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Highlights • A new approach for predicting the mass distribution of behind-armor debris (BAD) generated during the normal penetration of variable cross-section explosive formed projectile (EFP) on rolled homogeneous armor (RHA) steel is proposed. • The influence of the variable cross-section characteristic of EFP on number of BAD from target and EFP is analyzed. • The variable cross-section characteristic of EFP, the strength of EFP, the axial length of mushroom of EFP, the nose shape of the EFP are all considered. Abstract Since the mass distribution of behind-armor debris (BAD) is an important measurement to evaluate the level of destruction caused by BAD, this work proposes a new approach for predicting the mass distribution of BAD generated during the normal penetration of variable cross-section explosive formed projectile (EFP) on rolled homogeneous armor (RHA) steel. Few papers considered the variable cross-section characteristic of EFP, and it is an important influencing factor on number of BAD from target and EFP. In this paper, the variable cross-section characteristic of EFP, the strength of EFP, the axial length of mushroom of EFP, the nose shape of the EFP are all considered, besides, the fit factor of the average strain rate and the fit factor of Mott formula are introduced. The number of BAD from target and EFP as well as the mass distribution of BAD from target and EFP, could both be predicted by modified formula on the base of theoretical analysis and numerical simulation, then it is verified by the experiment. The results indicate that: 1) compared with ignoring the variable cross-section characteristic of EFP, the accuracy of the number of BAD from target and EFP could be improved as the variable cross-section characteristic of EFP is considered; 2) the modified Mott formula can describe the mass distribution of more than 90% BAD from target and EFP. [ABSTRACT FROM AUTHOR]

• Two innovative retrofit methods are presented in this paper. • Pre-stressed steel strapping technique is applied to retrofit deficient RC joint. • A numerical model is proposed to simulate the cyclic behaviors of specimens. • Softened strut and tie model is applied to obtain the shear capacity of specimens. This paper presents the results of an experimental and numerical study on strapping method for retrofitting deficient interior RC beam-column joints, which do not meet the requirements of current seismic design codes due to some deficiencies including low strength of concrete, inadequate transverse reinforcements, and low construction quality. In order to explore the seismic behavior of the retrofitted RC joints, six interior joint specimens, including two deficient RC joints with inadequate transverse rebar, three RC joints retrofitted with prestressed high-strength steel strips and one RC joint retrofitted with adhesively-bonded steel and prestressed high-strength steel strips, were designed and tested under cyclic loading. The main variables included the retrofit methods, axial compression ratio and volume of steel strips. The test results indicated that the prestressed steel strips worked together well with the deficient RC joints, and the retrofitted specimens exhibited better seismic behavior than the deficient control specimens, especially in deformability and energy dissipation. On the basis of the experimental study, the corresponding numerical model was established using the Open System for Earthquake Engineering Simulation (OpenSEES) and then verified to be valid. Finally, the modified softened strut and tie model was proposed in this paper to calculate the shear capacities of the specimens, and the calculated results agreed well with the test results. [ABSTRACT FROM AUTHOR]

• Sectional analysis and moment curvature approach provide accurate results. • Type of material models strongly affect the predicted fire resistance and deformation of a column. • Temperature elongation of materials has significant effect on column deformation. In the paper, a numerical procedure for investigation of slender reinforced concrete columns and steel-concrete composite columns at normal and high temperatures is presented. The procedure is based on sectional analysis and moment-curvature approach. Its applicability is illustrated on validation examples in which the results obtained by the simulations are compared with the test data given in literature. It is shown that the procedure provides sufficiently accurate results. The procedure was implemented in an in-house MATLAB code. The code is employed for the calculation of the examples presented in the paper. The code was also included in freely available scientific computer programs. The procedure is applicable for normal and high temperature conditions and for columns of symmetrical cross-sections of any type and shape. It is applicable in connection with any type of temperature-time curve, heat transfer model, and material models. [ABSTRACT FROM AUTHOR]

Shear design and verification of bridge deck slabs subjected to concentrated loads (as those of wheels from traffic) is a topic subjected to scientific and engineering debate, where several questions remain open. Several design procedures have been proposed in the past to determine suitable values of the internal forces for design, such as the so-called load-spreading rule or considering a smoothing length for redistribution of the internal forces calculated based on linear elastic approaches. Despite these previous efforts, several instrumental aspects governing the response of bridge deck slabs still need to be clarified and subjected to scientific discussion. An important one relates to the location of the governing control section. Typically, for the case of cantilever bridge deck slabs, two control sections are checked: one close to the webs (acting as linear support) and another near the concentrated loads. While there is no debate about the shear check performed at the section close to the linear support (similar to a one-way slab response), how the check has to be done at the section close to the load introduction zone remains unclear (which can be interpreted as punching or as a one-way shear phenomenon). Another aspect under discussion is the determination of the internal forces considering the redistributions related to the non-linear behavior of the slab, avoiding too simplistic and overly conservative rules. To better understand the phenomenon and to lead to more comprehensive and consistent design approaches, the behavior of cantilever bridge deck slabs subjected to concentrated loads is thoroughly investigated in this paper. The study starts with several phenomenological observations on shear failures in cantilever bridge deck slabs obtained from previous experimental programs. Then, a refined analysis is presented considering a realistic out-of-plane shear response of reinforced concrete slabs. From these analyses, the internal forces can be evaluated in a sound manner accounting for a gradual reduction of the out-of-plane shear stiffness as a function of bending moments and shear forces. This new feature allows tracking the location of the potential shear-critical regions and examining the forces redistributions related to non-linear behavior. Unlike traditional approaches (like the "load-spreading rule" or smoothing lengths), the presented numerical analyses can consider shear failures at any location. The main findings from the physical observations and refined analysis are eventually used to propose a simple but phenomenologically consistent design methodology aimed at practical applications. • Observation on bridge deck tests collected from the literature indicates significant internal forces redistribution. • The geometry and kinematics of the failure cracks of such bridge decks are more similar to the shear cracking of beams without shear reinforcement. • A novel numerical modeling strategy was developed based on a smeared approach to account for the presence of shear redistribution. • A parametric (numerical) study on full-size bridge decks confirmed the influence of direct strutting and flexural reinforcement curtailment. • A phenomenologically consistent design methodology aimed at practical applications was ultimately proposed. [ABSTRACT FROM AUTHOR]

