated by a macro modelling nonlinear analysis with a flexibility based formulation. The flexural effects are obtained investigating the nonlinear curvature distribution among several monitoring sections along column axis. The nonlinear shear effects are due to a monotonic shear force-distortion relation with a hysteretic model. In accordance with fiber concept the uniaxial material hysteretic constitutive laws and external force diagrams are being satisfied during analysis. The results of cyclic loading tests of four specimens are compared with the analytical simulations. The analytical results agree well with those of cyclic loading tests. In order to discover more features of the suggested nonlinear cyclic fiber model, the contribution of flexure and shear in total hysteretic behavior besides analytical curvature distribution in selected RC column specimens are investigated in this paper.

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It is known that the prediction of the flexural strength of reinforced concrete columns on the basis of confined concrete stress block is conservative. The purpose of this research is to propose a method in which the flexural strength can be calculated accurately. Stress-strain relationship of concrete around the end of columns is presumed based on the results of compression test, and the flexural strength is calculated on the basis of the stress block. It is compared with previous experimental results of reinforced concrete columns and the validity of the calculation method is confirmed. Some factors are assumed to be variables, and numerical calculation is conducted. Main factor that influences the flexural strength is extracted, and abbreviated calculation method is proposed.

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Seismic performance of existing RC buildings is evaluated by computing seismic capacity index, Is, using the Standard for Seismic Evaluation of Existing Buildings. Old buildings constructed before 1971, which are mostly composed of "Shear Column" prescribed by the Standard for Seismic Evaluation, are in danger of suffering heavy damages in the event of severe earthquakes. It is deemed an important research subject from the viewpoint of life safety to study on how much value of Is is required for those buildings so that they can escape collapse. This paper is intended to do it for various model buildings consisting of a single type of "Shear Column" whose structural performance until collapse is diverse. For this purpose dynamic analyses are conducted for ground motions with a design level, and maximum and residual interstory drifts are computed. The effect of aftershocks is also examined.

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An experimental and analytical study was conducted to evaluate the effects of induced deformation caused by the thermal elongation of connected heated steel beams on the buckling behavior of steel columns at increasingly higher temperatures under a constant axial load. The buckling tests were performed using steel columns (SN490B JIS grade) with rectangular cross-sections. The result of tests indicated that the reduction in the column failure temperature Tcr due to induced deformation can be from 10℃ to 50℃. depending on the axial force ratio. And also, the behavior of tests were simulated by the one-dimensional finite-element procedure, and the evaluation of the effect of induced joint translation angle on the column failure temperature Tcr was carried out.

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