Title:
Effect of Reinforcement Detailing on Cyclic Behavior of Reinforced Concrete Column-Footing Connections
Author(s):
M.-Y. Cheng, P.-J. Chen, C.-H. Chen, B. L. Worsfold, G. J. Parra-Montesinos, and J. P. Moehle
Publication:
Structural Journal
Volume:
122
Issue:
4
Appears on pages(s):
19-34
Keywords:
column-footing connection; head; hook; strength; transverse reinforcement
DOI:
10.14359/51746671
Date:
7/1/2025
Abstract:
Recent tests showed that anchorage failure could be the primary
mechanism that limits the strength and deformation capacity of
column-footing connections. An experimental program consisting
of the reversed cyclic load testing of 16 approximately full-scale
column-footing subassemblages was thus conducted to investigate
the effect of various reinforcement details on connection strength,
drift capacity, and failure mode. The main parameters evaluated
were type of anchorage for the column longitudinal bars (either
hooks or heads), extension of column transverse reinforcement into
the footing, and longitudinal and transverse reinforcement ratios
in the footing. Test results indicate that even when column longitudinal reinforcement extends into the joint with a development
length in accordance with ACI 318-19, a cone-shaped concrete
breakout failure may occur, limiting connection strength and deformation capacity. The use of transverse reinforcement in the connection over a region extending up to one footing effective depth away from each column face proved effective in preventing a concrete breakout failure. However, for the specimens with column headed bars, extensive concrete crushing adjacent to the bearing side of the heads and spalling beyond the back side of the heads led to
significant bar slip and “pinching” in the load versus drift hysteresis
loops at drift ratios greater than 3%. The use of U-shaped
bars in the joint between the column and the footing or slab, as
recommended in ACI 352R-02, led to improved behavior in terms
of strength and deformation capacity, although it did not prevent
the propagation of a cone-shaped failure surface outside the joint
region. Based on the test results, the basic concrete breakout
strength, Nb, corresponding to a 50% fractile, in combination with
a cracking factor ψc,N = 1.25, is recommended when using Section
17.6.2. of ACI 318-19 for calculation of concrete breakout strength
in connections similar to those tested in this investigation.