A mathematical mechanism of the stability of the numerical integral by one-step Euler method is discussed in applying to a viscoplastic constitutive equation. The algorithm of one-step Euler method is represented by a nonlinear dynamic system and it is shown that its stability can be examined through an analysis of eigen values of the Jacobian at the fixed point of the dynamic system.
Numerical experiments of the viscoplastic deformation give the validity of the theory.

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In this paper, the author have developped the elastic-plastic fracture analysis code “FRACT-2D” using the finite element method for evaluating the nonlinear fracture parameter J-integral of an axi-symmetric crack problems in addition to the J-integral. Applying this code to the shell-to-bottom junction of a 113, 000kl oil storage tank, the J-integral of a crack assumed at the toe of the fillet weld was evaluated numerically under the filling and emptying operation of the tank. Then, following results were obtained;
(1) Filling the tank with liquid, the J-integral coincides well with the J-integral at the lower liquid level. Futher filling, the difference between both parameters increases gradually and the J-integral becomes lower than the J-integral by about 15% when the tank is full.
(2) Emptying the tank, the J-integral decreases along the history of the filling operation. Then, it takes a negative value due to compressive residual stresses distributed at the crack-tip when the tank is empty
(3) The J-integral has a path-independence during the filling and emptying operation of the tank.

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This paper describes an outline of computer simulation techniques for material failuers under a High Velocity Impact Phenomena.
Basic equations are solved by finite difference method and material models are taken into onsideration of strain rate effect, thermal softning effect, Tillotson's state equation for thermodynanic effect and espcially Mescall's failure criteria.
We are justified for this techniques that are very effective, becase we compared calculation results with experimental ones and confirmed that both are good fitable.

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Large scale buckling test under vacuum pressure was carried out to check the buckling strength of the tank. The test tank was the inner tank of the existing LPG above ground tank. The test was performed using depressurization method by evacuating the water contained in the inner tank. In the test, the first buckling response occurred at the pressure of 1.72kPa and the buckling deformation in less than 90% area of circumferential direction occurred at the pressure of 2.21kPa. Buckling was also confirmed to be an elastic buckling. The reduction factor against the calculated value of buckling pressure was 0.7, which was almost the same as the value already obtained for a small and middle size test specimens. Then, many important information on buckling was obtained.

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Since a gas holder is a huge steel structure, it is important to keep its rigidity and strength considering piston movement and gas sealing.
In this paper the fatigue strength of side wall of a newly developed COS-type gas holder was studied based on the structural analysis by the finite element method. And the side wall deformation under strong wind was also analyzed to know the wall/piston interaction and the effect to the strength of the gas holder. The following conclusions are obtained.
(1) The fatigue strength of a cylindrical COS-type gas holder is verified superior to that of a polygonal POS-type gas holder.
(2) As the side wall deformation under wind load increases in accordance with gas holder capacity, the flexibility of the sealing device is much more required. The gas sealing device of COS-type, whose packing ring is composed of reinforced rubber, is applicable to the larger size because of its flexibility.
(3) It is necessary to consider the deformation effect of the shell structure in designing the stanchion and the base under wind load, because beam theory tends to underestimate the force of windward stanchions.

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A Research has been executed to find the accuracy with which a dimension of reinforcement steel bars can be measured quantitatively by a electro-magnetic induction method. This paper describes the trial manufacture of various types of probe coils and the investigation of reinforcing steels in concrete with various changes of test frequencies.
As a result, it was found that the magnitude of signals was influenced by various probe coils, covering depth (the distance between probe coil and reinforcing steel), diameter of reinforcing steels and so on. In the case that the steel was of similar quality and the same diameter, the signal magnitude was influenced by the covering depth. When the covering depth was constant, it was obvious that the similar quality steels with different diameters had an effect on the phase angle and the signal magnitude.

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