Resumo em Inglês:

Abstract Approximate seismic evaluation procedures based on the capacity curve have gained wide acceptance in practical engineering owing to their straightforward application and the valuable insights they provide, although they do not always yield results consistent with numerically robust methods. This study presents an investigation into the reliability of results obtained through so-called approximate procedures for constructing the capacity curve, comparing them with those derived from more robust and complex approaches, primarily based on the finite element method. The approximations examined are assessed against results from an experimental study on a full-scale three-dimensional frame tested by another research group, and from a non-linear analysis using the finite element software ATENA, which models the structure under identical conditions. Finally, the study discusses the findings and challenges analysts may face when modelling structures using both numerically refined and approximate procedures, such as those implemented in commercial software like ATENA.

Resumo em Inglês:

Abstract This study presents a systematic investigation of the tensile behavior of FFF-printed PLA specimens, with a specific emphasis on the role of hole fabrication methods—post-drilled versus integrated printed holes—on structural integrity. Unlike prior works that primarily addressed raster orientation and infill effects, this research isolates the influence of hole manufacturing techniques under standardized ASTM D638 and D5766 testing. Stress concentration factors (Kt) were calculated using classical analytical expressions, and their limitations for anisotropic FFF parts are acknowledged and further discussed in the Results and Discussion section. The results revealed that, although raster angle and infill density affected overall strength, the decisive factor was the method of hole generation: post-drilled holes consistently outperformed printed-hole counterparts in tensile resistance and failure behavior. Microscopic analysis confirmed that printed holes introduced interlayer misalignment and shell–infill discontinuities, accelerating crack initiation. These findings demonstrate that hole geometry alone is insufficient to guarantee mechanical reliability, and that the fabrication method of stress concentrators must be considered a critical design parameter in FFF applications.

Resumo em Inglês:

Abstract In this study, two novel machine learning (ML) models, developed using Gene Expression Programming (GEP) and Multi Expression Programming (MEP) algorithms, are proposed for predicting the punching shear capacity of reinforced concrete (RC) slab-column connections with fiber reinforced polymers (FRP) as longitudinal bars. Using the GEP and MEP models, the values of statistical indicators obtained from the training dataset were very close to those values obtained from the testing dataset. In addition, a comparative study was conducted on experimental results and prediction results from the design codes, existing models in the literature and proposed ML models. The comparison revealed that the two models with the highest coefficient of determination (R2) and the lowest mean absolute percentage error (MAPE), root mean square error (RMSE), and coefficient of variation (COV) values belong to the GEP and the MEP model. The results indicated that the proposed GEP and MEP models outperformed the other models in terms of prediction accuracy and robustness. Finally, sensitivity and parametric analyses were conducted.

Resumo em Inglês:

Abstract While the Youla–Kučera (Y–K) parameterization can suppress unknown and time-varying narrow-band disturbances, its performance depends heavily on an accurate secondary-path model, which is often difficult or impossible to obtain in practice. To address this limitation, this work proposes a direct feedback robust adaptive micro-vibration control algorithm that does not rely on secondary-path identification. The controller integrates the Y–K framework with a variable step-size LMS (VSSLMS) scheme for real-time parameter adaptation, ensuring closed-loop stability while improving convergence and robustness under multi-frequency time-varying disturbances. Experiments on an active micro-vibration platform show that the proposed method achieves over 60% improvement in steady-state suppression compared with conventional FxLMS and Y–K + LMS algorithms, particularly under dual-frequency disturbances with spectrum and amplitude variations. These results demonstrate that the method provides a model-independent and robust solution for micro-vibration suppression in precision satellite systems.

Resumo em Inglês:

Abstract Explosively formed projectile (EFP), characterized by its insensitivity to stand-off distance and high kinetic energy, demonstrates considerable potential for application in anti-missile munitions. Numerical simulation, theoretical modeling, and experimental studies were conducted to investigate the impact initiation of both unconfined and confined explosives by EFP. A simulation model for EFP formation and its subsequent impact initiation process was developed using Autodyn software. The initiation mechanisms of explosives under varying cover plate thicknesses were analyzed, revealing a transition in the initiation mode from shock wave initiation to direct impact initiation by the residual EFP. Based on the simulation results, an equivalent diameter calculation method was proposed to characterize the impact initiation behavior of annular cross-section EFP. By integrating the A-T penetration model and the Held criterion, an engineering model for predicting the critical initiation threshold of explosives by EFP impact was established. Experimental results verify the capability of this engineering model to predict the critical cover plate thickness, as well as the accuracy of the numerical simulations.

