A canopy for selectively covering an area, such as a sports field includes at least two beams which span the area, at least two cross beams which are displaceable along the beams, a cloth which is attached to the cross beams, a drive which is configured to displace the cross beams with the cloth attached thereto along the beams, and a substantially flexible tensioning member fastened between the cross beams.

A composite structural member for a building structure comprises a first elongate portion having a first end region and a second end region and a second elongate portion having a first end region and a second end region. The second end region of the first elongate portion is connected to the first end region of the second elongate portion so that the composite structural member provided thereby is substantially longer than either of the first and second elongate portions. The first elongate portion may comprise a first member suited for resisting high magnitude forces and the second elongate portion may be a second member, less well suited for resisting high forces but having lower cost per unit length. The composite structural member may be a rafter, especially a rafter of a portal frame.

A moment frame is disclosed for a sloped roof construction. The moment frame includes a lateral bracing system having a high initial stiffness and including yield links capable of effectively dissipating energy generated within the lateral bracing system under lateral loads.

A beam system and method of erecting a supporting arch enables large roofed structures to be erected quickly and economically. The method includes aligning a plurality of structural elements longitudinally; connecting upper corners of the structural elements to upper corners of adjacent structural elements, wherein adjacent lower corners of the structural elements remain unconnected; elevating first and second structural elements in a middle of the supporting arch; connecting lower corners of the first and second structural elements together; elevating third and fourth structural elements adjacent the first and second structural elements, respectively; and connecting lower corners of the third and fourth structural elements to lower corners of the first and second structural elements, respectively.

A beam system and method of erecting a supporting arch enables large roofed structures to be erected quickly and economically. The method includes aligning a plurality of structural elements longitudinally; connecting upper corners of the structural elements to upper corners of adjacent structural elements, wherein adjacent lower corners of the structural elements remain unconnected; elevating first and second structural elements in a middle of the supporting arch; connecting lower corners of the first and second structural elements together; elevating third and fourth structural elements adjacent the first and second structural elements, respectively; and connecting lower corners of the third and fourth structural elements to lower corners of the first and second structural elements, respectively.

A composite structural member for a building structure comprises a first elongate portion having a first end region and a second end region and a second elongate portion having a first end region and a second end region. The second end region of the first elongate portion is connected to the first end region of the second elongate portion so that the composite structural member provided thereby is substantially longer than either of the first and second elongate portions. The first elongate portion may comprise a first member suited for resisting high magnitude forces and the second elongate portion may be a second member, less well suited for resisting high forces but having lower cost per unit length. The composite structural member may be a rafter, especially a rafter of a portal frame.