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.

Development of a New Method of Baseline Correction on Earthquake Strong Motions and Its Application to Long Period Sloshing Responses of Liquid Storage Tanks During Strong Earthquakes

In this paper, a new method of baseline correction on strong motion acceleration records is presented and the fundamental concept for baseline corrections on the earthquake strong motions is described. Considering the filtering effect, the earthquakes ground motion displacements of 1995 JMA KOBE, 1999 Kocaeli YPT and 1999 Chi-Chi TCU068 are discussed. Also, the linear sloshing responses of large liquid tanks subjected to these motions were discussed. Since liquid storage tanks show the low frequency (long period) sloshing characteristics and the strong motion characteristics of 1999 Kocaeli and Chi-Chi earthquakes are also low frequencies and large permanent displacements, the sloshing responses in large liquid tanks, especially in long natural periods, were significantly affected by the low frequency motions (large permanent displacements) of these devastating earthquakes. It is very important to use suitable ground motion characterized low frequency content for earthquake resistant design of liquid storage tanks. The baseline correction method presented in the paper may be adequately used to correct strong motion records for large liquid storage design.

Confirmation of Reduction Effect Due to Tank’s Rocking Behavior and Proposal for a Simplified Evaluation Method of Nonlinear Seismic Response

Aboveground LNG storage tank consists of inner and outer cylindrical containers. LNG is stored in the inner container made by 9%Ni steel. Anchorages are attached to some tanks in order to prevent bottom plate from excessive uplifting by seismic overturning moment. However tanks without anchorages have some probability that the seismic response factor decreases since the resonance period of tank is lengthened by nonlinear behaviors, for example uplifting of bottom plate (rocking behavior). In this paper, the reduction effect of response factor due to rocking behavior was quantitatively confirmed by 3-dimensional FEM nonlinear analysis and time-history nonlinear analysis that was modeled with single-degree-of-freedom spring-mass system. And a simplified evaluation method that allows easily calculating the reduction effect was proposed. As the result of study, it was proved that this method gave valid and conservative results.

Performance Goal-Based Seismic Design Standards for Critical Facilities in the United States

For more than the last fifteen years, the United States Department of Energy (DOE) has been using a probabilistic performance goal-based seismic design method for structures, systems, and components (SSCs) in its nuclear and hazardous facilities. Using a graded approach, the method permits the selection of probabilistic performance goals or acceptable failure rates for SSCs based on the severity level of SSC failure consequences. The method uses a site-specific probabilistic seismic hazard curve as the basic seismic input motion definition, but utilizes the existing national industry consensus design codes for specifying load combination and design acceptance criteria in such a way that the target probabilistic performance goals are met. Recently, the American Nuclear Society (ANS) and the American Society of Civil Engineers (ASCE) have undertaken the development of a number of national consensus standards that will utilize the performance goal-based seismic design experience base in the DOE complex. These standards are presently in various stages of development, some nearing completion. Once completed, these standards are likely to be adopted by various agencies and organizations in the United States. In addition to the graded approach of DOE’s method, these standards incorporate design provisions that permit seismic design of SSCs to several levels of functional performance. This flexibility of choosing a functional performance level in the design process results in an optimum, but risk-consistent design. The paper will provide an outline of two of these standards-in-progress and will present the author’s understanding of their basic philosophies and technical bases. Even though the author is an active member of the development committees for these two standards, the technical opinions expressed in this paper are author’s own, and does not reflect the views of any of the committees or the views of the organizations with which any member of the committees are affiliated.

Experimental Study for Highly Plastic Material Damper

Earthquakes can result in terrible disasters. The new technology of structural control has been acknowledged as the better way to reduce the seismic responses of structures during strong ground motions. The passive control that belongs to the structural control technology can be classified into the base isolation and energy dissipation systems. In this study, a new energy dissipation device called as highly plastic material damper has been proposed. This study focuses on testing and exploring the mechanical behavior of the highly plastic damper proposed by the research group in Feng Chia University, Taichung, Taiwan. The damper was tested in the MTS System to sustain cyclic loadings. The tests include the material stability, durability, the relationship between the force and velocity, and the temperature effect on energy dissipation capacity, etc. From experimental results, it is shown that the force-deformation hysteresis loop of the highly plastic material damper looks like an ellipse in shape for small amplitudes, and a quadrilateral shape for large amplitudes. These results express that the mechanical behavior of the highly plastic material damper depends on the velocity in small amplitudes, and on the displacement in large amplitudes. Based on these observations, the highly plastic material damper could be suitable not only for resisting wind loads but also for controlling seismic responses of a structure during earthquakes.

A Numerical Model of Lead Material and Its Applicability to Simulation of Isolation Devices

This paper proposes a new numerical model of lead material to predict mechanical properties of isolation and vibration control devices using lead as damping material. Shear and tensile loading tests of lead were carried out to make the numerical model. Shear loading test specimen were constructed from a circumferential lead part welded at the top and bottom to steel flanges. Cyclic stress-strain relations in large strain region were obtained from shear loading test results. The elastic constants and the initial yield stress were given from tensile loading test results. Therefore a numerical model was made using both shear loading and tensile loading test results. Mechanical properties of lead dampers and isolated rubber bearings were simulated using the proposed numerical model via finite element method to show applicability of the model.

Seismic Proving Test of Eroded Piping: Status of Eroded Piping Component and System Test

In FY 2000, a 3-year testing program of eroded piping was initiated with the following objectives: 1) to ascertain the seismic safety margins for eroded piping designed under the current seismic design code, 2) to clarify the elasto-plastic response and ultimate strength of eroded nuclear piping. A series of tests on eroded piping components and eroded piping systems was planned. In this paper, the results of those tests are presented and analyzed, focusing on the influence of the form and the number of thinned-wall portions on the fatigue life of the piping.

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.

Fragility Analysis for Highway Bridges in Taiwan

This paper presents the methods developed to enhance the transportation lifelines module in HAZ-Taiwan for highway bridges. The objective of this paper is to define the bridge classification and provide the fragility functions of the North-South Freeway in Taiwan that by utilize the available investigation data. The organization of this paper is as follows. First, the available bridge classes of the North-South freeway in Taiwan are reviewed and a new classification based on the available data to be implemented in Haz-Taiwan is proposed. Second, the description of failure mechanisms and criteria in different damage states adopted in this research are summarized. Third, the theoretical methodology of the fragility analysis for the new bridge classes and examples for freeway bridges are presented. Parameters for describing the fragility functions for each class are also generated and shown in the paper.

Seismic Behavior of Insulated Hollow-Brick Cavity Walls Using Quasi-Static Experimentation

This paper focuses on an experimental investigation of different types of insulated hollow-brick cavity walls, i.e. the walls with door opening, with window opening and without any opening characterized with different tie bar arrangements, subjected to slowly applied cyclic loads. The cracking and damage patterns, strength and stiffness degradation and deterioration, energy dissipation capacity and hysteretic feature were analyzed. Based on the experimental results, the formulas of calculation for cracking load and ultimate load of cavity wall are mathematically established. The evaluation equation of strength and stiffness degradation of walls is presented and its parameters are numerically given from regression results. The original characteristic curves of recovery force-displacement of actual specimens under cyclic loads were discussed, and then a standard recovery force-displacement model is suggested with convenient forms for implementation.