Carlo Giovanni Lai

The ASCE/COPRI 61-14 seismic design standard for pier and wharves prescribes an in-ground life safety (LS) strain limit for steel pipe-piles. The adequacy of this limit has been the topic of much discussion within the marine structural engineering community. It has been argued that steel pipes cannot achieve the LS strain limit before undergoing local buckling. In response, researchers have proposed critical strain ( ε c r ) equations for replacement of the standing LS strain limit. The critical strain has been obtained by curve fitting data from numerous pipe flexure tests. Although these studies have provided valuable insights into pipe flexural behavior, most were conducted using three- or four- point in-air bending tests and in the absence of axial load; conditions that differ from those encountered in the field. This paper presents two 1:3-scale experiments on axially loaded soil-embedded steel pipe-piles: one subject to quasi-static monotonic and another to reversed cyclic lateral loading. The test data were used to calibrate a detailed nonlinear finite-element model (FEM) for soil-embedded steel pipe-piles. The model was employed to perform a numerical study on pile deformation capacity within the context of critical strain ε c r . Practical ranges for select variables that steer pier-wharf design were considered in the numerical study. Results show that ε c r is overly conservative, inconsistent, and fails to capture the influence of axial load; an undesirable attribute for capacity-driving metrics. Furthermore, in practice, the use of strain as a damage-indicating engineering parameter requires the use of an equivalent plastic hinge length, a parameter which adds uncertainty. The paper proposes the use of a strength-targeted plastic rotation capacity ( θ p c ) which is shown to be an intuitive capacity indicator and makes use of a regression analysis on a subset of numerical results to postulate analytical θ p c expressions for displacement-based design of steel pipe-piles.

Seismic pounding between adjacent masonry units involves alternating contact, frictional sliding, and strongly nonlinear force–displacement response, all of which challenge conventional finite element formulations. Fully implicit solvers frequently lose convergence at contact discontinuities, while explicit schemes require small time steps. In prior studies of the SERA-AIMS shake-table experiment on a half-scale stone masonry aggregate, continuum models reproduced elastic flexibility but struggled with gap opening, while discrete models captured failure mechanisms but required extensive calibration of effective stiffness and capacity. This study presents an implicit–explicit (IMPL-EX) contact element with coupled Hertz contact and Coulomb friction represented by a Drucker–Prager surface in 3D, implemented in OpenSees to couple adjacent continuum damage-plasticity masonry models. First, the element is tested on a friction-isolated frame benchmark, achieving stable solutions at time steps up to Δt = 0.001 s and up to 50% lower computational cost at comparable accuracy relative to a fully implicit solution. Applied to the shake-table experiment, the elements provide a stable and accurate solution during the strong pounding cycles. The continuum model is calibrated to the low-intensity experimental run. The model is then extended to the high-intensity run, reproducing cracking patterns, base-shear–displacement hysteresis, and longitudinal gap-opening histories, including the second-storey out-of-plane hinge mechanism observed in the test, with key damage events reproduced in phase at 8 s, 9 s, and 12.68 s. Together, the benchmark and shake-table results indicate that the IMPL-EX contact element is a robust and efficient tool for high-fidelity seismic pounding simulation of masonry structures.

Accounting for the finite spatial extent of earthquake rupture is critical for effective regional Earthquake Early Warning (EEW), particularly for large events where point-source assumptions may fail. The Finite fault rupture Detector (FinDer) algorithm addresses this challenge by rapidly inferring the location, extent, and orientation of an ongoing earthquake fault rupture through comparison of the observed spatial distributions of high-frequency ground-motion amplitudes with pre-calculated templates derived from empirical ground motion models. Northeastern Italy, characterized by moderate-to-large seismicity primarily associated with active reverse and strike-slip faulting, represents a suitable test region for finite-fault-based EEW. We evaluate FinDer performance using a combination of real-time detections (MW < 4.5) and offline playback experiments (5.5 < MW < 6.7), acknowledging that real-time EEW timeliness is affected by telemetry latency in the current seismic station network. Results show rapid convergence toward stable event locations and magnitudes, while line-source orientation remains weakly constrained, especially for small magnitude events. Sensitivity analyses indicate that increasing station density improves the stability of source-parameter estimates, and that amplification factor-based adjustments for site effects reduce systematic biases in FinDer’s template-matching solutions. Lead times estimated from offline playback tests are also evaluated relative to macroseismic intensity thresholds corresponding to slight damage in unreinforced masonry buildings, with selected scenarios yielding non-negligible lead times. Overall, the results suggest that a properly configured FinDer-based EEW system, supported by real-time telemetry, could provide significant benefits for seismic-risk mitigation in Northeastern Italy. Nevertheless, template simplifications and the neglect of radiation-pattern effects remain major limitations, particularly for reliable strike estimation in smaller events (MW < 4.5).

