The present invention relates to the development of a
composite girder, comprising steel web members, a concrete lower cord member and a concrete
upper floor plate. Conventional composite truss girders having a concrete lower cord member have problems to be solved such as the generation of localized large sectional force in a connection
system section due to the use of a firmly coupled connection
system, and problems caused by mounting a partition wall in a middle support, or the like. The present invention uses various patterns for web members instead of a conventional triangular truss structure so as to smoothly transfer force between members and to develop a
composite girder bridge for converting the
structure type of a main girder from a truss structure to a beam structure according to a main construction step. To this end, the
composite girder of the present invention comprises: a framed structure made from a steel material of which the structural behavior is similar to a truss; a concrete lower cord member for completely surrounding the lower steel material of the framed structure; a concrete web member for filling a part of a
web space of the framed structure; and a concrete
floor plate coupled to the upper cord member of the framed structure. The composite girder of the present invention can appropriately utilize the advantages of the truss structure and the beam structure and the advantages of the steel material and the concrete according to construction conditions and construction steps.