A Multi-Objective Ground Motion Selection Approach Matching the Acceleration and Displacement Response Spectra

For seismic resilience-based design (RBD), a selection of recorded time histories for dynamic structural analysis is usually required. In order to make individual structures and communities regain their target functions as promptly as possible, uncertainty of the structural response estimates is in great need of reduction. The ground motion (GM) selection based on a single target response spectrum, such as acceleration or displacement response spectrum, would bias structural response estimates leading significant uncertainty, even though response spectrum variance is taken into account. In addition, resilience of an individual structure is not governed by its own performance, but depends severely on the performance of other systems in the same community. Thus, evaluation of resilience of a community using records matching target spectrum at whole periods would be reasonable because the fundamental periods of systems in the community may be varied. This paper presents a GM selection approach based on a probabilistic framework to find an optimal set of records to match multiple target spectra, including acceleration and displacement response spectra. Two major steps are included in that framework. Generation of multiple sub-spectra from target displacement response spectrum for selecting sets of GMs was proposed as the first step. Likewise, the process as genetic algorithm (GA), evolvement of individuals previously generated, is the second step, rather than using crossover and mutation techniques. A novel technique improving the match between acceleration response spectra of samples and targets is proposed as the second evolvement step. It is proved computationally efficient for the proposed algorithm by comparing with two developed GM selection algorithms. Finally, the proposed algorithm is applied to select GM records according to seismic codes for analysis of four archetype reinforced concrete (RC) frames aiming to evaluate the influence of GM selection considering two design response spectra on structural responses. The implications of design response spectra especially the displacement response spectrum and GM selection algorithm are summarized

Probabilistic Generalization of a Comprehensive Model for the Deterioration Prediction of RC Structure under Extreme Corrosion Environments

In some extreme corrosion environments, the erosion of chloride ions and carbon dioxide can occur simultaneously, causing deterioration of reinforced concrete (RC) structures. This study presents a probabilistic model for the sustainability prediction of the service life of RC structures, taking into account that combined deterioration. Because of the high computational cost, we also present a series of simplifications to improve the model. Meanwhile, a semi-empirical method is also developed for this combined effect. By probabilistic generalization, this simplified method can swiftly handle the original reliability analysis which needs to be based on large amounts of data. A comparison of results obtained by the models with and without the above simplifications supports the significance of these improvements

Application of the Hybrid Simulation Method for the Full-Scale Precast Reinforced Concrete Shear Wall Structure

The hybrid simulation (HS) testing method combines physical test and numerical simulation, and provides a viable alternative to evaluate the structural seismic performance. Most studies focused on the accuracy, stability and reliability of the HS method in the small-scale tests. It is a challenge to evaluate the seismic performance of a twelve-story pre-cast reinforced concrete shear-wall structure using this HS method which takes the full-scale bottom three-story structural model as the physical substructure and the elastic non-linear model as the numerical substructure. This paper employs an equivalent force control (EFC) method with implicit integration algorithm to deal with the numerical integration of the equation of motion (EOM) and the control of the loading device. Because of the arrangement of the test model, an elastic non-linear numerical model is used to simulate the numerical substructure. And non-subdivision strategy for the displacement inflection point of numerical substructure is used to easily realize the simulation of the numerical substructure and thus reduce the measured error. The parameters of the EFC method are calculated basing on analytical and numerical studies and used to the actual full-scale HS test. Finally, the accuracy and feasibility of the EFC-based HS method is verified experimentally through the substructure HS tests of the pre-cast reinforced concrete shear-wall structure model. And the testing results of the descending stage can be conveniently obtained from the EFC-based HS method

Application of the Hybrid Simulation Method for the Full-Scale Precast Reinforced Concrete Shear Wall Structure