• Proposing a novel model for conveniently representing stitching threads. • The mechanism of the interaction between damage modes is explained by this model. • The damage evolution feature is well captured and analyzed by this model. • The mechanism of damage inhibition from stitching threads is understood by this model. • Illustrating the universality of the model and broadening its application scope. 3D stitching composites have already sparked great interest among researchers due to their ability to effectively improve the weak inter-laminar properties in composite laminate structures. In this paper, a systematic analysis on mode I fracture and low-velocity impact damage of 3D stitched composites has been demonstrated via a novel multi-scale model which is capable of efficiently characterizing the distribution of stitching threads. The damage modes including intra-laminar cracks, inter-laminar delamination and stitching thread breakage are identified via a combination of continuum damage mechanics (CDM), cohesive zone model (CZM) element and truss element. This novel modeling approach enables an association analysis of stitching thread breakage status and other damage morphologies, promoting an in-depth study for the influence of stitching thread on damage evolution, which has not been reported yet. The introduction of stitching threads effectively suppresses the sharp propagation of delamination after peak load, avoiding the catastrophic destruction during mode I fracture. The mechanism of damage inhibition from stitching threads is well revealed by the numerical simulation. Furthermore, the capability of 3D stitched composites to resist low-velocity impact damage is effectively predicted in terms of peak load, damage area and damage morphology, finding that the increase of stitch density inhibits the propagation of matrix crack, as well as delamination. The universality and the expanding application of the model are also evaluated, demonstrating that it is suitable for various 3D stitched composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to heat losses of preferential areas of packed-bed energy storage systems, transverse temperature variations may occur during the charging, discharging and standby processes. Furthermore, the heat losses of preferential areas of the storage tank cause a lower pressure drop in these areas resulting in an increased mass flow rate and further cooling, and thereby an enhanced transverse temperature variation, in a positive feedback loop – a phenomenon called instability. The transverse temperature variations may deteriorate the performance and thereby the economic feasibility of packed-bed energy storage systems. In this paper, numerical and experimental investigations of an air-based packed-bed rock thermal energy storage system for large-scale high temperature applications are presented. The objective of the study is to predict the instability and to analyze the effect of different standby durations and storage size on the instability of the air-based packed-bed system. Transient axisymmetric computational fluid dynamics models were developed for the standby and discharging processes of the packed-bed thermal energy storage systems. In addition, experimental investigations were carried out at a test facility located at Stiesdal Storage, Denmark, using magnetite rocks as heat storage material and air as heat transfer fluid. The results suggest that the numerical predictions are in good agreement with the test data. The instability phenomenon is found to increase with the standby duration, resulting in a maximum difference of 161 K between the maximum rock temperature and the outlet air temperature for a standby period of 10 h followed by a discharging process. Moreover, the results indicate that the maximum difference between the rock temperature and outlet temperature is 73 K and 56 K for a reduced-scale and a full-scale system (no standby period), respectively. • Experiments were conducted on an air-based packed-bed thermal energy storage system. • CFD models were developed and validated for both static and dynamic operation. • Instability in packed-bed systems is predicted during the discharging process. • Increase in instability is observed with the increase in standby duration. • Comparison of reduced-scale and full-scale packed-bed systems is presented. [ABSTRACT FROM AUTHOR]

This paper aims to report the transient-chaos-induced chaotic bursting oscillations in a smooth three-dimensional dynamic model with a low-frequency excitation when an order gap exists between the excitation frequency and the natural frequency. Based on the Nosé-Hoover system, a periodically driven nonlinear system is modelled, in which the transient chaos induced by boundary crisis route can be observed. Through theoretical analysis and numerical simulation, the stability conditions of the equilibrium point and six transient-chaos-induced chaotic bifurcation structures are obtained. Six typical cases in which different routes of the trajectories pass through the transient chaos areas, leading to different patterns of bursting oscillations. It can be found that not only the bifurcation structures but also the bifurcation delay behavior can influence the bursting patterns. In addition, in the transient chaos areas, the bifurcation delay behavior can result in the disappearance of the periodic signals in the small periodic windows. • The transient chaos induced by the boundary crisis route can be observed. • Six different chaotic bifurcation structures can be observed. • Chaotic bursting oscillations are investigated by the modified fast/slow analysis method. • The sensitivity of system parameters on the dynamic evolutions is analyzed. [ABSTRACT FROM AUTHOR]

The prediction of the penetration resistance of stiffened caisson involves uncertainties due to the complex soil failure mechanisms, which makes an obstacle for its application. In this paper, stiffened caisson installations in single-layer uniform and double-layer soft-over-stiff clays are investigated. Large deformation finite-element (LDFE) analyses are employed to simulate the caisson installation process. Soil flow mechanisms, especially inside the caisson along the inner stiffeners, and the caisson installation resistance are studied. Along the inner stiffeners, both soil/soil sliding and soil/skirt sliding mechanisms are observed based on the soil strength and caisson geometry, especially the stiffener geometry and spacing. During the caisson installation in soft-over-stiff clays, the soil flow mechanisms observed in the single layer uniform clay can be replicated in the top soft clay layer before the caisson penetrates into the bottom stiff clay. Caisson full installation resistance can be predicted based on the combined soil-flow mechanisms revealed in single- and double-layer uniform clays. [ABSTRACT FROM AUTHOR]

Vapor chamber is a promising thermal solution for high-power electronics. However, achieving its full potential requires well-designed sintered powder pillars, including pillar diameter, porosity, and pitch. Neglecting these pillar design factors can adversely affect thermal-hydraulic performance, leading to further failures. This paper utilizes numerical simulation and analysis of variance to visualize and analyze the phase change flow behaviors of the pillar-reinforced vapor chamber, then examines the influence of each pillar design factor on thermal resistance, temperature uniformity, and total pressure drop. The results show that, for thermal resistance, pillar porosity has the highest contribution (51.6%), while pillar pitch is moderate (13.6%), and pillar diameter only contributes 0.3%. Nonetheless, pillar diameter has the highest contribution on temperature uniformity (72.1%) and total pressure drops (49.0%). Besides, the results also suggest that when the pillar diameter is larger than a certain value, the thermal resistance and total pressure drop can increase due to excessive vapor flow resistance and limited liquid circulation to the heat source. The optimization results suggest that the desirability of 0.77 balances all responses for the best overall thermal-hydraulic performance. The results inform that the trend of each response is generally aligned for some factors and opposite for others. [ABSTRACT FROM AUTHOR]

Cement-based columns in combination with geosynthetic reinforcement is a well-established soft ground improvement technique to enhance embankment stability. This paper aims to present a finite-element (FE) study based on a case history of a geosynthetic-reinforced column-supported (GRCS) embankment over soft soil. In this study, the columns are simulated with an advanced Concrete model to simulate the development of possible cracking and induced strain-softening. Numerical results are compared against published centrifuge tests, giving confidence to the established FE model with the Concrete model. New insights into the progressive failure mechanisms of GRCS embankments over soft soil are then discussed by examining the stress paths, internal forces, and cracks, as well as the plastic failure zones of columns. In addition, the role of columns and geosynthetics on the progressive failure mechanisms (failure loads and sequences) is also examined by an extensive parametric study. The results suggest that provided the optimization of compressive and tensile forces in the columns combined with the tensile stiffness of the geosynthetics is put in place, more columns can be mobilized to resist global sliding failure and to improve the bearing capacity of GRCS embankments. • The crack-induced softening of DCM columns is captured using the Concrete model. • Progressive mechanisms of GRCS embankments over soft clay are interpreted. • The role of geosynthetic and columns on progressive failure mechanisms of GRCS embankments are identified. [ABSTRACT FROM AUTHOR]

The tuned inerter damper (TID) is a viable solution for addressing the vibration issue of the adjacent-building system. However, the conventional optimal calibration of the TID is conducted based on the classic 3-degree-of-freedom (3-DOF) model with one resonant DOF for each structure, which ignored the background flexibility contribution that comes from non-resonant modes of each one, and thus leads to non-optimal control performance. This paper developed a novel analogue 3-DOF model, in which the background flexibility contribution of each flexible building at the damper attachment location is represented by an equivalent stiffness element. An enhanced formula for the TID optimal frequency is developed accordingly (targeting the fundamental mode of the taller building) using the 'root-locus' method, where the background flexibility as well as the resonant mode contributions that come from both buildings are accounted for. For completeness, the optimal frequency formula that ignores the background flexibility contribution is derived based on the classic 3-DOF model. A robust approach is adopted to determine the optimal damping ratio based on the classic model. Numerical analysis is conducted based on a 25-15 floors adjacent-building system. Results demonstrate that when the enhanced frequency-tuning formula is used, a much more balanced frequency response curve of the taller building is achieved. Further, time-domain seismic analysis indicates that the TID performance is consistently improved when background flexibility is accounted for in the design formulas. • A 3DOF TID-adjacent-building model developed involving background flexibility. • Optimal TID frequency formula developed with background flexibility represented. • Theoretically prove the incapability of TID for controlling similar adjacent buildings. • The proposed formula leads to superior control performance than the classic one. • Increase of inertance value cannot always guarantee a better control performance. [ABSTRACT FROM AUTHOR]

