A case study on fire damage assessment of a two-story building with precast pretensioned hollow core slabs

Abstract

The study comprises conducting a structural assessment of a two-story building operated as a textile factory. The floor slabs are composed of pre-tensioned precast hollow core slab units of 1.2 m width, 9.0 m length and 0.265 m thickness each. The slab units are assembled side by side to make up the floor slabs. The remaining structural elements of the building are of reinforced concrete. The work involved assessment of the damage using various tools such as on-site inspection for a preliminary evaluation of the construction and the assessment of the severity of fire attack. Then field and laboratory testing were carried out to estimate the amount of damage.Onsite inspection and testing indicated that the fire severity in the first floor was more than that in the second floor. Nondestructive testing indicated that the residual strength of concrete in the first floor for slabs and columns were as low as 58% and 62% of concrete design strength respectively. The pre-tensioned slab panels that made up the floor slabs suffered from discrepancies in the soffit levels. Based on the low existing loads when the fire erupted and the provided strands thermal insulation, a heat transfer analysis was carried out on a finite element model of a precast pretensioned hollow core slab unit. Then a two stage structural analysis was performed to determine the fire endurance exposure time. Ultimately, the fire endurance exposure time was estimated to be one hour. The predicted maximum mid span deflection at the structural end point was 3.26 times larger than the maximum mid span deflection at ambient conditions.The study encompasses proposing appropriate repair methods or to decide whether the demolition of elements or the whole structure is more appropriate. Based on the carried out study, it was concluded that the demolition of the structure is more convenient.