A method for constructing a multi-story building having floor shelves to support floors, comprising: assembling a plurality of wall trusses , each comprising a moment frame, consisting of a plurality of vertical members (101 - 105), adjacent ones of which are interconnected at the top and bottom by horizontal beams (111 - 114, 121 - 124), spanning the space between adjacent vertical members and connected to a respective side of the vertical members, the interconnection being fixed joints, wherein at least two vertical members of the wall truss comprise hollow columns; for at least two floors of the multi-story building: placing floor shelves (331 -337) on a top horizontal beam of a wall truss, wherein the floor shelf includes a substantially planar surface extending in a horizontal direction perpendicular to the top horizontal beam into the interior of the multi-story building; stacking additional wall trusses on top of the plurality of wall trusses installed for the floor below, inserting a mating member (341 - 350) into the hollow columns (301 - 309, 311-319) of at least two of the vertical members for each wall truss and additional wall truss , where the mating member (341 - 350) extends into both the hollow columns (301 - 309) of each wall truss and the hollow columns (311 - 319) of the additional wall trusses; depositing a floor module on top of the floor shelves (331-337) to span the distance between facing wall trusses; and pouring a floor slab on top of the floor module to cover the space between facing wall trusses. assembling a plurality of wall trusses , each comprising a moment frame, consisting of a plurality of vertical members (101 - 105), adjacent ones of which are interconnected at the top and bottom by horizontal beams (111 - 114, 121 - 124), spanning the space between adjacent vertical members and connected to a respective side of the vertical members, the interconnection being fixed joints, wherein at least two vertical members of the wall truss comprise hollow columns; for at least two floors of the multi-story building: placing floor shelves (331 -337) on a top horizontal beam of a wall truss, wherein the floor shelf includes a substantially planar surface extending in a horizontal direction perpendicular to the top horizontal beam into the interior of the multi-story building; stacking additional wall trusses on top of the plurality of wall trusses installed for the floor below, inserting a mating member (341 - 350) into the hollow columns (301 - 309, 311-319) of at least two of the vertical members for each wall truss and additional wall truss , where the mating member (341 - 350) extends into both the hollow columns (301 - 309) of each wall truss and the hollow columns (311 - 319) of the additional wall trusses; depositing a floor module on top of the floor shelves (331-337) to span the distance between facing wall trusses; and pouring a floor slab on top of the floor module to cover the space between facing wall trusses. placing floor shelves (331 -337) on a top horizontal beam of a wall truss, wherein the floor shelf includes a substantially planar surface extending in a horizontal direction perpendicular to the top horizontal beam into the interior of the multi-story building; stacking additional wall trusses on top of the plurality of wall trusses installed for the floor below, inserting a mating member (341 - 350) into the hollow columns (301 - 309, 311-319) of at least two of the vertical members for each wall truss and additional wall truss , where the mating member (341 - 350) extends into both the hollow columns (301 - 309) of each wall truss and the hollow columns (311 - 319) of the additional wall trusses; depositing a floor module on top of the floor shelves (331-337) to span the distance between facing wall trusses; and pouring a floor slab on top of the floor module to cover the space between facing wall trusses. <EOS>