• Considering the two-way coupling between fluid and particles, the position and rate of erosion are analyzed. • The three zones of the oil and gas pump are pump are vulnerable to particle erosion. • Increased fluid velocity or particle mass flow leads to intensified erosion. • Research on erosion wear mechanism through particle impact phenomenon. In the process of oil and natural gas production, solid particle erosion is an important reason affecting the safe operation of oil and gas multiphase pumps. To reduce equipment failure rates, it is urgent to predict positions that are vulnerable to erosion damage. However, the erosion regularities of oil and gas multiphase pumps have rarely been studied in the past. In this paper, the Euler-Lagrange method is used to analyze the gas-liquid-solid flow phenomena in oil and gas multiphase pumps under different operating conditions, combined with the Oka model for erosion prediction. The validity of the erosion prediction method is verified using numerical simulation results of erosion at 90° elbows. To explore the erosion mechanism between fluid and entrained particle flow behavior, the relationship between particle parameters and erosion position and regularities is emphatically studied. The research results indicate that in a certain range, the maximum erosion rate of the oil and gas multiphase pump decreases with the increase of particle density, but increases linearly with the fluid velocity and is also affected by gas volume fraction and other particle parameters. In addition, the erosion usually occurs on the inlet, outlet wall, and the leading edge of the pump chamber, due to the different particle parameters, the erosion range will be slightly different. According to the particle trajectory, it is found that the leading edge of the pump chamber is the most erodible region due to the high frequency and intensity of particle impact. These results provide a reference for optimizing the structural design of the oil and gas multiphase pumps and help to predict their performance against wear. [ABSTRACT FROM AUTHOR]

Extensive numerical studies and analysis are presented to gain insights into the mechanism of load transfer in T- and K-type concrete-filled steel tube (CFST) connections. The new mechanism of load transfer investigated in this paper manifests that the shear load is transferred non-uniformly in the CFST column. Using validated finite element (FE) models, contact pressure stresses of the concrete-tube and angle-concrete interfaces are investigated to examine the interfacial interaction between each component. It indicates that the friction resistances between three components occur almost throughout the loading process, which is non-uniformly distributed along the column length. In addition, stress in each component is evaluated to determine the region of non-uniform load transfer in the column. For T-type connection, non-uniform load transfer shall only be considered for concrete-tube interface. For K-type connection, non-uniform load transfer should be considered for both concrete-tube and angle-concrete interfaces. Non-uniform load transfer mainly occurs in the connecting region and one time diameter of column above the connecting region for theses connections. Finally, the uneven transferred load of each component for the connections is analysed, whilst different force allocation schemes are compared. Based on the shear stresses at the tube-concrete and concrete-angle interfaces, non-uniform load transfer factor of each interface is calculated to quantitatively evaluate the non-uniformity of load transfer for the T- and K-type CFST connections. • Numerically assesses the mechanism of non-uniform load transfer in K- and T-type connections. • Investigate region of non-uniform load transfer of tube-concrete and concrete-angle interfaces. • Analyses non-uniform load transfer of tube, concrete and encased angles. • Compare strength and stiffness allocation schemes of load transfer in connections. • Propose using non-uniform load transfer factors to evaluate new load transfer mechanism. [ABSTRACT FROM AUTHOR]

This paper examines the influence of perforations on the buckling instability and load-bearing capacity of advanced high-strength steel channel section (C-section) columns. Experimental tests were first conducted on 19 column specimens made of complex phrase steel HC700CP980 under axial compression, followed by finite element (FE) analysis. Two section types, the flat web C-section and the web-stiffened C-section, were considered, with perforations categorised as web-only or both web and flanges. Material tests and initial imperfection measurements were conducted and reported. Using test results, finite element models were established and parameter analysis was carried out. Analysis of test results and finite element data revealed that perforations had a noticeable impact on the buckling deformation of flat web C-sections but had a minor effect on load-bearing capacity. In contrast, web-stiffened C-sections exhibited intensified deformation post-perforation, significantly reducing their axial stiffness and load-bearing capacity. The Direct Strength Method (DSM) was assessed based on combined test and FE data. It revealed that the DSM resulted in a high level of inaccuracy and scatter in the load-bearing capacity predictions of high-strength steel C-sections after perforation. To address this, a modified method incorporating a perforation strength reduction factor was proposed, offering straightforward and intuitive calculations with improved design accuracy and consistency. • Tests and numerical analysis conducted on advanced high-strength steel channel section columns with perforations. • Influence of perforations on the buckling instability of columns examined. • Applicability of the Direct Strength Method (DSM) assessed. • Modified DSM with a perforation strength reduction factor proposed for improved design accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes an assembled flange core-tube column connection with self-tapping bolt (AFCS), with high assembly efficiency, low pollution and high joint. Two different core tube thicknesses were set and static low circumferential reciprocation tests were performed. It was found that the core tube thickness has a small effect on the mechanical properties, and the hysteresis curves of the two members are basically the same. The two members in the tests were torn at the foot of the column, and it was concluded that the AFCS possesses good mechanical properties and can satisfy the design criteria of "strong joint, weak member". At the same time, the self-tapping bolts performed well, and the slip did not increase after 0.03 rad, which can proof that the overall safety and reliability requirements were met. The finite element model (FEM) was established by ABAQUS, and the reliability was verified by changing the gap between the core tube and the column wall, the number and diameter of the self-tapping bolts. It was also concluded that the gap should not exceed 1/100 of the column wall width and the influence of each parameter on the mechanical properties of the connection from the largest to the smallest was the number of self-tapping bolts, the diameter of self-tapping bolts, and the gap between the core tube and the column wall. Finally, a theoretical analysis was conducted to derive the strength equations of the core tube and self-tapping bolt as well as the design method of the flange plate. • An innovative assembled steel column-column connection with self-tapping bolts (AFCS) is proposed. • The new connection utilizes both inner sleeve and flange. • Detailed experimental procedures and analysis are presented. • Accurate finite element model is created. • Reasonable theoretical analysis and formula derivation of the key parts are carried out. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical analysis of carbon fiber-reinforced thermoplastic polymer (CF-PETG) made using fused filament fabrication (FFF) technology on dumbbell-shaped specimens under static tensile tests for both honeycomb (NIDA) and rectilinear (RECT) fill patterns at different infill densities (20%, 50%, 75%, and 100%). The tensile test is meticulously executed using the state-of-the-art INSTRON 5969 testing apparatus, with a precise displacement speed set at 2 mm per minute, ensuring the utmost accuracy in our measurements. The experimental results show that the mechanical behavior of each specimen is elastoplastic. The honeycomb pattern showed better strength and stiffness when compared to the rectilinear pattern. The Digimat material model allows for the simulation of complex material behavior, including nonlinear and anisotropic behavior, considering microstructure effects. The numerical model developed using Abaqus/Digimat coupling with experimental results shows a good correlation between the obtained results. [Display omitted] [ABSTRACT FROM AUTHOR]

In the US, a Fusion Pilot Plant (FPP) is considered as a near-future machine to produce electricity on the net. While the FPP concept is being evolved, the common view is that a stronger compared to present fusion devices magnetic field B will be used for plasma confinement. All previous blanket studies have been limited to B <10 T. The paper presents new results of integrated studies for a Dual Coolant Lead Lithium (DCLL) blanket for B = 10–20 T. The blanket geometry, materials and thermal loads are adopted from the existing DCLL design for the US Fusion Nuclear Science Facility (FNSF). The computed results of magnetohydrodynamic flows, heat transfer, and corrosion for the reference DCLL blanket at PbLi T i n / T o u t =350 °C/550 °C suggest the maximum allowable magnetic field of 16 T. High temperature DCLL was found to exhibit acceptable MHD pressure drop even at B = 20 T but the corrosion losses may exceed the conventional limit of 20 µm/year. The analyses suggest that the DCLL blanket is a perspective blanket candidate for future fusion devices with a very high magnetic field >10 T. [ABSTRACT FROM AUTHOR]

