Effectiveness of embedded through-section technique in strengthening reinforced concrete spandrel beams

Spandrel beams are typically subjected to a series of vertical eccentric loadings when used in parking structures or the abutments of bridges. The embedded Through-Section (ETS) technique is a recently developed technique to increase the shear capacity of reinforced concrete members using steel reinforcing bars. This study presents an experimental program conducted on spandrel beams to get a deeper understanding considering different parameters including the aspect ratio of the section (i.e., height/thickness) and the strengthening system (i.e., the implementation of the ETS technique). This study focuses on the test results including the ultimate shear-torsion capacity, cracking load, load-twisting, and load-deflection responses. The outcomes had shown the superior performance of the ETS technique, where the increase in torsion capacity attained 45% compared to the control spandrel beams. Also, the embedded steel bars restricted the progress of the deflection and rotation of spandrel beams due to the improvement of the spandrel's stiffness. The rotation improvement for the strengthened spandrel beams attained 50% compared to the control spandrel beams. The skewed failure plane for the strengthened spandrel beams attained the web's top surface which is attributed to the positive influence provided by embedded steel bars. The results obtained for spandrel beam strength were found to be in good agreement with the predicted by the PCA notes on the ACI code outcomes.