Damage To Tanks Research Articles

On the seismic behavior of cylindrical base-isolated liquid storage tanks excited by long-period ground motions

A common effective method to reduce the seismic response of liquid storage tanks is to isolate them at base using base-isolation systems. It has been observed that in many earthquakes, the foregoing systems significantly affect on the whole system response reduction. However, in exceptional cases of excitation by long-period shaking, the base-isolation systems could have adverse effects. Such earthquakes could cause tank damage due to excessive liquid sloshing. Therefore, the numerical seismic response of liquid storage tanks isolated by bilinear hysteretic bearing elements is investigated under long-period ground motions in this research. For this purpose, finite shell elements for the tank structure and boundary elements for the liquid region are employed. Subsequently, fluid–structure equations of motion are coupled with governing equation of base-isolation system, to represent the whole system behavior. The governing equations of motion of the whole system are solved by an iterative and step-by-step algorithm to evaluate the response of the whole system to the horizontal component of three ground motions. The variations of seismic shear forces, liquid sloshing heights, and tank wall radial displacements are plotted under various system parameters such as the tank geometry aspect ratio (height to radius), and the flexibility of the isolation system, to critically examine the effects of various system parameters on the effectiveness of the base-isolation systems against long-period ground motions. From these analyses, it may be concluded that with the installation of this type of base-isolation system in liquid tanks, the dynamic response of tanks during seismic ground motions can be considerably reduced. Moreover, in the special case of long-period ground motions, the seismic response of base-isolated tanks may be controlled by the isolation system only at particular conditions of slender and broad tanks. For the case of medium tanks, remarkable attentions would be required to be devoted to the design of base-isolation systems expected to experience long-period ground motions.

A seismological overview of long-period ground motion

Long-period ground motion has become an increasingly important consideration because of the recent rapid increase in the number of large-scale structures, such as high-rise buildings and oil storage tanks. Large subduction-zone earthquakes and moderate to large crustal earthquakes can generate far-source long-period ground motions in distant sedimentary basins with the help of path effects. Near-fault long-period ground motions are generated, for the most part, by the source effects of forward rupture directivity. Far-source long-period ground motions consist primarily of surface waves with longer durations than near-fault long-period ground motions. They were first recognized in the seismograms of the 1968 Tokachi-oki and 1966 Parkfield earthquakes, and their identification has been applied to the 1964 Niigata earthquake and earlier earthquakes. Even if there is no seismogram, we can identify far-source long-period ground motions through the investigation of tank damage by liquid sloshing.

Performance of Storage Tanks in Oil Facilities Damaged by Hurricanes Katrina and Rita

This paper presents a qualitative description of structural damage in aboveground steel tanks in oil refineries and facilities, which were observed during reconnaissance missions to the states of Texas and Louisiana following Hurricanes Katrina and Rita in 2005. Qualitative evidence of damage is shown using photographs taken during the reconnaissance mission in October/November 2005. Damage of tanks occurred due to wind pressures in facilities that were along the path of Hurricane Katrina (such as in Pt. Sulphur, La.) and Hurricane Rita. However, most of the damage and the most significant consequences occurred due to flooding during the days after the hurricane (such as in Chalmette, La.). Flood caused tanks to dislodge from their foundation and move away from their original location. Damage due to hurricane Rita occurred almost exclusively due to direct wind action with damage in the form of localized buckling of the shell or damage to the insulation cladding. Differences between the two events were related to the different wind speed, which was higher in Hurricane Katrina, and due to flooding of oil facilities, which only occurred in areas affected by Katrina. Research needs are identified based on the failure modes observed.

On the analysis of vertical circular cylindrical tanks under earthquake excitation at its base

Based on two international well accepted design standards, Eurocode 8 Part 4—Tanks, Silos and Pipelines and API Standard 650—Seismic Design of Storage Tanks, the structural response of seismically excited vertical circular cylindrical tanks is analysed from a novel perspective. The common basic assumption, adopted from Haroun-Housner and Veletsos, that a circular cylindrical tank containing liquid behaves like a cantilever beam without deformation of its cross-section is obsolete. Instead the authors consider the shell modal forms in order to generate a refined model. Emphasis is laid on the analysis of the fundamental frequencies for the tank-liquid-system. They are calculated by a new method, based on Galerkin’s approximations for cylindrical shells. As the results differ significantly from those calculated by the proposed formulae in both EC8 and API Standard 650, the new results are compared with tank failures during recent earthquakes. This comparison is astonishing. It can be seen from recent examples of tank damage that most failures are caused by resonance effects, which are taken into account neither in EC8 nor in API Standard 650. And, therefore, we take into account a high safety risk. This leads to the conclusion that the basic assumptions for current design provisions are no longer tenable under the present knowledge of shell theory and shell design, and, therefore should be reconsidered.

Building a Real Time System for Evaluating Oil Storage Tank Damage due to Earthquakes in Petroleum Stockpiling Bases

Building a Real Time System for Evaluating Oil Storage Tank Damage due to Earthquakes in Petroleum Stockpiling Bases

Sloshing Impact of a Rectangular Water Tank. Water Tank Damage Caused by the Kobe Earthquake.

Sloshing Impact of a Rectangular Water Tank. Water Tank Damage Caused by the Kobe Earthquake.

Differential Settlements in Steel Tanks

Case histories of tank settlement and damage are examined to determine which factors control the magnitude of differential settlements of tanks. The available data are used to assess the accuracy of conventional settlement analysis procedures as applied to steel tanks on compressible foundation soils and to determine the magnitudes of differential settlement that tanks can tolerate without damage. New criteria for tolerable settlements of tanks are recommended. These new criteria apply to the three settlement profile shapes found to develop in actual tanks. The new criteria are easier to apply than some of the criteria proposed previously, because they do not require determination of the distance from the tank edge to the point of maximum settlement, a quantity that cannot be calculated using any simple analytical procedure. The influence of this distance, important in determining the distortion of the tank bottom, is incorporated in the new criteria through use of different magnitudes of tolerable settle...

Tank damage during the may 1983 coalinga earthquake

AbstractThe magnitude M = 6‐5 Coalinga earthquake of 2 May 1983 caused intense ground shaking throughout the epicentral region. Unanchored cylindrical ground supported tanks located at six sites within this oil producing area were damaged; damages included elephant's foot buckling at the base of three moderate sized tanks, joint rupture and top shell buckling in one large old rivetted tank, bottom plate rupture of a relatively new welded tank and damage to the floating roofs of 11 tanks. Also oil spilled over the top of many tanks and secondary damages occurred in pipe connections, ladders, etc.In this paper an estimate is made of the intensity of ground motion at each of the tank sites, based on strong motion records made during the main shock and the strongest aftershock. Then response parameters specified by current codes are correlated with the damages observed at each tank site. Based on this comparison, it is concluded that current U.S. practice under‐estimates the sloshing response of tanks with floating roofs and does not adequately address the uplifting mechanism of unanchored ground supported tanks.

Risk Analysis Of Industrial Structures Due ToChemical Explosions

A modular analysis package is assembled for assessing risk in typical industrial structural units, such as circular cylindrical storage tanks, due to atmospheric blasts from chemical explosions. The components of the methodology are i) description of the overpressure, ii) nonlinear finite element analysis of the tank, iii) development of 3D equivalent stick-type structural models, iv) introduction of soil-structure interaction effects, v) probabilistic description of load and material properties and vi) generation of fragility curves for estimation of storage tank damage level.