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Intercity networks constitute a highly important civil infrastructure in developed countries, as they contribute to the prosperity and development of the connected communities. This was evident after recent strong earthquakes that caused extensive structural damage to key transportation components, such as bridges, overpasses, tunnels and geotechnical works, that in turn led to a significant additional loss associated with the prolonged traffic disruption. In cases of seismic events in developed societies with complex and coupled intercity transportation systems, the interdependency between citizens’ life and road functionality has further amplified the seismically-induced loss. Quantifying therefore, the resilience of road networks, defined as their ability to withstand, adapt to, and rapidly recover after a disruptive event, is a challenging issue of paramount importance towards holistic disaster risk mitigation and management. This study takes into account the above aspects of network resilience to earthquake loading and establishes a comprehensive, multi-criterion framework for mitigating the overall loss expected to be experienced by the community due to future earthquake events. The latter is decoupled into the direct structural damage-related loss and the indirect loss associated with the travel delays of the network users, as well as the wider socio-economic consequences in the affected area. In order to reflect the multi-dimensional nature of loss, a set of novel, time-variant indicators is herein introduced, while cumulative indicators are proposed for assessing the total loss incurred throughout the entire recovery period. This probabilistic risk management framework is implemented into a software to facilitate informed decisions of the stakeholders, both before and after a major earthquake event, thus prioritizing the pre-disruption strengthening schemes and accelerating the inspection and recovery measures, respectively.

Schools represent a reference point for communities in any part of the world. Therefore, their safety and resilience against natural catastrophes is of paramount importance. The recent 2015 Gorkha earthquake has unfortunately shown that Nepalese school buildings are highly vulnerable to seismic actions. Most of them are indeed constituted by low-quality unreinforced masonry (URM). The quantification of URM vulnerability is fundamental to estimate the risk associated to school building portfolios at territorial scale. This work discusses statistics available for Nepalese schools and then presents analytical fragility curves for three recurrent URM typologies covering more than 50% of the school building stock. The methodology adopted to derive fragilities is spectral-based and accounts for out-of-plane and in-plane damage potential in a single easy-to-use analytical framework. Inter-building, intra-building and record-to-record variabilities are directly considered in the analysis. The obtained fragilities integrate the studies available for the region and can be used for pre-/post-earthquake risk assessment and prioritization of interventions at country level.

Empirical vulnerability models are fundamental tools to assess the impact of future earthquakes on urban settlements and communities. Generally, they consist of sets of fragility curves that are derived from georeferenced post-earthquake damage data. Following the 2015 Nepal earthquake sequence, the World Bank, through the Global Program for Safer Schools, conducted a Structural Integrity and Damage Assessment (SIDA) of about 18,000 school buildings in the earthquake-affected area. In this work, the database is utilized to identify the main structural characteristics of the Nepalese school building stock. For the first time, extended SIDA school damage data is processed to derive fragility curves for the main structural typologies. Data sets for each structural typology are used for a Bayesian updating of existing fragilities to obtain regional models for Nepalese schools. These fragility estimates can be adopted to assess potential seismic losses of the school infrastructure in Nepal. Additionally, they can be used for calibrating loss assessment studies in the wider Himalayan region where the structural typologies are similar.

This paper presents an extended set of numerical fragility functions for the structural assessment of buried steel natural gas (NG) pipelines subjected to axial compression caused by transient seismic ground deformations. The study focuses on NG pipelines crossing sites with a vertical geotechnical discontinuity, where high compression straining of a buried pipeline is expected to occur under seismic transient ground deformations. A de-coupled numerical framework is developed for this purpose, which includes a 3D finite element model of the pipe–trench system employed to evaluate rigorously the soil–pipe interaction effects on the pipeline axial response in a quasi-static manner. One-dimensional soil response analyses are used to determine critical ground deformation patterns at the vicinity of the geotechnical discontinuity, caused by the ground shaking. A comprehensive parametric analysis is performed by implementing the proposed analytical framework for an ensemble of 40 recorded earthquake ground motions. Crucial parameters that affect the seismic response and therefore the seismic vulnerability of buried steel NG pipelines namely, the diameter, wall thickness, burial depth and internal pressure of the pipeline, the backfill compaction level, the pipe–soil interface friction characteristics, the soil deposits characteristics, as well as initial geometric imperfections of the walls of the pipeline, are systematically considered. The analytical fragility functions are developed in terms of peak ground velocity at the ground surface, for four performance limit states, considering all the associated uncertainties. The study contributes towards a reliable quantitative risk assessment of buried steel NG pipelines, crossing similar sites, subjected to seismically-induced transient ground deformations.

