Dynamic Fragility Research Articles

Temperature dependence of structural evolution and fragility of glass-forming monohydroxy alcohols

The dynamic, structural, and thermodynamic properties of thirty-four monohydroxy alcohols with varying molecular architectures, including differences in alkyl chain length, OH group position, and presence/type of carbon ring, were investigated. Results of dielectric spectroscopy, temperature-modulated differential scanning calorimetry, and X-ray diffraction, were analyzed to verify correlations between the glass transition temperature (Tg), molar mass (M), boiling temperature (Tb), dynamic and thermodynamic fragility (mα and m), and the structurally related parameter (S). The collected data revealed that primary and secondary alcohols generally adhere to the correlations Tg ∝ M0.51 and Tb = 132 + 2.2Tg, while alcohols with phenyl ring deviate from these trends. Moreover, it was found that the changes in the width of the main diffraction peak normalized by the peak position ΔQM/QM over temperature scaled by Tg correspond to the variable m. However, the extent and course of this relationship varies across alcohols belonging to different structural groups. The weakest correlation and largest scatter between S and m occur for phenyl alcohols exhibiting the greatest structural heterogeneity. This study underscores the challenges of establishing universal correlations between physical variables within the diverse group of monohydroxy alcohols and emphasizes the importance of considering specific molecular features in predicting glass-forming behaviour.

Fragility analysis of existing RCC frame structure

This In recent years, number of studies have been carried out for the evaluation of vulnerability of structure during seismic events. Fragility analysis is one of the important probabilistic approach to estimate the damage data at different damage state during seismic events. The G+7 Reinforced Concrete frame structure is considered for analysis. The structure is analyzed in ETABS by Non-linear Pushover Analysis. Fragility curve developed for Non-linear Pushover Analysis from results obtained by capacity spectrum method for different damage states. The fragility curves are derived from analytical method. The fragility points for different damage states are derived from analytical formula. Fragility curve is plotted for probability in Y-axis and spectral displacement in X-axis for 4 different damage states from Non-linear Pushover Analysis. From Incremental Dynamic Analysis fragility curve plotted for probability in Y-axis and peak ground acceleration in X-axis for five different damage state. The behavior of fragility curve after achieving the 100% probability for different damage state is constant.

A simplified model for seismic risk assessment of three-dimensional irregular steel moment frame buildings

Seismic risk assessment of irregular buildings requires nonlinear dynamic analysis and three-dimensional (3D) models. However, creating and analyzing such models can be intricate and time-consuming, making the assessment process challenging. Furthermore, this complexity escalates when evaluating building stocks or generating a dataset of buildings with diverse attributes for use in learning algorithms. Therefore, this paper proposes an energy-based model for irregular steel moment-resisting frame buildings to simplify 3D models and improve the time efficiency of structural assessment compared to conventional 3D models. The proposed model is derived from the fish-bone model but has enhanced configuration, elastic, and inelastic properties. These improvements aim to broaden its applicability to encompass 3D irregular mid-rise buildings. Four-, six-, and nine-story irregular buildings in plan and height are utilized to validate the proposed model. The responses investigated in these buildings include eigenvalues, pushover curves, time history responses, incremental dynamic analysis results, fragility curves, and risk analysis outcomes. The findings demonstrate that the simplified model responses are in close agreement with those of 3D models. The comparison of results between the proposed simplified model and existing models indicates that the accuracy of the simplified model is at least 2.2 times that of the existing models. Moreover, it provides an average error reduction of 60 % in contrast to the existing models. These advancements have been achieved while the proposed simplified model maintains a level of time efficiency comparable to the current models. The results from the analysis of the created buildings using the proposed simplified model indicate that the model is suitable for application in the seismic risk assessment of building inventories and generating datasets for future research involving machine learning-based methodologies.

