Seismic response of exterior RC wide beam-narrow column joints: Earthquake-resistant versus as-built joints

This paper presents the results of a two-part experimental investigation undertaken for evaluating the seismic behavior of exterior wide beam-narrow column connections of the type constructed in Middle Eastern region. In the first part of the investigation, two full-scale gravity - load designed or “as-built” joints were tested under quasi-static cyclic loading. The joints failed prematurely by developing joint shear failure at considerably low drift ratios between 1.0% and 1.5% and therefore their resistance against lateral earthquake load was deemed insignificant. In the second part of the investigation, guided by the test results of the as-built joints, two additional “earthquake-resistant” joints were tested. The corresponding joints were designed assuming gravity load similar to the “as-built” joints, except that their reinforcing detailing were slightly improved particularly by adding transverse steel reinforcement within the joint core and increasing the development lengths of the beam reinforcement, partly in accordance with the recommendations of ACI 318-08 and ACI-ASCE 352-02. Despite violating the requirements of joint dimensions set forth in ACI 318-08, the “earthquake-resistant” joints performed considerably better than the “as-built” joints by preventing or delaying joint shear failure; developing higher lateral load, deformation, and energy absorption and dissipation capacities; and displaying stable overall hysteretic response.