Field tests on the blast-resisting performance of mild steel circular tubes after exposure to fire

摘要

Fires and blasts usually take place simultaneously and threaten the safety of engineering structures. In the present work, field tests were carried out to understand the blast-resisting performance of Q390B mild steel circular tubes after exposure to natural fire. An innovative experimental platform was designed to enable the loading of a blast load within seconds after a fire. By defining and quantifying the deformation characteristics of the circular tubes, four typical failure modes were summarized. In addition, it was found that the occurrence of a fracture influenced the variation of relevant deformation parameters. Results of the metallographic examination of the sag area after the explosion impact revealed that the pearlite distribution in Q390B steel was relatively dispersed and disordered compared with that at high temperature, which might have resulted in relatively greater resistance to the dislocation movement. The scanning electron microscopy (SEM) of the fracture showed that many dimples were distributed on the surface of the fracture, and the dimples were larger and deeper at high temperature. Finally, the engineering calculation formulas for the influences of the temperature and the blast scaled distance on the global deflection of the circular tubes were established.