A multifunctional hybrid glass fiber-reinforced polymer (GFRP)/steel joint has been developed for the transfer of compression and shear forces in thermal insulation sections of concrete slab structures used in building construction. The new pultruded cellular GFRP element improves considerably the energy savings of buildings due to its low thermal conductivity. The quasi-static behavior of the GFRP element in insulating and load- transferring joints at the fixed support of cantilever beams was investigated. Two loading modes were investigated: a moment dominant mode and a shear dominant mode. Results show that the GFRP element is not critical at the ultimate limit state. Ductile failure occurs either in the concrete during yielding of the steel bars, or only in the steel bars that penetrate the hybrid GFRP/steel joint. In moment mode, the GFRP element only transfers the compressive forces from the bending moments. In shear mode, in addition to the moment transfer, about 43-63% of the shear forces are transferred in the element webs at ultimate limit state due to tilting of the element. The application proves that multifunctionality can lead to competitive solutions for GFRP composites used in load-carrying components and can compensate for the relatively high material cost. © 2006 ASCE