Strength and fire resistance of connections based on glued-in rods

A short summary of extensive research on joints of glulam structures based on glued-in ribbed steel rods has been reported. On the basis of research work a calculation method of structures with these connections has been developed and presented. The main concern is on ease of manufacturing and construction as well as fire safety. This paper presents also results of fire resistance tests performed on loaded glulam beams connected together with the joints based on glued-in ribbed steel rods. The tests were carried out at VTT Building Technology, Fire Technology. The structure of the connections was the same in all tests but the thickness of the fire protection and the wood covering of the steel rods were varied in order to achieve fire resistance classes R30, R60 and R90. Rock wool (density 140 kg/m3) covered by steel sheet was used as the fire protection on the bare steel parts of the joint. The test load corresponded 40 % of the design load at the normal temperature design. The furnace temperature was controlled according to the standard ISO 834. The deflection of the beams began to increase remarkably about ten minutes before the failure of the joint. Fire resistance classes of R30, R60 and R90 were achieved with 20 mm, 40 mm and 60 mm thick rock wool fire protection and wood coverings of the steel rods respectively.