This paper presents a thorough experimental/numerical validation of optimised multi-material structures fabricated by material jetting technology. The proposed methodology uses, on the one hand, non-uniform rational basis spline (NURBS) entities to represent the geometric descriptor associated with each material phase constituting the continuum and, on the other hand, a general multi-phase material interpolation scheme to penalise the stiffness tensor of the structure. Two design requirements are included in the problem formulation: the lightness and the minimum length scale of each material phase. The influence of the integer parameters intervening in the definition of the NURBS entity and the influence of different combinations of material phases on the optimised solutions are investigated. The proposed approach is applied to 2D and 3D benchmark structures subjected to prescribed displacements representative of a three-point bending test. Based on the result of the topology optimisation process one of the optimised solutions, balancing the requirements of structural stiffness, lightness, and manufacturing constraints, is selected, manufactured and tested. A comparison between experimental and numerical results (obtained by non-linear analyses) is carried out to show the effectiveness of the approach. [ABSTRACT FROM AUTHOR]

High-strength centrifugal precast (HSCP) reinforced concrete (RC) hollow pipe columns using grouted corrugated duct connection (GCDC) is a novel structure form in accelerated bridge construction (ABC). Nevertheless, the confinement effect of the HSCP hollow column core concrete provided by single-layer transverse rebar and its impact on ductility is not clear. Therefore, in this paper, the confinement effect and the ductility of hollow columns is studied using finite element analysis (FEA) method. A modified model is established to evaluate the constitutive relation of the core concrete confined by single layer transverse rebar. Based on the modified model, a simplified fiber model for predicting the hysteric response of HSCP hollow pipe column using GCDC, which considers bond-slip effect in GCDC joint was developed. The results indicate that the confinement effect of HSCP hollow pipe column is sensitive to the wall thickness ratio. When the wall thickness ratio decreases, the ultimate strain of the core concrete significantly decreases, while the effect on strength is not significant. The simplified model which considers confinement effect is more accurate in predicting the ductility of HSCP hollow columns. It proves that the weak confinement effects can lead to early cracking of the inner wall of hollow columns, which leads a significant impact on the ductility of HSCP hollow columns. Based on the parametric analysis, the peak load of the hollow column increases by 16.7% when the wall thickness ratio rises from 0.1 to 0.2, but only slightly changes when the wall thickness ratio is increased beyond 0.2. The wall thickness ratio of HSCP hollow pipe columns should be set above 0.2 to ensure the strength and ductility. In addition, a ductility evaluation method and a design example were developed to guide preliminary ductile design of HSCP hollow columns. • A modified model is proposed to predict the constitutive relation of HSCP hollow column core concrete. • A simplified fiber model is developed to predict the hysteretic response of HSCP hollow pipe columns using GCDC. • A ductility evaluation method is developed to guide seismic design of HSCP hollow pipe columns using GCDC. [ABSTRACT FROM AUTHOR]

Numerical investigation of the mechanical behaviour of concrete-filled wire arc additively manufactured (WAAM) steel tube under axial compression is presented in this paper. Typical structural performances of concrete-filled WAAM steel tube are extensively analyzed based on the experimental results firstly. FE models are established based on 3D models obtained by 3D laser scan technology, whilst the material anisotropy of WAAM steel tube is taken into account. The sensitivity study on the finite element (FE) model parameters is developed to assess their influence on the simulation results. The established FE models are verified against the test results demonstrating their effectiveness in predicting the structural behaviour of the concrete-filled WAAM steel tube. The composite action between the WAAM steel tube and inner concrete is analyzed through the validated FE models, indicating that it should be emphasized within the strain range from 0.003 to 0.01. The influences of the concrete and steel strengths are evaluated to investigate the confinement effect, showing that the concrete and steel strength exhibit a negative and positive impact on the confinement effect, respectively, and a positive correlation between the steel strength and biaxial stresses of the WAAM steel tube can be obtained. Finally, the design method of concrete-filled WAAM steel tube under axial compression, which considers the effect of the geometric undulations and material anisotropy of the WAAM steel tube, is proposed based on the theory of confining effect. The comparison results indicate that the proposed method can predict the axial compressive strengths of the concrete-filled WAAM steel tubes with reasonable accuracy. • Axial compressive behaviour of concrete-filled WAAM steel tube numerically assessed. • Structural performances of concrete-filled WAAM steel tube experimentally analyzed. • Sensitivity study of FE model parameters developed. • Composite action between the WAAM steel tube and inner concrete analyzed. • Design method of concrete-filled WAAM steel tube under axial compression proposed. [ABSTRACT FROM AUTHOR]

This paper innovatively introduces PID control to the phase-change transpiration cooling process and numerically investigates the multi-physics process of coupled control, flow, and heat transfer through mathematical modeling. Based on numerical simulations, the critical equal-amplitude oscillation characteristics in PID-controlled phase-change transpiration cooling, the PID tuning method for the cooling system's fast stabilization, and the applicability of PID tuning strategies at various control conditions are discussed. The discussions show that liquid phase change significantly influences the PID-controlled response process. The response process is prone to large temperature fluctuations and overshoots when the final phase change position is far from that in the corresponding open-loop process. In addition, the classical tuning parameters from the Ziegler-Nichols critical proportional tuning method are not fully applicable due to the significant heat transfer hysteresis in the liquid phase change and must be revised. After revision, the PID tuning strategy can contribute to excellent control consistency and reliability when the target temperature keeps away from the saturated temperature of the coolant or the feedback location moves within the superheated vapor area. [ABSTRACT FROM AUTHOR]

Solar-powered aircraft have advantages such as quite long flight time and resource conservation. In recent years, with the improvements in solar cell efficiency, lightweight structural design, microelectronics, and automation control technology, more and more countries and organizations have conducted research on solar-powered aircraft. Solar cells are an important component of solar-powered aircraft systems. Perovskite solar cells have the advantages of high flexibility, lightweight, and high specific power, making them the ideal material for solar-powered aircraft wings. To receive as much sunlight radiation as possible and improve the lift-to-drag ratio of the entire aircraft, solar-powered aircraft have a high aspect ratio, making them more sensitive to changes in airflow. Therefore, the stability zones and vibration of perovskite solar cell (PSC) panels in subsonic airflow were studied for the first time. Additionally, to enhance the novelty of the paper and present more comprehensive results, the effect of the nanomaterial properties of one-layered perovskite solar cell substrates reinforced by carbon nanotubes and graphene platelets on the flutter and divergence phenomenon was investigated. To accurately simulate the displacement field after the composite perovskite panel is bent, Reddy's high-order shear deformation theory was adopted. The PSC panel's aerodynamic-elastic coupling motion equations were established by combining Hamilton's principle with the linear potential flow theory and the Bernoulli equation. The dynamic equations were discretized using a meshless numerical method to obtain the generalized multi-parameter characteristic equations. The obtained natural frequencies and critical divergence speeds were compared with published literature to validate the correctness of the aerodynamic model and laminated board model. The divergence instability and flutter instability of the PSC nanocomposite panel were investigated for changing the thickness, nano-fillers, porosity, laying angle, and aspect ratio of the substrate. We showed, that the PSC panel has a divergence instability state first, and then flutter instability appears. Additionally, the substrate nanomaterial parameters of the PSC panel significantly affect shifting divergence and flutter zones. Interestingly, the corresponding natural frequency increases when flutter occurs with an increase in the porosity volume. [ABSTRACT FROM AUTHOR]

