HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT DYTRAN BENCHMARK ANALYSIS OF SEISMICALLY INDUCED FLUID STRUCTURE INTERACTION IN FLAT TOP TANKS
The work reported in this document was performed in support of a project entitled ''Double-Shell Tank (DST) Integrity Project - DST Thermal and Seismic Analyses''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST System at Hanford. The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). The work herein was motivated by review comments from a Project Review Meeting held on March 20-21, 2006. One of the recommendations from that meeting was that the effects of the interaction between the tank liquid and the roof be further studied (Rinker, Deibler, Johnson, Karri, Pilli, Abatt, Carpenter, and Hendrix - Appendix E of RPP-RPT-28968, Rev. 1). The reviewers recommended that solutions be obtained for seismic excitation of flat roof tanks containing liquid with varying headspace between the top of the liquid and the tank roof. It was recommended that the solutions be compared with simple, approximate procedures described in BNL (1995) and Malhotra (2005). This report documents the results of the requested studies and compares the predictions of Dytran simulations to the approximate procedures in BNL (1995) and Malhotra (2005) for flat roof tanks. The four cases analyzed all employed a rigid circular cylindrical flat top tank with a radius of 450 in. and a height of 500 in. The initial liquid levels in the tank were 460,480,490, and 500 in. For the given tank geometry and the selected seismic input, the maximum unconstrained slosh height of the liquid is slightly greater than 25 in. Thus, the initial liquid level of 460 in. represents an effectively roofless tank, the two intermediate liquid levels lead to intermittent interaction between the liquid and tank roof, and the 500 in. liquid level represents a completely full tank with no sloshing. Although this work was performed in support of the seismic analysis of the Hanford DSTs, the tank models in this study are for an idealized flat top configuration. Moreover, the liquid levels used in the present models are for study purposes only and are independent of the actual operating levels of the DSTs. The response parameters that are evaluated in this study are the total hydrodynamic reaction forces, the peak convective hydrodynamic forces, the fundamental convective frequencies, the liquid pressures, and peak slosh heights. The results show that the Dytran solutions agree well with the known solutions for the roofless tank and completely full tank. At the two intermediate liquid levels, there are some significant differences between the Dytran results and the approximate estimates. The results show that the estimates of peak hydrodynamic reaction forces appearing in BNL (1995) and Malhotra (2005) are reasonable and generally conservative relative to the Dytran solutions. At the 460 and 480 in. liquid levels, Dytran underestimates the convective component of the reaction force compared to the estimated in BNL (1995) and Malhotra (2005), but the convective component of the reaction force is small relative to the total reaction force. At the 490 in. liquid levels, the peak convective reaction force is more than twice as large as predicted by the approximate methods in BNL (1995) and Malhotra (2005). All three methods give similar answers for the fundamental convective frequency at the 460 and 480 in. liquid levels, but the Dytran solution indicates a significant increase in the apparent convective frequency at the 490 in. liquid level that is caused by the interaction with the roof. The peak wall pressures in the tank at the two intermediate liquid levels are essentially the same as for a roofless tank in the lower two-thirds of the tank wall, but diverge from that solution in the upper third of the tank wall. The estimates of peak wall pressures appearing in BNL (1995) are quite conservative lower in the tank, but may underestimate the peak wall pressures closer to the tank roof. Finally, the peak roof pressures predicted by Dytran at the 480 and 490 in. liquid levels are approximately twice as large as those predicted using the methodology of Appendix D of BNL (1995) and are ten to twenty times higher than predicted using the simple hydrostatic approach in Malhotra (2005).
- Research Organization:
- Hanford Site (HNF), Richland, WA (United States)
- Sponsoring Organization:
- USDOE - Office of Environmental Management (EM)
- DOE Contract Number:
- DE-AC27-99RL14047
- OSTI ID:
- 901434
- Report Number(s):
- RPP-RPT-30807 Rev 0; TRN: US0702607
- Country of Publication:
- United States
- Language:
- English
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