TESTS OF FIRE-RESISTANT BOLTS AND JOINTS

This paper reports on the results of experimental studies on the high- temperature mechanical properties of high-strength fire-resistant (FR) bolts for fire-resistant steel (FR steel), and the shear strength of the friction joints using FR bolts at high temperatures. Since the FR bolts have been adopted for joints made of FR steels to be used at tem peratures as high as 600-degrees-C, this study placed emphasis on the shear strength after slip occurs in addition to the conventional slip load. The results led to the following conclusions. The tensile streng th of FR bolts at high temperatures is superior to that of conventiona l high-strength bolts. The slip load of the joints can be roughly esti mated on the basis of the results of relaxation tests for bolt materia ls. The slip load of the joints using FR bolts decreases rapidly in te mperatures over 400-degrees-C, and the shear strength is still greater than allowable shear force at temperatures up to 650-degrees-C.