Experimental and Numerical Study of UHPFRC Continuous Deep Beams with Openings

To study the performance of UHPFRC continuous deep beams with openings, experimental and numerical investigations have been carried out. The test program included seven continuous deep beams with openings, in addition to one similar solid beam. The variables were the ratio of transverse reinforcement and the position, height, and width of the opening. The results showed that the failure mode of UHPFRC two-span continuous deep beams depends mainly on the position and size of the opening in the shear span. The shear failure occurs in the diagonal strut between the support and the applied force through the opening edges. The maximum spacing between stirrups (s(v)(,max)) of ACI 318-2019 was not suitable for UHPFRC. Providing stirrups with spacing 129% greater than s(v)(,max) of ACI 318-2019 had a slight effect on the failure load. Web openings of 20% of beam height reduced the failure load by 31.6% to 43.0% compared with a similar solid beam. For specimens with the same opening height and position, increasing the width of the opening by about 75% more than that of a similar beam reduced the failure load by about 27.8%. The proposed 3-D numerical model successfully predicted the failure load and performance of UHPFRC continuous deep beams.