Browsing by Author "Muhammed Jemal"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    An Experimental Investigation on The Effect and Mechanism of Side Cover for Deep Beams
    (Addis Ababa University, 2025-06) Muhammed Jemal; Esayas Gebreyouhannes (PhD)
    This study investigates the effect and underlying mechanism of side cover spalling in reinforced concrete deep beams subjected to shear. While prior research, such as that by [2], has focused on slender beams, this thesis addresses a critical gap by examining deep beams, whose shear behavior is governed by arch action rather than flexural beam theory. A series of six full-scale deep beams with varying side cover thicknesses and stirrup cage configurations were experimentally tested under three-point monotonic loading. Two configurations were explored: SA-series beams, which maintained a constant outer width and reduced the core with increasing cover, and SB-series beams, which preserved the core width while increasing total width by adding cover externally. The primary aim was to determine whether large concrete covers compromise shear performance due to premature side cover spalling. Observations revealed that spalling initiates near peak load, particularly when the stirrup cage is confined by a reduced core, as in the SA-series. Despite observable spalling in all specimens, the presence of adequate core concrete and stirrup confinement significantly influenced the beams' ability to reach peak load without premature failure. Finite element modeling results from Vector2 were compared with the experimental findings. The Experimental findings highlighted the limitations of current two-dimensional analyses in capturing out-of-plane spalling. Importantly, the results demonstrate that increasing the concrete side cover does not enhance the stiffness (except for the initial stiffness) or peak load capacity of deep beams. This finding sharply contrasts with the assumptions in most building design codes, such as ACI 318 and Eurocode 2, which treat the entire crosssectional width—including the cover zones—as fully effective in resisting shear and flexure. The test results suggest that once the core (stirrup-confined zone) is sufficient, additional concrete cover adds little to structural performance and may even introduce weaknesses due to spalling risk. Additionally, SB-series beams display stable load-displacement behavior with limited post-peak softening, indicating improved ductility relative to SA-series specimens. This research contributes to a more accurate understanding of D-region behavior in deep beams and underscores the need to re-evaluate code provisions related to effective shear/flexure width, particularly in the presence of large concrete covers.