RC Coupling Beams with High-Strength Steel Bars: Summary of Test Results

Abstract

The use of high-strength steel bars in reinforced concrete coupling beams is expected to reduce reinforcement congestion. A series of tests was conducted to investigate the effects of high-strength reinforcement on coupling beam behavior. This report summarizes the test program and test results.

Eleven large-scale coupling beam specimens were tested under fully reversed cyclic displacements of increasing magnitude. The main variables of the test program included: yield stress of the primary longitudinal reinforcement (Grade 80, Grade 100, and Grade 120 [550, 690, and 830]), span-to-depth (aspect) ratio (1.5, 2.5, and 3.5), and layout of the primary longitudinal reinforcement (diagonal [D] and parallel [P]). All beams had the same nominal concrete compressive strength (8,000 psi [55 MPa]) and cross-sectional dimensions (12 by 18 in. [305 by 457 mm]). Beams were designed for a target shear strength based on the upper limits specified in ACI 318-14. All transverse reinforcement was Grade 80 (550), except one specimen that had Grade 120 (830) transverse reinforcement.

The test program is documented by presenting the details of specimen construction, test setup, instrumentation, and loading protocol. Documentation of test results include material properties and cyclic force-deformation response.