Edge states and topological insulating phases generated by curving a nanowire with Rashba spin-orbit coupling

We prove that curvature effects in low-dimensional nanomaterials can promote the generation of topological states of matter by considering the paradigmatic example of quantum wires with Rashba spin-orbit coupling, which are periodically corrugated at the nanometer scale. The effect of the periodic curvature generally results in the appearance of insulating phases with a corresponding novel butterfly spectrum characterized by the formation of fine measure complex regions of forbidden energies. When the Fermi energy lies in the gaps, the system displays localized end states protected by topology. We further show that for certain corrugation periods the system possesses topologically non-trivial insulating phases at half-filling. Our results suggest that the local curvature and the topology of the electronic states are inextricably intertwined in geometrically deformed nanomaterials.Comment: 5 pages, 5 figure

Curvature-induced Rashba spin-orbit interaction in strain-driven nanostructures

We derive the effective dimensionally reduced Schr\"odinger equation with spin-orbit interaction in low-dimensional electronic strain driven nanostructures. A method of adiabatic separation among fast normal quantum degrees of freedom and slow tangential quantum degrees of freedom is used to show the emergence of a strain-induced Rashba-like spin-orbit interaction (SOI). By applying this analysis to one-dimensional curved quantum wires we demonstrate that the curvature-induced Rashba SOI leads to enhanced spin-orbit effects.Comment: 5 pages, 3 figures, to be published in SPIN (World Scientific) as Topical Issue on Functional Nanomembrane

Designing Electron Spin Textures and Spin Interferometers by Shape Deformations

We demonstrate that the spin orientation of an electron propagating in a one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be manipulated on demand by changing the geometry of the nanosystem. Shape deformations that result in a non-uniform curvature give rise to complex three-dimensional spin textures in space. We employ the paradigmatic example of an elliptically deformed quantum ring to unveil the way to get an all-geometrical and all-electrical control of the spin orientation. The resulting spin textures exhibit a tunable topological character with windings around the radial and the out-of-plane directions. We show that these topologically non trivial spin patterns affect the spin interference effect in the deformed ring, thereby resulting in different geometry-driven ballistic electronic transport behaviors. Our results establish a deep connection between electronic spin textures, spin transport and the nanoscale shape of the system.Comment: 8 pages, 4 figure

Simulation-based consequence models of seismic direct loss and repair time for archetype reinforced concrete frames

Seismic risk management of building portfolios requires a reliable evaluation of earthquake-induced losses. This is commonly performed using consequence models linking structure-specific damage states (DSs) experienced by a building to a given loss metric (or decision variable). This study demonstrates a simulation-based procedure that derives refined probabilistic consequence models considering two essential loss metrics: direct-loss and repair-time ratios (repair cost or time normalised by the corresponding reconstruction values). Nine case-study reinforced concrete frames with various heights and design-code levels are developed to represent common residential buildings in Italy and the Mediterranean region. The proposed procedure starts by defining building-level, structure-specific DSs that reflect the increasing structural and nonstructural damage for the nine frames. Their seismic response is then assessed by analysing two-dimensional nonlinear numerical models and deriving building-level fragility relationships. Next, component-based direct-loss and repair-time analysis is conducted via the FEMA P-58 methodology, which computes such metrics at multiple ground-shaking intensities using Monte Carlo sampling. The consequence models are finally characterised by fitting probabilistic distributions to the direct-loss and repair-time realisations after conditioning them on the respective global DSs sustained by each case-study frame. This procedure enables deriving enhanced consequence models that can be easily implemented in risk analysis of building portfolios to obtain quick loss estimates. This study finally sheds some light on the possibility of correlating repair time to direct loss, which might be useful in estimating indirect losses resulting from downtime, particularly in cases where repair-time data or models are unavailable

Surrogate modeling for risk-targeted seismic design of isolated structures using friction pendulum systems

Base isolation has been used in the last decades to provide structures with enhanced seismic performance, especially to meet the requirements of risk-critical buildings (e.g., healthcare facilities). This calls for risk-targeted design approaches that consider the explicit computation of various decision variables (e.g., expected annual loss or mean annual frequency of exceeding various damage states). Nonetheless, most of these structures are still designed following implicit risk/reliability considerations derived from building codes. The main hurdle to an explicit risk-based design is the computational effort and time required for seismic performance assessments, given the iterative nature of a typical risk/loss-based design process. This paper proposes using Gaussian-process-regression-based surrogate probabilistic seismic demand models (PSDMs) of equivalent single-degree-of-freedom systems (i.e., the probability distribution of peak horizontal displacements and accelerations on top of the isolation layer conditional on different ground-motion intensity levels) to address these challenges. This enables a risk-targeted methodology for the seismic design of low-rise structures equipped with friction pendulums that virtually requires no design iterations. First, the definition, training, and validation of the surrogate PSDMs are presented. Then, a brief description of a tentative risk-targeted procedure enabled by the proposed surrogate PSDMs is presented. The predictive power of the surrogate PSDMs is verified using a 10-fold cross-validation technique, resulting in normalised root mean square error below 3% for the parameters of the PSDMs and below 7% for their standard deviation

Modelling multi-hazards interactions in life-cycle analysis of engineering systems

