Abstract: A structural system including a panel having a pair of parallel planar outer walls, reinforcing ribs joining the outer walls with reinforced shoulders at the intersection of the ribs with the walls, and a panel connecting member for joining the panel to an adjacent panel by slidably engaging an interlocking panel joining member. The panel connecting member includes a head portion and a neck portion which form a pair of opposed keyways and permits interlocking with the interlocking lips of variously configured panel joining members. A variety of interlocking panel joining members allow assembly of the structural panels in end-to-end configurations, T-intersections, cross-intersections and other configurations to form structural systems. Also disclosed are interlocking end trim members, bolted interlock members and edge insert members which may be used to assemble a complete structure.