Search Results (140)

Hysteretic energy, a critical component of seismic input energy, is predominantly dissipated through the hysteretic behavior of structural members in most conventional structures. The motivation is to establish the conditional probabilistic model of normalized hysteretic energy of the structure after determining its displacement, thereby facilitating the estimation of the Park–Ang damage index. This study develops a probabilistic model for normalized hysteretic energy conditional on the ductility ratio. Three macroscopic hysteretic models, representative of the hysteretic behavior of distinct structural types, are employed to quantify the effects of ground motion characteristics (e.g., magnitude, distance, pulse, duration, and site conditions) and structural properties (e.g., post-yield stiffness and damping ratio). The findings reveal that a lognormal distribution effectively characterizes the normalized hysteretic energy. Among the investigated parameters, ground motion duration leads to a significant influence on the distribution of normalized hysteretic energy (maximum difference up to 30%). To facilitate practical applications, a set of predictive expressions is proposed to estimate the mean and standard deviation of normalized hysteretic energy. The resulting conditional distribution reproduces the empirical distribution derived from the original data, with an average error of approximately 5%. Using established expressions, the required ductility capacity under specified performance objectives can be probabilistically determined in seismic design. Moreover, the established distribution can be used to determine the potential hysteretic energy of the structure for assessing its damage state after an earthquake, as demonstrated through a full-scale shaking table test. Full article

The nitrile butadiene rubber-based viscoelastic damper (NVED) has been proven effective in improving the seismic performance of various types of structures. This study proposes to enhance the hysteretic behavior of traditional Chinese wooden joints using the NVED. The cyclic tests on the NVED are first conducted to derive their mechanical properties. Secondly, two configurations of the mortise-tenon joints are selected as the prototype models to fabricate four specimens, and the hysteretic loading tests are conducted on the specimens to derive their hysteretic behaviors. Comparisons are made between the models with and without the NVED to clarify its reinforcing effects. On the basis of the test results of the mortise-tenon joints and the NVED, a simplified simulation method is proposed to represent the joints with the NVED. The test results show that the installation of the NVED can remarkably improve the hysteretic performance of mortise-tenon joints throughout the entire loading process. Compared with the unreinforced joints, the bearing capacity and energy dissipation of the NVED-reinforced specimens can increase by approximately 40%, particularly under large deformation conditions. The proposed simplified simulation method, which adopts zero-length elements to simulate the rotational response of the joints and the NVED, can adequately capture the pinching effect as well as the stiffness and strength degradation of the NVED-reinforced mortise-tenon joint models. Full article

The mechanical behavior of lead/rubber bearings (LRBs) is strongly influenced by both ambient temperature and hysteretic heating under seismic loading; however, their coupled effects and underlying mechanisms remain insufficiently understood. This study presents a systematic investigation of the thermo-mechanical response of LRBs through combined experimental and numerical approaches. Dynamic cyclic tests were conducted on full-scale LRBs (700 mm in diameter) over a wide range of ambient temperatures, revealing that ambient temperature and hysteretic heating jointly govern the evolution of key mechanical properties, including stiffness, characteristic strength, and energy dissipation capacity. Specifically, decreasing temperature leads to stiffness and strength enhancement, whereas hysteretic heating induced by cyclic plastic deformation of the lead core results in progressive softening and degradation of restoring force. Based on the experimental observations, a modified uniaxial Bouc–Wen constitutive model is developed, incorporating the coupled effects of ambient temperature, hysteretic heating, and large-strain hardening. The proposed model is implemented in a single-degree-of-freedom (SDOF) base-isolated system to evaluate the seismic response under different temperature conditions. The results reveal a competing mechanism between ambient temperature and hysteretic heating: low temperatures tend to increase base shear and reduce displacement, while hysteretic heating produces the opposite effect, with their relative dominance depending on temperature level and ground motion intensity. Neglecting such thermo-mechanical coupling may lead to significant misestimation of structural response, particularly under long-duration strong ground motions. This study provides new insights into the coupled temperature-dependent behavior of LRBs and establishes a robust modeling framework for the seismic analysis and design of isolation systems under complex service conditions. Full article

