Journal of Structural and Construction Engineering

Journal of Structural and Construction Engineering

Experimental investigation into the effect of hook orientation of longitudinal rebars in columns on the performance of column-foundation connections

Document Type : Original Article

Authors
mohammad hossein naserifard 1
Reza Morshed 2
abolfazl eslami hassanabadi 3
1 PhD candidate, civil Eng. department, Yazd university, Yazd,, Iran
2 Associate Professor, Civil Engineering Department, Yazd University, Yazd, Iran
3 Associate professor, Civil Eng. department, Yazd university, Yazd,, Iran
10.22065/jsce.2025.487159.3563
Abstract
In a structural building system, columns play a crucial role in transferring the forces exerted on the structure down to the foundation. Consequently, the method used to connect the columns to the foundation is vital, as it greatly influences the structural strength. Prior to the recent version of ACI 318, the typical approach for the hook orientation of column bars in the foundation was to bend at 90 degrees outward. However, in ACI 318-19, the requirement has shifted to a 90-degree bend towards the center of the column (inward). As a result, the 1399 edition of the 9th topic of the National Building Regulations now mandates that the hook orientation of the column reinforcing bars in the foundation be directed inward. Considering that previous studies have not examined the effect of hook orientation of the column reinforcements in the foundation, further research are needed to explore it. In this study, to assess the effect of hook orientation of the column bars (either inward or outward) on the performance of column-foundation connection, six specimens were built with identical dimensions and different percentages of longitudinal reinforcement in the columns. The results indicate that the load-carrying capacity of columns with longitudinal reinforcement bent inward exhibited a minor increase (ranging from 1 to 5%) in comparison to those with outward hooks. Where the column hook orientation of bars was directed inward toward the core, strength deterioration was postponed at greater drifts. This indicates that while the performance of the samples with an inward hooks is superior to those with an outward hooks, the difference was not significant to justify the code obligation for an inward orientation. Particularly, orienting the hook inward the column core at the column-foundation connections could come with difficulties in real field construction.
Keywords
Reinforced Concrete
Column
Root Bars
Rebar hook orientation
Column To Foundation joint

Subjects

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Journal of Structural and Construction Engineering
Volume 12, Issue 08 - Serial Number 97
November 2025
Pages 120-137

  • Receive Date 11 November 2024
  • Revise Date 16 January 2025
  • Accept Date 05 February 2025