Francesco Castelli

Numerical analysis of kinematic soil—pile interaction

In the present study, the response of singles pile to kinematic seismic loading is investigated using the computer program SAP2000@. The objectives of the study are: (1) to develop a numerical model that can realistically simulate kinematic soil‐structure interaction for piles accounting for discontinuity conditions at the pile‐soil interface, energy dissipation and wave propagation; (2) to use the model for evaluating kinematic interaction effects on pile response as function of input ground motion; and (3) to present a case study in which theoretical predictions are compared with results obtained from other formulations. To evaluate the effects of kinematic loading, the responses of both the free‐field soil (with no piles) and the pile were compared. Time history and static pushover analyses were conducted to estimate the displacement and kinematic pile bending under seismic loadings.

Experimental analysis of waste compressibility

Mechanical behavior of the waste body controls many aspects of landfill lining system design and performance, including stability issues and integrity of the geosynthetic components. The compression behavior of municipal waste is influenced by the properties of the individual constituents and on their composition, and particularly characterized by large amounts of settlements which are time- dependant. Mechanical properties of waste are often described by application of soil mechanics principles so that conventional shear or compression parameters can be determined. But data from literature are scarce and show large variations. In this paper test results on the determination of waste compressibility are reported and analyzed.

Seismic Bearing Capacity of Shallow Foundations

The seismic risk mitigation is one of the greatest challenges of the Civil Engineering and an important contribution toward this challenge can be given by the Geotechnical Earthquake Engineering. Lesson learned by recent destructive earthquakes (January 2010 Port-au-Prince region of Haiti and March 2011 Tohoku Japan), confirms that local soil conditions can play a significant role on earthquake ground motions. Earthquake-induced damage in Port-au-Prince was devastating and widespread. Yet, there were clearly areas of the city where little to no damage occurred, and areas of the city where an overwhelming majority of the buildings were severely damaged or destroyed. These types of damage patterns are common in earthquakes, and a wide number of factors need to be considered in order to conclusively piece together the causes. For a given earthquake, these factors include, but are not limited to: (a) relative distance from the fault rupture plane, (b) construction type and quality, (c) local soil conditions (i.e. strength/stiffness of the soil foundation, depth to bedrock, impedance contrasts, geology), (d) topography (topographic and basin effects), and (e) near fault effects (rupture directivity, fling step, hanging wall effects, polarity effects, etc.). Often several of these factors work together and it can be difficult to identify the primary cause of damage. Design of foundations in seismic areas needs special considerations compared to the static case. The inadequate performance of structures during recent earthquakes has motivated researchers to revise existing methods and to develop new methods for seismic-resistant design. This includes new design concepts, such as, performance-based design (PBD) (Priestley et al., 2005) and new measures of the structure performance based on energy concepts and damage indexes (Park et al., 1987; Moustafa, 2011). Similarly, the widespread damage and inadequate performance of code-designed structures during the 1994 Northridge (California) and the 1995 Kobe (Japan) earthquakes have prompted seismologists and engineers of the essential importance of characterizing and modelling near-field ground motions with impulsive nature (Moustafa & Takewaki, 2010). For foundations of structures built in seismic areas, the demands to sustain load and deformation during an earthquake will probably be the most severe in their design life. As stressed by Hudson (1981) the soil-structure interaction is a crucial point for the evaluation of the seismic response of structures.

An Analytical Expression for the Nonlinear Evaluation of the Soil-Pile Interaction

Pile foundations are commonly used for many types of structures and vertical and/or lateral loading design considerations are very important because the performance of the piles significantly influences the integrity of the structures supported by them. Current design methods of pile foundations often involve an estimation of a constant stiffness as an input, to model the soil-foundation interaction. Nevertheless, pile lateral response is nonlinear. It is therefore desirable to analyze the behavior of the foundation considering this nonlinearity. In the paper an analytical expression to predict the nonlinear behavior of a pile foundation is presented. To validate this closed form solution, computed results were compared with measures derived from loading tests, and it has been shown, that this solution can be used successfully for a provision of the nonlinear response of a soil-pile system.