Loading Conditions

The loading on the model occurs from 1) hydrostatic/dynamic pressure of water and 2) the interaction of the container with the water at the water-container interface. The nodes defining the rigid container model impact the water surface with an impact velocity V0, determined from rigid body mechanics:

Vo = sl2gh (3)

Where h is the drop height and g is the gravitational constant.

The relative location of the container to the pool walls and loading platforms are given in Figure 6. The topological information of the drop is given in the following.

Weight of container

Drop Orientation in Pool

Distance of container from pool short wall

Distance of container from pool long Wall

Drop height above water surface, h

Impact velocity from (3)

4. Assumptions

The key assumptions made in the simulation are as follows:

i) Given the localized nature of the drop scenario considered, only part of the water in the main storage in the proximity of the pool is included in the assessment. Since the water mass in the main storage is relatively large, a silent (non-reflective) boundary as shown in Figure 1 ensures that erroneous reflective waves are not included in the simulation.

ii) Since the main storage is not directly connected to the pool the main storage is modelled using rigid shell elements.

iii) To ensure that the main storage’s contribution to the lateral stability and rigidity of the adjacent pool concrete wall is minimized, the channel that connects the main storage to the pool is modelled in a manner that will minimize the transfer of load to the pool. This is warranted, as the pool is not connected to the main storage.

iv) Failure in the concrete occurs when the principal stress exceeds a fraction (1/3) of the maximum tensile stress for the concrete material. This assumption ensures that the final results are conservative and no extra credit is given to concrete tensile strength.

v) Failure is assumed to occur in the stainless steel components and reinforcing rebar when the material continues to flow plastically beyond a specified effective plastic failure strain.

vi) No damping is assumed. The material’s hysteresis arising from the non-linear response and failure provides the damping.

vii) It is assumed that the stainless steel liner is flush against the pool’s concrete wall. The stainless steel liner is modelled explicitly to include its effect on the transfer of the shock wave from the
water to the reinforced concrete wall. However, it is prevented from contributing to the pool’s rigidity and lateral stability.

viii) Inspection platforms are modelled with beam and shell elements that interact with water elements through common nodes. This ensures that the deformation of the platforms due to shock wave and water movement is conservatively captured.