Seismic Analysis of Aging Reinforced Concrete Structures Considering Material Properties Obtained from Non-Destructive Tests Using STAAD.Pro

Abstract

A lot of Aging Reinforced Concrete (RC) structures in India are vulnerable to seismic hazards, as they are aging structures and most of them were built before the enactment of modern seismic design code and do not have any analytical model which accurately presents progressive degradation of concrete material properties in them. This study proposes an integrated approach for seismic performance assessment of an existing G+4 RC frame building in Bhopal city of Madhya Pradesh, which is located in the seismic zone II under IS 1893:2016, where the in-situ material property of the building has been characterized using Schmidt Rebound Hammer (non-destructive test), which is directly incorporated in STAAD.Pro finite-element models. The NDT campaign has shown that the compressive strength of the column concrete (18.72 N/mm²) and beam concrete (17.80 N/mm²) are around 25–29% less than the nominal M-25 design strength, thus establishing the material deterioration. The two structural configurations were considered, namely, existing as-built structure and the retrofitted structure with diagonal strut elements and additional column supports, with response-spectrum loading as specified in IS 1893:2016.Seismic analyses were carried out for the two structural configurations: as-built (existing) structure and retrofitted structure with diagonal strut elements and additional column supports for response-spectrum loading as given in IS 1893:2016. The maximum bending moment reduced by 37.04%, maximum shear force reduced by 35.45% and maximum axial force reduced by 8.40% through the retrofit strategy. In the X direction, Storey-level lateral displacements decreased by 19-62% and in the Z direction by 15-56%, with all the post-retrofit values meeting IS 1893:2016 drift limits. The NDT-calibrated approach is also revealed to generate 9–14% increased structural demands over those generated by nominal-property models, indicating that the seismic risk in aging structures is underestimated by ignoring material degradation.

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