Assessment of the dynamic response of unreinforced masonry structures using a macroelement modeling approach

The seismic performance of unreinforced masonry structures is strongly associated with the interaction between in‐plane and out‐of‐plane mechanisms. The seismic response of these structures has been thoroughly investigated by means of experimental testing, analytical procedures, and computational approaches. Within the framework of the numerical simulations, models based on the finite element method provide a good prediction of the seismic performance of unreinforced masonry structures. However, they usually require a high computational cost and advanced user expertise to define appropriate mechanical properties and to interpret the numerical results. Because of these limitations, simplified models for practical applications have been developed during the last decades. Despite this, a great number of these models focus mostly on the evaluation of the in‐plane response, assuming box (or integral) behavior of the structure. In this paper, a simplified macroelement modeling approach is used to simulate the seismic response of 2 masonry prototypes taking into consideration the combined in‐plane and out‐of‐plane action. The numerical investigations were performed in the static and dynamic fields by using pushover analyses and nonlinear dynamic analyses respectively. The latter is a novel implementation of a model previously developed for static analysis. The results obtained from this study are in good agreement with those provided by a detailed nonlinear continuum FE approach, demonstrating the applicability of this macroelement model with a significant reduction of the computational cost.     

The use of the slope–area function to analyse process domains in complex badland landscapes

This paper explores the effectiveness of the widely-used functional relationship between drainage area (A in m²) and slope (S in m/m) to identify local process domains and aid interpretation of process interactions in a complex badland landscape. In order to perform this investigation, a series of sub-basins tributary to the Formone River in the Orcia catchment (central Italy) were selected as a suitable study area within which to explore our questions, given these basins' general representativeness of local terrain, the availability of a high resolution digital terrain model and previous extensive geomorphological research. Eroding basins containing both calanchi and landslides are common in the sub-humid badland landscape of central Italy, where field observation identifies a complex pattern of erosive processes associated with a history of uplift, despite which parts of the local landscape appear disconnected. Results reveal that the shape of all S–A curves (plotted using S data binned on log A) is comparable with that described in the literature, although sub-basins containing calanchi generally plot with higher S values than non-calanchi ones, except in the ‘fluvial’ section of the plots. Second, when viewed on total data (non-binned) S–A plots, landslide source area domains and calanchi domains are entirely coincident in all basins, supporting a cause–effect relationship. Additional plotting of the frequency characteristics of the raw data in a new way supports the interpretation that calanchi frequently initiate in landslide scars. In general though, although the S–A plots can contribute to the disentanglement of geomorphological behaviour in some complex erosional landscapes, it became apparent that in this landscape, process domains do not separate out with clarity along the A axis as suggested by theory. Despite this, an alternative, broader-scale morphoevolutive model can be proposed for the development of within-landslide calanchi, driven by changes to basin connectivity to the base channel. © 2018 John Wiley & Sons, Ltd.     

Neo-deterministic seismic hazard scenarios for India—a preventive tool for disaster mitigation

Current computational resources and physical knowledge of the seismic wave generation and propagation processes allow for reliable numerical and analytical models of waveform generation and propagation. From the simulation of ground motion, it is easy to extract the desired earthquake hazard parameters. Accordingly, a scenario-based approach to seismic hazard assessment has been developed, namely the neo-deterministic seismic hazard assessment (NDSHA), which allows for a wide range of possible seismic sources to be used in the definition of reliable scenarios by means of realistic waveforms modelling. Such reliable and comprehensive characterization of expected earthquake ground motion is essential to improve building codes, particularly for the protection of critical infrastructures and for land use planning. Parvez et al. (Geophys J Int 155:489–508, 2003) published the first ever neo-deterministic seismic hazard map of India by computing synthetic seismograms with input data set consisting of structural models, seismogenic zones, focal mechanisms and earthquake catalogues. As described in Panza et al. (Adv Geophys 53:93–165, 2012), the NDSHA methodology evolved with respect to the original formulation used by Parvez et al. (Geophys J Int 155:489–508, 2003): the computer codes were improved to better fit the need of producing realistic ground shaking maps and ground shaking scenarios, at different scale levels, exploiting the most significant pertinent progresses in data acquisition and modelling. Accordingly, the present study supplies a revised NDSHA map for India. The seismic hazard, expressed in terms of maximum displacement (Dmax), maximum velocity (Vmax) and design ground acceleration (DGA), has been extracted from the synthetic signals and mapped on a regular grid over the studied territory.     

Improved evaluation of inelastic displacement demands for short‐period masonry structures

This work discusses the simplified estimation of earthquake‐induced nonlinear displacement demands as required by nonlinear static procedures, with particular attention on short‐period masonry structures. The study focuses on systems with fundamental periods between 0.1 and 0.5 s, for which inelastic amplification of the elastic displacement demand is more pronounced; hysteretic force‐displacement relationships characteristic of masonry structures are adopted, because these structures are more commonly found within the considered period range. Referring to the results of nonlinear dynamic analyses of single‐degree‐of‐freedom oscillators, some limitations of the Eurocode 8 and Italian Building Code formulations are first discussed, then an improved equation is calibrated that relates inelastic and elastic displacement demands. Numerical values of the equation parameters are obtained, considering the amount of hysteretic energy dissipation associated with various damage mechanisms observed in masonry structures. Safety factors are also calculated to determine several percentiles of the displacement demand. It is shown that the proposed equation can be extended to more dissipative systems. Finally, the same formulation is adapted to the estimation of seismic displacements when elastic analysis procedures are employed. Copyright © 2017 John Wiley & Sons, Ltd.     

