Experimental study of the mechanical properties and development length of large-diameter, high-strength headed deformed bars
Journal
Journal of Building Engineering
Journal Volume
129
Start Page
116954
ISSN
2352-7102
Date Issued
2026-07-01
Author(s)
Abstract
This study presents an experimental program to advance the application of large-diameter, high-strength headed deformed bars (SD 550W D43) with a diameter of 43 mm (No. 14) and a specified yield strength of 550 MPa in reinforced concrete structures. Material and mechanical qualification tests first confirmed that the SD 550W D43 headed bars and their couplers satisfy seismic performance requirements, demonstrating readiness for practical use. However, current provisions in ACI 318-25 and AASHTO LRFD 2024 limit headed bar diameters to 36 mm (No. 11) for development-length design. To address this limitation, twenty-four large-scale pullout tests incorporating SD 550W D43 headed bars were conducted to examine the effects of concrete strength, embedment length, parallel tie reinforcement, and center-to-center bar spacing on anchorage behavior. Headed bar development length was subsequently evaluated based on the bar stress at concrete breakout failure. The results indicate that both codes provide conservative predictions, with ACI exhibiting higher accuracy and AASHTO greater conservatism for SD 550W D43 headed bars. These trends were further confirmed using a compiled database of ninety tests from the present study and the literature, including headed bars with diameters of 43 and 57 mm and specified yield strengths of 550 and 830 MPa, supporting the potential extension of current provisions to SD 550W D43 headed bars. In addition, the test results provide evidence that reducing the center-to-center bar spacing to 2.5 bar diameters, below the code minimum of 3 bar diameters, may be feasible for the development-length design of SD 550W D43 (No. 14) headed bars when a vertically staggered head configuration is employed.
Subjects
Anchorage behavior
Development length
Headed bars
High-strength steel bars
Large-diameter
Publisher
Elsevier BV
Type
journal article