Pammi Raghu Nandan Vyas, supervised by Prof. Pradeep Kumar R received his doctorate in Civil Engineering (CE). Here’s a summary of his research work on Framework for Improving the Seismic Behaviour of Stepped RC Buildings Resting on Hill Slopes:
In the past decade, India witnessed a surge in concentrated urban growth to manifolds, and the same trend is visible in regions on hilly terrain like the North Eastern region (NER). In addition, urban growth has increased the construction of multi-story reinforced concrete buildings on mild-to-steep slopes with weak soil underneath. However, the region noticed a considerable number of earthquakes in the past. The recorded ground motion data reveals that though the observed Peak Ground Accelerations (PGAs) are on par with the design PGAs, the damages reported are brittle, which is not in accordance with the design philosophy. Reasons for such unanticipated damages can be attributed to landslides, slope instability, liquefaction, etc. Existing guidelines tend to define and limit irregularities from various site, architectural, structural, and construction practices. Though definitions are violated, limits imposed by existing guidelines are not stringent. In this context, there is a need to identify parameters through which limits can be imposed. In addition, the lack of design guidelines for buildings on hilly terrain also plays a key role in affecting the anticipated behavior. Lack of guidelines leads to the blindfolded application of assumptions that are valid for flat land buildings, ignoring the critical issues. The existing guidelines tend to treat the problem of building on slopes as a force control problem, hence the suggestion of considering the total height of the building as short column height in calculating the natural period of the building. The actual problem of building on slopes is the concentration of shear force near the uphill column due to the short column effect, for which there are no suggestions. In this context, the relevance of the natural period (T) calculation mentioned in IS 1893:2016 from the perspective of building behavior is verified. Current work identifies critical issues that affect the sloped building. A parametric study is formulated by varying critical parameters like building footprint, the height of the building, and the slope. A study is formulated by varying the critical parameters that affect the system’s response, such as building footprint, story height, and slope angle. A total of 40 models designed according to the Indian standard codes of practice are used to develop correlation matrices for design forces, dynamic characteristics, and dynamic response of the buildings. It is observed that a steady increase in the slenderness ratio has a positive effect in terms of flexural stress distribution, modal properties, and deformations of the building. Similarly, a negative correlation of flexural forces is observed with the aspect ratio. Increasing the aspect ratio increases shear stresses in uphill columns and axial stresses in beams corresponding to uphill columns, which leads to story mechanism. Further, nonlinear analysis is performed using a reference structure to detect the failure pattern. It is observed that the predominant failure is due to shear in all uphill columns, followed by the yielding of an immediate story for spectral acceleration values as low as 0.2g. Finally, a framework is proposed to (I) restrict the shear failure and (II) improve the base shear distribution, flexural deformations, and modal properties along and across the valley, respectively.
November 2023