Slenderness effect on the behavior of composite RC columns under eccentric loads

Abstract

The structural performance of reinforced concrete (RC) columns plays a pivotal role in ensuring the safety and stability of buildings and infrastructure. In structural engineering, the quest for optimizing the design and behavior of RC columns has been a persistent pursuit. This research is focused on the columns having a “large” height that the secondary bending moments induced will affect the behavior of the RC column element. Therefore, one critical aspect that has garnered considerable attention is the influence of slenderness on the behavior of these columns, particularly when subjected to eccentric loading. As structures become taller and larger, slenderness is valuable to meet the demands of modern architectural design and urbanization, and understanding how slenderness affects the response of composite RC columns becomes increasingly vital. This study is focused on the strength of composite RC slender columns under eccentric loading. As such, it aims to contribute valuable insights to structural engineering, ultimately enhancing our ability to design resilient and efficient structural systems in a world where tall and slender buildings continue to shape our urban landscapes. Due to its numerous benefits, the concrete-steel composite column with a partially enclosed or full steel section encasement is currently more attractive to people than the reinforced concrete column. Strengthening RC columns by steel channel cross-section embedded in the column will contribute to the column stiffness for ultimate strength capacity and decrease the lateral deformation. Twelve RC columns were tested under eccentric loading, a rectangular cross-section of (150×200) mm. Six have a steel structural channel embedded in the cross-section, while the rest of the RC columns have the same cross-section properties but without a steel channel inside. The improvement in column capacity was (65 to 74)% for columns under moderate eccentricity axial loading and (35 to 50)% for columns under large eccentricity axial loading. Also, the improvement in column stiffness for the lateral deflection was (142 to 69)% for columns under moderate eccentricity axial loading and 84% to 87% for columns under large eccentricity axial loading.

Keywords

• reinforced concrete columns
• eccentric loading
• slenderness effect
• composite cross sections
• stability analysis