Large reinforced-concrete deep beams with web openings: test and strut-and-tie results

This paper investigates the behaviour and shear strength of large reinforced-concrete deep beams with web openings. A total of three pierced deep beams and a solid beam with compressive strengths in the range 35 MPa ≤ f′_c ≤ 44 MPa are reported, which were tested to failure under two-point symmetric top loading to determine their ultimate shear strengths. All the four beams had an overall depth of 2000 mm, an overall length of 4000 mm and a web thickness of 220 mm, which were probably the largest pierced deep beam specimens tested so far. They represent very valuable test data for verifications of code predictions or strut-and-tie results. Web openings of the same size were located in the shear span of three pierced beams. The only difference among the three pierced beams was that their shear spans ranged from 500 to 900 mm. Test results show that a web opening can reduce the ultimate strength of a large deep beam significantly, if the web opening intersects the force path between the load point and the support. The observed crack patterns clearly illustrate a strut-and-tie system in large pierced deep beams. An improved strut-and-tie approach is also presented in the current paper to predict the ultimate shear strength.