SLOSHING AND DYNAMIC INTERACTION BETWEEN LIQUID AND FLOATING ROOF IN A STORAGE TANK UNDER SEISMIC EXCITATION

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ANALYTICAL SOLUTIONS HAVE BEEN PRESENTED FOR THE SLOSHING IN A CYLINDRICAL LIQUID STORAGE TANK WITH A UNIFORM ISOTROPIC FLOATING ROOF AND A SINGLE-DECK TYPE FLOATING ROOF UNDER SEISMIC EXCITATION. DYNAMIC INTERACTION BETWEEN THE LIQUID AND THE FLOATING ROOF HAS BEEN TAKEN INTO ACCOUNT EXACTLY WITHIN THE FRAMEWORK OF LINEAR POTENTIAL THEORY A COMPUTATIONAL METHOD BASEN ON COUPLED FINITE ELEMEMT AND ANALYTICAL SOLUTIONS HAS ALSO BEEN PROPOSED TO DEAL WITH AFLOATING ROOF COMPOSED OF AN ORTHCYIROPIC PLATE OF VARIABLE THICKNESS. IN ORDER TO CONFIRM THE VALIDITY OF THE THEORETICAL APPROACH, SHAING TABLE TESTS HAVE BEEN PERFORMED USING A SMALL-SCALE TANK MODEL THE CONCLUSIONS ARISING FROM THE PRESENT STUDY CAN BE SUMMARIZED AS FOLLOWS : 1) THE EFFECT OF THE SINGLE-DECK TYPE ROOF ON REDUCING THE WAVE ELEVATION IS SO SMALL THAT THE ROOF DISPLACEMENT IS NOT SO DIFFERENT FROM THE FREE SURFACE ELEVATION. THE DOUBLE-DECK TYPE ROOF AND THE RIB-STIFFENED ROOF MOVE PREDOMINANTLY IN THE RIGID-BODY MODE … More . THE DISPLACEMENT IN AN INNER REGION IS REDUCED CONSIDERABLY, WHILE THE DISPLACEMENT ALONG THE TANK WAIL IS NOT SO CHANGED FROM THE FREE SURFACE ELEVATION. 2) THE HYDRODYNAMIC PRESSURE ON THE SINGLE-DECK TYPE ROOF IS RELATIVELY LOW UNDER THE INNER DECK, WHILE IT BECOMES RELATIVELY HIGH ALONG THE PONTOON BOTTOM LARGE BENDING STRESSES ARISE IN THE INNER DECK ALONG THE CONNECTION WITH THE OUTER PONTOON, WHICH IS COMPARATIVE IN MAGNITUDE ID THE YIELDING STRESS OF THE STEEL THE HYDRODYNAMIC PRESSURE ON THE DOUBLE-DECK-TYPE ROOF AND THE RIB-STIFFENED ROOF BECOMES HIGHER THAN THAT ON THE INNER DECK OF THE SINGLE-DECK TYPE ROOF, BUT THE BENDING STRESSES REMAIN WELL BELOW THE YIELDING STRESS OF THE STEEL 3) THE ANALYTICAL SOLUTIONS FOR THE ROOF DISPLACEMENT COINCIDE WELL WITH THOSE MEASURED BY THE SHAKING TABLE TESTS, WHILE NON-LINEAR BI-HARMONIC RESONANCE OSCILLATION IS OBSERVED TO OCCUR IN THE INNER DECK OF THE SINGLE-DECK TYPE ROOF. 4) IN ORDER TO PREVENT THE DAMAGES OF THE FLOATING ROOF AS EXPERIENCED DURING THE 2003 TOKACHIOKI EARTHQUAKE, IT IS RECOMMENDED TO REPRACE THE SINGLE-DECK TYPE ROOF BY THE DOBLE-DECK TYPE ROOF OR THE RIB-STIFFENED ROOF. Less