Seismic performance of double-inclined beam-column joints and adoption of engineering cementitious composites for performance remediation

The demand for architectural aesthetics leads to inclined columns in modern constructions, resulting in inclined beam-column joints (BCJs). Although seismic performance and shear strength of BCJs have been widely reported, those specifically for double-inclined BCJs remain limited. In this work, 5 BCJs were tested to reveal the influence of the column double-inclination on their seismic performance and shear strength, as well as the feasibility of adopting engineered cementitious composites (ECC) for performance remediation and joint stirrup reduction. After that, finite element analysis was performed to study the effects of key parameters on the shear strengths of double-inclined ECC BCJs. Results indicated that the column inclination induced initial stress on the column and joint core under axial load, accelerating crack development and leading to 10% lower ductility, 9% less energy dissipation and 15% lower shear strength. The adoption of ECC effectively restrained damage development, leading to loading and deformation capacity substantially enhanced by 50% and 35%. Furthermore, the joint stirrups can be eliminated without significantly affecting the behavior of double-inclined BCJs. As revealed by finite element analysis, the lower joint shear strength of double-inclined BCJs was mainly attributed to the uneven width of concrete strut, resulting in different shear strengths in opposite directions. Moreover, the detrimental effects of column inclination were amplified at higher inclination, while greater column axial loads contributed to higher shear strength of double-inclined ECC BCJs. The ECC was recommended to extend into the beam and column by 150% of sectional height.