Background: Corylin (3-(2,2-dimethylchromen-6-yl)-7-hydroxychromen-4-one), a bioactive flavonoid, has been reported to exercise anti-inflammatory, antineoplastic, and antioxidant effects, and may also possess lifespan-extending properties. Objectives: Any modifications of transmembrane ionic currents produced by corylin remain largely unknown. Methods: The patch-clamp technique and docking prediction were used in this study. Results: In pituitary GH₃ somatolactotrophs, corylin concentration-dependently increased the magnitude of the M-type K⁺ current (I_K(M)), with an EC₅₀ of 3.8 μM. Concurrently, the activation time constant of I_K(M) was shortened. The addition of linopirdine (10 μM), an I_K(M) inhibitor, suppressed the current amplitude. Corylin also induced a leftward shift in the steady-state activation curve and enhanced I_K(M) during pulse-train stimulation. Moreover, corylin increases the hysteretic strength of I_K(M) evoked by a long-lasting triangular ramp pulse; this effect was attenuated by linopirdine. The stimulatory effect of corylin on I_K(M) was not altered by carvedilol or iberiotoxin but was reduced by dapagliflozin. In contrast, depolarization-activated I_K(M) was not affected by 17β-estradiol alone. In cell-attached recordings, corylin increased M-type K⁺ (K_M)-channel activity with minimal change in single-channel amplitude, while prolonging the mean open time. This stimulatory effect was reversed by linopirdine or dapagliflozin. Additionally, corylin slightly inhibited the erg-mediated current. Docking analysis further suggested that corylin potentially interacts with residues in KCNQ2 or KCNH2 channels via hydrogen bonding and hydrophobic interactions. Conclusions: These findings suggest that corylin modulates ionic currents, primarily through K_M (KCNQ/K_V7) channels, which may underlie its in vivo actions and those of related flavonoids. These effects may contribute to the regulation of functional activities of neuronal, neuroendocrine, and endocrine cells. Full article

Wire rope isolators (WRIs) exhibit typical nonlinear and asymmetric hysteretic behavior, with their mechanical performance being significantly influenced by the coupled effects of multiple parameters. This study investigates the dynamic response of large-sized spiral WRIs under axial loading. Within the framework of an asymmetric hysteresis model, a novel algebraic closed-form formulation is adopted for parameter identification and numerical simulation. Furthermore, a characteristic parameter, A, is introduced to quantify the unique mechanical behavior induced by the structural configuration of WRIs. Five types of large-sized spiral WRIs are selected as test specimens. For each WRI, tests are conducted under 30 distinct working conditions, yielding a total of 150 cyclic loading tests across all scenarios. By systematically varying the displacement amplitude, loading frequency, and preloading pressure, the influences of these key parameters on the dynamic characteristics of WRIs are comprehensively analyzed. These characteristics encompass the axial hysteresis loop shape, energy dissipation capacity, equivalent viscous damping, and average secant stiffness. The results indicate that these three loading parameters exert substantial effects on the mechanical properties of large-sized WRIs. Additionally, the simulated hysteresis curves derived from the identified parameters exhibit excellent agreement with the experimental observations. Compared with conventional mechanical models, the proposed algebraic closed-form model demonstrates slightly higher fitting accuracy, thereby validating its effectiveness and applicability in characterizing the mechanical behavior of large-sized WRIs. This research provides a crucial reference for the engineering application of large-sized spiral WRIs and facilitates the broader adoption of the proposed modeling approach. Full article

