Nowadays, 3D effect of considering the soil behavior under spread foundations is an important subject during the seismic analysis and design process of buildings with tall moment resisting frames. The main structural purpose of this importance is the additional bending moments of structural elements originating from differential settlements. In addition in a geotechnical point of view the different values of subgrade reaction modulus during the earthquake must be taken into account. Although the importance of such a 3D analysis is clear but it's usually neglected because of some calculative limitations of ordinary computers and usual numerical soft wares. In this paper, we will show a case study of 3D analysis of soil and structure together to achieve the realistic values of soil reaction modulus. The other main purpose of this study was to see if design forces of structural elements will change by assuming the soil layers or not. By considering the complete geometry of structure and the equivalent static loading of earthquake, the overall behavior of model will be discussed and the resulting bending moments in the structure will be illustrated. Subgrade reaction modulus (Ks) will be calculated by dividing the interface area of soil and foundation into separated zones and using the obtained values of displacement and pressure in each zone. Finally the Ks values will be illustrated and compared with the values obtained from the plate loading test results.
展开▼