A variational-based non-smooth contact dynamics approach for the seismic analysis of historical masonry structures

A variational formulation of the non-smooth contact dynamics method is proposed to address the dynamic response of historical masonry structures modeled as systems of 3D rigid blocks and subjected to ground excitation. Upon assuming a unilateral-frictional contact law between the blocks, the equations of motions are formulated in a time-discrete impulse theorem format in the unknown block velocities and contact impulses. The variational structure of the problem to be solved at each time step is proven. On that basis, the numerical method requires at each time step to perform a collision detection that identifies antagonist contact points based on the given structural configuration, to solve a second-order conic programming problem that outputs block velocities and contact impulses, and to update the structural configuration for the solution to advance in time. As a merit of the formulation, large-scale problems can be robustly and efficiently addressed thanks to the convex setting of the time-step optimization problem. Numerical results are presented to test the computational performances of the proposed approach. Benchmark problems provide numerical evidence that the formulation is consistent with event-driven solutions based on the classical Housner impact model. The dynamic response, failure domains, and fragility functions of real-size masonry structures are then explored under ground impulse or earthquake excitation. The obtained results prove the reliability of the present computational method for the dynamic analysis and seismic assessment of historical masonry constructions of engineering interest.

Self-organization in computation and chemistry: Return to AlChemy.

How do complex adaptive systems, such as life, emerge from simple constituent parts? In the 1990s, Walter Fontana and Leo Buss proposed a novel modeling approach to this question, based on a formal model of computation known as the λ calculus. The model demonstrated how simple rules, embedded in a combinatorially large space of possibilities, could yield complex, dynamically stable organizations, reminiscent of biochemical reaction networks. Here, we revisit this classic model, called AlChemy, which has been understudied over the past 30 years. We reproduce the original results and study the robustness of those results using the greater computing resources available today. Our analysis reveals several unanticipated features of the system, demonstrating a surprising mix of dynamical robustness and fragility. Specifically, we find that complex, stable organizations emerge more frequently than previously expected, that these organizations are robust against collapse into trivial fixed points, but that these stable organizations cannot be easily combined into higher order entities. We also study the role played by the random generators used in the model, characterizing the initial distribution of objects produced by two random expression generators, and their consequences on the results. Finally, we provide a constructive proof that shows how an extension of the model, based on the typed λ calculus, could simulate transitions between arbitrary states in any possible chemical reaction network, thus indicating a concrete connection between AlChemy and chemical reaction networks. We conclude with a discussion of possible applications of AlChemy to self-organization in modern programming languages and quantitative approaches to the origin of life.

Seismic vulnerability and performance-based assessment of monopile offshore wind turbine considering turbine blades

This paper investigated the seismic vulnerability and performance-based assessment of offshore monopile wind turbine (OWT) considering turbine blades. A three-dimensional finite-element model of NREL 5-MW OWT was established with detailed consideration of the nonlinear-behavior of turbine, monopile, blades, pile-soil interactions and pile-water interaction etc. Subsequently, incremental dynamic analysis and fragility evaluation were conducted via a great number of nonlinear time history analysis involving far-field and near-fault records with and without pulse characteristics. It is found that the ignorance of turbine blades in conventional lumped mass (LM) model would significantly underestimate the vulnerability of OWT's acceleration responses, and more importantly, underestimates the stress level at turbine top, misleading the failure pattern of OWT which may be probably damaged at both top and middle part of OWT rather than solely the middle part as estimated by the LM model ignoring the effect of turbine blades. Finally, it can be concluded that the modeling of turbine blades should be consider in the numerical studies.

Fragility Assessment of Single Concrete Pier and Pile-Soil Interaction Impact under Near and Far-Fault Earthquakes

Civil engineers face a significant challenge in assessing seismic vulnerability due to the complex of soil-pile-structureinteraction system. This research aims to evaluate the seismic vulnerability of individual piers under various seismicground motions. Factors like sand type, pile diameter, pier height, and mass placed were investigated for their impacton the seismic fragility of concrete piers. Using incremental dynamic analysis with a beam on a nonlinear Winklerfoundation model, the study compared the effects of near and far ground motions. Results from the dynamic analysisand fragility assessment demonstrated the effects of the parameters above-mentioned on the design of fragilitycurves, as well as its relationships to fundamental period of structural system.

