Title: Minimum Joint Depth for Moment Frames with High- Strength Materials

Author(s): H.-J. Lee, R. D. Lequesne, A. Lepage, J.-X. Lin, J.-C. Wang, and S. Y.-L. Yin

Publication: Structural Journal

Volume: 120

Issue: 1

Appears on pages(s): 225-239

Keywords: beam-column joint; bond; cyclic test; earthquake resistance; high-strength concrete; high-strength reinforcement; joint shear

DOI: 10.14359/51737141

Date: 1/1/2023

Abstract:
This paper reports results from four large-scale interior beam column connections without transverse beams or slabs tested under reversed cyclic displacements. The specimens, which included the first of interior beam-column connections constructed with Grade 100 (690) reinforcement with bar deformations similar to those available in U.S. practice, had Grade 60 or 100 (420 or 690) bars, 4 or 10 ksi (28 or 69 MPa) concrete, and varied column depthto-beam bar diameter ratios. The specimens all exhibited strengths greater than the nominal strength, retained at least 80% of their strength to drift ratios exceeding 5%, and exceeded ACI 374 acceptance criteria at a 3% drift ratio for components of special moment frames, demonstrating that well-detailed joints constructed with high-strength materials behave satisfactorily. The data add evidence that joints constructed with high-strength concrete exhibit less bond decay, and recommendations are made for accounting for this effect in design. Results from the specimen constructed with normal-strength materials, considered in the context of prior tests, suggest a need to increase the minimum joint depth for special moment frames. Considerable improvement in behavior associated with reduced bond damage within the joint is obtained from a 20% increase in the minimum column depth-to-beam bar diameter ratio required in ACI 318-19.