In numerical analysis of frame structures, modeling of the connection between structural members often requires the introduction of rigid end offsets to correctly describe the stiffness of the joints. This is typical of beam-to-column connections in civil constructions but is also common in lattice materials, where the element overlapping at the joints locally increases the stiffness of the nodes. However, when nonlinear geometric effects are included, correct simulation of such phenomena is challenging. This paper presents a geometrically nonlinear three-dimensional force-based beam finite element that efficiently accounts for the effects of rigid joint offsets. The model imposes the element equilibrium in the local reference system referring to the element deformed configuration, considering the von Kármán nonlinear terms, and exploits a corotational formulation to account for rigid large displacements and rotations of the beam. Two alternative approaches are used to introduce the rigid offsets. The first derives from an existing proposal where kinematic and static nonlinear operators are adopted to describe the behavior of the rigid portions at the element ends. The second is a novel approach, easier to implement and use, that involves modifying the integration, along the element axis, of the cross-section strains and flexibility. This can be easily defined for beam models under linear geometry assumption but requires particular attention for the analysis of frame structures under large displacements and strains. Both approaches are validated through numerical examples, including comparison with other numerical methods and experimental results available in the literature. • Corotational force-based 3D Timoshenko beam model with large deformations. • Introduction of the end rigid offset contribution into the corotational formulation. • Alternative simpler approach to model end rigid offsets under nonlinear geometry. • Simulation of experimentally tested lattice structures under nonlinear response. [ABSTRACT FROM AUTHOR]

This paper deals with the numerical analysis of ductile damage and fracture behavior under non-proportional biaxial reverse loading conditions. A two-surface anisotropic cyclic elastic–plastic-damage continuum model is adequately presented, which takes into account the Bauschinger effect, the stress-differential effect, and the change of hardening rate after reverse loading. An efficient Euler explicit numerical integration algorithm, based on the inelastic (plastic or plastic-damage) predictor-elastic corrector approach, is utilized to analyze the stress and finite strain loading histories. Detailed discussions are provided on different numerical integration-related consistent tangent operators that achieve convergence within the global Newton–Raphson scheme. The proposed continuum model is implemented into the commercial software Ansys as a user-defined subroutine (UMAT). Furthermore, the novel non-proportional biaxial tensile reverse experiments are performed to validate the proposed continuum model. The associated numerical simulations investigate the stability and accuracy of the proposed algorithm and material model. • A two-surface anisotropic elastic–plastic-damage model with combined hardening and softening rules is presented. • The Bauschinger effect, the stress-differential effect, and the non-hardening effect are properly modeled. • An efficient explicit inelastic (plastic-damage) predictor-elastic corrector approach is used to address the cyclic plasticity and damage issues. • Tensile cyclic tests superimposed by various preloaded shear strains with biaxially loaded HC-specimen. • Different plastic and damage evolution processes are numerically predicted and verified by DIC analysis and SEM images. [ABSTRACT FROM AUTHOR]

This paper presents a novel damping plate-restrained isolation bearing (DP-bearing) that exhibits a range of advantages such as multi-stage energy dissipation, multi-directional restraining effect, and easily assembled/dismountable. The study commences with introducing the fundamental working principle of the proposed DP-bearing, followed by an investigation into the material properties of the damping plates using monotonic tensile and quasi-static cyclic tests. Subsequently, full-scale DP-bearing specimens, considering different numbers and orientations of the inserting damping plates as well as various free traveling distances ("predetermined gaps"), are tested. The test results confirm the multi-function of the damping plates which serve as energy dissipation sources and restrainers simultaneously. Prior to the predetermined gap, the load-displacement curves exhibit a rectangular shape that results from Coulomb friction. Once the gap is reached, the damping plates are activated and provide damping and restraint through shear or tension. The shear and tensile damping plates contribute to over 90% of the total horizontal peak resistance, with the former contributing to more than 70% of the energy dissipation. The study then presents a simplified numerical modeling approach, followed by design recommendations based on the simulation results. Furthermore, the numerical investigations provide supplementary evidence illustrating the effectiveness of the DP-bearing in different loading directions. The variations in the loading angle may induce a combined shear-tensile damage mode that differs from the modes observed in the tests. • A novel damping plate-restrained bearing is proposed. • Both the monotonic and cyclic loading material tests are conducted. • Experimental study on a full-scale bearing specimen is conducted. • The analytical model provides a straightforward method for designing the bearing. • Numerical studies validate and further interpret the experimental results. [ABSTRACT FROM AUTHOR]

• New computer-aided optimization design and additive manufacturing paradigm for steel joints in spatial grid structures is proposed. • Parametric topology optimization design method and numerical model for optimized joints are developed. • The structural performance of the optimized joints is investigated and compared with traditional joints. • A case study on double-layer spatial grid structure with hundreds of joints is presented to illustrate the applicability of the proposed paradigm. • Representative optimized joint is additively manufactured by selective laser melting using 316L stainless steel. This paper presents a complete computer-aided workflow for the parametric topology optimization (TO) design, numerical analysis and additive manufacturing (AM) of steel joints in spatial grid structures. A fully parametric TO design framework for steel joints in spatial grid structure was developed based on the Grasshopper platform. The joint models were parametrically established based on subdivision surface technology and further topology optimized through the bi-directional evolutionary structural optimization (BESO) algorithm with the support of cloud computing server. The structural performance of the optimized joints was thoroughly investigated via the parametric finite element analysis. Variables of loading conditions and TO parameters (target volume and filter radius) that affect the compliance, maximum displacement, maximum stress and stress distribution were taken into account. Analysis showed that the target volume governed the joint structural behaviour while the filter radius affected the geometric details of optimized joint. The practicability of proposed workflow was demonstrated through a parametric optimization design framework of a double-layer spatial grid structure with hundreds of steel joints. A typical optimized joint made of 316L stainless steel was additively manufactured using selective laser melting. This workflow is highly automatic and featured by high design flexibility and integration degree as well as good transplanted ability. [ABSTRACT FROM AUTHOR]

The rotary friction welding (RFW) is a robust, precise, productive and economical joining process that is used in many areas of mechanical engineering to produce lightweight structures consisting of combinations of ferrous and non-ferrous materials, for instance aluminium alloy and steel. Crucial for the design of such lightweight structures is the knowledge about the bonding strength. The bonding strength is the result of the bond formation depending on the present transient kinematic, kinetic and thermal states during the welding process being directly determined by the welding process parameters. Despite several years of empirical research, no reliable numerical modelling approach exists for the RFW process to analyse the bonding strength based on these transient state variables. For this reason, an improvement of the bond formation and therefore an increase in the bonding strength can only be tested experimentally. The main motivation of this paper is to develop an appropriate modelling approach for the estimation of the bonding strength for friction welded lightweight structures manufactured of an aluminium alloy and a structural steel. Therefore, a couple of aluminium alloy and steel welding experiments with different process parameters were performed and subsequently analysed concerning to the resulting bonding strength. Moreover, all the welding experiments were simulated in regard to the corresponding welding process in order to determine the present kinematic, kinetic and thermal state variables, like the strain rate, the stress and the temperature. Thus, a model for the characterization of the bond formation can be developed, which allows a correlation between the bond formation and the resulting bond strength based on the chosen welding process parameters. Finally, the model will be examined and discussed in terms of its plausibility and applicability. • Process simulation of friction welded lightweight structures made of aluminium alloy and structural steel. • Estimation of the transient kinematic, kinetic and thermal state variables in the welding contact zone. • Detailed derivation of a numerical modelling approach to analyse the bonding strength based on the state variables. • Experimental validation. [ABSTRACT FROM AUTHOR]

In this paper, we study the lepton flavor violating decays of the l j → l i γ γ (j=2, 3; i=1, 2) processes under the U (1) X SSM. The U (1) X SSM is the addition of three singlet new Higgs superfields and right-handed neutrinos to the minimal supersymmetric standard model (MSSM). Based on the latest experimental constraints of l j → l i γ γ , we analyze the effects of different sensitive parameters on the results and made reasonable predictions for future experimental development. Numerical analysis shows that many parameters have a greater or lesser effect on lepton flavor violation (LFV), but the main sensitive parameters and sources leading to LFV are the non-diagonal elements involving the initial and final leptons. This work could provide a basis for the discovery of the existence of new physics (NP). [ABSTRACT FROM AUTHOR]

