Abstract: A ceiling structure which comprises a plurality of mutually parallel, mutually spaced apart, hollow, metallic and longitudinal members formed of a plurality of longitudinal segments in end to end relation, a plurality of metallic transverse members having inwardly facing surfaces, and terminally secured to the longitudinal members and extending therebetween to form a grid-like structure including open spaces and having electrical continuity throughout its longitudinal members, and being adapted to receive insulated electrical cables disposed within at least some of the longitudinal members, junction plates fastened on opposite sides of the longitudinal segments at their ends, joining same together in end to end relation, attachment flanges on the junction plates, a pair of connector ribs, fastened on opposite inwardly facing, surfaces of the transverse members at their ends, and dimensioned to fit around respective attachment flanges and interlockable therewith in self-supporting relation, locking clip means