A system for assembling a load-bearing support structure, and structure assembled with such a system. The system includes at least one supporting member, at least one connecting member, and at least one complementary member. Each supporting member includes an upper surface being provided with at least one section having at least one bulge protruding from the upper surface. Each connecting member is used for connecting a supporting member to at least one other member of the system. Each complementary member, typically a floor panel, is used for affixing onto a corresponding supporting member, and has at least one orifice being positioned, shaped and sized for inserting into a corresponding bulge of the corresponding supporting member so as form the load-bearing support structure. The system further includes at least one securing member cooperable between a given complementary member and a given supporting member for securing the complementary member onto the supporting member.