This paper presented a series of tests to investigate the behaviour of the extended end-plate connection utilizing high strength Q960 steel. A total of 8 specimens were tested, including two under ambient temperature and three under high temperature. The results of the tests indicated that increasing the end-plate thickness from 8 mm to 12 mm significantly enhances the flexural capacity and initial rotational stiffness of the connections but reduces the critical temperature and ultimate rotation. In addition, a higher beam bending moment ratio was found to increase the ultimate rotation of the connections while having minimal impact on the critical temperature. Then, the finite element model of the connections was established to investigate the parametric effect, including column axial pressure ratio, beam bending moment ratio, and end-plate thickness on fire resistance. The numerical analysis indicated that increased column axial pressure ratio and end-plate thickness decreased fire endurance, critical temperature, and ultimate rotation of the connections. On the other hand, increasing the beam-bending moment ratio enhanced the ultimate rotation of the connections. Lastly, a rotation-temperature relationship model was proposed to accurately predict the temperature-rotation curve of high-strength steel Q960 end-plate connections, which was validated with experimental data. • Fire tests on response of high strength Q960 steel connections were carried out. • Numerical models were developed to simulate the behaviour of Q960 teel connections at elevated temperatures. • Parametric studies were performed to investigate the effect of key factors on fire resistance of the connections. • A rotation-temperature relationship model was proposed to predict the fire behaviour of Q960 steel connections. [ABSTRACT FROM AUTHOR]

Steel-concrete composite frames have been widely used in high-rise buildings. To improve the utilization efficiency of the indoor area, irregular-shaped concrete-filled steel tubular (CFST) columns were proposed for an alternative of the traditional rectangular CFST columns. In this paper, the L-shaped multi-cellular CFST (LM-CFST) frame was proposed, consisting of LM-CFST columns and H-shaped steel beams. Firstly, four LM-CFST frames were tested under combined axial compression and cyclic lateral loads. The local buckling was observed at both the top and bottom ends of the column, and fracture of steel occurred when the drift ratio was large. The hysteresis curves were spindle-shaped with the ductility indexes of 2.61–3.24. Then, a refined finite element model was established and validated against the test results. A parametric analysis was conducted to study the effect of axial compression ratio, web cell length, concrete strength and steel tube thickness on the seismic performance of LM-CFST frames. It was found that the axial compression ratio could affect the seismic performance of LM-CFST frames significantly, while the concrete strength had little effect. Finally, the compression-bending capacities obtained from the sectional analysis method specified in EC4 were compared with those obtained from tests. It was found that this method could predict the compression-bending capacity of the LM-CFST frame under combined axial compression and cyclic lateral loads with reasonable discrepancies. • Four 1/2 scale LM-CFST frames were tested under combined axial compression and cyclic loads. • The failure modes and hysteretic responses were discussed. • A validated FE model was established for further investigation. • A parametric analysis was conducted to investigate the influence on the seismic performance of the LM-CFST frames. • A simplified method was proposed to evaluate the compression-bending capacity of the LM-CFST frame. [ABSTRACT FROM AUTHOR]

• A turbine blade whose shroud is fractured is numerically studied by peridynamics. • The cracking behaviors of the blade shroud are accurately described. • Corrosion-induced acceleration of crack growth is captured. Fracture analysis of turbine blades is a critical aspect of turbomachinery design. However, direct numerical analysis of fractures on blades is limited by the complexity of blade structures and discontinuity-induced singularities it meets. Peridynamics (PD) methods are applied to describe discontinuous problems and thus promising for simulating blade fractures. In this paper, a PD method is used to numerically analyze a blade whose shroud is fractured. The established model effectively describes the cracking process and predicts the cracking path. Besides, corrosion-accelerated cracking behaviors are numerically examined, highlighting the ability of PD to solve multi-physical cracking problems in complex structures. [ABSTRACT FROM AUTHOR]

• FE models of the circular CFT columns with ring-shaped voids are established and validated. • Parameters' effects on the impact behaviour of the circular CFT column with ring-shaped voids are revealed systematically. • Detailed responses of typical time history curves, failure modes, force diffusion path and contact actions are analyzed. • Design formulas are proposed to assess the transverse impact resistance of the circular CFT column with ring-shaped void. Presently, the research on the impact performance of the concrete-filled steel tubular (CFT) members has never considered the problem of void defect. Hence, this paper fosters a refined finite element (FE) model of the circular CFT column with ring-shaped voids under transverse impact, which considers the initial contact status of concrete. After validating the accuracy of FE models, the effects of void ratio, steel ratio, impact speed and mass of the drop hammer on the dynamic behaviour of the circular CFT column with ring-shaped voids are explored. Detailed impacting mechanisms of the defect column are acknowledged by elaborating its dynamic time history curves, failure morphology, impact force diffusion path, contact process, and stress/strain distribution rule. Calculation methods for evaluating the impact resistance of the circular CFT column with ring-shaped voids are proposed. The results declare that the appearance of ring-shaped voids would significantly weaken the impact resistance of the CFT column. The impact force and energy dissipation are greatly decreased with the increase in void ratio. Under the transverse impact, the steel tube would be seriously depressed due to the absence of effective support acted by concrete with ring-shaped void, and the core concrete would be heavily damaged in return. [ABSTRACT FROM AUTHOR]

• Water storage tanks for fire suppression can be utilized to fulfill the function of structure control as Tuned Liquid Damper (TLD) if properly designed. • A TLD is outfitted with a perforated floor to allow for water passage between compartments to meet both volume and flow rate fire code requirements. • A 2D macroscopic SPH model is employed to model the dual function rectangular tank with a perforated floor. • The model showed excellent agreement when compared with an explicit microscopic model (MM), with significant decrease in computational time. • For a structure-TLD system subjected to random excitation, the tank with a perforated floor was tested against tanks with a solid floor and a fire reserve. • The tank with a perforated floor enhanced the performance of the TLD compared to other tanks, while obtaining the required water volume for fire suppression. Exceeding serviceability limits due to wind-induced motions in tall buildings can cause discomfort for residents and adversely affect auxiliary building services, such as elevator operations. A tuned liquid damper (TLD) is an attractive type of dynamic absorber because of its simplicity and affordability. However, its dimensions and geometry can be limited by available floor space. Utilizing dual-purpose water tanks for both damping and fire suppression purposes can be a feasible resolution to fire code requirements and building motion control. Several design criteria need to be considered to accommodate the fire code requirements and the proper tuning of the TLD. Consequently, in this study, a TLD tank is fitted with a perforated floor to divide it into two compartments that allow water transmission to meet fire code requirements. However, the sloshing motion within the tank is complex and computationally expensive to capture when using traditional simulation models. This paper presents a 2D ISPH code equipped with a macro-level model to capture the effect of the perforated floor on the overall sloshing response of the tank. The model is first evaluated using existing results from previous studies on tanks with horizontal baffles. Next, the ISPH model is used to numerically model the perforated floor using the Ergun resistance (ER) macro-level model. In addition, the perforated floor is also explicitly micro-level modelled using rigid boundary particles to validate the proposed ER model. A numerical analysis is then conducted under different excitation amplitudes and frequencies, with both time history and frequency response results being presented. A structure-TLD model is subsequently used to capture the structure-TLD system response under random excitation. Results show that the ER model can efficiently model tanks with dual functions under both harmonic and random excitation and across a wide range of amplitudes and frequencies, with appreciable computational time savings. The proposed tank with a perforated floor is found to be effective in serving as a dual-purpose TLD and storage tank for fire suppression in buildings. [ABSTRACT FROM AUTHOR]

