Effect of radial base-plate welds on ULCF capacity of unanchored tank connections

Abstract

The base of large steel liquid storage tanks can uplift during severe earthquakes, causing large inelastic rotations at the connection between the tank shell and tank base. While recent experimental studies indicate significantly higher connection rotation capacity than what is specified in the current Eurocode standard (set at 0.2 rad), additional radial base-plate welds (present in some tank connection details due to fabrication methods) have never been considered in tests. This study experimentally investigates the effects of these radial base-plate welds on the fatigue capacity of tank shell-to-base connections during uplift. Twelve tank shell-to-base connection specimens taken from existing tanks throughout Switzerland are tested at rotation ranges greater than the current Eurocode limit (eight specimens with radial welds and four specimens without radial welds). Testing indicates that tank base-plate sections containing radial welds govern the shell-to-base rotation capacity during uplift. The rotation capacity of connections containing radial welds was nearly 30% lower (on average) than equivalent connections without radial welds. This reduced capacity is directly related to the reduced base-plate ductility created by the radial weld heat affected zone. All connection capacities were far greater than the current Eurocode limit.

Structural behavior of steel components under strong cyclic loading

“…The global rotation of the connection " " is used in the present study, defined in Figure 48. This rotation is similar to the one reported in previous experiment [107], [110]- [112]. Moreover, a plastic rotation (" p ") is also employed, defined as the inelastic part of the relative rotation of two crosssections at distance "L p " equal to twice the plate thickness, shown in Figure 76.…”

“…Furthermore, they verified the argument that the rotation capacity of the fillet-welded connection is larger than the one specified by current code limits. More recently, Prinz and Nussbaumer [112] investigated experimentally the effects of the radial base-plate welds on the fatigue capacity of tank shell-to-base connections during uplift. Despite the influence of the radial weld on the base-plate ductility of the fillet welded connection, all tested joints indicated a fatigue resistance far greater than the current deformation limit stated in [108] and [109].…”

Hazard consistent record selection procedures accounting for horizontal and vertical components of the ground motion: Application to liquid storage tanks

“…During a strong ground motion, part of the contained fluid in a liquid storage tank oscillates rigidly with the tank wall, while the remaining portion exhibits long-period oscillations that result in sloshing of the free fluid surface. 56 The former is known as the impulsive mass (m i ) component and is tied to the uplift mechanism that can potentially trigger elephant's foot buckling (EFB) of the tank wall 55,57 and base plate damage 55,[58][59][60] ; the latter forms the convective mass (m c ) component, which can cause damage at the upper courses of the tank wall and/or the roof. 58,61,62 While several reduced-order models are available in the literature regarding the seismic response of liquid storage tanks, the vast majority ignores the effect of the vertical ground motion component, focusing only on the application of the horizontal one(s).…”

State-of-the-Art Review on the Seismic Performance Assessment of On-Ground Steel Cylindrical Tanks

“…Cubrinovski et al [112] investigated the seismic response of pile-supported tanks subjected to liquefaction. Prinz and Nussbaumer studied the capacity of radial baseplate welds [113]. In addition, some researchers focus on the low-cycle fatigue of the shell-to-baseplate connection of the unanchored tanks [114][115][116].…”