To investigate the mechanical property degradation laws of 6061-T6 aluminum alloy under the synergistic effect of coastal corrosive environments and cyclic loading, the effects of various corrosion durations (0 h, 600 h, 900 h, and 1200 h) on the static performance, hysteretic characteristics, and energy dissipation capacity of the material were studied through indoor accelerated salt spray corrosion tests, monotonic tensile tests, and multi-regime cyclic loading tests. The results indicate that after 1200 h of corrosion, the yield strength and ultimate strength decreased by an average of 2.28% and 5.16%, respectively, with the peak stress point shifting significantly forward. Corrosion significantly inhibits the cyclic hardening effect and accelerates the loss of ductility, with the ductility loss of 1200 h specimens reaching up to 44.0%. Strain is the key factor in activating the energy dissipation potential of the material; when the loading amplitude exceeds 4%, the energy dissipation coefficient stabilizes between 3.0 and 3.3. However, the combination of corrosion and random loading exacerbates the decay of energy dissipation capacity. This study aims to provide a theoretical foundation for the performance assessment and safety assurance of aluminum alloy structures in coastal engineering. Full article

With the growing demand for seismic resilience in urban building structures, the development of high-performance energy-dissipation components has become critical for enhancing structural safety and mitigating earthquake-induced damage. Traditional buckling restrained braces (BRBs) are typically designed to remain elastic under frequent earthquakes, limiting their ability to dissipate early seismic energy input. To address this limitation, a novel friction-damped double-stage yield buckling restrained brace (FD-DYBRB) is proposed by integrating friction dampers (FDs) with a conventional BRB. The mechanical performance of both the traditional BRB and the proposed FD-DYBRB was investigated through cyclic loading tests. Additionally, to evaluate the performance differences among various configurations, a cross-shaped double-stage yield BRB was also tested for comparison. The experimental results demonstrate that the proposed FD-DYBRB design is highly effective, exhibiting plump hysteretic curves and distinct double-stage yielding characteristics. Specifically, the FD-DYBRB possesses an initial stiffness ranging from 249.38 kN/mm to 250.31 kN/mm, which is comparable to traditional BRBs. Under small displacements, its equivalent damping ratio increases by approximately 7% for every 50 kN increase in friction force, achieving continuous early-stage energy dissipation. Furthermore, the proposed brace realizes full-process energy dissipation by maintaining stable average tensile and compressive capacities of 87.08 kN and 84.50 kN, respectively, even after the core plate fractures. Compared to the traditional BRB, the maximum dissipated energy of the FD-DYBRB increases by 23.55% to 54.75%, and its maximum equivalent damping ratio exceeds that of the cross-shaped DYBRB by 5%. These findings offer a reliable technical solution for improving the seismic performance of high-rise and long-span buildings, ultimately helping to mitigate structural damage and protect life and property during seismic events. Full article

This review develops a materials-to-clinic framework for patient-specific, functionally graded (FG) NiTi shape memory alloy (SMA) rods as a complementary paradigm for scoliosis correction that targets durable alignment with motion preservation. The article synthesizes the thermomechanical basis of NiTi (thermoelastic martensitic transformation, near constant superelastic plateau, and hysteretic damping) while leveraging additive manufacturing (AM) capabilities to spatially program transformation temperatures (e.g., A_f), effective stiffness, and geometric inertia along the rod. Consolidated process–structure–property linkages are provided for the PBF-LB, DED, and BJAM routes, together with contamination and composition-control strategies (mitigation of Ni volatilization; management of O/C uptake; gradient heat treatments) and segment-level quality assurance (DSC mapping, micro-CT, EBSD/indentation, and bench bending/torsion in physiologic media). Building on clinical curve classification, the methodology formalizes a grading mask and target moment vector that drive multi-objective optimization of the segmental A_f, relative density/architecture, and cross-section, followed by route-specific build plans and acceptance tolerances. A phenomenological constitutive description provides the forward map from local design variables to temperature-dependent moment–curvature loops for finite element verification and uncertainty control. Surgical handling and activation policies are codified (cold shaping in martensite and controlled intra-/postoperative warming within tissue-safe bounds), and a translational roadmap is outlined, encompassing prospective calibration of classification-to-design mappings, AM process maps with in situ monitoring, digital twin planning, and long-horizon fatigue/corrosion protocols. The proposed graded structures provide an adaptive transformation temperature gradient and tunable mechanical response, representing an important design direction toward 3D-printed, patient-specific SMA rods for durable, adjustable, and efficient scoliosis correction. Full article

