Experimental and Numerical Study of Postfire Strengthening Methods for Fire-Damaged Two-Way Composite-Topped Precast Concrete Slabs

Abstract

The results of an experimental study of the flexural performance of full-scale, fire-damaged, two-way composite-topped precast concrete slabs with different postfire exposure-strengthening methods are presented. Four slabs were subjected to the standard ISO 834 fire conditions for varying exposure times (30, 60, 90 min and failure at 133 min). A fifth control slab was tested without having been exposed to fire conditions. Different strengthening methods, selected based upon the extent of fire damage, included externally bonded carbon fiber–reinforced polymer (CFRP) sheets, steel strips, and combining CFRP sheets and midspan I-beam support were demonstrated to restore fire-damaged slab load-bearing capacity, although postfire exposure stiffness was degraded in every case. Load-carrying capacity of the strengthened fire-damaged slabs was increased at least 23% over the capacity of the control specimen without strengthening. Finite-element modeling combining an initial thermal analysis followed by a mechanical analysis which accounted for temperature-degraded material properties was conducted to capture the mechanical behavior of the strengthened slabs after fire. The results were shown to correlate well with experimentally determined results, exhibiting conservative errors of less than 20%.