Butt welded joints assessment after fire exposure

Abstract

The need of in service life of a steel structure after being exposed to fire raises the problem of strengthening or replacement of some structural elements. In many cases, after structural safety assessment, fire exposed steel structures can be reused. Establishing the post-fire residual capacity of the structure has a major importance in overall assessment process. The paper presents a study for fire behavior of the butt-welded joints subjected to low cycle fatigue loading, taken into account the post fire conditions and the possibility of welding strengthening. There is presented a case study - a building structural element subjected to dynamic loading after fire exposure. For the in case study, post fire investigations revealed several welding flaws including welding surface type flaws. An assessment was needed in order to determine the structural integrity and life assessment of some structural elements. From the fracture mechanics point of view, a Failure Assessment Diagrams FAD - level 2 procedure was applied in order to determine the in service safety of the structure. Several flaws types were assessed and conclusions were taken. The results can be used for damage assessment and strengthening technique of post fire steel structures.