Effects of the Soil-Foundation-Structure Interaction on the Component Demand Modifier Factor of Concrete Gravity Beams based on ASCE 41-06 Standard

The aim of the present paper is to evaluate the influence of the Soil- Foundation- Structure Interaction (SFSI) effects on the component demand modifier factor of concrete gravity beams based on ASCE 41-06 standard. To this end, the beam on the nonlinear Winkler foundation approach is employed which is a simple and efficient method. At first, four sets of 3-, 6-, 10- and 15-storey concrete momentresisting frames founded on soft, medium and hard soils are designed and analysed for the case of fixed-base and flexible-base assumptions. A comparison is then made between the results of the nonlinear response history analysis of each frame in the flexible-base and fixed-base conditions with the response based on the equivalent linear static approach. The findings show that the equivalent linear static approach loads for gravity beams, which are controlled by deformation actions, can lead to non-conservative predictions of seismic demand. Finally, a modified load combination is proposed to be used in the equivalent linear static approach to avoid this imperfection.