Cost-effective methods for flexural strengthening of one-way RC precast flat slab bridges in South Carolina

Abstract

In South Carolina, there are one-way precast RC flat slab bridges that were constructed in the 1950 s for H-10 and H-15 design trucks (lower than the current design standards) and have deteriorated over time. To ensure public safety and continued usage, strengthening the bridges is imperative. Various methods exist for flexural strengthening, including application of UHPC from above and strengthening from below with FRP, steel plates, and external prestressing. However, these methods may compromise the ductile behavior of the slabs and they are also challenging, labor-intensive, and expensive to apply. The innovation of this paper lies in investigating the methods for strengthening from above that have the potential to improve both the flexural strength and ductility of slabs, while offering advantages in terms of ease of implementation and cost-effectiveness compared to existing methods. Five slabs obtained from decommissioned bridges in South Carolina were tested under monotonic loading to failure: one reference slab; one slab strengthened with steel channel sections from above; one slab strengthened with steel plate sections from above, and two slabs connected at the joint by near surface mounted steel rebars for strengthening. Strengthening the slabs with steel channel sections from above effectively improved the flexural strength and ductility of the slabs while being more economical and easier to implement than other methods of strengthening. Following strengthening, some slabs may require overlays to cover the steel sections and ensure that bridge traffic may go on them. Even after accounting for reduction in strength gain due to the deadload of the overlay, a positive net strength gain in measured peak moment was observed in the strengthened slabs. The moment capacities of the slabs, as determined through design calculations following the ACI 318–19 code, exhibit a good agreement with the measured peak moment observed in experimental tests, thus validating their reliability as a dependable alternative to solely relying on experimental tests.