Floating in Air: Using Cantilevers to Support an Entire Room

A home built with an entire section that floats in air seems futuristic and nearly impossible. Just how could this section be supported? Is it structurally safe? In fact the design is safe and the floating room is supported by cantilevers. While this is a unique concept in housing, cantilevers have been used for ages as a very strong support method.

A cantilever is defined as a beam that is only supported on one end. The load, or weight, on the unsupported end is carried to the supported end where it is countered by shear stress or moment of force. The use of a cantilever system is frequently found in bridges that need to span large areas. A balcony, or a diving board on a swimming pool, is another example of support achieved through cantilever. Put more simply, a cantilever system balances the weight that it supports.

The support of a cantilever depends on a system of counterbalances. A vertical force offsets the horizontal force. Using cantilevers to support a bridge or section of a home actually provides more support than just using beams that run from one support to another. Calculations are made to determine the shear force, or vertical force, that will be needed to counterbalance the free floating section. This is the total of the weight of the beam and the load the beam will carry. In a home this amount would be the total weight of the building materials and the maximum amount of weight the room will need to support.

Calculations also need to be made for the bending moment of the beam and the load weight. For beam calculations this is the amount of force, in Newton, times the perpendicular distance to the force. If a force of 20 Newton is applied, at a location 5 meters from the support, the bending moment is 100 Newton-meters. For calculating the moment of the weight for the load, the weight at the center of the load must be determined. Multiplying that weight by the distance from the support gives the bending moment for the load weight. Both of these calculations are then added together to obtain the total bending moment.

While the look of a home that employs a cantilever system for free floating rooms is impressive it is not a job for the average handyman. The engineering calculations must be done correctly or the results could be disastrous. The Architect that recently finished his personal creation in Massachusetts not only cantilevered an entire room but then enclosed it with glass. While the idea may not be for the timid, a room with an incredible view that seemingly floats in air is an impressive design.

References:

http://www.efunda.com/formulae/solid_mechanics/beams/casestudy_bc_cantilever.cfm