The present study attempts to determine the optimum cable-stay forces for the design of prestressed concrete (PC) cable-stayed bridges. Unlike the steel cable-stayed bridges, PC cable-stayed bridges have two stress adjustment systems, which are systems for cable-stay forces themselves and internal prestress in the main girders. A formulation combining these systems has been presented as a problem of optimization of cable-stay forces. Also formulated is the mechanism of changes in forces due to creep of the concrete and treated is the creep in the optimization process. As a result, determination of the optimum stay forces for PC cable-stayed bridges requires solving two simultaneous systems of the stay forces and the internal prestress. Another result shows that the stay forces tend to approach the characteristic stay forces which are inherent in the individual structure.

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Aiming to establish the life term prediction method of existing hydropower steel structures, various techniques which reported previously, such as simplified data aquisition, structural analysis program, data base, and expert system, were investigated.
The purpose of this paper is to describe the configuration and knowledge bases of the expert system in detail, and to show the application results of the system to radial gates of 25 sites. Especially, effectiveness of AHP (Analytic Hierarchy Process) Method to determine the weights among ambiguous qualitative data, such as appearance, operational condition, environment and others, is emphasized, and essential diagnosis rules for the expert system of existing structures are pointed out.

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Horizontal translational vibrations of a circular disk on an elastic half space are investigated mathematically. The problem is formulated in terms of an integral equation which describes explicitly the relation between the horizontal displacement of the disk and the shearing stress of contact. Its integral kernel is represented in a rigorous but simple form: its singularity is separated and is reduced to an elliptic integral while the regular part is expressed in terms of a definite integral of some higher analytic functions over a finite interval. These higher functions, defined as definite integrals of trigonometric functions over a finite interval, are readily evaluated. The presented formula is proved correct by applying it to a rigid disk and comparing the results with those of conventional methods.

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In this paper the authors developed a new subsystem modes synthesis method as one of the dynamic substructure methods for the analysis of soil-foundation-superstructure for seismic motions. This method has an advantage over the impedance method in that each subsystem (namely, the soil-foundation system and the superstructure) is characterized by the respective vibration modes of appropriately fixed or free interface conditions and the release modes. The accuracy is investigated from the comparison with the impedance method analysis by taking a blast furnacee structure on a grouped piles foundation as an example. A remarkable reduction of computing time is observed for the response analysis of the integrated soil-foundation-superstructure system.

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Hammond has analyzed the non-stationary response of both single and multimode systems subjected to non-stationary excitations by using Priestley's evolutionary spectral density. Unfortunately, his method has a fatal drawback, because a modulating function representing non-stationary state of excitation is restricted to real positive values. Furthermore, certain asymptotic forms of the response are intuitively assumed. After two years, Shinozuka showed that the input-output relationship derived by Hammond is also valid without such restriction even under the assumption of asymptotic form. However, this relationship could not have been concretely applied to the response analysis of dynamic systems because of a difficulty in estimating a modulating function included in it. In this paper, an effective method to evaluate a modulating function is developed by using complex demodulation analysis. Then, the present method is applied, as an example, to the response problem of a single-degree-of-freedom system subjected to earthquake ground motion to demonstrate its rationality and efficiency. The method can be also applied to actual multimode dynamic systems.

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The authors have suggested to use the actual restoring force of soil in an analysis of surface ground motion during earthquake. The analytical equipment consists of a microcomputer to calculate the vibration equation and dynamic triaxial testing machine to obtain the actual restoring force of soil.
The micro-computer has two limits in the respect of a calculation velocity and a memory capacity. In order to remove the above limits, we develop new analytical equipment that uses a digital computer in a computer center. This computer is electrically connected to a dynamic triaxial testing machine by TSS (Time Shearing System). The dynamic behavior of very soft surface ground during the earthquake, such as a reclaimed ground, is analyzed.

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A prediction technique of bed rock motions during strong earthquakes is studied using strong-motion accelerograms obtained at ground surface. The method is not due to the earthquake response analysis of soil layers, which is employed in general, but due to a statistical technique by which the nonstationary spectra of strong-motion earthquake records are scaled with the earthquake factors and local soil conditions. It is shown from the statistical analyses how the nonstationary characteristics of earthquake motions are affected by the factors of earthquake source as well as local soil conditions. By using the technique presented here, possible motions of bed rock can be estimated provided that the earthquake factors such as magnitude, focal depth and epicentral distance are available, and they agree comparatively well with recorded motions.

