Experimental and numerical analysis of reinforced concrete beams strengthened in shear with steel bars using the near-surface mounted (NSM) technique

ABSTRACT

There is a growing need for intervention in existing structures to recover or increase strength capacity. The use of composite materials, such as carbon fiber, has been efficient, but cost is an obstacle. The application of steel bars as a strengthening element is an alternative and technically viable material, but there are few studies in the literature. This work carried out an experimental series with three reinforced concrete beams without transverse reinforcement, and strengthened in shear with steel bars using the near-surface mounted (NSM) technique. The load, displacement and cracking pattern were monitored in the experiment. The results demonstrated the efficiency of the strengthening with an increase of 69% in the ultimate load and 63% in the load for the appearance of the first cracks compared to the reference beam. The strengthening also increased the ductility of the beams before sudden shear failure. Numerical models via the finite element method (FEM) were carried out in the ABAQUS software using different elements and meshes. The numerical results were validated with the experimental results, and it was observed that the use of quadratic elements compared to linear elements can better represent the cracking pattern and the load capacity of the beams. The mean ratio of numerical/experimental results for maximum load of strengthening beams was 0.94.

Keywords
Structural strengthening; steel bars; shear