To investigate the cyclic behavior of FRP-reinforced steel fiber reinforced concrete (SFRC) composite walls, this paper proposes a section-based finite spring calculation method (FSCM) to reliably predict the cyclic response of such walls under seismic loads. The proposed model accounts for the bond-slip effect of FRP bars and the confining action of transverse reinforcement in the boundary elements. Numerical calculations were conducted on six composite wall specimens with varying longitudinal bar types, fiber volume fractions, concrete strengths, and axial compression ratios. The results indicate that the established calculation method efficiently characterizes the “pinching” effect induced by the linear-elastic properties of FRP bars, and the obtained hysteretic curves are in good agreement with experimental data. Furthermore, the model accurately predicts the load-bearing capacity and residual displacements of the FRP-reinforced SFRC composite walls. Specifically, the average error of peak load calculation for all specimens ranges from −3.36% to 7.36%, and the predicted residual displacements correlate well with the experimental data. These findings demonstrate the applicability of the proposed model for key seismic performance indicators and provide a reliable basis for the research and engineering application of FRP-reinforced SFRC composite walls. Full article

We report coherent X-ray imaging of antiferromagnetic (AFM) domains and domain walls in MnBi₂${\mathrm{Te}}_4$, an intrinsic AFM topological insulator. This technique enables direct visualization of domain morphology without reconstruction algorithms, allowing us to resolve antiphase domain walls as distinct dark lines arising from the A-type AFM structure. The wall width is determined to be 550(30) nm, in good agreement with earlier magnetic force microscopy results. The temperature dependence of the AFM order parameter extracted from our images closely follows previous neutron scattering data. Remarkably, however, we find a pronounced hysteresis in the evolution of domains and domain walls: upon cooling, dynamic reorganizations occur within a narrow ∼1 K interval below $T_N$, whereas upon warming, the domain configuration remains largely unchanged until AFM order disappears. These findings reveal a complex energy landscape in Mn${\mathrm{Bi}}_2$${\mathrm{Te}}_4$, governed by the interplay of exchange, anisotropy, and domain-wall energies, and underscore the critical role of AFM domain-wall dynamics in shaping its physical properties. These sharply defined and hysteretically evolving walls may provide a controllable AFM texture in Mn${\mathrm{Bi}}_2$${\mathrm{Te}}_4$, hinting at potential use in low-power spintronic devices based on domain-wall dynamics. Full article

Ductility, as a fundamental mechanical property, allows structures to undergo inelastic deformations and dissipate seismic energy while maintaining their load-carrying capacity without substantial strength degradation. Thus, the estimation of structural ductility demand has consistently constituted an essential topic of research interest in earthquake engineering. In this study, an iterative procedure for estimating the ductility demand of elastoplastic single-degree-of-freedom (SDOF) systems through dissipated energy is introduced. The proposed procedure helps the determination of ductility demand by use of only elastic response spectra. It initially estimates the hysteretic energy as a proportion of the total input energy. Then, ductility demand is estimated with the help of a developed equation by performing regression analyses based on the nonlinear time history analyses results of elastoplastic single-degree-of-freedom (SDOF) systems with a certain strength. Time history analyses were carried out by using an extensive earthquake ground motion database, which includes a total of 268 far-field records, two horizontal components from 134 recording stations located on firm soil sites. Full article

