Seismic Study of Soil Structure Interaction Modelling Approaches

In this paper we study certain modelling techniques by which the concept of soil structure interaction can be simulated in engineering problems and become fruitful for modern construction methods. For practical examination, a baseline model is prepared and put in comparison with an isolated base model which conforms to a rigid bathtub model with spring arrangement. Soil flexibility is taken into consideration during modeling. These modelling techniques are analysed using response spectrum analysis to get the maximum response of seismic parameters like storey forces and spectral acceleration. The study showed that the isolated base model had a superior seismic response and may be used in a variety of engineering applications, such as the design of new infrastructure, such as structures for storing water or other types of sediment, geotechnical modelling. Keywords: Baseline Model, Storey Forces, Spectral Acceleration, Soil Flexibility Rigid Bathtub Model

Finite Element Method Analysis Applied to Different Foundations Structures Systems

In the conventional static analysis of building frames, the base is idealised on rigid supports and the building is subdivided into three parts namely, the superstructure, the foundation and the ground soil, before design. In real life situations, the soil underneath the building undergoes deformations which may alter the performance of the structure. In this paper, it is studied the effect of soil type and foundation type on the response of a building frame system with both fixed base and flexible base. The Winkler model of soil-structure interaction is adopted to study the influence of soil flexibility and foundation rigidity on a 4 storey RC building with a regular plan resting on three types of soils namely, the light peat marshy ground, wet clay and medium gravel with fine sand. Three types of foundations are considered in the study: isolated footings, tied foundation and the raft (with and without overhangs) foundations. Winkler model is developed using springs by Finite Element Method in SAP2000. The settlement, the bending moment, the shear force and the axial force are the parameters placed forth for the comparative study. Results obtained reveal an increase in the response of the structure with respect to the soil flexibility and foundation rigidity.

Effect of Soil Classification on Seismic Behavior of SMFs considering Soil-Structure Interaction and Near-Field Earthquakes

Seismic response of a structure is affected by its dynamic properties and soil flexibility does not have an impact on it when the bottom soil of foundation is supposedly frigid, and the soil flexibility is also ignored. Hence, utilizing the results obtained through fixed-base buildings can lead to having an insecure design. Being close to the source of an earthquake production causes the majority of earthquake’s energy to reach the structure as a long-period pulse. Therefore, near-field earthquakes produce many seismic needs so that they force the structure to dissipate output energy by relatively large displacements. Hence, in this paper, the seismic response of 5- and 8-story steel buildings equipped with special moment frames (SMFs) which have been designed based on type-II and III soils (according to the seismic code of Iran-Standard 2800) has been studied. The effects of soil-structure interaction and modeling of the panel zone were considered in all of the two structures. In order to model radiation damping and prevent the reflection of outward propagating dilatational and shear waves back into the model, the vertical and horizontal Lysmer–Kuhlemeyer dashpots as seen in the figures are adopted in the free-field boundary of soil. The selected near- and far-field records were used in the nonlinear time-history analysis, and structure response was compared in both states. The results obtained from the analysis showed that the values for the shear force, displacement, column axial force, and column moment force on type-III soil are greater than the corresponding values on type-II soil; however, it cannot be discussed for drift in general.