An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability of the groundwater table has been conducted. To gain deeper understanding seven historical liquefaction records located adjacent to borehole datapoints (published in SAFER/GEO-591) were used to compare two methods for the estimation of liquefaction potential. Standard Penetration Test (SPT) blowcount data from 75 boreholes inform the new liquefaction potential maps. Various scenarios were modelled, i.e., seasonal variation of the groundwater table and peak ground acceleration. Ordinary kriging, implemented in ArcGIS, was used to prepare maps at urban scale. Liquefaction potential calculations using the methodology from (Sonmez, Environ Geol 44:862–871, 2003) provided a good match to the historical liquefaction records in the region. Seasonal variation of the groundwater table is shown to have a significant effect on the spatial distribution of calculated liquefaction potential across the valley. The less than anticipated liquefaction manifestations due to the Gorkha earthquake are possibly due to the seasonal water table level.

This paper describes the results of an experimental investigation on the coefficient of friction at the interface of a PVC–sand–PVC layer that is utilised as part of a low-cost geotechnical seismic isolation devised to be used in low-income countries. The PVC–sand–PVC configuration consists of two smooth PVC surfaces enclosing a single layer of sand grains, with surface densities between 0.5 kg/m2 and 3 kg/m2, which aim to facilitate relative sliding at friction resistance between 0.15 and 0.30 depending on the design acceleration, by acting like “non-perfectly rounded ball bearings”. The latter isolation method has been extensively studied both numerically and experimentally by means of large-scale testing at the shaking table of the EQUALS Earthquake Laboratory of the University of Bristol. However, in the light of the construction of the first building worldwide to be designed and constructed in Nepal with the particular low-cost PVC–sand–PVC sliding interface, it was deemed necessary to reliably assess the mean and dispersion of the coefficient of friction as a function of vertical pressure, sand density and degree of saturation. The results of the tests performed using an improved direct shear apparatus are presented herein using sand samples and PVC sheets that were locally resourced in Nepal to be used in construction. The results indicate that the variation of friction is reasonably low and in any case within the desirable range, irrespectively of the parameters examined, thus establishing confidence to the forthcoming design of the novel isolated building.

The present work investigates the effect of soil–structure interaction (SSI) on foundation motion recorded at accelerometric stations installed at the lowest level of buildings. For this purpose, two sites of instrumented buildings, for which foundation and free-field strong motion recordings are available, are studied in terms of transfer functions as well as strong motion intensity and frequency content. The importance of such an instrumentation scheme is highlighted, especially when it comes to assessing the filtering action of the foundation on moderate to high frequency components of free-field motions. The effect of ground motion filtering at the soil–foundation interface is further quantified in terms of amplitude and frequency content. The recordings are supplemented by a parametric analysis of the sub-structured soil–structure system leading to regression expressions that associate the intensity and frequency parameters of the recordings obtained at the base of the instrumented buildings and the corresponding free-field ones. It is shown that kinematic and inertial decoupling of SSI is not only a useful but also a necessary task for correcting earthquake records obtained at building basements particularly for high frequency-dominated ground motions.

Numerous existing steel framed buildings located in earthquake prone regions world-wide were designed without seismic provisions. Slender beam-columns, as well as non-ductile beam-to-column connections have been employed for multi-storey moment-resisting frames (MRFs) built before the 80’s. Thus, widespread damage due to brittle failure has been commonly observed in the past earthquakes for steel MRFs. A recent post-earthquake survey carried out in the aftermath of the 2016-2017 Central Italy seismic swarm has pointed out that steel structures may survive the shaking caused by several main-shocks and strong aftershocks without collapsing. Inevitably, significant lateral deformations are experienced, and, in turn, non-structural components are severely damaged thus inhibiting the use of the steel building structures. The present papers illustrates the outcomes of a recent preliminary numerical study carried out for the case of a steel MRF building located in Amatrice, Central Italy, which experienced a series of ground motion excitations suffering significant damage to the masonry infills without collapsing. A refined numerical model of the sample structure has been developed on the basis of the data collected on site. Given the lack of design drawings, the structure has been re-designed in compliance with the Italian regulations imposed at the time of construction employing the allowable stress method. The earthquake performance of the case study MRF has been then investigated through advanced nonlinear dynamic analyses and its structural performance has been evaluated according to Eurocode 8-Part 3 for existing buildings. The reliability of the codified approaches has been evaluated and possible improvements emphasized.

The paper aims to evaluate the way Eurocode 8 treats the consideration of asynchronous earthquake ground motion during the seismic design of bridges, and to discuss alternative solutions for cases wherein existing provisions do not lead to satisfactory results. The evaluation of EC8-2 new provisions and simplified methods is performed through comparison with a more refined approach whereas an effort is made to quantitatively assess the relative importance of various design and analysis assumptions that have to be made when spatial variability of ground motion is taken into consideration, based on the study of the dynamic response of 27 different bridges. It is concluded that, despite the complexity of the problem, there are specific cases where EC8 provisions can be safely and easily applied in practice, while in other cases ignoring the effect of asynchronous excitation or performing simplified calculations can significantly underestimate the actual seismic demand.