Complex engineering systems must be designed to sustain the occurrence of multiple natural and man-made hazards during their service life. To properly quantify multi-hazard effects on the performance of engineering systems, we need to identify the interactions in both occurrence rates of multiple hazards and associated consequences. Recent literature has established a common nomenclature for multi-hazard design, separating occurrence interactions from consequence interactions. In terms of occurrence, hazards are classified as concurrent (if they tend to occur simultaneously) and successive (if one hazard intensifies the occurrence rate of another). In terms of consequences, cascading effects are identified whenever a hazard's occurrence modifies the system's properties, changing the effects of a subsequent hazard. However, the available literature mainly looks at the problem from a qualitative perspective that classifies interactions but does not translate the resulting taxonomy to the mathematical modelling of the hazards and their effects. This paper aims to fill this gap by identifying modelling approaches associated with different hazard interdependencies. In particular, we focus on occurrence interactions, and we develop a simulation-based approach for generating multihazard scenarios (i.e., a sequence of hazard events and associated features through the system’s life cycle) based on the theory of competing Poisson processes. The proposed approach incorporates the different types of interactions in a sequential Monte Carlo sampling method. The method outputs potential sequences of events throughout a system’s life cycle, which can be integrated into LCA frameworks to quantify interacting hazard consequences. A simple application is presented to illustrate the potential of the proposed method

A fragility-oriented approach for seismic retrofit design

This study proposes a practical fragility-oriented approach for the seismic retrofit design of case-study structures. This approach relies on mapping the increase of the global displacement-based ratio of capacity to life-safety demand ( CDRLS) to the building-level fragility reduction. Specifically, the increase of CDRLS due to retrofitting is correlated with the corresponding shift in the fragility median values of multiple structure-specific damage states, observing that a pseudo-linear trend is appropriate under certain conditions. Accordingly, a practical approach is proposed to fit such a (structure-specific) linear trend and then use it by first specifying the desired fragility median and subsequently finding the corresponding target value of CDRLS that must be achieved through retrofit design. The validity of the proposed approach is illustrated for an archetype reinforced concrete (RC) structure not conforming to modern seismic design requirements, which has been retrofitted using various techniques, namely, fiber-reinforced polymers wrapping of columns and joints, RC jacketing, and steel jacketing

Environmental impacts of seismic damage for a case-study reinforced RC building in Italy

This study evaluates the environmental impacts resulting from the repair of earthquakeinduced damage, considering an older reinforced concrete (RC) frame representative of those built in Italy before the 1970s. Such impacts, expressed in terms of embodied carbon, represent a considerable component of buildings’ life-cycle embodied carbon in seismically-prone regions. Embodied carbon is a metric that measures the total greenhouse gas emissions associated with material extraction, manufacturing, transporting, construction, maintenance, and disposal. The seismic damage sustained by the case-study frame is first evaluated using the FEMA P-58 approach. Specifically, the frame’s nonlinear response is analysed against increasing groundshaking intensities, followed by estimating the damage incurred by its individual components via ad-hoc fragility models. Damage is then converted to embodied carbon by using consequence models specifically derived in this study for Italian structural/non-structural building components. This is accomplished by: 1) collecting environmental-impact data from Italian manufacturers of relevant construction materials and; 2) defining suitable structure-specific damage levels and the required repair work for every component. Results show that the embodied carbon induced by seismic damage throughout the case-study building’s life cycle might exceed 25% of that generated during its initial construction (pre-use phase)

Geometric driving of two-level quantum systems

We investigate a class of cyclic evolutions for %the cyclic evolution of driven two-level quantum systems (effective spin-1/2) with a particular focus on the geometric characteristics of the driving and their specific imprints on the quantum dynamics. By introducing the concept of geometric field curvature for any field trajectory in the parameter space we are able to unveil underlying patterns in the overall quantum behavior: the knowledge of the field curvature provides a non-standard and fresh access to the interrelation between field and spin trajectories, and the corresponding quantum phases acquired in non-adiabatic cyclic evolutions. In this context, we single out setups in which the driving field curvature can be employed to demonstrate a pure geometric control of the quantum phases. Furthermore, the driving field curvature can be naturally exploited to introduce the geometrical torque and derive a general expression for the total quantum phase acquired in a cycle. Remarkably, such relation allows to access the mechanisms controlling the changeover of the quantum phase across a topological transition and to disentangle the role of the spin and field topological windings. As for implementations, we discuss a series of physical systems and platforms to demonstrate how the geometric control of the quantum phases can be realized for pendular field drivings. This includes setups based on superconducting islands coupled to a Josephson junction and inversion asymmetric nanochannels with suitably tailored geometric shapes.Comment: 13 pages, 5 figure

Time-dependent fragility analysis of deteriorating structural systems under seismic sequences

: Structural systems in seismic-prone areas often experience multiple ground motions throughout their service life, including mainshocks, aftershocks, and other earthquakes triggered by mainshocks on nearby fault segments. These successive ground motions can significantly damage a system’s structural and non-structural components, leading to significant earthquakeinduced losses. Despite this, the impact of pre-existing damage during ground-motion sequences is typically disregarded when assessing nonlinear structural performance. Moreover, deterioration mechanisms caused by environmental factors can worsen damage/losses due to ground-motion sequences over the system's service life; however, these combined effects are frequently overlooked. This paper proposes an end-to-end computational methodology to derive fragility relationships that account for the damage state achieved by a structural system during a prior ground motion while deteriorating due to chloride-induced corrosion. To this end, a vector-valued probabilistic seismic demand model is formulated to relate the maximum inter-storey drift of the first ground motion and the intensity measure of the second ground motion to the dissipated hysteretic energy during the entire ground-motion sequence for a given corrosion deterioration level. Furthermore, a vector-valued collapse generalised logistic model is developed to estimate the probability of collapse, conditioned on the same parameters as the probabilistic seismic demand model. Monte-Carlo simulation is then employed to model the time-dependent evolution of fragility relationships' parameters using an appropriate chloride-penetration model, capturing the continuous nature of the deterioration processes. The proposed methodology is demonstrated by applying it to a case-study reinforced concrete building, revealing reductions of up to 33.3% in fragility median values due to deteriorating effects caused by the multi-hazard threat