Research on the equivalent deformation parameters of grouted arch dam abutment rock masses has recently emerged as a key in the design, construction and stability assessment of arch dams. With the aim of synthetically considering scale effects and anisotropy of the rock mass equivalent deformation parameters after grouting, in this paper, a practical numerical calculation method is developed. First, the Latin hypercube sampling method is introduced to generate a network of fractures of the arch dam abutment rock mass. Subsequently, the finite element models of the rock masses with different sizes in various directions are constructed. On this basis, equivalent continuum theory and cohesive element model are applied for numerical calculation of grouting fractured rock masses. Then, the scale effect and anisotropy of the deformation modulus of rock mass under different grouting conditions are investigated. Finally, the Jinping super-high arch dam is taken as an example to validate the theoretical significance and application effect of the proposed method. The analysis results indicate that the process of fracture and fragmentation of grouted rock masses is characterized precisely, and the deformation of material units can be described as fully as possible to calculate more realistic equivalent deformation parameters of the fractured rock masses. [ABSTRACT FROM AUTHOR]

This paper adopted both the numerical and analytical methods to investigate the excavation stability against base heave failure. The finite element limit analysis method (OPTUM) was firstly employed to calculate the safety factor of the excavation stability against base heave failure, and the failure mechanism of the excavation was obtained. Based on the analysis and observation of the numerical results, a rigid block rotational failure mechanism was proposed, and the analytical formula of the safety factor of the excavation was developed through the upper bound method of limit analysis. In order to verify the rationality of the proposed failure mechanism, the analytical formula of the safety factor and the failure pattern of excavation were compared with the numerical results and the existing classical failure mechanism. Furthermore, the influences of soil and excavation conditions on the excavation stability were analyzed and discussed. Finally, a rigid block rotational failure mechanism under stratified stratum conditions was also proposed to consider effects of the complex soil conditions on the excavation stability. The results show that the proposed rigid block rotational failure mechanism provides a more critical safety factor calculation result for actual engineering examples and obtains a more continuous and smooth failure surface, which can serve as an alternative for the analytical method of excavation stability. [ABSTRACT FROM AUTHOR]

This paper proposes and validates a computationally efficient, non-linear numerical macro-modelling strategy to predict and assess the global and local response of steel-concrete composite joints, when subjected to seismic loads. The reference numerical model takes the form of a component-based strategy in which each component can be efficiently characterized in resistance and stiffness terms, and each constituent material has a typical non-linear behaviour with hysteresis (Takeda model for concrete, Pivot model the T-stub components and kinematic model for all the other steel members). The major advantage is the possibility to adapt the same unified modelling strategy to different configurations of steel-concrete composite joints, which may differ for geometrical and mechanical configurations of constituent members, position of joint (i.e., interior or exterior), connection type (welded or bolted), etc. As shown, due to the presented modelling approach, even under simplified assumptions, a rather close agreement is generally found between the present numerical predictions and the cyclic response of a selection of three different steel-concrete composite joints of literature, which have been investigated on full-scale experimental configurations. Most importantly, the contribution of steel members and the concrete slab can be efficiently taken into account, and allow to develop the typical mechanisms in which the slab itself is involved for the complex performance of composite frames under seismic events. • A non-linear macro-model for steel-concrete composite joints is presented. • Possible mechanisms of the concrete slab are efficiently included. • Numerical analyses are presented to study the contribution of joint components. • The unified macro-modelling approach is validated by past full-scale test results. • Results confirm its efficiency and potential for steel-concrete composite joints. [ABSTRACT FROM AUTHOR]

This paper introduces a novel cross-sectional design for concrete-filled steel tubular (CFST) columns termed "concrete-filled double square steel tube" (CFDSST). The CFDSST columns incorporate an inner square steel tube positioned diagonally at 45° relative to the outer square steel tube, which serves as a stiffener for the outer tube. A three-dimensional finite element simulation model is presented to accurately predict the behavior of axially loaded CFDSST short columns. This model considers the influence of concrete confinement by the steel tubes. Experimental data are employed to validate the accuracy of the finite element model. The validated model is then utilized to assess the performance of the proposed columns, considering various geometric and material properties. The results highlight the substantial enhancement in structural performance achieved by the innovative CFDSST column configuration compared to conventional square CFST columns. The integration of the inner CFST components enhances both buckling resistance and the confinement mechanism of the column. This contributes to the increased load-bearing capacity, ductility, and residual strength of the columns. Notably, the steel tube thickness, the yield strength, and the concrete compressive strength greatly affect the performance of the column. Lastly, a simplified design model is formulated to predict the compressive capacity of the CFDSST stub columns, providing accurate outcomes validated by numerical analysis. • A new configuration of CFST columns is introduced. • Finite-element simulation model for CFDSST stub columns is developed. • The behavior of CFDSST stub columns is parametrically studied. • The proposed finite-element simulation and design models provide accurate predictions. [ABSTRACT FROM AUTHOR]

The application of E xternal D iaphragm (ED) in steel frame system is able to reinforce the stiffness of joint and provide efficient protection for the critical part of joint. However, due to the limitation of the existing design codes, the inside space of building is affected frequently by the excessive size of the ED. To reduce the size effect of ED, a hysteretic experiment on four steel joint specimens is first carried out in this paper, the effects of the width ratio (the ratio of ED width to beam flange width) and connection type (B olted web- W elded flange (BW) connection and F ull B olted (FB) connection) are investigated. Then, a numerical analysis is conducted to further explore the influence of the width ratio and the thickness ratio (the ratio of ED thickness to beam flange thickness). The results indicate that the specimen with BW connection exhibits larger stiffness and bearing capacity, but the specimen with FB connection has obvious ascendancy on the ultimate deformation capacity and ductility. Moreover, Changing the width ratio and thickness ratio are unable to cause significant variation on the seismic performance of steel joint if the thickness ratio is larger than 1.25. Therefore, the thickness of the ED is more critical than width to the seismic performance of steel joint. Meanwhile, in the circumstance of the thickness ratio is equal to 1, the width ratio of 0.1 is recommended for the minimum limited value in structure design. • The effect of connection type on the seismic performance of a steel joints with external diaphragm is examined through experimental study. • The impact of the width of external diaphragm on hysteretic behavior of joint is explored through experimental study. • The comprehensive effect of the width and thickness of external diaphragm is discussed through numerical analysis. [ABSTRACT FROM AUTHOR]

A duopoly maritime transportation system with two ocean carriers providing cargo transport services between two sea ports is investigated in this paper. Pricing game models are developed to describe the competitive relationship between the two ocean carriers with/without blockchain adoption. Empty container repositioning is characterized in the models. Through model analysis, the pricing equilibria are derived. Using theoretical analysis and numerical studies, we find that (1) only when the fixed cost of blockchain is low do carriers adopt blockchain technology; (2) regardless of whether or not the competitor adopts blockchain technology, the carrier is better off by adopting it; (3) when both participants choose to adopt blockchain technology, the impact of blockchain on actual demand is not always positive unless the original operational costs are relatively high; and (4) sometimes, empty containers caused by demand imbalance in the two transportation directions are helpful in increasing the carrier's profit. [ABSTRACT FROM AUTHOR]

The diffusive-viscous wave equation arises in a variety of applications in geophysics, and it plays an important role in seismic exploration. In this paper, semi-discrete and fully discrete numerical methods are introduced to solve a general initial-boundary value problem of the diffusive-viscous wave equation. The spatial discretization is carried out through the finite element method, whereas the time derivatives are approximated by finite differences. Optimal order error estimates are derived for the numerical methods. Numerical results on a test problem are reported to illustrate the numerical convergence orders. [ABSTRACT FROM AUTHOR]

In the analytical solutions of satellite equations of motion, the precession-nutation and polar motion (PNPM) effects are usually not considered. For the first-order orbit theory, the magnitude of these effects is small enough to be neglected; however, it might be a different case for a higher order solution, which could possibly be applied in precise orbit prediction or determination in the near future. To clarify the influence of PNPM acting on the Keplerian elements of near-Earth satellite orbits in analytical theory, this paper gives both theoretical and numerical analysis of these effects based on Gaussian equations of motion. From the analysis, the impact of PNPM can be divided into two parts. The first part is a rotational error on the perturbing force vector since the force vector is converted into a coordinate system without considering PNPM; the other part is caused by the error of the satellite coordinates computed in the Earth-Centered Earth-Fixed (ECEF) or True-of-Date (TOD) coordinate system when the PNPM effects are neglected. More importantly, an easy-to-use semi-analytical correction procedure is proposed. It can be applied to the Keplerian elements directly without having to derive again the solutions. With this method, the error caused by neglecting the PNPM can be well corrected. [ABSTRACT FROM AUTHOR]

