Design of non-prismatic RC beams using strut-and-tie models

Abstract

This study deals with the application of the strut-and-tie models in the analysis and design of non-prismatic reinforced concrete beams. Seven beams were designed, fabricated and tested to failure. Test results showed that the ultimate loads exceeded the design loads for all beams. Non-prismatic beams with a recess through the web performed satisfactorily, compared to beams with equivalent transverse rectangular openings. For non-prismatic beams with a recess at the bottom, an increase in the recess width resulted in a decrease in the stiffness and an increase in the beam deflection. Non-prismatic beams with a recess in the compression zone performed better with regards to cracking but not deflection, compared to beams with a recess in the tensile zone. Also, beams strengthened with carbon fibre-reinforced polymer (FRP) plates performed satisfactory with regard to strength; however, the deflection and crack widths increased rapidly thereafter, leading to a sudden and non-ductile failure of the beam.