The mast truss utilizes cable bracing as a strategy to reduce visual mass. This structural type is named after its nautical origins: a central compression element (or mast) is stiffened by cable bracing that incorporates spreaders to give shape to tensile elements, thereby stiffening the mast along its length in resistance to buckling forces. Braces can be positioned with bilateral, trilateral or quadrilateral symmetry about the center mast. Mast trusses are often used as the primary structure in a hierarchical truss system.
Here a mast truss with bilateral symmetry is suspended from an outrigger tied back to the primary building structure. The outer end of the outrigger incorporates a vertical dead load cable that supports the outer end of the truss spreaders and carries the dead load of the glass. Point fixings at the tips of spreaders tie the glass to the truss, transferring lateral loads onto the truss system.
Mast trusses are capable of accommodating a wide range of scale. The mast trusses employed here act as the primary structural component, spanning over 100 feet (33 meters). The same mast truss is also used to support a secondary system of horizontal cable trusses that in turn support the glass.
300 New Jersey Avenue’s glass atrium relies upon an elegant mast truss with trilateral symmetry to support its cantilevered roof.