Impact torsional behavior and strengthening of reinforced concrete spandrel beams

The exterior L-shaped spandrel beams frequently experience various forms of eccentric loading that induce torsional stress when used in parking structures. The purpose of the study was to investigate the effect of strengthening techniques on the impact responses and torsional behavior of reinforced concrete slender and compact spandrel beams subjected to eccentric impact loads. The study focused on two strengthening systems: the Embedded Through-Section (ETS) technique and the application of carbon fiber-reinforced polymer (CFRP) sheets. Six L-shaped RC spandrel beams were exposed to concentrated impact loading. The impact force was generated by dropping a steel mass of 26.5 kg onto the ledge top surface at the mid-span of the specimens from two different heights: 1.0 m and 2.0 m. According to test data, the increase in the impact force attained 46% and 14.5% as compared to their values before strengthening for the strengthened specimens with CFRP sheets and the ETS method, respectively. Meanwhile, compared to the control specimens, the ETS strengthening technique achieved more torsional capability. The embedded steel bars offered more residual static strength for slender and compact spandrel beams of 23.5% and 27.5%, respectively. It is recommended that this study be expanded to include the effects of other dynamic loadings (e.g., explosions, harmonics, etc.). This study confirms that structural stiffness affects impact forces; the stiffer the structure, the greater the impact forces, since the increase in the impact force attained 46% for specimens with CFRP sheets.