This study quantifies the seismic fragility assessment of shallow-founded buildings in liquefiable and treated soils, enhanced by drainage and densification, considering both short-and long-term behaviors. A conceptual framework is proposed for developing seismic fragility curves based on engineering demand parameters (EDPs) of buildings subjected to various earthquake magnitudes. The framework for establishing seismic fragility curves involves three essential steps. First, nonlinear dynamic analyses of soil-building systems are performed to assess both the short-term response, which occurs immediately following an earthquake, and the longterm response, when excess pore water pressure completely dissipates, and generate a dataset of building settlements. The seismic responses are compared in terms of excess pore water pressure buildup, immediate and residual ground deformation, and building settlement to explore the dynamic mechanisms of soil-building systems and evaluate the performance of enhanced drainage and densification over short-and long-term periods. Second, 38 commonly used and newly proposed intensity measures (IMs) of ground motions (GMs) are comprehensively evaluated using five statistical measures, such as correlation, efficiency, practicality, proficiency, and sufficiency, to identify optimal IMs of GMs. Third, fragility curves are developed to quantify probability of exceeding various capacity limit states, based on structural damage observed in Taiwan, for both liquefaction-induced immediate and residual settlements of buildings under different levels of IMs. Overall, this study proposes a rapid and straightforward probabilistic assessment approach for buildings in liquefiable soils, along with remedial countermeasures to enhance seismic resilience.

Current practice to model the occurrence of submarine landslides is based on methods that assess the potential of site-specific failures, all with the objective of providing elements to identify and quantify regional features associated to geohazards, before a project development takes place. Also, survey data to estimate parameters required to model submarine landslides show typically limited availability, mainly because of the cost associated to offshore surveying campaigns. In this paper, a probabilistic calibration approach is introduced using Bayesian statistical inference to maximize the use of available site investigation data, and to best estimate the occurrence of a marine landslide. For this purpose, a landslide model thought for its simplicity is used to illustrate the applicability and potential of the calibration methodology. The aim is to introduce a systematic approach to produce prior probability distributions of the model parameters, based on an actual integrated marine site investigation including geological, geophysical, and geomatics data, to then compare it with a posterior probability distribution of the same model parameters, but estimated after collecting in situ soil samples and testing them in the laboratory to produce the corresponding soil strength properties. This comparison allows to explore (a) the influence of the number of in situ samples, (b) the influence of a landslide factor of safety, and (c) the influence of the soil heterogeneity, into the likelihood of the occurrence of a marine landslide. The model parameters that are considered for calibration include the initial state of the submerged and saturated soil unit weight, the thickness of the soils' unit layers, the pseudo-static seismic coefficient, and the slope angle, while the soil undrained shear strength is considered as the reference parameter to conduct the calibration (i.e., to compare model predictions vs. actual observations). Results show the potential of the proposed methodology to produce landslide geohazard maps, which are needed for the planning and design of marine infrastructure.

Soil displacement along Balboa Boulevard during the 1994 Northridge earthquake ruptured natural gas transmission and distribution pipelines as well as two pressurized water trunk lines. Four other buried pipelines in the ground displacement zone were not damaged. This study probabilistically assesses the performance of the buried pipelines in the framework of performance-based earthquake engineering. The main aspects of pipeline performance follow from the geotechnical characteristics of the site. Uncertainty in each of the key soil-pipeline system parameters is estimated, including length of the seismic ground displacement zone, amount of seismic ground displacement, soil-pipeline interface shear stress, pipe steel yield strength and Young's modulus, and shapes of the pipe steel stress-strain curves. Monte Carlo simulations are performed with an analytical model to assess the pipe strain response. New fragility functions are proposed to evaluate pipeline performance in response to tensile or compressive longitudinal strain. The resulting probabilities of failure are compared with the results of a conventional analysis in which the modeled pipeline strains are evaluated with respect to the critical strains that cause either tensile or compressive failure. The failure probabilities compare well with the pipeline performance observed during the Northridge earthquake, except for one natural gas transmission line. A sensitivity analysis is performed for this line to investigate the reasons for the discrepancy. Advantages and limitations of probabilistic analyses are discussed.

