In reinforced concrete terminology, what do 'longitudinal bars' refer to?

Longitudinal bars in reinforced concrete are essential components of the structural design, as they primarily refer to the main reinforcing bars that run parallel to the length of a structural element, such as beams or slabs. Their primary function is to absorb tensile stresses that occur when the element is subjected to bending forces.

These bars are strategically placed along the length of the concrete to enhance the composite action of the concrete and steel. Concrete is strong in compression but weak in tension, meaning that when the concrete experiences bending, the longitudinal bars help resist the tensile forces, preventing cracking and ensuring the overall integrity of the structure.

In the context of reinforced concrete, it is critical to understand the role of these longitudinal bars in the overall load-bearing capacity and performance of the structural element. The other options do not accurately describe the function or placement of longitudinal bars in reinforced concrete. For example, vertical members used for decoration do not provide structural support, short bars for temporary support are typically used in formwork rather than in the final design, and horizontal members for stability pertain more to structural framework than the definition of longitudinal bars.