Seismic behavior of concentric and eccentric New-RCS through-beam joints

Composite frame structures with high-strength reinforced concrete columns (New RC) and steel beams (S) are called New RCS systems. The key to the development of the New RCS system is the development of beam-column joint details. Thus, in this study, four large-scale beam-column subassembly specimens: three interior joint specimens, and one exterior joint specimen, were designed and cyclically tested to investigate the seismic behavior of the New RCS joint. Two tested interior joint specimens had beams framing to the New RC column with eccentricities, while the other specimens had concentrically framing beams. All the specimens exhibited stable and ductile hysteretic responses. The experimental study showed that the proposed joint details could develop the desirable beam flexural yielding while limiting joint damage for drift levels up to 6%. However, at very high drift levels (≥ 6%), the overstrength of the highly compact cross-section of the steel beams of the test specimens resulted in significant joint damage for the interior joint specimens. The experimental study demonstrated that the proposed New RCS joints were able to accommodate eccentrically framing beams without hampering the seismic response.