Support structure for supporting foamable material on hollow structural member

A support structure for supporting a foamable material on a hollow structural member, comprising:

• a foamable material located in a cavity of a hollow structural member for blocking the cavity of the hollow structural member when it is foamed by external heating, said foamable material having a plate-like shape and having an external dimension smaller than the dimension of the cross section of the cavity;
• and
• a support member for supporting said foamable material, said support member being disposed in the cavity and mounted on the hollow structural member by a mounting device, said support member comprising a pair of support plates for supporting both side surfaces of said foamable material and a desired number of connecting pieces located along a lower periphery of said support plates for integrally connecting said support plates, said support plates being adapted to be elastically spread and narrowed about said connecting pieces and being directed to an exterior surface of the hollow structural member at an upper periphery thereof.