Limit for Economic Concrete Columns.
—Eight-story warehouses with basement appear to be ample in height for ordinary conditions. Meeting the insistent demands of building ordinances in some cities like Chicago, these can be constructed of reinforced concrete with a maximum column diameter of twenty-eight inches, with all floors designed for 200 pounds per square foot. This height of building with such loadings approximates the practical limit of sustaining on footings on the usual underlying earth, with building panels sixteen feet square, the column spacing best adapted to storage purposes.
Types of Construction.
—In concrete buildings just referred to, our preference in style of construction is either of the mushroom type, that is, flat ceilings without girders; or secondly, with girders extending in one direction only. An inexperienced engineer in his efforts to minimize the quantity of steel and concrete requirement will invariably wish to carry girders from column to column and cross beams between girders, making the ceiling look like a checkerboard, losing perhaps twenty inches or more head room on every story and making a much more expensive building to construct and operate. The same fault is noticeable in steel frame buildings, since nearly always there are cross beams between girders. This drops the chilling pipes, curtailing head room and makes an unsatisfactory arrangement. Whereas with a mushroom or flat ceiling with girders in one direction, the difficulty is overcome.
Space Losses; Beams Two Directions.
—In an eight-story building the additional height above referred to amounts to from ten to fifteen feet of unnecessary building and adds greatly to the construction cost.
Exterior Walls.
—As for the exterior surface of the building, this should be brick, the lighter the color the better, making absorption of heat less probable. When building reinforced concrete frame with curtain walls, the design should be such that the brick work entirely covers the concrete frame, since it is very difficult to obtain tight joints abutting beams and columns when attempting to build panels of brick in concrete framing. It is desirable to prevent air and moisture leakage.
FIG. 31.—GROUND PLAN OF A FREEZER AND STORAGE BUILDING.