Smart city e smart people: dalla realtà urbana alla realtà mista

Il presente studio si pone come obiettivo la sperimentazione in ambienti urbani di una delle tecnologie che sta rivoluzionando il mercato tecnologico: la realtà virtuale (VR) e più genericamente delle tecnologie appartenenti al mondo della realtà estesa (XR), intesi come possibili strumenti a supporto della pianificazione, per affrontare le attuali sfide urbane. La matrice culturale e l’ambito di applicazione di questo studio sono le smart city. L’obiettivo è quello di migliorare la qualità della vita dei cittadini con il supporto delle più moderne tecnologie ICT, tenendo conto delle esigenze sociali, culturali, ambientali e fisiche di una società. La gestione e la visualizzazione dei dati e quindi delle informazioni, sono due elementi chiave nella pianificazione per il raggiungimento della smartness, una delle principali sfide per professionisti e pianificatori. È esattamente da queste riflessioni che si può intendere come la XR e tutte le tecnologie da essa derivanti rappresentano uno dei potenziali strumenti per raffigurare ed enfatizzare il valore delle informazioni all’interno di una città intelligente, aiutando non solo i tecnici di settore, ma supportando i cittadini nella comprensione delle politiche pianificatorie, soprattutto nelle fasi iniziali della progettazione. Inoltre, sarà brevemente descritta la sperimentazione eseguita nella Circoscrizione 2 della Città di Torino

Energy Dissipation Efficiency of Geotechnical Seismic Isolation with Gravel-Rubber Mixtures:Insights from FE Non-Linear Numerical Analysis

This paper provides new and useful insights into the performance and efficiency of geotechnical seismic isolation (GSI) systems with gravel-rubber mixtures containing 10%, 25% and 40% volumetric rubber content (VRC). Finite element numerical models were developed in OpenSees and subjected to sinusoidal ground motions with varying input base acceleration and frequency. The best seismic performance was attained for VRC = 40% at a frequency of 8 Hz. Using a newly developed GSI efficiency index, the energy dissipation efficiency of VRC = 40% was found to vary between good to excellent, while that of VRC = 10% and 25% is poor.</p

Development of a dissipative controlled rocking system for bridge columns supported on monopiles

In this research, low-damage seismic design detailing is developed for bridge columns supported by monopile foundations. The low-damage system aims to minimise, and potentially eliminate, the repair time and costs to a bridge after an earthquake. The low-damage design uses a dissipative controlled rocking (DCR) connection at the base of the column, which replaces the column plastic hinge. The DCR system combines unbonded post-tensioning and replaceable internal dissipaters to provide selfcentring and energy absorption capabilities for the bridge pier, respectively. Additionally, this research validates the lateral seismic response of a DCR bridge pier with the contribution of soilfoundation-structure interaction. Specifically, this research studies how additional rotations at the head of the pile foundation delay the onset of column yielding, and how the foundation damping influences the behaviour of the DCR system. This paper includes a description of the prototype structure being investigated, an overview of the experimental testing that will occur as part of the experimental campaign, and the results of the numerical modelling that aims to predict the behaviour of the structure during testing

The 2015 Gorkha Nepal Earthquake: Insights from Earthquake Damage Survey

The 2015 Gorkha Nepal earthquake caused tremendous damage and loss. To gain valuable lessons from this tragic event, an earthquake damage investigation team was dispatched to Nepal from 1 May 2015 to 7 May 2015. A unique aspect of the earthquake damage investigation is that first-hand earthquake damage data were obtained 6–11 days after the mainshock. To gain deeper understanding of the observed earthquake damage in Nepal, the paper reviews the seismotectonic setting and regional seismicity in Nepal and analyzes available aftershock data and ground motion data. The earthquake damage observations indicate that the majority of the damaged buildings were stone/brick masonry structures with no seismic detailing, whereas the most of RC buildings were undamaged. This indicates that adequate structural design is the key to reduce the earthquake risk in Nepal. To share the gathered damage data widely, the collected damage data (geo-tagged photos and observation comments) are organized using Google Earth and the kmz file is made publicly available

Extremely large post-liquefaction deformations of saturated sand under cyclic torsional shear loading

The effect of static shear stress on the undrained cyclic behavior of saturated Toyoura sand was studied by conducting a series of torsional shear tests up to double amplitude shear strain of about 100%. After being isotropically consolidated, the specimens were subjected to drained monotonic torsional shear loading, and then, cyclic torsional shear stress was applied under undrained condition. The amplitude of combined static and cyclic shear stress was kept constant by correcting the measured value for the effect of membrane force. Based on these test results, it was found that the effective stress path and the stress-strain curve were affected by the initial static shear stress. Accumulation of shear strain was clearly noticed in the same direction where the static shear stress was applied. Localization of specimen deformation, which increases with the shear strain level, was observed

