The Johnson Wax Research Tower
Racine, Wisconsin, USA

Frank Lloyd Wright, architect

Location

History

The S. C. Johnson Wax corporate headquarters in Racine, Wisconsin is a complex of structurally remarkable buildings by Frank Lloyd Wright. The Research Tower, the second and final phase of the project, was the first known completely cantilevered building of this magnitude.

Physical Description

The foundation is a fifty-four foot deep "tap root" that is reminiscent in section of the capitals of the famous "dendriform" columns in the earlier administration building. The foundation of the tower begins as a broad, flat disk on a "petal" acting as a spread footing that stabilizes the nineteen foot shaft at the bottom of the foundation. This shaft acts only in absorbing the compressional forces of the structure, and is made of poured in place unreinforced concrete. No formwork was used in the pou ring, so the concrete would bond better with the surrounding soil.

The core of the tower, from which all the floors and mezzanines are hung, was the trickiest portion of the building to construct. It is through this element of the structure that all service and utility chases must pass as well as the stair and elevator.

The 1600 square foot floors and 1100 square foot round mezzanines are supported solely by the central core. The hollow floor slabs are thick where they join the central support and thin at their extremes, reflecting where and how the loads and stresses a re acting on the structure.

The facade of the research tower is a non-structural skin of materials chosen to integrate with the administration building. The Cherokee-red brick formed a thin, decorative veneer which covered over the edges of the concrete floors. To complete the ski n, Wright used Pyrex glass tubing laid row upon row on metal racks with vinyl gaskets and silicone caulking between. The silicone rubber caulking was created specifically for the unique problems encountered with weatherproofing. The Pyrex tubing is now used widely for more conventional purposes.

The dead loads which the building must withstand are that of its own weight and weight of permanent fixtures such as the equipment of the labratories. The live loads whichit must withstand are the daily loadings of the human occupants and furniture actin g under gravity loads and lateral loading created by the wind. The structure was also designed to take into account the event of an explosion which could occur in one of the labratories.

Building Process

The approximately fourteen foot wide core, with walls of only seven to ten inches thick, needed to be constructed with great precision as well as strength. The steel rods and mesh that reinforce the concrete was so densely packed that tiny pea gravel agg regate had to be used so the concrete would fill completely.

During construction of the cantilevered floors, the lower layer was poured into formwork and then cured. On top of this the pipes and conduits servicing the research facilities were laid, over which steel sheets and a framework of reinforcing bars were w elded in place to handle radial stresses and shear. Finally, the concrete floor was poured and trowelled smooth.

Structural Descripton/Aspects

Vertical Loading
The construction of the tower with its floors cantilevered from a central core makes the distribution of veritcal loading fairly simple. To begin with, the round, central core of the building protrudes through the roof and is the highest part of the buil ding. This is logical, for all the loads are eventually carried over to and down through this main member. Suttounding the central core is another circular piece, a little shorter, perhaps supporting the core. Below that lies the top floor. These thre e top elements create a stepping pattern in section, going from tallest in the middle to shortest on the outside. Therefore, the greatest amount of load is in the center, the least is on the outer edge. This is reasonable since the further from the cent er the load is, the more likely the cantilever will becom unstable, whereas the closer the load is to the centroid, the less likely it will produce a dynamic load.

Another crucial member involved in transferring vertical loads is the shape of the floors. Near the centroid, they are thick, and at the outer edges, they taper into a thin slab. This shape has to do with the dead load of the structure itself, and creat es and even stress throughout the length of the floor. Thr greatest dead load of each floor slab is near the cntral core and the least dead load is at the outer edges.

Lateral Loading
As with the vertical loading, the path of lateral loads is also relatively simple, for it involves only a few members. The tower, being tall and also small in width, seems a likely candidate for falling over due to the lateral forces of wind or earthquak es.

As stated above, the outer skin is non-structural, maning it does not participate in resisting loads either lateral or vertical. The tower is a free standing structure and therefore, its resistance to lateral loads such as wind and earthquakes must resid e in the formation and structure of the foundation.

At the foundation, we find a giant "mushroom column" shaped system. The top plate which acts as a spread footing, is an important member when considering the results of lateral loading. Not only does thes plate distribute vertical loads, but it provides a balance and helps stabilize the large central core from tipping or swaying laterally. When a lateral load acts on the tower, the spread footing will push against the soil that is packed above it, and the pressure of that soil acting down resists the m oment created by the force. In a sense, the lateral load and the foundation footing create a couple, and the force of the soil acting upon the spread footing create a couple in the opposite direction, keeping the tower in equilibrium.

Conclusions

All of the vertical loads, live and dead are transferred through these cantilevered floors and down throught the central core of the building. This central core continues down through the earth and is the deepest portion of the foundation. This strong, vertical, central axis is the stabilizing element of the structural system. All loads are carried over to it and down through it into the boundation and out through the ground. A magnificent yet simple structure of stability and strength.

The Johnson Wax Research Tower, although seemingly simple because of its minimalist approach, is a very complex structure in one way- precision. The only way it is possible for the tower to stand upright, the only way it could withstand the vertical, lat eral, shear and radial forces was through absolute precision of construction.

Bibliography

Associated Buildings

Jamie Watson and Naomi Sutton
ARCH 461/561 Spring 1995

Do you have questions about adding a case? or a building to suggest??????? send a message to me....... chrisl@aaa.uoregon.edu

The Johnson Wax Research Tower Racine, Wisconsin, USA