Owing to their dimensions and high aspect ratio, magnetic nanowires possess distinctive physical and chemical properties and are of great importance in building nanoelectronics devices. Nanowires are traditionally produced by electrochemical deposition methods using alumina or polycarbonate membranes, and their parameters (porosity, size, and arrangement of pores) strongly influence the magnetic properties of nanowires. However, very often, the effect that cannot be neglected during synthesis is overdeposition. The influence of overdeposition on the magnetic properties of nanowires is often overlooked, but it can strongly alter the magnetic behavior of the system. In this study, we use micromagnetic simulations to investigate how different levels of overdeposition affect the hysteretic behavior of nanowires and their magnetization switching mechanism. It was shown that the formation of hemispherical caps on the ends of the nanowires may alter the out-of-plane magnetic anisotropy of the nanowires and strongly influence the squareness of the hysteresis loop. The demagnetizing field distribution for nanowires with overdeposition was also investigated, showing a strong influence of its spatial distribution change on the reversal mechanism and interaction between nanowires. The obtained results were compared to existing experimental observations, showing good agreement with the magnetic behavior of the system. Performed research can be of great interest to experimental groups, as it highlights the importance of controlling overdeposition during nanowire synthesis and its potential influence on magnetic performance. Full article

The use of dissipative bracing systems by hysteretic dampers represents one of the most efficient innovative techniques for the seismic retrofitting of existing structures, especially for reinforced concrete (RC) frame buildings. Many studies on design approaches and case studies have been developed in recent decades and are still in progress; however, the importance of the relation between the properties of the existing structure and of the damper system has not been analyzed, and the influence of the type of arrangement inside or outside the structure, has not been pointed out. In this paper, an innovative dimensionless approach is proposed to describe the dynamic structural properties of the retrofitted structure introducing ratios between the properties of the existing structure and damper system. Therefore, indications to optimize the design of the passive energy dissipation (PED) system can be clearly established for each case. Furthermore, a generalization of the design approach considering different solutions with internal and external bracings is proposed. The application of the dimensionless parameters to the design of a dissipation system for a single-bay three-story RC frame building and points out that damping can be reduced by two times if the capacity of the existing structure is used, further reducing the base shear transmitted to foundation. This result is also obtained by mounting the PED system on an external structure. The effect of infill walls on the stiffness of the existing structure requires an increment of the stiffness of the PED system with double the stiffness of the devices further than the buckling-restrained braces (BRBs). Full article

Reinforced concrete structures are widely used, and the contact type between steel and concrete directly affects the mechanical properties of the structure. Setting unbonded segments on ordinary rebars can effectively improve the ductility and energy dissipation capacity of the structure. So, in order to study the hysteretic performance of ordinary rebar with unbonded segments (OR-US) in detail, this study considered the influence of the unbonded length, rebar diameter, rebar strength, and concrete strength and performed hysteretic tests on five specimens, aiming to analyze the damage phenomenon, hysteretic characteristics, ductility and energy dissipation capacity. The results indicated that all the specimens exhibited earlier yielding of bonded rebar at the loading end than the unbonded rebar; a decrease in the unbonded length or an increase in the rebar diameter or the rebar strength resulted in the delayed yielding of bonded rebar at the loading end; compared to the rebar strength, an increase in rebar diameter led to the later yielding of the OR-US specimen; increasing the unbonded length could improve the ductility and energy dissipation capacity of the specimen; the concrete strength, however, had less impact on the ductility and energy dissipation capacity of the specimen. A bond–slip model for the OR-US was put forward, and the errors between theoretical results and test results were within 10%, indicating the theoretical results were in good agreement with the test results, which provides reference for engineering application of the OR-US. Full article

Buckling-restrained braces (BRBs) are widely recognized as effective energy-dissipation components that enhance the seismic resilience of structures. This study introduces a segmented buckling-restrained brace (S-BRB), composed of a Q235 steel core plate, restraining members, limiting plates, and bolts. A prototype S-BRB was designed, fabricated, and tested under quasi-static loading to investigate its failure mechanisms and hysteretic behavior. A corresponding numerical model was developed in ABAQUS to further evaluate its seismic performance. Test results demonstrate that the limiting plates effectively restrict the deformation of each core plate segment, enabling progressive yielding and preventing premature fracture at weaker sections. The S-BRB exhibited stable hysteretic loops, excellent energy-dissipation capacity, and strong deformation ability. Overall, the S-BRB shows reliable seismic behavior and adaptability in design, indicating strong potential for meeting practical seismic performance requirements. Full article