Evaluating debris-flow and anthropogenic disturbance on 10Be concentration in mountain drainage basins: implications for functional connectivity and denudation rates across time scales

We examine the sensitivity of ¹⁰Be concentrations (and derived denudation rates), to debris-flow and anthropogenic perturbations in steep settings of the Eastern Alps, and explore possible relations with structural geomorphic connectivity. Using cosmogenic ¹⁰Be as a tracer for functional geomorphic connectivity, we conduct sampling replications across four seasons in Gadria, Strimm and Allitz Creek. Sampling sites encompass a range of structural connectivity configurations, including the conditioning of a sackung, all assessed through a geomorphometric index (IC). By combining information on contemporary depth of erosion and sediment yield, disturbance history and post-LGM (Last Glacial Maximum) sedimentation rates, we constrain the effects of debris-flow disturbance on ¹⁰Be concentrations at the Gadria sites. Here, we argue that bedrock weakening imparted by the sackung promotes high depth of erosion. Consequently, debris flows recruit sediment beyond the critical depth of spallogenic production (e.g., >3 m), which in turn, episodically, due to predominantly muogenic production pathways, lowers ¹⁰Be concentration by a factor of 4, for at least 2 years. In contrast, steady erosion in Strimm Creek yields very stable ¹⁰Be concentrations through time. In Allitz Creek, we observe two- to fourfold seasonal fluctuations in ¹⁰Be concentrations, which we explain as the combined effects of water diversion and hydraulic structures on sediment mixing. We further show that ¹⁰Be concentration correlates inversely with the IC index, where sub-basins characterized by high concentrations (long residence times) exhibit low IC values (structurally disconnected) and vice versa, implying that, over millennial time scales a direct relation exists between functional and structural connectivity, and that the IC index performed as a suitable metric for structural connectivity. The index performs comparably better than other metrics (i.e., mean slope and mean normalized channel steepness index) previously used to assess topographic controls on denudation rates in active unglaciated ranges. In terms of landscape evolution, we argue that the sackung, by favouring intense debris-flow activity across the Holocene, has aided rapid postglacial reshaping of the Gadria basin, which currently exhibits a topographic signature characteristic of unglaciated debris-flow systems. © 2020 John Wiley & Sons, Ltd.     

Occurrence and distribution pattern of Palaemon spp. shrimps in a shallow submarine cave environment: a study case in South‐eastern Italy

The common shrimps of the genus Palaemon are often reported as living in Mediterranean submarine caves. The present study quantifies the distribution pattern of a Palaemon spp. populations throughout 1 year of observations in a shallow submarine cave in South‐eastern Italy, Ionian Sea. The cave was subdivided into six sectors from the entrance towards the inner portion of the ‘blind cave’ and 16 dives (four per season, during both day and night) were performed with SCUBA equipment. The population was estimated in situ using visual census. Four different species of Palaemon were identified. This study has shown that Palaemon spp. assemblages live throughout the year in submarine caves. Moreover, the results suggest submarine caves play an important role in the biology of Palaemon spp. populations, by providing refuge, juvenile recruitment and food resources.     

Spectral properties of volcanic materials from hyperspectral field and satellite data compared with LiDAR data at Mt. Etna

Spectral properties of volcanic materials in the optical region (350–2500 nm) of the electromagnetic spectrum are analyzed. The goal is to characterize air-fall deposits, recent lava flows, and old lava flows based on their spectral reflectance properties and on the textural characteristics (grain size) of pyroclastic deposits at an active basaltic volcano. Data were acquired during a spectroradiometric field survey at Mt. Etna (Italy) in summer 2003 and combined with hyperspectral satellite (Hyperion) and airborne LiDAR (Light Detection and Ranging) data. In addition, air-fall deposits produced by the highly explosive 2002–2003 eruption have been sampled and spectrally characterized at different distances from the new vents. The spectral analysis shows that air-fall deposits are characterized by low reflectance values besides variations in grain size. This distinguishes them from other surface materials. Old lava flows show highest reflectance values due to weathering and vegetation cover. The spectral data set derived from the field survey has been compared to corrected satellite hyperspectral data in order to investigate the Hyperion capabilities to differentiate the surface cover using the reflectance properties. This has allowed us to identify the 2002–2003 air-fall deposits in a thematic image just few months after their emplacement. Moreover, the observed differences in the field spectra of volcanic surfaces have been compared with differences in the signal intensity detected by airborne LiDAR survey showing the possibility to include information on the texture of volcanic surfaces at Mt. Etna. The approach presented here may be particularly useful for remote and inaccessible volcanic areas and also represents a potentially powerful tool for the exploration of extraterrestrial volcanic surfaces.     

Seasonal variations of exposure biomarkers, oxidative stress responses and cell damage in the clams, Tapes philippinarum, and mussels, Mytilus galloprovincialis, from Adriatic sea

This work investigated the natural variability of several biomarkers in Tapes philippinarum and Mytilus galloprovincialis, sampled from Northern Adriatic where these organisms are important sentinel species for future environmental impact assessment. Levels of metallothioneins, peroxisomal enzymes and acetylcholinesterase, showed a significant seasonality and marked differences between clams and mussels. Among antioxidant enzymes, catalase and GST decreased during the warmer period, the latter enzyme activity resulting particularly high in clams. The total oxyradical scavenging capacity toward peroxyl radicals decreased in mussels from winter to summer, indicating a prooxidant challenge due to higher seawater temperature and intensity of light irradiance. Lysosomal membrane stability did not exhibit significant seasonal variations, while some variations were observed for DNA damages. Overall results indicated a significant influence of seasonal variability on several biomarkers and species-specific differences which should be considered to discriminate the appearance of anthropogenic disturbance.