Eiji Shirai

Investigation on Buckling Behavior of Cylindrical Liquid Storage Tanks Under Seismic Excitation: 2nd Report — Investigation on the Nonlinear Ovaling Vibration at the Upper Wall

When a thin walled cylindrical liquid storage tank suffers a large seismic base excitation, buckling phenomena such as elephant foot bulge at the bottom portion and nonlinear ovaling vibration at the upper portion shows nonlinearity between the input and response level and suddenly occurs for the excessive input level, thus will be called as “nonlinear ovaling vibration” hereafter in this paper, may be caused. In the 1st report, the elephant foot bulge phenomena and the liquid pressure effects were investigated. In this 2nd report of the series of studies, the effect of nonlinear ovaling vibration phenomena were investigated based on the dynamic buckling tests using scaled models of thin walled cylindrical liquid storage tanks for nuclear power plants. The mechanism and the effect of vertical excitation and liquid sloshing were also studied and discussed.Copyright

Investigation on Buckling Behavior of Cylindrical Liquid Storage Tanks Under Seismic Excitation: 1st Report — Investigation on Elephant Foot Bulge

When a thin walled cylindrical liquid storage tank suffers a large seismic base excitation, buckling phenomena may be caused such as bending buckling at the bottom portion and shear buckling at the middle portion of the tank. However, the dynamic behaviors of the tanks is not fully clarified, especially those from the occurrence of buckling to some failures. In this study, bending buckling phenomena were focused which will be categorized as diamond buckling and elephant foot bulge. As ones of a series of studies, dynamic buckling tests were performed using large scale liquid storage tank models simulating thin walled cylindrical liquid storage tanks in nuclear power plants. The input seismic acceleration was increased until the elephant foot bulge occurred, and the vibrational behavior before and after buckling was investigated. In addition to the large scaled model tests, fundamental tests using small scaled tank models were also performed in order to clarify the effects of dynamic liquid pressure on the buckling threshold and deformation patterns.Copyright

Proposal of rationalized assessment procedure for buckling of thin-walled cylindrical tanks

As for thin walled cylindrical liquid storage tanks in nuclear power plants, the current elastic design guideline against seismic loading might result in too conservative component design. Therefore, it is thought possible to make the design procedure more reasonable by taking dynamic response reduction into account. Experiments using scaled models as well as numerical analyses were carried out, and seismic behavior of thin walled cylindrical liquid storage tanks was simulated to investigate energy absorption capacity and seismic resistance of those tanks. Based on the test and analysis results, assessment procedure for buckling considering post-buckling behavior has been proposed.

Study on Dynamic Buckling Behavior of a Cylindrical Liquid Storage Tanks under Seismic Excitation (1st Report, Effects of Liquid Pressure on Elephant Foot Bulge)

When a thin walled cylindrical liquid storage tank is exposed to a very large seismic base excitation, buckling phenomena may be caused such as bending buckling where diamond buckling pattern or elephant foot bulge pattern will be found at the bottom portion, and shear buckling at the middle portion of the tank. In this study, dynamic buckling tests were performed using scale models of thin cylindrical liquid storage tanks for the nuclear power plants. The input seismic acceleration was increased until the elephant foot bulge occurred and the vibrational behavior before and after buckling was investigated. And the effects of static and dynamic liquid pressure on the bending buckling patterns and the buckling critical force was investigated by fundamental tests using small tank models.

Investigation on Buckling Behavior of Cylindrical Liquid Storage Tanks Under Seismic Loading: 3rd Report — Proposed Design Procedure Considering Dynamic Response Reduction

As for thin walled cylindrical liquid storage tanks in nuclear power plants, the current elastic design guideline against seismic loading might result in too conservative component design as compared with elasto-plastic design in general industries. Therefore, it is thought possible to make the design guideline more reasonable by taking dynamic response reduction into account. In this series of study, experiments using scaled models were carried out, and seismic behavior of thin walled cylindrical liquid storage tanks was simulated to investigate energy absorption capacity and seismic resistance of those tanks. In this 3rd report of series of studies, seismic behavior of tanks was simulated to estimate a dynamic response reduction factor. This factor is based on the energy absorption capacity of structures. Through experiments and numerical study, a response reduction factor to design thin walled cylindrical liquid storage tanks has been proposed.Copyright