The hybrid simulation (HS) testing method combines physical test and numerical simulation, and provides a viable alternative to evaluate the structural seismic performance. Most studies focused on the accuracy, stability and reliability of the HS method in the small-scale tests. It is a challenge to evaluate the seismic performance of a twelve-story pre-cast reinforced concrete shear-wall structure using this HS method which takes the full-scale bottom three-story structural model as the physical substructure and the elastic non-linear model as the numerical substructure. This paper employs an equivalent force control (EFC) method with implicit integration algorithm to deal with the numerical integration of the equation of motion (EOM) and the control of the loading device. Because of the arrangement of the test model, an elastic non-linear numerical model is used to simulate the numerical substructure. And non-subdivision strategy for the displacement inflection point of numerical substructure is used to easily realize the simulation of the numerical substructure and thus reduce the measured error. The parameters of the EFC method are calculated basing on analytical and numerical studies and used to the actual full-scale HS test. Finally, the accuracy and feasibility of the EFC-based HS method is verified experimentally through the substructure HS tests of the pre-cast reinforced concrete shear-wall structure model. And the testing results of the descending stage can be conveniently obtained from the EFC-based HS method

Data-driven simultaneous identification of the 6DOF dynamic model and wave load for a ship in waves

In marine operations, the performance of model-based automatic control design and decision support systems highly relies on the accuracy of the representative mathematical models. Model fidelity can be crucial for safe voyages and offshore operations. This paper proposes a data-driven parametric model identification of a ship with 6 degrees of freedom (6DOF) exposed to waves using sparse regression according to the vessel motion measurements. The features of the complex ship dynamics are extracted and expressed as a linear combination of several functions. Thruster inputs and environmental loads are considered. The hydrodynamic coefficients and wave-induced loads are simultaneously estimated. Unlike earlier studies using a limited number of unknown functions, a library of abundant candidate functions is applied to fully consider the coupling effects among all DOFs. The benefit of the proposed method is that it does not require the exact construction of the library functions. Based on the estimated model, short-term motion prediction is achievable. The algorithm is verified through experiments. The method can be extended to other types of floating structures

Phase engineering of Cr₅Te₈ with colossal anomalous Hall effect

Two-dimensional materials that are intrinsically ferromagnetic are crucial for the development of compact spintronic devices. However, most non-layered 2D magnets with a strong ferromagnetic order are difficult to synthesize. Here we show that the flakes of trigonal and monoclinic Cr5Te8 can be grown via a chemical vapour deposition method. Using magneto-optical and magnetotransport measurements, we show that both phases exhibit robust ferromagnetism with strong perpendicular anisotropy at thicknesses of a few nanometres. A high Curie temperature of up to 200 K can be obtained by manipulating the phase structure and thickness. We also observe a colossal anomalous Hall effect in the more structurally distorted monoclinic Cr5Te8, with an anomalous Hall conductivity of 650 Ω−1 cm−1 and anomalous Hall angle of 5%.Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionZ.L. acknowledges support from the National Research Foundation Singapore (NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007). This research is also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002), and AcRF Tier 1 RG161/19. W.G. acknowledges support from the National Research Foundation Singapore (NRF-CRP22-2019-0004). J.L. acknowledges support from the National Natural Science Foundation of China (grant no. 11974156); Guangdong International Science Collaboration Project (grant no. 2019A050510001); Guangdong Innovative and Entrepreneurial Research Team Program (grant no. 2019ZT08C044); Shenzhen Science and Technology Program (no. KQTD20190929173815000 and 20200925161102001); the Science, Technology and Innovation Commission of Shenzhen Municipality (no. ZDSYS20190902092905285); and assistance of SUSTech Core Research Facilities, especially technical support from the Pico-Centre that receives support from the Presidential fund and Development and Reform Commission of Shenzhen Municipality. J.Z. acknowledges support from the Beijing Institute of Technology (grant no. 2021CX11013) and National Natural Science Foundation of China (grant no. 62174013)

Phase-pure two-dimensional FeₓGeTe₂ magnets with near-room-temperature Tc

Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D FexGeTe2 ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown FexGeTe2. As a result, high-quality Fe3GeTe2 and Fe5GeTe2 flakes have been grown selectively using the CS-CVD technique. Curie temperature (TC) of the as-grown FexGeTe2 can be up to ∼ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe5GeTe2 reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe5GeTe2 display the highest conductivity among other FexGeTe2 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices. [Figure not available: see fulltext.].Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionThis work was supported from National Research Foundation Singapore programme NRF-CRP22-2019-0007, NRF-CRP22- 2019-0004 and NRF-CRP21-2018-0007. This work was also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002), AcRF Tier 2 (MOE2019-T2-2-105) and AcRF Tier 1 RG4/17 and RG7/18. We also thank the funding support from National Research foundation (NRF-CRP22- 2019-0004)