Selection criteria for pile diameter in seismic areas

According to modern seismic codes such as Eurocode 8, pile foundations in earthquake-prone areas must resist two different, yet simultaneous bending actions resulting from kinematic and inertial interaction. Due to the different nature of the two demands, pile must resist seismic actions following different patters, thus leading to different design requirements. In this work, analytical solutions are presented to define maximum and a minimum pile diameters required to resist kinematic and inertial effects in an essentially elastic manner, respectively. It is shown that the range of admissible diameters decreases with decreasing soil stiffness and with increasing design acceleration, collapsing into a single admissible diameter for certain problem configurations. Regions where no pile diameter can guarantee elastic response during strong seismic shaking are identified

A new three object triangulation algorithm based on the power center of three circles

peer reviewedaudience: researcher, professional, popularizationPositioning is a fundamental issue in mobile robot applications that can be achieved in multiple ways. Among these methods, triangulation is a proven technique. As it exists for a long time, many variants of triangulation have been proposed. Which variant is most appropriate depends on the application because some methods ignore the beacon ordering while other have blind spots. Some methods are reliable but at a price of increasing complexity or special cases study. In this paper, we present a simple and new three object triangulation algorithm. Our algorithm works in the whole plane (except when the beacons and the robot are concyclic or colinear), and for any beacon ordering. Moreover, it does not need special cases study and has a strong geometrical meaning. Benchmarks show that our algorithm is faster than existing and comparable algorithms. Finally, a quality measure is intrinsically derived for the triangulation result in the whole plane, which can be used to identify the pathological cases, or as a validation gate in Kalman filters

The Holocene Evolution of the Volturno Coastal Plain (Northern Campania, Southern Italy): Implications for the Understanding of Subsidence Patterns

In the Mediterranean area, several alluvial coastal plains, developed after the Holocene transgression, are affected by subsidence. The Volturno alluvial‐coastal plain, along the eastern Tyrrhenian Sea (southern Italy) is characterized by subsidence rates determined through InSAR data analysis and ranging between 0 and <−20 mm/yr in an area of about 750 kmq across the Volturno River. Inside this area, the pattern of subsidence shows sites with apparently anomalous localized subsidence. To understand the driving mechanisms of this process, a lithostratigraphic reconstruction was provided focusing on the spatial distribution of the horizons considered weak by a geotechnical point of view; then, the subsidence map was overlain spatially with geological data in a Geographic Information System (GIS) environment. The spatial analysis highlighted the major ground deformation occurring within the outer boundary of the incised paleo‐valley, corresponding to the Holocene alluvial/transitional filling that overlies a compaction‐free Pleistocene basement. Inside this general trend, differential compaction was detected corresponding to the thick occurrence of clay and peat deposits, suggesting that the subsidence rate registered in the plain are due in part to the consolidation of primary settlements of soft and compressible soils that characterize the subsoil of these areas, and in large part to the secondary consolidation settlements

Strength anisotropy of fibre-reinforced sands under multiaxial loading

The strength anisotropy of fibre-reinforced sands in the multiaxial stress space has been investigated using a hollow cylinder torsional apparatus. Probing stress paths under constant cell pressure have been performed on both unreinforced and reinforced sand specimens to assess the influence of the orientation of the principal stress directions on the fibre strengthening contribution. For the first time, a deviatoric strength envelope for fibre-reinforced soils in the multiaxial stress space was identified. The addition of fibres produces an anisotropic increase and a distortion of the deviatoric strength envelope if compared to the unreinforced soil matrix. The fibre strengthening contribution is governed by the tensile strain domain developed and the fibre orientation distribution. Further observations on the effect of the addition of fibres on the volumetric response, principal stress and strain rate non-coaxiality, as well as the shear bands formation of the composite, are presented. An analytical model to capture the anisotropic fibre strengthening contribution is developed and discussed. </jats:p

Size Limitations for Piles in Seismic Regions

A novel theoretical study exploring the importance of pile diameter in resisting seismic actions of both the kinematic and the inertial type, is reported. With reference to a pile under a restraining cap, is shown analytically that for any given set of design parameters, a range of admissible pile diameters exists, bounded by a minimum and a maximum value above and below which the pile will yield at the top even with highest material quality and amount of reinforcement. The critical diameters depend mainly on seismicity, soil stiffness and safety factor against gravity loading, and to a lesser extent on structural strength. This scale effect is not present at interfaces separating soil layers of different stiffness, yet it may govern design at the pile head. The work at hand deals with both steel and concrete piles embedded in soils of uniform or increasing stiffness with depth. Closed-form solutions are derived for a number of cases, while others are treated numerically. Application examples and design issues are discussed