A connector assembly, comprising an upper connector coupled to a lower connector and a gusset plate sandwiched between the upper and lower connectors (102, 2), the lower connector comprising: a lower connector body having a lower connector body column receiving end and a lower connector body gusset contact end, the column receiving end being adapted for receiving a first end of a first module frame and the gusset contact end being adapted for coupling to the gusset plate; at least a pair of lower connector arms, each lower connector arm coupled to and extending from the lower connector body and having lower connector arm inner face, a lower connector arm outer face, a lower connector arm gusset contact face, a lower connector arm load bearing face and a lower connector arm beam contact face, the beam contact face being positioned distal from the lower connector body, and each lower connector arm having at least one fixing aperture on the load bearing face for receiving a fastening means to couple the lower connector to the upper connector; and a lower connector arm boss coupled to and extending from the beam contact face of each arm, the boss having a lower connector arm weld receiving bevel extending from the distal end of the arm and a lower connector arm weld backer extending from the bevel; the upper connector comprising: an upper connector body having an upper connector body column receiving end and an upper connector body gusset contact end, the column receiving end being adapted for receiving a first end of a second module frame and the gusset contact end being adapted for coupling to the gusset plate; at least a pair of upper connector arms, each upper connector arm coupled to and extending from the upper connector body and having an upper connector arm inner face, an upper connector arm outer face, an upper connector arm gusset contact face, an upper connector arm load bearing face and an upper connector arm beam contact face, the beam contact face being positioned distal from the upper connector body, and each upper connector arm having at least one upper connector arm fixing aperture for receiving a fastening means to couple the lower connector to the upper connector and at least one upper connector arm gusset coupling aperture for receiving a second fastening means to couple the upper connector to the gusset plate; and an upper connector arm boss coupled to and extending from the upper connector arm beam contact face of each upper connector arm, the boss having an upper connector arm weld receiving bevel extending from the distal end of the arm and an upper connector arm weld backer extending from the bevel; the gusset plate comprising: a gusset plate first face, a gusset plate second face and gusset plate through holes (85 or 86)for receiving the coupling and fastening means to couple the upper and lower connectors (102, 2). a lower connector body having a lower connector body column receiving end and a lower connector body gusset contact end, the column receiving end being adapted for receiving a first end of a first module frame and the gusset contact end being adapted for coupling to the gusset plate; at least a pair of lower connector arms, each lower connector arm coupled to and extending from the lower connector body and having lower connector arm inner face, a lower connector arm outer face, a lower connector arm gusset contact face, a lower connector arm load bearing face and a lower connector arm beam contact face, the beam contact face being positioned distal from the lower connector body, and each lower connector arm having at least one fixing aperture on the load bearing face for receiving a fastening means to couple the lower connector to the upper connector; and a lower connector arm boss coupled to and extending from the beam contact face of each arm, the boss having a lower connector arm weld receiving bevel extending from the distal end of the arm and a lower connector arm weld backer extending from the bevel; an upper connector body having an upper connector body column receiving end and an upper connector body gusset contact end, the column receiving end being adapted for receiving a first end of a second module frame and the gusset contact end being adapted for coupling to the gusset plate; at least a pair of upper connector arms, each upper connector arm coupled to and extending from the upper connector body and having an upper connector arm inner face, an upper connector arm outer face, an upper connector arm gusset contact face, an upper connector arm load bearing face and an upper connector arm beam contact face, the beam contact face being positioned distal from the upper connector body, and each upper connector arm having at least one upper connector arm fixing aperture for receiving a fastening means to couple the lower connector to the upper connector and at least one upper connector arm gusset coupling aperture for receiving a second fastening means to couple the upper connector to the gusset plate; and an upper connector arm boss coupled to and extending from the upper connector arm beam contact face of each upper connector arm, the boss having an upper connector arm weld receiving bevel extending from the distal end of the arm and an upper connector arm weld backer extending from the bevel;