Minimum longitudinal reinforcement in rectangular and flanged reinforced concrete walls

Abstract

The amount of longitudinal steel in reinforced concrete walls is a key point in the damage distribution along the wall, although it is usually associated mainly with the prevention of temperature and shrinkage problems. A recent earthquake in New Zealand pointed out its relevance after the observation of a localized failure mode found in walls due to insufficient longitudinal steel reinforcement. Low amounts of longitudinal steel reinforcement prevent the correct distribution of the damage and can even lead to an early fracture of the reinforcement. The following study analyzes walls with different sections, such as T, L, and C-shaped walls, among others, subjected to pushover analysis, where the amount of longitudinal boundary reinforcement is varied, using values close to the minimum provided by ACI 318-19 code. The main parameter under analysis was the strain at the boundaries, revealing different behavior depending on the amount of boundary steel. When using steel amounts less than the minimum provided by the code, a greater growth for the tensile strain is observed, which in turn localizes the damage in a few zones along the wall height at low drift levels. This is overcome when using the recommended minimum steel amount. In addition, regarding the strength-to-cracking moment ratio (Mn/Mcr), although related to the growth of tensile strains, there is no specific value that can be recommended for all wall cross-sections.