The Effect of Longitudinal Hollows on the Carbon Footprint and Economic Behavior of RC Deep Beams

Introduction/ Objective
This study investigates the environmental and economic impact of using longitudinal hollows in RC deep beams, identifying the optimal hollow configuration based on weight reduction compared to peak load.

Methods
Sixteen deep beams were cast and tested, fifteen of which contained longitudinal hollows, along with a control beam. The deep beams were divided into five groups to study the effects of the number and depth of hollows, the geometric shape of the hollows, the diameter of the hollows, and the slope of the hollows.

Results
The results illustrated that using longitudinal hollows decreases the peak load of the beams by 2.8% to 20.1%, leads to a reduction in weight of 3.56% to 12.35%, reduces CO$_2$ emissions by 3.82% to 13.82%, and decreases embodied energy consumption by 3.48% to 13.80%.

Discussion
Economic analysis indicates that the construction costs of the deep beams are reduced by 3.81% to 13.71% compared to the control beam. Moreover, the behavior of beams with fewer hollows was better, and the smaller hollow diameters resulted in improved peak load capacity. The deep beam with a circular hollow section performed better than other shapes, especially when centered and without a slope, as a slope reduces its peak load capacity.
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The construction cost of the deep beams is reduced by 3.81% to 13.71% compared to the control beam. Moreover, the behavior of beams with fewer hollows was better, and the smaller hollow diameters resulted in improved peak load capacity. The deep beam with a circular hollow section performed better than other shapes, especially when centered and without a slope, as a slope reduces its peak load capacity.

Conclusion
Using longitudinal hollows in RC deep beams presents a viable alternative for reducing environmental impact, as well as lowering the cost and waste of raw materials used in their construction, while maintaining satisfactory structural performance, especially for beams with small hollow diameters.