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When a large vertical load is applied on the cap of pile foundation, slidings occur between the surface of piles and sorrounding soil. An analytical solution is deduced on the basis of the 3-dimensional theory of elasticity taking the slidings into consideration. It leads to obtain the load sharing ratios and the coefficient of group effects of piles. The results of the numerical calculations are as follows. The larger the vertical displacement of pile top becomes, the closer the coefficient of group effects of piles approaches to the value of 1 and the load sharing ratios approach to the average load sharing ratio. Comparing the region of sliding in a single pile with those in piles in group, the latter are smaller than the former. The vertical coefficient of group effects of piles decreases with increment of the number of piles in group.

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Damages on buried pipelines connected to structures such as manholes and buildings are not uncommon due to differential ground settlement along the direction of pipeline stretches. First, we obtained fundamental data of the mechanical behavior of a buried UPVC (Unplasticized Poly Vinyl Chloride) pipeline jointed to a manhole when it was subjected to uneven ground settlement using Sinking Soil Box. Experimental results were then compared with the theoretical ones obtained by non-linear analyses using transfer matrix method. Both results were in good agreements. Next, the same experiments were carried out for a developed pipeline as a countermeasure for large ground settlements. The developed UPVC pipeline system may stand up to 45cm of ground settlement, while ordinary pipeline system may yield to not less than 15cm of ground settlement.

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In this paper, it was investigated that how the friction or cohesion on the interface between pile and footing effects on the stress distribution in the connection between pile-head and footing. The connection was idealized as an axisymmetric body subjected to non-axisymmetric loading, and semi-analytical procedure with Fourier representation was adopted. For modeling the debonding or slip on the interface, an axisymmetric joint element was adopted. The results of the investigations suggest that the friction and cohesion on the interface are significant factors for preventing from stress concentration at bottom of footing or at pile-top in the connection, and the combined effects of pilehead loadings on the stress distribution in the connection should be considered in the safety check formulas.

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The present paper proposed design formulae and equivalent spring constants of ground used for design propose of buried pipelines subject to large ground settlements. The formulae obtained by a beam theory on an elastic foundation can estimate joint rotation angles and joint expansions as well as the maximum bending strains of the pipes. The equivalent spring constants of ground were so determined that calculated values of pipe responses by the design formulae including spring constants were well matched with many experimental values. The determined equivalent spring constants associated with an amount of ground settlements are rather conservative values from a view point of design of buried pipes. Next, resisting capacities of various kinds of pipes to large ground settlements were evaluated by using the proposed design formulae and the equivalent spring constants.

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It is said that the concrete filled steel column, so called the composite column, possesses good strength and ideal ductility. However, its behavior under load is not clear enough at present. We made experiments to compare the effect of shear connectors with that of projections on steel plate for the simplest column under the axial load. During the axial loading, the authors gave impact on the specimens and measured induced elastic wave. Spectrum analysis of the elastic wave gave the information about composite action between concrete and steel. By these experiments the following were observed. The column with shear connectors had the highest rigidity, the one with projections the second and the one of flat steel the lowest. The strength was almost the same to the column with shear connectors and the one with projections. As for the ductility, the steel with projections was better than the one with shear connectors.

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Though a transmission line has tremendously numerous modes, responses of transmission lines subjected to earthquakes can be computed by the method of modal analysis adopting only a few symmetric modes of transversal wave in low frequencies and modes longitudinal one in high frequencies. This paper presents simplified nomograms for computing natural frequencies, additional tensions and participation factors of their modes of diverse transmission lines for analyzing earthquake responses of towers and transmission lines systems.

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The dynamic behavior of highway bridges under moving vehicles is analyzed, and then the effects of roadway roughness to dynamic response of the bridges are investigated quantitatively. In this study the dynamic behavior of bridges under moving vehicles is termed the “dynamic factor”, and the spectral characteristics of roadway roughness on bridges is classified into the four categories according to the method of evaluation of roadway condition indicating by authors's investigation. Numerical calculations are presented to investigate the effects of roadway characteristics to the dynamic response.

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