Numerical Simulation

Soil-structure interaction may be critical for the design against static and seismic loading of a variety of engineering systems, including pile groups and piled rafts, shallow foundations, retaining systems and underground structures and quay walls. A variety of analysis methods have been developed and validated for the investigation of key factors governing the response of such systems. Static and dynamic loading is analyzed employing state-of-the-art software, simulating material (soil and structure) and geometric (detachment, uplifting, sliding, and P-Δ effects) nonlinearities.

Numerical analysis of shallow foundations is performed either under plane strain conditions or using fully 3-dimensional simulation. The response of such foundations has been investigated under a plethora of possible loading types including earthquake, fault outcropping, differential displacement, landsliding and machine vibrations. A simplified constitutive model has been recently developed and incorporated in Finite Elements analysis code which allows for the realistic simulation of shallow foundations, accurately capturing the effect of fully non-linear phenomena such as footing detachment (uplift) or slippage and soil yielding.

For piled foundations, problems are analyzed either through Winkler-spring and P-y based approaches, or through fully 3D finite element analyses. Seismic response is simulated through nonlinear dynamic time history analysis, utilizing advanced soil constitutive models, calibrated and validated through published experimental results. Special interface elements may be utilized to realistically simulate pile slippage and/or pinching. The structure is incorporated in the analysis, modelled in a realistically simplified manner. This way, inertial loading form the superstructure is combined with kinematic pile loading, allowing for a complete assessment of pile distress to be used in design.

In the case of retaining structures, the problem is typically analyzed in 2D, assuming plane-strain conditions. State-of-the-art finite element analysis software is utilized to model in detail the sequence of construction. Seismic response is analyzed through nonlinear dynamic time history analysis, utilizing extensively validated soil constitutive models. LSM has a vast experience in the analysis of almost any type of retaining structure, ranging from simple gravity structures, to anchored walls, and to shaft-type systems. Similar analysis methods are employed for analysis and design of tunnels and underground structures.

Significant research has been conducted in the field of soil dynamics and site effects. Due to the model dimensions, such analyses are typically performed under plane strain conditions. Optimizing the mesh discretization and using appropriate constitutive modelling of the soil response enables capturing all possible waveforms and explaining their propagation. Analyses are performed integrating fully inelastic soil response on the investigation of valley effects. Recently performed soil-structure-interaction analyses have highlighted the potentially detrimental role of the parasitic vertical acceleration (developed in alluvial valleys) for overlying structures and the role of incoherent ground motion.