Dynamics and Internal Structure Evolution during the Glass Transition of the Ethylene-Cyclic Olefin Copolymers: A Molecular Dynamics Simulation.

Amorphous ethylene-cyclic olefin copolymers (COCs) which can be used in cell phone lenses and prefilled syringes have attracted increasing attention due to their excellent and tunable thermal properties. In order to better explain the influence of COC microstructure (cyclic olefin types and content) on the glass transition mechanism, we used molecular dynamics (MD) simulations to track the evolution of free volume, diffusion coefficients, atomic mobility, trans conformation probabilities, and characteristic parameters of α-relaxation kinetics during the quenching process. MD results show that for the classic COC E-co-NB (ethylene-norbornene copolymer), an increase in cyclic olefin content from 25 to 50 mol % reduces atomic mobility, limiting the molecular chain movement at higher temperatures and improving Tg. Compared to NB, the more rigid rings in tricyclopentadiene (TCPD) and exo-1,4,4a,9,9a,10-hexahydro-9,10(1',2')-bridged phenylidene-1,4-bridged methylideneanthracene (HBM) have the following effects: (1) reducing the thermal expansion coefficient and overall chain mobility; (2) enhancing the diffusion energy barrier; (3) promoting the formation of local ordered structures; (4) accelerating α-relaxation dynamics at high temperatures and improving the dynamic fragility m. These lead to an upward shift in the temperature region where chain movement is limited and thus improve Tg and high-temperature dimensional stability. In this simulation, the correlation equation between Tg, m, and the microstructural parameters of COCs is established, which is of great significance for the development of COCs with high performance.

Seismic Retrofitting of Existing Reinforced Concrete Buildings Using Aluminium Shear Links and Eccentric Steel Chevron Braces

Many existing reinforced concrete buildings have been designed based on earlier codes of practice that underestimated seismic forces, making them vulnerable to damage during seismic action. Equipping existing buildings with shear links and eccentric braces is one of the available seismic retrofitting methods to dissipate seismic energy away from the main structural members. In this paper, a proposal for the seismic retrofitting of two existing reinforced concrete buildings using aluminium shear links and steel braces is presented. First, a capacity-based design approach is followed to determine the required sizes of the shear links and eccentric braces. Second, numerical analyses are used to compare how the original and retrofitted buildings responded. These tests include pushover analysis, nonlinear time-history analysis, damage analysis, incremental dynamic analysis, fragility and reliability analysis, and damage analysis. The results reveal that the proposed retrofitting method can sufficiently upgrade the performance level of the buildings and reduce their storey displacements and interstorey drifts, as shear links are found to absorb almost all seismic energy, therefore keeping other structural members responding elastically. Yet, using shear links alters the local behaviour of the surrounding structural members, which should be considered in the design process. Furthermore, compared to the original buildings, retrofitted buildings are expected to undergo less structural damage as they have lower damage indices. Meanwhile, the fragility of retrofitted buildings is significantly reduced compared to the original ones, which indicates the efficiency of the proposed retrofitting methods in upgrading the performance of seismically deficient reinforced concrete buildings.

Fragility and Tendency to Crystallization for Structurally Related Compounds.

The present study was designed to investigate the physical stability of three organic materials with similar chemical structures. The examined compounds revealed completely different crystallization tendencies in their supercooled liquid states and were classified into three distinct classes based on their tendency to crystallize. (S)-4-Benzyl-2-oxazolidinone easily crystallizes during cooling from the melt; (S)-4-Benzylthiazolidine-2-thione does not crystallize during cooling from the melt, but crystallizes easily during subsequent reheating above Tg; and (S)-4-Benzyloxazolidine-2-thione does not crystallize either during cooling from the melt or during reheating. Such different tendencies to crystallize are observed despite the very similar chemical structures of the compounds, which only differ in oxide or sulfur atoms in one of their rings. We also studied the isothermal crystallization kinetics of the materials that were shown to transform into a crystalline state. Molecular dynamics and thermal properties were thoroughly investigated using broadband dielectric spectroscopy, as well as conventional and temperature-modulated differential scanning calorimetry in the wide temperature range. It was found that all three glass formers have the same dynamic fragility (m = 93), calculated directly from dielectric structural relaxation times. This result verifies that dynamic fragility is not related to the tendency to crystallize. In addition, thermodynamic fragility predictions were also made using calorimetric data. It was found that the thermodynamic fragility evaluated based on the width of the glass transition, observed in the temperature dependence of heat capacity, correlates best with the tendency to crystallize.

