A PROPOSED TECHNIQUE TO ESTIMATE AN ADEQUATE SEISMIC GAP IN MID-RISE BUILDINGS

Abstract

In order to mitigate pounding effects, international seismic provisions and standards have proposed using a minimum separation distance between adjacent buildings. However, such standards have considered only peak floor drifts to determine seismic gap distance, but not the relative movement between these buildings. This may lead to either excessive gap distance between adjacent buildings in many cases with high fundamental period ratios, or insufficient distance in cases with low fundamental period ratios. This study aims to propose a more accurate and economic technique to determine seismic gap separation distance compared to techniques mentioned in international seismic provisions. To address the above, twenty-eight RC buildings; and three stiff structures; are analytically modeled and analyzed under the action of four earthquake records. More than a hundred pounding scenarios are generated, and then numerically studied to calculate the required minimum separation distance. It is worth mentioning that the analysis are performed according to some assumptions. It is assumed that considering the foundation system is isolated footing, therefore all columns shall be hinged-base constraints. The structures are designed to withstand gravity and seismic loads however, some ECP-201 limitations are not considered which are: section [8-7-1-3] which refers to the effective inertia of structural elements due to cracks but the SeismoStruct software considers the reduction of stiffness due to non-linearity of the materials, section [8-7-3-4] which recommends that when using non-linear time history analysis, and section [8-8-3-2] which refers to the serviceability limitations of inter-story drifts. Finally, asymmetric pounding is studied considering forty-two asymmetric pounding scenarios with seven eccentricities under the action of two different earthquake records.

CONCLUSION 1. The analytical fundamental period of bare RC frame buildings may reach up to three times the values calculated by the European standards. This period is expected to be reduced when infill walls are implemented in modeling.

2. Yield and ultimate roof drifts of RC buildings designed to fulfill the European standard requirements are around 1.07 and 2.67 percentage of building height, respectively. These values are expected to be reduced for a higher percentage of infill walls. In addition, the stiffness of RC buildings is directly proportional to their weight and inversely proportional to their height.

3. Roof drift ratios are around 1.65%, 1.05%, and 0.35% for collapse prevention,