Performance Evaluation of Bi Diaphragm Haunch Retrofit for RC Beam Column Joints

Abstract

In the realm of structural forensics, the seismic vulnerability of Reinforced Concrete (RC) framed structures, especially those with limited ductility, hinges significantly on resilience of the exterior column-beam joints. Despite extensive research, the assessment of realistic shear strength in these joints remains a contentious subject. Surprisingly, the valuable insights gleaned from post-seismic damage surveys often languish unheeded in professional practice. The prevalence of poorly detailed joints in RC buildings persists, leaving a majority of structures vulnerable to seismic or cyclonic forces. newlineThe present research endeavours to address the gaps in understanding and practice by delving into the intricate facets of exterior joints. Emphasis is placed on unravelling the complexities surrounding shear strength assessment. The overarching goal is to provide an actionable framework for strengthening deficient buildings, thereby fostering resilience in the face of seismic and cyclonic challenges. newlineThe present investigation unfolds in distinct phases including preliminary investigations, examination of as-built sub-assemblies, innovative strengthening solutions, performance assessment of strengthened specimens, and a real life application. newlineCritical assessment of joint shear capacity models from various National Codes and empirical research, reveals an overestimation trend. A refined semi-analytical model is proposed, yielding a remarkable prediction accuracy of 13%, the highest amongst available models. newlineTwelve scaled-down sub-assemblies, mirroring site conditions in sub-urban India are manufactured. An indigenous test apparatus is crafted from local resources, due to the unavailability of a suitable equipment. Reversed cyclic pseudo-static displacement-controlled loading cycles on four sub-assemblies unveil failure modes and highlight the need for strengthening. Results of micro- and macro-modelling, using FEM analysis software, are validated by experimental results, providing useful parametric evaluations. newlineExp