API-RP2EQ (2021) has recommended annual probabilities of failure for Jacket-Type Offshore Platforms (JTOPs) against earthquake events and has specified that catastrophic failure modes that can lead to environmental damage or loss of structural integrity shall not occur during an Abnormal Level Earthquake (ALE). In this study some structural and non-structural limit states are proposed for the seismic evaluation of JTOPs and a comprehensive methodology is used for evaluating the probabilities of reaching relevant limit states, considering the nonlinear dynamic behavior of JTOPs, soil-pile interaction, pipeline risers, and relevant uncertainties. Incremental Dynamic Analysis (IDA) has been carried out on finite element models of platforms, and record-to- record and epistemic uncertainties have been considered in deriving fragility curves. Results show that the slope-based limit states derived from nonlinear static pushover curves provide a fairly good estimate of the target annual probability of structural failure. They also show that a non-structural limit state associated with containment leakage of pipeline risers should also be considered in the analysis. The research provides valuable insights into probabilistic performance-based seismic assessment of steel jacket-type offshore platforms and indicates that the reserve strength coefficients recommended in the relevant standard may be too conservative.

Soil-water characteristics, which vary with hydrological events such as rainfall, significantly influence soil strength properties. These properties are crucial determinants of the bearing capacity of foundations. Moreover, shear strength characteristics of soils are inherently spatially variable, and considering them as homogeneous parameters can result in unreliable design. This paper presents a probabilistic study of the two-dimensional bearing capacity of a strip footing on spatially random, unsaturated fine-grained soil using Monte Carlo simulation. The study employs the hydro-mechanical random finite difference method through MATLAB programming along with FLAC2D software. The undrained shear strength under saturated conditions is modelled as random fields using a log-normal distribution. The generated random values are then made depth-dependent by correlating them with matric suction. Initially, matric suction is assumed to be under a hydrostatic condition and decreases linearly with depth to zero at the groundwater level. Afterward, unsaturated soil is subjected to rainfall with different durations, resulting in the non-linear distribution of matric suction and, consequently, the mean value of undrained shear strength in depth. The results showed that rainfall infiltration impacts the strength characteristics of near-surface heterogeneous strata, leading to significant effects on the bearing capacity and failure mechanism of footing.

Assessment of seismic deformations of geosynthetic reinforced soil (GRS) walls in literature has dealt with unsolved challenges, encompassing time-consuming analyses, lack of probabilistic-based analyses, ignored inherent uncertainties of seismic loadings and limited investigated scenarios of these structures, especially for tall walls. Hence, a novel multiple analysis method has been proposed, founded on over 257,400 machine learning simulations (trained with 1582 finite element method analyses) and numerous performance-based fragility curves, to promptly evaluate the seismic vulnerability. The conducted probabilistic parametric study revealed that simultaneously considering several intensity measures for fragility curves is inevitable, preventing engineering judgement bias (up to 52% discrepancies in damage possibilities). Up to 75% contrasts between failure possibilities of 8 and 20 m walls, especially under earthquakes with common intensities (e.g. PGA <= 0.3g), raised serious concerns in the application of height-independent designing methods of GRS walls (e.g. AASHTO Simplified Method). Decreases in deformation possibilities were nearly the same due to increasing reinforcement stiffness (J) (1000 to 2000 kN/m) and reinforcement length to wall height ratio (L/H) (0.8 to 1.5); a decisive superiority of J variations over increasing L/H, as a remedial plan. The proposed methodology privileges engineers to swiftly assess the seismic deformations of multiple GRS walls at the design stage.

This research investigates a methodology for probabilistic life prediction of buried steel pipelines subjected to external corrosion. A unified methodology is developed considering multiple stages of degradation related to external corrosion (due to soil) and fatigue. These stages include corrosion pit nucleation, pit growth, transition from pit to short crack, short crack growth, transition from short to long crack, stable long crack growth, and unstable fracture. The methodology is useful in obtaining stage-specific forecasts for the fatigue life of buried steel pipelines subjected to external pitting corrosion fatigue. State-of-the-art computational models are used to predict damage initiation and evolution at each stage. The variability in environmental, material, and loading parameters is propagated through these models to obtain a probabilistic estimate of the remaining service life (RSL) of the pipe. Insights from probabilistic RSL prediction highlight the influence of soil type and pipe coating material on corrosion fatigue life. Global sensitivity analysis is then employed to quantify the relative importance of environmental factors (pH, pipe/soil potential, and chloride concentration), material properties (threshold stress intensity factor), and the range of cyclic stress experienced by the pipe.

