Abstract
Recent, light earthquakes induced by the extraction of gas in the north of the Netherlands have been linked to light, mostly aesthetic damage of the traditional masonry structures in the region; this is also connected to economic losses and societal unrest. To be able to accurately assess the light damage, detailed finite element models are necessary and need to include realistic soil movement, wave propagation, and soil-structure interaction boundaries. Moreover, the minute deformation of the soil, including the rocking and translational components of seismic ground motion, has shown to be influential to light damage. Consequently, this study has pursued the definition of efficient soil-structure interaction boundaries to implement in finite element models of buildings.A methodology, following the sub-structure method for the seismic Soil-Structure-Interaction (SSI) is defined and presented. The soil-structure-system is divided into three sub-systems: the far-field soil, the near-field soil and the superstructure. First, a 3 km deep and 8 km wide, plane-strain model of the soil is employed to study the behaviour of the soil at the surface due to deep, simplified seismic events. The soil model is linear-elastic since only light seismic excitations are considered. Next, a smaller, 30 × 300 m (shallow) soil model with a building on top, is given boundary elements calibrated to replicate the behaviour observed at the surface in the larger model. Finally, 2D models of masonry façades set on the intermediate soil model are used to reduce the soil-structure interaction to representative interface elements. The models are matched in terms of dynamic behaviour, strains, cracking, and displacements, and the behaviour is compared to existing ground motion data for the Zeerijp and Westerwijtwerd earthquakes. It is demonstrated that the equivalent interface allows efficient modelling of seismic excitations considering a detailed soil-structure interaction for complex, smeared non-linear, time-history analyses of wall models to assess (light) damage in probabilistic studies. Models with this equivalent interface show greater damage than comparison models without it.
Highlights
The interaction of soil and structure can be paramount when assessing the impact of vibrations on a structure
Light earthquakes induced by the extraction of gas in the north of the Netherlands have been linked to light, mostly aesthetic damage of the traditional masonry structures in the region; this is connected to economic losses and societal unrest
The methodology presented was developed to assess the sensitive response of masonry structures and their potential damage due to light seismic events, taking into account the soil-structure-interaction in a straightforward manner
Summary
The interaction of soil and structure can be paramount when assessing the impact of vibrations on a structure. The assessment of minor or light damage, in this context identified as damage state one (DS1) [31], requires the use of complex models so as to include as many relevant effects as possible These models can be elaborated using the finite element method [32,33], where both the structure and the soil are depicted using small cells or elements that can simulate the strain or stress of the various materials in the model and its development during a vibration time series. Appropriate boundary conditions are selected for the case of the soil models, so that outward waves are absorbed in the boundaries, where necessary This decoupling of the structural non-linear finite element model from the soil model, allows the study of extensive variations of the structure, such as different material models and parameters or differing geometries. These variations are essential when assessing a wide range of structures or performing probabilistic estimations of light damage
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