Structural Behavior of Reinforced Concrete Deep Beams with Longitudinal Holes

Abstract

Abstract Deep beams made of reinforced concrete with a hollow core feature longitudinal openings along the length of their span and have many advantages. The longitudinal openings in the hollow reinforced concrete beams reduce the quantity of concrete used, lowering dead loads and construction costs while allowing for a longer span. Additionally, these hollows are used to pass mechanical and electrical services. Due to the decreased CO2 emissions, concrete abatement aids in the sustainability process. The current study includes an experimental investigation of the structural behavior of hollow reinforced concrete deep beams. The experimental program included casting and testing sixteen reinforced concrete deep beams with dimensions of 1400 mm length, 150 mm width, and 320 mm total depth. The shear span is 375 mm and the clear span is 1060 mm. Fifteen of the samples had longitudinal hollows with a reference solid sample. The variables studied are the number of longitudinal hollows (one to three), the size of the hollows (25 mm to 50 mm), the depth of the hollow (76 mm to 200 mm), the geometric shape of the hollow (circular, rhombic, rectangular), and the inclination of the longitudinal hollow (0% to 8.86%) to their effects on the structural behavior of hollow reinforced concrete deep beams. Experimental results showed that the use of hollows with numbers from one to three reduces the first crack load for flexural by 17.33% to 22.66% and reduces the first crack load for diagonal by 10.71% to 14.28%, as well as the ultimate strength decreased between 8. 12% and 20.1%, and the use of hollows with diameters from 25 to 50 mm reduces the load of the first crack for flexural by 2.66% to 22.66%, and the load of the first crack for diagonal decreased by 2.14% to 14.28% as well as The ultimate IV strength decreased between 2.8% to 20.2%. When using hollows with depth variations from 76 mm to 200 mm, the first crack load for flexural is reduced by 17.33% to 1.33%, the first crack diagonal load is reduced by 10.71% to 1.42%, and the ultimate load strength is between 8. 12% to 13.4 %. In addition, the load of the first crack to flexural decreased by 2.67% to 8%, and the load of the first crack for diagonal decreased by 3.56% to 10%, as for the ultimate load resistance it decreased by 6.72% to 11.76% at using the longitudinal hollows of the circular, rhombic and rectangular shape, respectively. Also, the presence of hollow with a slope from 0% to 8.86% reduces the load of the first crack for flexural by 2.67% to 6.67% and reduces the load of the crack slit for diagonal by 3.57% to 7.14%, and the last decrease of the ultimate load resistance is reduced By 6.72% to 11.20%. It was reported that the stiffness factor decreased by 25.51to 56.22% when using one to three hollows, respectively, while the stiffness factor decreased by 8.45% to 56.22% when using hollows with a diameter of 25 mm to 50 mm respectively. While changing the depths of the hollow from 76 mm to 200 mm leads to a reduction in the stiffness factor of 25.51% to 21.72%, respectively. While a decrease of 18.95% to 30.55% was reported when using circular, rhombic, and rectangular hollows, respectively. A slope of 0% to 8.86% reduces the stiffness factor by 18.95% to 30%, respectively. Using hollow reinforced concrete deep beams will lower the weight of the raw materials to 13.8% % saving up to 13.8 % in costs. Furthermore, reduced the embedded energy and CO2 emission by about 13.82%.