The constitutive model is essential for predicting the deformation and stability of rock-soil mass. The estimation of constitutive model parameters is a necessary and important task for the reliable characterization of mechanical behaviors. However, constitutive model parameters cannot be evaluated accurately with a limited amount of test data, resulting in uncertainty in the prediction of stress-strain curves. This paper proposes a Bayesian analysis framework to address this issue. It combines the Bayesian updating with the structural reliability and adaptive conditional sampling methods to assess the equation parameter of constitutive models. Based on the triaxial and ring shear tests on shear zone soils from the Huangtupo landslide, a statistical damage constitutive model and a critical state hypoplastic constitutive model were used to demonstrate the effectiveness of the proposed framework. Moreover, the parameter uncertainty effects of the damage constitutive model on landslide stability were investigated. Results show that reasonable assessments of the constitutive model parameter can be well realized. The variability of stress-strain curves is strongly related to the model prediction performance. The estimation uncertainty of constitutive model parameters should not be ignored for the landslide stability calculation. Our study provides a reference for uncertainty analysis and parameter assessment of the constitutive model.

Probability-based seismic fragility analysis provides a quantitative evaluation of the seismic performance exhibited by structures. This study introduces a framework to perform seismic fragility analysis of utility tunnel and internal pipeline system considering wave passage effect of the ground motion spatial variation. The numerical model of a double-beam system resting on a nonlinear foundation is established to simulate the soiltunnel-pipeline interactions. 17 pairs of earthquake records are chosen and scaled as inputs at the outcrop. One-dimensional (1D) free-field analyses are conducted to obtain the ground motion time histories at the bottom slab of the utility tunnel, and then incremental dynamic analysis (IDA) is performed for the utility tunnel-internal pipeline system. The damage states (DSs) are defined by the maximum joint opening for the utility tunnel and maximum strain for the internal pipeline, and the peak bedrock velocity (PBV) is determined to be the most representative intensity measure (IM) for developing the seismic fragility curves. The seismic fragility curves of the system are constructed using the joint probabilistic seismic demand model (JPSDM) and Monte Carlo sampling method. The research findings indicate that: (1) the framework proposed in this study is suitable for the fragility assessment of long-extended utility tunnel-internal pipeline system; (2) the utility tunnel and internal pipeline as a system exhibit greater fragility compared to either one of the components, and the JPSDM and Monte Carlo sampling method for the system fragility analysis is more precise than the first-order bound method; (3) the proposed fragility curves in this study provide quantitative damage probabilities for the individual components and system under different seismic intensity levels. (4) The IM values corresponding to 50% exceedance failure probability of the whole system is 1%-3% lager than that of the upper bounds, and it is 3% to 5% less than that of the lower bounds. The conservative upper bound is a more suitable approximation for system fragility. (5) It should be noted that the obtained fragility curves are valid for the considered tunnel-pipeline structure and site conditions. For different tunnel structures and site conditions, the fragility curves can be constructed following the same steps outlined in this study.

The selection of representative ground motion intensity measure (IM) and structural engineering demand parameter (EDP) is the crucial prerequisite for evaluating structural seismic performance within the performance-based earthquake engineering (PBEE) framework. This study focuses on this crucial step in developing the probabilistic seismic demand model for two-story and three-span subway stations exposed to transverse seismic loadings in three different ground conditions. The equivalent linearization approach is used to simulate the shear modulus degradation and the increase in damping characteristics of the soil under seismic excitation. Nonlinear fiber beam-column elements are adopted to characterize the nonlinear hysteretic degradation of the subway station structure during seismic events. A total of 21 far-field ground motions are selected from the PEER strong ground motion database. Nonlinear incremental dynamic analyses (IDAs) are conducted to evaluate the seismic response of the subway station. A suite of 23 ground motion IMs is evaluated using the criteria of correlation, efficiency, practicality, and proficiency. Then, a multi-level fuzzy evaluation method is employed to integrate these evaluation criteria and determine the optimal ground motion IMs in different ground conditions. The peak ground acceleration and sustained maximum acceleration are demonstrated to be the optimal ground motion IM candidates for shallowly buried rectangular underground structures in site classes I, II, and III, while the root-mean-square displacement and compound displacement are found to be not suitable for this purpose.