• Harmonic vibrations of VE laminate plates with exponential complex-conjugate solution form and harmonic balance method. • The use of refined zig-zag theory for the description of layered plate kinematics. • Application of fractional Zener material model with separation of volumetric and deviatoric strain. The paper is devoted to the theoretical formulation of the harmonic vibrations problem for laminate plates in the von Kàrmàn geometrically non-linear regime. The plate layers are modelled as viscoelastic using the fractional Zener material with the linear elastic material being a special case. The model of the material is formulated with the separation of the volumetric and deviatoric strain. The laminate plate kinematics is described using the refined zig-zag theory. The vibrations of the plate are formulated using the alternative exponential form with complex-conjugate amplitudes. The harmonic balance method and the time-averaging are applied to derive the amplitude equation of the problem in hand. The efficiency and correctness of the formulation is verified in the continuation paper Part 2 – numerical analysis. [ABSTRACT FROM AUTHOR]

• FE solution of harmonic vibrations for VE layered plates with exponential complex-conjugate form and refined zig-zag theory. • Effective application of the continuation method to solve the discretised amplitude equation. • Numerous analyses of the influence of various plate and formulation parameters on the resonance behaviour of laminate plates. The paper is devoted to the numerical analysis of the harmonic vibrations of laminate plates with viscoelastic layers in the von Kàrmàn geometrically non-linear regime. The amplitude equation derived in the prequel paper Part 1 – theoretical background is discretized using the 8-noded bi-quadratic plate finite elements. The response curves are obtained using the continuation method to solve the discretised amplitude equation treated as the equation with the frequency of vibrations as a parameter. The proposed method of solution is verified by comparing the results with those from available literature. Furthermore, several numerical analyses are performed, including testing of FE mesh density, plate aspect ratio, various VE materials, support conditions and layers layout as well as the possibility of simplification of the complex-valued zig-zag function used in the description of plate kinematics. Several results of practical importance are found and discussed in the conclusions. [ABSTRACT FROM AUTHOR]

This paper devotes to addressing the finite-time containment control for the multi-UAVs with input saturation and velocity constraints. A novel smooth function is presented to estimate the saturation function with adjustable estimate errors. By utilizing the mean-value theorem, the containment control for UAVs with input saturation can be turned into a variable gain control problem. To address this issue, the Nussbaum-based method is used to design the controller in this paper. Besides, based on the backstepping method, the controller can constrain the velocity states of UAVs within a desired time-varying asymmetric region by limiting the values of virtual velocity commands and the Lyapunov function. Finally, the finite-time convergence of the errors and the practicability of the control law are verified by Lyapunov stability analysis and numerical simulations. [ABSTRACT FROM AUTHOR]

Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C). [ABSTRACT FROM AUTHOR]

The goal of this paper is to introduce and study a new class of fractional differential hemivariational inequality formulated by an evolutionary hemivariational inequality and a fractional differential equation in Banach spaces. By employing the Rothe method and the surjectivity result, we derive the existence of unique solution for such a problem under some mild conditions. Moreover, we use the fully discrete scheme to approximate the fractional differential hemivariational inequality and provide an error estimate for the approximation. Finally, the main results are applied to obtain the unique solvability as well as the numerical analysis for a viscoelastic frictional contact problem with adhesion. [ABSTRACT FROM AUTHOR]

This paper presents the numerical analysis for a variant of the nonlinear multiscale Dynamic Diffusion (DD) method for the advection-diffusion-reaction equation initially proposed by Arruda et al. [1] and recently studied by Valli et al. [2]. The new DD method, based on a two-scale approach, introduces locally and dynamically an extra stability through a nonlinear operator acting in all scales of the discretization. We prove existence of discrete solutions, stability, and a priori error estimates. We theoretically show that the new DD method has convergence rate of O (h 1 / 2) in the energy norm, and numerical experiments have led to optimal convergence rates in the L 2 (Ω) , H 1 (Ω) , and energy norms. [ABSTRACT FROM AUTHOR]

In this paper, a novel third-order autonomous memristor-based chaotic circuit is proposed. The circuit has simple topology and contains only four elements including one linear negative impedance converter-based resistor, one linear capacitor, one linear inductor, and one nonlinear current-controlled memristor. Firstly, the voltage-current characteristic analysis of the memristor emulator for different driving amplitudes and frequencies are presented. With dimensionless system, the symmetry, equilibrium point and its stability are analysed. It is shown that the system has two unstable saddle-foci and one unstable saddle. A set of typical parameters are chosen for the generation of chaotic attractor. Differing from the common period-doubling bifurcation route in smooth dynamical systems, this memristive system shows abrupt transition from the coexisting period-1 limit cycles to robust chaos when varying system parameters. Various dynamical behaviors are analysed using the numerical simulations and circuit verifications. • A novel current-controlled memristor-based chaotic circuit is proposed. • Dynamical behaviors of robust chaos and coexisting attractors are investigated. • Both numerical analyses and circuit simulation validated the feasibility of the chaotic oscillator. [ABSTRACT FROM AUTHOR]

In this paper, a reduced-order finite element (FE) method preserving the unconditional energy-stability is proposed to simulate the Allen-Cahn phase field model, based on the proper orthogonal decomposition (POD) method with the snapshot technique. We first derive the full order FE formulation of the Allen-Cahn model and compute its FE full solutions, from which we choose a few spatio-temporal solutions as snapshots. Based on the POD technique, we then build a set of optimal POD bases maximizing the energy content in the original ensemble data, and in the new low-dimensional space spanned by the POD bases, we establish a low-order numerical model of stable reduced-order FE (SROFE) formulation for the Allen-Cahn phase field model. We also prove error estimates of the SROFE solutions of the Allen-Cahn phase field model. Finally, some numerical results are provided to test the validity of the SROFE formulation. [ABSTRACT FROM AUTHOR]

The activities presented under this paper were focused on designing, manufacturing, testing and evaluation of a metallic antenna reflector for space applications. The main challenge was to obtain a low mass, while maintaining the reflector capability to withstand the mechanical loads encountered during the launching phase, as well as the harsh space environment with significant temperature variations, without any detrimental effect over the dimensional stability of the reflective surface. The chosen material was titanium alloy for the reflector and stainless steel for fasteners and mounting supports. Manufacturing parameters have been investigated aiming for low internal stresses during processing and to obtain the best results in terms of dimensional accuracy and surface roughness. One of the five analysed reflector architectures (reflector breadboards) was selected and manufactured using two different finishing operations, milling and turning, the latter being the one presenting the best results. Dimensional accuracy of the reflector breadboard, before and after vibration and environmental tests, was found to be smaller than the imposed requirements, thus validating the reflector proposed design. After the breadboarding activity, an optimized version of the antenna reflector (demonstrator), also validated by structural analysis, was developed. Unfortunately, the measured profile deviation of the demonstrator was higher than the imposed requirements (by 50%), mainly due to internal stresses during mechanical processing of the new geometry. Before the experimental evaluation of the reflector demonstrator, a surface coating was developed and applied to the reflective surface of the demonstrator. Despite the profile deviation, the demonstrator meets the imposed mechanical requirements and offers important lessons to be applied in the future development activities. • Design for a spacecraft antenna reflector with low mass and high dimensional stability of the reflective surface. • Development and optimization process for a titanium antenna reflector. • Stiffening structure design for a thin wall titanium antenna reflector. [ABSTRACT FROM AUTHOR]