NORTH LIGHT SHELLS
This type of shell structure is used to provide large areas of north light windows for factories requiring excellent natural lighting. The windows may be slanting as shown here, or may be vertical. The edge member at the bottom forms a drainage trough with the curved shell and materially assists in stiffening the structure. The effective depth of the shell is not the vertical distance between the two ends but is more nearly represented b the depth if the shell is laid flat with the ends of the circle on the same horizontal line. Therefore, the spans for a north light shell must be rather small in comparison to the vertical depth of construction. The edges of adjacent shells should be tied together by concrete struts serving as mullions between the window glazing.