This paper introduces a procedure to estimate moment magnitude ( M _W ) in earthquake‐induced soil liquefaction probabilistic risk assessment. The method is based on using the historical seismicity modelled with a truncated Gutenberg‐Richter (G‐R) relation, jointly with an empirical model linking the M _W to the maximum source‐to‐site distance at which soil liquefaction was observed in past earthquakes. The proposed method predicts M _W as a function of the recurrence intervals, which are assimilated to return periods (RPs), and it may be used in probabilistic or semi‐probabilistic seismic design as prescribed by modern building codes worldwide. Moreover, it is independent from any intensity measure (IM) of ground motion, and this is a desirable feature since the selection of the optimal IM for liquefaction risk assessment does not meet a general agreement among specialists. The novel procedure to estimate M _W has been applied at five Italian sites with different levels of seismicity. The results obtained with the proposed method to define M _W have been compared with other approaches from the current Italian engineering practice. Then, the application was extended to the whole Italian territory to compute maps of the expected M _W for liquefaction risk assessment for the RPs of 475, 975, and 2,475 years. Such maps represent useful tools for practitioners in Italy when performing liquefaction‐triggering analyses. Although the proposed method to compute the expected M _W in soil liquefaction triggering studies has been developed with a specific focus on the Italian territory, the procedure may be applied elsewhere.

Liquefaction-induced surface manifestations are the result of a complex geological–geotechnical phenomenon, driven by several controlling factors. We propose a multidisciplinary methodological approach, involving engineering geologists, geomorphologists, sedimentologists, and geotechnical engineers, to build a 3D engineering geological model for liquefaction assessment studies. The study area is Cavezzo (Po Plain, Italy), which is a municipality hit by superficial liquefaction manifestations during the Emilia seismic crisis of May–June 2012. The site is characterized by a Holocene alluvial sequence of the floodplain, fluvial channel, and crevasse splay deposits prone to liquefaction. The integration of different geotechnical investigations, such as boreholes, CPTm, CPTu, and laboratory tests, allowed us to recognize potentially liquefiable lithological units, crucial for hazard assessment studies. The resulting 3D engineering geological model reveals a strict correlation of co-seismic surface manifestations with buried silty sands and sandy silts within the shallow 10 m in fluvial channel setting, which is capped and laterally confined by clayey and silty deposits.

Seismic attenuation and the associated quality factor (Q) have long been studied in various sub-disciplines of seismology, ranging from observational and engineering seismology to near-surface geophysics and soil/rock dynamics with particular emphasis on geotechnical earthquake engineering and engineering seismology. Within the broader framework of seismic site characterization, various experimental techniques have been adopted over the years to measure the near-surface shear-wave quality factor (Q_S). Common methods include active- and passive-source recording techniques performed at the free surface of soil deposits and within boreholes, as well as laboratory tests. This paper intends to provide an in-depth review of whatQis and, in particular, howQ_Sis estimated in the current practice. After motivating the importance of this parameter in seismology, we proceed by recalling various theoretical definitions ofQand its measurement through laboratory tests, considering various deformation modes, most notablyQ_PandQ_S. We next provide a review of the literature onQ_S estimation methods that use data from surface and borehole sensor recordings. We distinguish between active- and passive-source approaches, along with their pros and cons, as well as the state-of-the-practice and state-of-the-art. Finally, we summarize the phenomena associated with the high-frequency shear-wave attenuation factor (kappa) and its relation toQ, as well as other lesser-known attenuation parameters.

This paper presents a geospatial methodology for zoning the earthquake-induced soil liquefaction risk at a continental scale and set-up in a Geographic Information System (GIS) environment by coupling data-driven and knowledge-driven approaches. It is worth mentioning that liquefaction is a phenomenon of soil instability occurring at a very local spatial scale; thus, the mega-zonation of liquefaction risk at a continental scale is a hard facing challenge. Since the risk from natural disasters is the convolution of hazard, vulnerability, and exposure, the liquefaction risk mapping is based on the combination of geospatial explanatory variables, available at the continental scale, of the previously listed three assumed independent random variables. First, by applying a prediction model calibrated for Europe, the probability of liquefaction is mapped for the whole continent. Then, the Analytical Hierarchy Process (AHP) is adopted to identify areas that have a high risk of liquefaction, taking into account proxy data for exposure. The maps are computed for different levels of severity of ground shaking specified by three return periods (i.e., 475, 975, and 2475 years). A broad variety of stakeholders would benefit from the outcomes of this study, such as civil protection organizations, insurance and re-insurance companies, and infrastructure operators.