Controlled expansion structural beam and grid structure including same

Claim 1

A STRUCTURAL MAIN BEAM MEMBER COMPRISING IN COMBINATION: (A) A PAIR OF THERMALLY RESPONSIVE STRUCTURAL BEAMS IN END-TO-END RELATION, EACH HAVING (B) A WEB PORTION HAVING SPACED PARALLEL MARGINAL EDGES, (C) A FLANGE DISPOSED ALONG AT LEAST ONE OF SAID MARGINAL EDGES, (D) THE WEB OF AT LEAST ONE OF SAID BEAMS HAVING A CUT-OUT PORTION INTERMEDIATE THE EXTREMITIES OF SAID BEAM AND TRAVERSING THE OTHER OF SAID MARGINAL EDGES TO PROVIDE A LONGITUDINAL DISCONTINUITY IN SAID BEAM SPANNED BY SAID FLANGE, (E) A PLURALITY OF SPACED FLANGE DEFORMATION LOCALIZING NOTCHES FORMED IN SAID WEB ADJACENT SAID CUT-OUT PORTION, SAID NOTCHES EXTENDING SUBSTANTIALLY TO THE PLANE OF SAID FLANGE, AND (F) MEANS FOR RESTRAINING MOTION OF BEAM IN A PLANE TRANSVERSE TO THE PLANE OF THE WEB ADJACENT SAID CUTOUT PORTION, INCLUDING A REINFORCING BEAM HAVING A WEB FACING PORTION HAVING A PLURALITY OF KEYS DISPOSED IN SPACED LONGITUDINAL RELATION THEREON, THE WEB OF EACH OF SAID PAIR OF BEAMS INCLUDING KEY-SLOT MEANS ADAPTED TO RECEIVE SAID KEYS IN INTERLOCKING RELATION FOR MAINTAINING SAID BEAMS IN END-TO-END RELATION, THE WEB OF SAID ONE OF SAID BEAMS INCLUDING SAID CUT-OUT PORTION HAVING KEY-SLOT MEANS DISPOSED ON EITHER SIDE OF SAID CUT-OUT PORTION, THE KEY-SLOT MEANS ON ONE SIDE OF SAID CUT-OUT PORTION INCLUDING AN ELONGATED LONGITUDINALLY EXTENDING SLOT PORTION ADAPTED TO UNIDIRECTIONALLY SLIDABLY COAT WITH A KEY MEMBER IN RESPONSE TO LONGITUDINAL EXPANSION OF THE BEAM, AND INCLUDING KEY-SLOT MEANS ON THE OTHER SIDE OF SAID CUT-OUT PORTION HAVING A RESTRICTED PORTION TO RESTRAIN SAID BEAM AGAINST LONGITUDINAL RELATIVE MOTION DUE TO SAID EXPANSION.