A structural beam assembly is for use in supporting a fabric covered building includes a plurality of adjacent beam sections in end-to-end alignment and a means for interconnecting the adjacent beam sections. Each beam section comprises an upper member, a lower member and a reinforcing web extending between and interconnecting the upper and lower members. According to one embodiment, the upper and lower members are tubular and the connection means comprises a connection bracket having an upper tubular member sized for insertion into the upper tubular members of a two adjacent beam sections and a lower tubular member sized for insertion into the lower members two adjacent beam sections. In another embodiment, the upper and lower members are tubular and the connection means comprises a swaged portion integrally formed on the upper tubular member of one of the two adjacent beam sections and a swaged portion integrally formed on the lower tubular member of one of the two adjacent beam sections. In another embodiment, the reinforcing web comprises web plates and the connection means comprises overlapping portions formed on the web plates of adjacent beam sections. The overlapping portions are secured together by fasteners, such as bolts or rivets. In another embodiment, the connection means comprises connection brackets that extend between the web plates of adjacent beam sections and are secured thereto using fasteners. In another embodiment, the connection means connection means comprises a pinned connection assemblies. Each pinned connection assemblies comprises mating flanges formed on the ends of the adjacent beam sections and a pin that extend through apertures in the flanges to secure adjacent beam sections to one another.