A study on collapse temperature of steel frames including beam to beam connections fastened by high strength bolts at a fire

摘要

In the present paper, we investigate fire resistance of steel frames including a beam to beam connection fastened by high strength bolts. To estimate a collapse temperature of the steel frames subject to a fire, a theoretical verification method base on the simple plastic theory is proposed. The verification method offers two collapse modes for fractures of the connection at a high temperature: a shear fracture of the connection, and a bending fracture of it. For verifying validity of the theoretical method, we investigate behavior of the frame including the connections by using a finite element analysis, which is taken a finite element model of bolt connections into account. By making full use of the finite element analyses, we minutely investigate the behavior of the connection and the collapse temperature of the steel frame in the case when the connection fractures at the fire. As results, the connection in the frame subject to the fire fractures by the shear collapse mode in a lot of analytical cases. And the collapse temperatures of the steel frames are not affected by both thermal expansion and thermal stress occurring in the heated beam. It is, furthermore, clarified that the fire resistance of the steel frame including the connection can be estimated by the theoretical method based on the simple plastic theory.