A simplified approach to account for directionality effects on 2D dynamic soil-structure interaction analysis

Abstract

In this study, a simplified approach to account for directionality effects on twodimensional (2D) dynamic soil-structure interaction analyses (DSSI) is proposed. When an earthquake is recorded, the direction with the maximum intensities rarely corresponds with the orientation of accelerometers and, therefore, the maximum response of a system generally takes place at an intermediate unknown orientation. A straightforward approach is to perform DSSI analyses with a number of linear combinations of the horizontal as-recorded components to obtain the peak response parameters for each orientation. Nevertheless, DSSI analyses are computationally expensive especially when the nonlinear behavior of the soil is considered. Here, three hypotheses are evaluated for predicting the angle that generates the maximum response of a building. By determining this angle in advance, only one DSSI analysis would be required to obtain the maximum response of a system for a given earthquake. Here, a particular case is analyzed where a ground motion recorded at a rock outcrop is used to derive the input motion for a finite element model, including a soil deposit and a surface structure. A series of 2D dynamic finite element analyses were performed to assess the proposed approach where input motions were obtained from the linear combination of the horizontal as-recorded components of the 1976 Friuli earthquake. The obtained results show the importance of considering directionality effects in DSSI analyses. The maximum response of the system was reasonably captured with the orientation obtained through the simplified approach.