عنوان مقاله [English]
Torsion is recognized as one of the main failure modes of buildings in preceding earthquakes. Studies on the tunnel-form buildings show the primacy of torsional modes to translational modes in many models. This specification is unique to torsionally flexible buildings that eccentricity of mass, stiffness and torsional component of earthquake lead to an increase in both isplacement and force responses. There is much research surrounding asymmetric buildings. However, there are fewer studies reported on asymmetric tunnel form buildings.Despite its widespread use, there is not enough information regarding this new slab wall reinforced concrete tunnel-form system. Thus, identification and evaluation of performance of these buildings based on reasonable numerical results, including factors affecting response, are highly regarded by seismic codes.In this study, the sensitivity of tunnel-form buildings with 5 and 10 stories to in-plan one-way mass eccentricity is studied. Mass eccentricities are assumed to be 5\%, 10\%, 15\%, and 20\% of the plan dimension. The performance level of these buildings, including different mass eccentricities in design earthquake, is determined by time history analysis with one directional earthquake excitation as well as push-over analysis. The effect of spandrels on seismic behavior of the buildings is investigated as well. Moreover, fragility curves are determined for studied models by incremental dynamic analysis (IDA). The results show that tunnel-form buildings have high capacity and adequate
seismic performance under effect of torsion due to asymmetric distribution of mass in plan, in which both 5- and 10-storey tunnel-form buildings stay in the immediate occupancy performance level in design earthquake (475 years return period). It is also demonstrated that damage in the spandrels does not have considerable effect on overall seismic behavior of the buildings. Additionally, results indicate that mass center is not a reliable control point for displacement provisions, especially in high-rise buildings.