Effect of intermolecular hydrogen bonding strength on the dynamic fragility of amorphous polyamides.

Small-molecular-induced intermolecular hydrogen bonding (inter-HB) interactions were reported to increase the glass transition temperature (Tg) while decrease the dynamic fragility (m) of polymers. Herein, enthalpy relaxation parameters heat capacity jump (ΔCp) at Tg and enthalpy hysteresis (ΔHR) were investigated to help clarify the effect of macromolecular-induced inter-HB on Tg and m using amorphous polyamides as model polymers. The inter-HB strength was weakened by random copolymerization with varied chain rigidity, but was enhanced by decreasing steric hindrance. It was found that Tg and m increased after copolymerization due to the increased chain rigidity. Nevertheless, increasing steric hindrance leads to an increased Tg while anomalously reduced m. Further results found that m can be well correlated to Tg·ΔCp/ΔHR. ΔCp increases more significantly than ΔHR in co-polyamides, and thus the entropy change dominates the activation free energy of cooperative rearrangement. By contrast, ΔHR increases more significantly than ΔCp with increasing steric hindrance, and thus it is reasonable that Tg increases while m decreases. Most importantly, ΔCp and ΔHR decrease with increasing inter-HB strength regardless of the variation of Tg. These results indicate that the inter-HB strength may be very strong and insensitive to temperature in polyamides, thus behaving like physical cross-linking.

Dynamic fragility of slender and discontinuous rock pillars – an example from the Negev Desert, Israel

Dynamic fragility of slender and discontinuous rock pillars – an example from the Negev Desert, Israel

Study on seismic behavior and collapse risk of super high-rise braced mega frame-core tube structural system

The braced mega frame-core tube (BMFCT) structure could provide an efficient lateral-force resisting (LFR) system for high-rise or super high-rise buildings, especially for those higher than 500 m. The BMFCT structure is a dual LFR system, including the outer braced mega frame and the inner core tube. The seismic behavior and design method of this structural system is not clear. In this study, a parametric study based on collapse risk-targeted analysis is conducted to clarify seismic mechanism and performance and to make clear means of matching reasonable stiffness and setting energy-dissipation components. Five comparable BMFCT structures with different mega brace stiffness proportions and frame-tube stiffness ratios are designed. An efficient elasto-plastic modeling method is introduced to establish the accurate FE models. The corresponding collapse risks are calculated through Incremental Dynamic Analysis and fragility theory. The results show that the structural collapse risk increases with the increased frame-tube stiffness ratio. Therefore，the stiffness and bearing capacity of peripheral frames should be strengthened to ensure the structural collapse margin. On the other hand, the collapse resistance capacity gradually decreases with the increasing of the mega brace stiffness. Thus, the stiffness proportion of mega braces should be recommended to meet the basic lateral stiffness requirements, which shall not exceed 35 % of the overall structural stiffness. Moreover, the distribution feature and ideal arrangement of the energy dissipation components are proposed. The seismic design recommendation based on the uniform collapse risk is also proposed for the BMFCT system, which serves a reference for the structural design of super high-rise buildings.

Seismic Performance of Steel-SMA Reinforced Columns: Numerical Investigation

The residual displacement of a bridge column governs its functionality after a severe earthquake. A box girder bridge was selected as a case study. Pushover analysis, quasi-static cyclic analysis, incremental dynamic analysis and fragility analysis were conducted to compare the seismic performance of the reinforced concrete column, the unbonded prestressed reinforced concrete column (UBPRC column) and the unbonded prestressed reinforced concrete column using superelastic shape memory alloy (UBPRC-SMA column). The threshold loading plateau axial load ratio was recommended in designing a UBPRC-SMA column, thereby ensuring the self-centering performance of a bridge column with fewer superelastic SMA bars. The self-centering performance was considered in the fragility analysis, and the results show that the UBPRC-SMA column suffers the least damage for the collapse damage state.

