Buildings in central business district (CBD) of Yangon have been closely situated, very less or almost no gap. Moreover, due to the economic and construction development, many mid-rise buildings have been constructing in sub-urban area of Yangon. In Nov 2019, mid-rise buildings tilting and leaning problems, after slight earthquake of magnitude 4.1 Richter Scale with its epicenter near Yangon, have been reported in sub-urban areas. It highlighted the need of vulnerability assessment and importance of separation gap.
Two cases of adjacent RC building condition are considered in this analysis (Fig-1); case 1 (8-story next to 7-story) and case 2 (6-story next to 5-story building). Three different base conditions; fixed, SSI base (Vs 150 m/s) and SSI base (Vs 250 m/s), are considered under Northern Calif-03 earthquake event. Nonlinear time history analysis is carried out using the scaled ground motion that matched the target spectrum of Yangon.
The result shows that separation gap required to avoid pounding-induced damage seems to be affected by SSI. Soft soil case (Vs 150 m/s) exhibits the maximum displacement response for all building. In both adjacency cases, conventional fixed base analysis will underestimate the required clear distance between adjacent buildings and will lead to pounding during shaking. There is phase variance in displacement responses for different base conditions. Effect is prominent for 8-story building as shown in Fig-2. This may be due to the interaction effect between soil and foundation. Therefore, SSI effect should be accounted in estimating the behaviors of structures during earthquake. This study takes into account only one ground motion and it is planned to consider a large number of ground motions for general assessment in the future. Inventory of pounding potential building types can be a useful information for urban planning, limiting separation gap requirement and prioritization of retrofitting.