Liquefaction potential of sand-gravel mixtures: experimental observations

Case histories from at least 27 earthquakes worldwide (including three from New Zealand: 1929 Mw7.6 Murchison earthquake; 2010 Mw 7.1 Darfield earthquake; and 2016 Mw 7.8 Kaikoura earthquake) have indicated that liquefaction can occur in gravelly soils (both in natural deposits and manmade reclamations) inducing large ground deformation and causing severe damage to civil infrastructures. However, the evaluation of the liquefaction potential and deformation characteristics of gravelly soils remains to be a major challenge in geotechnical earthquake engineering. Aimed at providing new and useful insights on this important topic, in this study, a series of undrained cyclic triaxial tests were conducted on selected sand-gravel mixtures (SGMs), which were attained by varying the proportion by weight of a fine sand (New Brighton sand), a coarse sand (washed river sand) and a rounded pea gravel. Reconstituted specimens (height = 130 mm and diameter = 61 mm) were prepared at two relative density states of 25% and 45% by wet tamping method. Fully saturated specimens were then isotopically consolidated at 100 kPa confining pressure and subjected to cyclic stress ratio (CSR) levels ranging between 0.15 and 0.45. In this paper, preliminary results are presented and discussed in terms of effects density state – i.e., relative density (Dr), and inter-granular void ratios – and gravel content ( ), on the liquefaction potential of SGMs. It is shown that while the liquefaction potential tends to increase with both increasing Dr and , it can be more uniquely described by the equivalent void ratio that accounts simultaneously for both the density state and gravel content effects

Deformation and cyclic strength characteristics of loose and medium-dense clean sand under sloping ground conditions: insights from cyclic undrained torsional shear tests with static shear

The effects of liquefaction on sloping ground often include the development of extremely large deformation. Although such phenomenon has been repeatedly observed following major earthquakes, the triggering conditions are not fully understood yet. To provide new insights into this issue, in this paper, results of two series of large-strain undrained cyclic torsional shear tests with initial static shear conducted on loose and medium-dense Toyoura sand specimens (relative density of 25-30% and 44-48%) are presented and analyzed. The post-liquefaction response of Toyoura sand is assessed in terms of failure modes and cyclic resistance up to 50% single amplitude shear strain. It is shown that, depending on the combined magnitude of static and cyclic shear stresses, a sand in sloping ground will likely experience a sudden development of large shear deformation (flow deformation) if initial liquefaction takes place, or a more progressive accumulation of large residual deformation, which yet may bring sand to failure, when the onset of initial liquefaction is not achieved

Recycling of end-of-life tyres in seismic isolation foundation systems

Over 6.3 million waste tyres are produced annually in New Zealand (Tyrewise, 2021), leading to socioeconomic and environmental concerns. The 2010-11 Canterbury Earthquake Sequence inflicted extensive damage to ~6,000 residential buildings, highlighting the need to improve the seismic resilience of the residential housing sector. A cost-effective and sustainable eco-rubber geotechnical seismic isolation (ERGSI) foundation system for new low-rise buildings was developed by the authors. The ERGSI system integrates a horizontal geotechnical seismic isolation (GSI) layer i.e., a deformable seismic energy dissipative filter made of granulated tyre rubber (GTR) and gravel (G) – and a flexible rubberised concrete raft footing. Geotechnical experimental and numerical investigations demonstrated the effectiveness of the ERGSI system in reducing the seismic demand at the foundation level (i.e., reduced peak ground acceleration) (Hernandez et al., 2019; Tasalloti et al., 2021). However, it is essential to ensure that the ERGSI system has minimal leaching attributes and does not result in long-term negative impacts on the environment

Direct shear behavior of gravel-rubber mixtures: Discrete element modeling and microscopic investigations

In this paper, a newly developed 3-dimentional discrete element model (DEM) for gravel-rubber mixtures (GRMs), namely DEM4GRM, that is capable of accurately describing the macro-scale shear response (from small to large deformation) of GRMs in a direct shear box apparatus is presented. Rigid gravel grains are modelled as simple multi-shape clumps, while soft rubber particles are modeled by using deformable 35-ball body-centered-cubic clusters. Mixtures are prepared with different volumetric rubber content (VRC) at 0, 10, 25, 40 and 100%, statically compressed under 30, 60 and 100 kPa vertical stress and then sheared, by closely simulating a reference laboratory test procedure. The variation of micro-scale factors such as fabric, normal and tangential force anisotropy is carefully examined throughout the shearing process and described by means of novel micro-mechanical relationships valid for GRMs. Moreover, strong-force chains are scrutinized to identify the transition from rigid to soft granular skeleton and gain insights on the load transfer and deformation mechanisms of GRMs. It is shown that the development of the fabric and force anisotropy during shearing is closely related to the macro-scale shear strength of GRMs, and strongly depends on the VRC. Besides, strong-force chains appear to be primarily formed by gravel-gravel contacts (resulting in a rigid-like mechanical behavior) up to VRC = 30%, and by rubberrubber contacts (causing a soft-like mechanical response) beyond VRC = 60%. Alternatively, at 30% < VRC < 60%, gravel-rubber contacts are predominant in the strong-force network and an intermediate mechanical behavior is observed. This is consistent with the behavioral trends observed in the macro- and micro-mechanical responses