FIRE RESISTANCE OF GLUED-LAMINATED TIMBER BEAMS JOINTED WITH GUSSET PLATES MADE OF FIBER-REINFORCED-PLASTICS AND EPOXY-RESIN

We developed a new method to join glued-laminated timber at our instit ute. It is a glued joint using gusset plates made of fiber-reinforced- plastics (FRP) and epoxy resin. It is necessary to examine fire resist ance to put this method into practical construction use. This paper de scribes the strength of this method against bending loads under heated condition, and it also describes a fire test for actual-sized beams ( 15 cm X 30 cm X 480 cm). The fire test was conducted in accordance wit h the JIS (japan Industrial Standard) A 1304, similar to ISO (Intenati onal Standard Organization) 834 and other fire tests. Two types of spe cimens were prepared for the fire test. One was a vertical type and th e other was a horizontal type. Vertical means inserting the FRP gusset plates vertically into slits in the glued-laminated timbers. The outl ines of results are as follows: 1) An extreme change of bending streng th was started at 50-degrees-C, linearly decreasing with temperature r ise. The test specimens lost 60% of its strength at 70-degrees-C. It w as derived from the thermal properties of the epoxy resin. FRP and the epoxy resin are not completely heat-stable materials. 2) The fire tes t showed that the vertical type had 30 minutes of fire resistance, and the horizontal type had 20-25 minutes of fire resistance. 3) The temp erature of the area (7 cm X 26 cm) of the glued-laminated timber beam was estimated as being less than 50-degrees-C at 30 minutes. 4) This a rea was in accord with the calculated section size of a beam which was ruptured by a long duration load.