Most of Preload’s tanks incorporate a cast-in-place, spherical shell, dome roof. The design results in uniform compression throughout the dome shell, allowing thin sections of concrete to span large tank diameters.

The efficient dome shape provides a low profile as well. Rise-to-diameter ratios of 1:8 to 1:12 are standard, depending on tank diameter. The dome design also provides venting for adequate draft, and an access hatch for future entrance.

Reinforcing steel is placed in perpendicular directions throughout the dome shell. Then, the concrete is pumped onto the form, finely screeded and finished to the required spherical shape. The hatch and draft vent are both installed as integral parts of the concrete dome roof.

A thickened fillet section is incorporated at the dome perimeter to resist the bending moments resulting from shell edge discontinuity. Just below the edge, at the wall-dome intersection, is a specially designed connection detail, which provides
deflection compatibility under rotation and translation.