The horizontal force which acts on the shell plate of cylindrical tank is transmitted to the tank foundation through the bottom plate during an earthquake, and the shear stress in the bottom plate is caused by the horizontal force.
The shear stress distribution in the bottom plate under the seismic loading has not been clarified yet, except for the local stress distribution of the bottom annular plate adjacent to the shell plate.
In order to investigate the stress distribution in the bottom plate of an anchored cylindrical tank under the seismic loading, the static tilt test of a model tank was carried out, and the shear stress distribution in the bottom plate of the model tank was analyzed by the finite element method (FEM) in consideration of the friction force between the bottom plate and the foundation.
The calculation method of the shear stress, which occurs in the bottom plate especially at the location along the axis that is perpendicular to the direction of the seismic loading, was developed.
The calculated shear stresses were compared with the experimental results and the analysis results by FEM.
From this study, some conclusions were obtained as follows,
(1) The high shear stress occurs in the bottom plate under the seismic loading, and this shear stress is distributed in the sinusoidal mode along the circumferential direction.
(2) The values of the shear stress with the presented calculation method were in good agreement with those of the experimental results and those of FEM analysis.

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Criteria for safety of LPG storage tank has ever been based on toughness against fracture initation. However, the double integrity concept requesting high crack-arrestability is proposed recently to prevent the tank yard from total destruction. In this present study, the influence of low Ni content of base metals and weld metals on fracture characteristics was investigated to establish the new welding procedure for LPG tank with high arrestability.
As the results, welded joints with newly developed 2.5 (3.5) %Ni steel and low Ni content weld metal hold sufficient tensile strength and bending characteristics, and K_c-value of these welded joints is high enough to prevent fracture initiation. Even if fracture initiated, K_ca-value is high enough to arrest a long crack in case Ni content of weld metal is more than 6%.

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In the manufacture of composites with a thin Ta layer inserted between the WC-Co support and sintered diamond, as reported previously, the intermediate metallic layer is partly converted into carbide.
the carburizing reaction was investigated by treating specimens of systems Ta-C, Ta-Co and Ta-C-Co, each, at around 1700K, and comparing resulting products in terms of the structure and, chemical composition. It was shown that the TaC forming process from Ta comprised three steps; alloying of Ta with molten Co, deposition of fine TaC particles by a reaction between the Ta component of the melt and carbon from the support or dimamond, and subsequent growth by agglomeration of the finer crystals.

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This survey was undertaken in order to evaluate failures from the viewpoint of artificial miss or human error. A total of 38 failures was studied. These failures occured in structures such as tanks, bridges, ships, pressure vessels, boilers, cylinders, pipes as well as otheres. The great majority of failures apparently occur under the condition in which artificial miss or humman error was included. In short, careful design, proudent selection of materials, serious considerations given on workmanship, cautious examinations are of the great importance in the prevention of failures.

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