Impact of asymmetrical corrosion of piers on seismic fragility of ageing irregular concrete bridges

This article investigates the seismic fragility of ageing irregular multi-span reinforced concrete (RC) bridges. Different irregularity sources are considered, including: (i) substructure stiffness irregularity arising from the unequal-height piers, (ii) substructure stiffness irregularity arising from the spatially variable (asymmetrical) corrosion damage of piers and (iii) irregular distribution of effective tributary masses on piers of varying heights. To this end, a three-dimensional nonlinear finite element model is developed for multi-span RC bridges and verified against a large-scale shake table test results of a two-span concrete bridge specimen available in the literature. Nonlinear pushover, incremental dynamic and seismic fragility analyses are performed on three groups of two-span RC bridges with different configurations. Moreover, a time-dependent dimensionless local damage index is employed to evaluate the failure sequence and collapse probability of selected bridge layouts. The analysis results of the three studied irregularity sources show the considerable significance of spatially variable corrosion of bridge piers and substructure irregularity on the failure sequence of piers and seismic fragility of multi-span RC bridges. Furthermore, analysis outcomes show that uneven corrosion of piers triggers an unbalanced distribution of seismic ductility demands and irregular seismic response of equal-height multi-span RC bridges.

Comparison of Damage Indexes for Assessing Seismic Fragility of Bearings in an Offshore Bridge

This study analyzes the applicability of different damage indexes for bearings, focusing on the time-dependent deterioration of materials and the time-dependent bond-slip behavior between steel and concrete caused by chloride erosion. First, the methodology is proposed, encompassing the time-dependent deterioration of materials, the time-dependent bond-slip behavior, the quantification of different damage indexes of the bearing, and the fragility analysis for the bearings. Next, an offshore bridge is used as an example to investigate the detailed elements of the components and the time-varying effects. Thereafter, based on incremental dynamic analysis and fragility analysis, the discussion focuses on the comparison of damage indexes for assessing the seismic fragility of bearings in an offshore bridge. This study indicates that if the relative displacement ductility ratio is adopted as the criterion, the coverage of PGA obtained by the theoretical method is 167% greater than that obtained using the empirical method, and the relative displacement ductility ratio, which incorporates the shear deformation of piers, is better aligned with the performance-based ductility design concept and offers better economy. Safety-based damage indexes are recommended for the bridge in seismic zones, while economy-based indexes can be used in favorable bridge environments.

Study of the dynamic fragility of polymer nanocomposites: Correlation with damping

AbstractIn this work, an extensive study on the glass transition temperature (Tg), dynamic fragility and activation energy (Ea) for a variety polymeric nanocomposite materials, based on four different types of polymeric matrices reinforced with carbonaceous nanofillers, and SiO2 has been performed. Referring to the dynamic mechanical analysis data obtained in the author's previous works, the dynamic fragility and activation energy were calculated and examined. Depending on the polymeric type, different behavior was detected, as far as the fragility dependence on nanofiller type and loading is concerned, whereas the Tg variation was also investigated. A general trend of a decreasing dynamic fragility with increasing Tg was found, with the exception of Polylactic acid (PLA)/hybrid nanocomposites. A relation between nanofillers synergy and dynamic fragility variation has been achieved, namely the more homogenous nanofillers dispersion (and the synergistic effect between nanofillers), was associated with higher dynamic fragility values. Furthermore, the inter‐particle distance increment may lead to an increased fragility and the Resin/SiO2 nanocomposites appear to follow this rule. In addition, strain sweep experiments were conducted to analyze the connection between fragility and damping of the polymer nanocomposites. The PLA/hybrid carbonaceous nanocomposites reveal an essential damping enhancement, associated with fragility lowering.

