Experimental studies were carried out so as to estimate the influences of temperature and moisture migration on properties of concrete subjected to elevated temperatures. The test pieces were either sealed (up to 175℃) and unsealed (up to 600℃) during temperature exposure, mechanical and thermal properties were studied. The simulated mass concrete mock-up specimens were heated at one side, with maximum temperatures up to 600℃. After heating, the influences of temperature and moisture content on mechanical properties were studied. As a result.it is confirmed that the properties of concrete, subjected to elevated temperatures can be influenced signifficantly by moisture migration during heating.

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Short-period microtremors are measured at about 80 sites along a line crossing the Tokyo Bay area. The purpose of this study is to extract a reliable parameter from microtremors for site characterization in which source effects are excluded. The period of peak horizontal-to-vertical amplitude ratio of microtremors is found to be in good agreement with the natural site period, irrespective of source function of the site. It is shown that the good agreement is attributed to the predominance of Rayleigh waves in microtremor ground motions.

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An optimal aseismic design of massive structures requires detailed understanding of dynamic soil-structure interaction effects. The dynamic soil-structure interaction effects may be characterized by impedance functions that represent the force displacement relationship between the foundation and the surrounding soil. In this paper, the author has made a comparative study on dynamic impedance functions for surface foundations on an elastic half space by using various methods. One of the methods is a procedure newly proposed by the author, that is based on the direct numerical integration of Green's functions over the foundation when calculating impedance functions estimated by the displacement at the center point or the average displacement over the foundation. It should be noted that the proposed method is efficient for those cases and that the boundary element method is recommended when calculating impedance functions for rigid foundations.

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The damper investigated is an assemblage of a couple of units composed of two parallel steel plates and a layer of epoxy visco-elastic material (VEM) between them. When subjected to shear deformation, the VEM exhibits a hysteretic property or an energy absorbing capacity. The purpose of this paper is to present a method to construct a mechanical model to exactly simulate the dynamic behaviors of this damper, paving the way to putting it to practical use in the passive vibration-control design of buildings. A series of cyclic loading tests on the damper reveals that an equivalent stiffness and an equivalent damping coefficient, representing the hysteretic properties of the damper, are mainly dependent on the loading frequency and the current temperature. A linear three-element dashpot-spring model proposed has been confirmed capable of simulating these properties exactly .

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A large scale space truss for constructing an artificial ground above facilities, for example, a railroad track, a large river, existing buildings and so on, is required to have the capacity for supporting the heavy vertical load and also resisting the lateral load. In this paper, the mechanical behavior of the rigid joint space truss, which was developed to satisfy the required capacity, was experimentally investigated under vertical and lateral loading conditions. It is concluded that the space truss shows stable deformation behavior due to the re-allocation of stress and thus, that it possesses sufficient ultimate strength and plastic deformation capacity.

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Recently there are many cases in Japan to build by RC precast structures. It is important to make clear the shear behavior of RC precast structures, especially that of member-to-member joints. The easiness of connecting member with member is also important. The authors designed a new joint method connecting shear wall with floor slab, which was used by mesh bars under inclined arrangement. On this study the authors performed experiments under shear force to investigate the seismic behavior of this new joint method and to try to establish estimating method of the shear strength of joints on precast structure. We took the result that the new joint method hadgood capacity for shear force and good hysteresis, and that we can calculate the shear strength of the new method by the cumulative strength method to a certain extent.

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In the reinforced concrete buildings, it is important to prevent the columns from shear failure and improve the seismic performance of the columns. It is well known that the shear reinforcement is effective to improve the behavior of the reinforced concrete column by confining the core concrete of the columns. In this paper the authors present a new concept to improve the performance of columns subjected to large displacements in the inelastic range. To lead transverse cracks prevent slant cracks caused the shear failure. In order to verify the adequacy of this concept two tests are conducted, one is the cyclic shear bending test and the other is the monotonic compression test. The following findings can be obtained. 1) The cyclic loading performance of this new R/C columns can be improved much by inserting steel plates. 2) By inserting steel plates the monotonic loading performance can be also improved. 3) These effectiveness are brought by separating concrete section and steel plates reinforcement. 4) Various method is existent to improve the seismic performance of R/C column.

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In this study, the purpose is to investigate the effects of gas-pressure-welded splices on mechanical properties of reinforced concrete columns by experiment. The possibility of the gas-pressure-welded splices at the position where the stress in reinforcement is high and all welded splices-type in the same section of the reinforced concrete column were discussed. In the experiment, the effects of the existence and position of welded joints were not observed on the initial stiffnes, flexural strength and ductility of reinforced concrete columns. The crack width was relatively large near the welded splice for all welded splice-type at the critical section. The stress distribution neighbor to the welded splice was almost the same despite of the position of welded splices.

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To serve as a practical solution which seems still unavailable to the problem of estimating the period Ti of natural vibration of reinforced concrete floor slabs, an approximate approach is herein proposed including the effect of their cracking and time-dependency. Admittedly the estimation is a major consideration in their serviceability limit state design. Consequently it has been clarified that Ti is proportional to the square root of long-time slab deflection with the proportional constant satisfactorily expressed in function form in terms of the ratio of the long-time value to the elastic value of slab deflection. Hence in practice Ti is readily predictable from a long-time deflection which may be estimated by the AIJ' s or other prediction methods.

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Concrete filled steel tubular beam-column has a large deformation capacity combining steel and concrete rationally. However, it has not been used often in a practical construction. It is partly because non-destructive inspection method for concrete filling has not been established yet. It is also due to the lack of practical method of evaluating the deformation capacity of concrete filled steel tubular beam-columns. In this paper, the deformation capacity of collected sixty-six test beam-columns of concrete filled steel rectangular tube is evaluated in terms of ductility and is compared with that of bare steel tubular beam-columns. Finally, a classification method of deformation capacity of beam-columns of concrete filled steel rectangular tube is proposed.

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