Shear critical R/C columns under increasing axial load

Structural elements in old reinforced concrete (R/C) frame buildings are often prone to shear or flexure-shear failure, which can eventually lead to loss of axial load capacity of vertical elements and initiate vertical progressive collapse of a building. An experimental investigation of shear and flexure-shear critical R/C elements subjected to increasing axial load is reported herein. The focus is on the effect of vertical load redistribution from axially failing columns on the non-linear (pre- and post-peak) response of neighboring shear-dominated members. The test results along with an analysis of the recorded deformation, strength, stiffness and energy dissipation characteristics shed light on the performance of sub-standard columns under constant and increasing axial load subsequent, or just prior, to failing in shear, thus providing useful insights into the assessment of existing R/C structures.