Analysis of the importance coefficient of offshore bridges under earthquakes based on seismic fragility and incremental dynamic analysis

Focusing on the continuous damage and seismic-induced stability of offshore bridges, this paper presents an optimized quantification of the importance coefficient of bridges subjected to earthquakes. First, the time-depending durability analysis model of materials, probabilistic seismic demand model, damage indicator analysis, and input of earthquake ground motions are investigated. Subsequently, using incremental dynamic analysis, fragility, and reliability, a quantitative criterion of the importance coefficient for offshore bridges is proposed. Thereafter, a case of an offshore bridge is analyzed, including the description, finite-element modeling method, the efficient and refined simulation of materials, construction of the damage indicator, and classification of collapse scenarios, also, the collapse resistance of bridges under earthquakes. This study indicates that the importance coefficient increases with the extension of the service time, the time-depending durability damage effects have a significant influence on the importance coefficient. The mainshock-aftershock sequence is vital to the importance coefficient of a bridge during the whole life cycle, and the bridge will still have a certain service performance when it exceeds its design service life.

Mechanistic insights into the crystallization of coamorphous drug systems.

In our previous study, the coamorphous formulation of lurasidone hydrochloride (LH) with saccharin (SAC) showed significantly enhanced dissolution and physical stability compared to crystalline/amorphous LH. However, the coamorphous system is still in amorphous state, and has the tendency to recrystallization, which will in turn result in the loss of above advantages. In this study, the crystallization kinetics under isothermal and non-isothermal conditions was investigated. Compared to amorphous LH, coamorphous LH-SAC showed 68.3-361.2 and 2.6-6.1 times lower crystallization rates in glassy state and supercooled liquid state, respectively. After co-amorphization, the addition of SAC changed the crystallization mechanism of amorphous LH from nucleation-controlled to diffusion-controlled manner. Amorphous LH followed the site-saturated nucleation, whereas the coamorphous system exhibited a fixed number of nuclei. The non-isothermal crystallization indicated amorphous LH and coamorphous LH-SAC showed two-dimensional (JMAEK 2) and three-dimensional (JMAEK 3) growth of nuclei, respectively. Furthermore, coamorphous LH-SAC exhibited higher molecular mobility and dynamic fragility (mD) than amorphous LH, which is kinetically unfavorable for its physical stability. However, from thermodynamic perspective, coamorphous LH-SAC had a higher configurational entropy, i.e., a higher entropy barrier for crystallization, which is beneficial to hinder its crystallization. Therefore, it was concluded that the higher configurational entropy rather than the molecular mobility was proposed to be responsible for its improved stability. In addition, molecular dynamics simulations with miscibility, radial distribution function and binding energy calculations suggested coamorphous components exhibited good miscibility and strong intermolecular interactions, which was also conductive to the enhancement in its stability. This study offers an in-depth understanding about the effect of the coformer on the crystallization kinetics of coamorphous systems, and points out the important contribution of the configurational entropy in stabilizing the coamorphous systems.

Seismic Fragility of a Single Pillar-Column Under Near and Far Fault Soil Motion with Consideration of Soil-Pile Interaction

The soil-structure interaction is a significant challenge faced by civil engineers due to the complexity potential in terms of seismic fragility evaluation. This paper presents a seismic fragility estimation of a single pier considering seismic ground motion types. Furthermore, sand type, pile diameter, pier height, and mass variation were considered to estimate their effect on the seismic fragility of the concrete pier. Incremental dynamic analysis was performed using a beam on a nonlinear Winkler foundation model. The analysis model condition compared near- and far-ground motion effects. Dynamic analysis and fragility assessment of the single-pier structure showed that low mass center produced less vulnerability of the concrete pier in the two cases of the sand type under near- and far-ground motions. The near and far earthquake simulations at complete failure probability had a difference of less than 5% when 0.65s<T1<1s and 2.4<T1/T2, but the opposite was shown when T1<0.5s and 3<T1/T2 were present together.