Resumo em Inglês:

Abstract In this work we demonstrate the effectiveness of an a-posteriori error estimator based on the Prager Synge theorem for a wide range of problems: smooth problem, problem with a steep gradient, problem with a boundary condition induced singularity, problem with varying conductivity. A very simple but innovative strategy is presented for deciding on h or p adaptivity. Exponential convergence rates were obtained for all test problems. The reconstruction of H(div) compatible functions is applied to meshes with hanging nodes. We believe this work represents an important step towards a cost effective hp -adaptive strategy with a posteriori error estimation.

Resumo em Inglês:

Abstract To investigate the effect of variations in priming output pressure characteristics on action time in chamber and maximum chamber pressure. A collaborative test method of primer output-internal ballistics was proposed. Designed primer output test device and internal ballistic performance test device. Aiming at the six factors, experimental study was carried out using the control variable method, respectively. Analyzing the contribution of each influencing factor to internal ballistic performance parameters using principal component regression analysis. Results indicate that shortened pressure start time and pressure peak time of primer output, reduced action time in chamber of the internal ballistics. And within a certain range, when pressure peak of primer output decreased, maximum chamber pressure decreased and action time in chamber of internal ballistics prolonged. High impact of dose of priming composition, damp of primer and ambient temperature on internal ballistic performance. Mapping relationship between output pressure characteristics of primer and internal ballistic performance of bullet was established.

Resumo em Inglês:

Abstract This paper introduces an exact geometrically nonlinear 3D truss finite element based on the positional formulation, capable of accounting for arbitrarily varying axial rigidity along the element’s length. The proposed formulation accurately captures large-displacement behavior using a single element per member, without requiring mesh refinement. A key advantage is the elimination of local-to-global coordinate transformations, thereby reducing computational cost. The formulation derives the axial flexibility using the flexibility method and the principle of virtual forces, avoiding the need for exact shape functions. Numerical examples, including 2D and 3D trusses with polynomial axial rigidity variations, show perfect agreement with analytical solutions in terms of nodal displacements, nodal positions, axial forces, and limit loads. The method also exhibits faster convergence compared to existing approaches, confirming its accuracy, robustness, and efficiency as a powerful technique for geometrically nonlinear analysis of truss structures with arbitrarily varying axial rigidity.

Resumo em Inglês:

Abstract To investigate the ballistic performance of a five-layer composite target plate (steelconcrete-steel-concrete-steel) under the penetration effects of a shaped charge jet, a combined approach of static explosion tests and numerical simulations was employed.The study analyzed the ability of the steel target to enhance the penetration resistance of the composite target plate and explored the reasons behind this enhancement. The research results indicate that due to the influence of reflected and transmitted waves,the steel target effectively reduces the jet's ability to create holes and penetrate the subsequent concrete target; when facing the penetration of a 200-type standard projectile, a combination of three layers of 8mm steel targets is the optimal antipenetration structure, which can enhance the protective performance of the internal concrete protective structure by 65%; After adjusting the thickness ratios of the steel target plates in the composite target plate, it was found that when only increasing the thickness of a single layer of the target plate, the first layer must be increased to 24mm or the third layer to 22mm to fully resist the penetration of the shaped charge jet;Increasing the thickness of the third layer significantly impacts the composite target plate's penetration resistance, but thickening the first layer effectively reduces the diameter of holes in subsequent concrete target plates, thereby enhancing the stability of the composite protective structure. In the overall design of composite protection,adjusting the thickness ratios between different layers can be used to address variousscenarios.

Resumo em Inglês:

Abstract This study presents a detailed investigation into the stiffness characteristics and buckling behavior of heavy, tapered bi-material composite columns with the elliptical cross-section. These columns are laterally laminated using two distinct hybrid materials. The study addresses two primary objectives: (1) deriving explicit expressions for flexural rigidity and mass per unit length, and (2) applying these formulations to evaluate buckling behavior under self-weight conditions. The taper is represented by a linear variation along the bending axis of the elliptical cross-section. A governing differential equation for the buckled mode shape is formulated, and numerical techniques are applied to determine critical buckling loads and corresponding mode shapes. Parametric studies illustrate the influence of geometric and material variations, with the results presented through tables and figures.

Resumo em Inglês:

Abstract This paper presents a precast concrete composite slab-steel truss formwork system incorporating demountable joints to achieve composite behavior between the upper slab and the lower truss, thereby facilitating truss reuse. The system enables shoring-free construction for medium to long spans(3.0m~6.0m), enhancing construction efficiency and reducing material consumption. To assess its performance under realistic conditions, three full-scale specimens were subjected to vertical static bending tests involving a loading-unloading procedure. A finite-element model was developed and calibrated against experimental results, followed by a parametric analysis. The system demonstrated excellent flexural performance with minimal residual deformations after unloading, indicating high recoverability and reliable reusability. Parametric studies reveal that increasing slab thickness primarily enhances the slab's behavior with negligible influence on the global structural response, whereas truss height and member cross-sections predominantly govern overall stiffness and load-bearing capacity. Based on experimental and numerical findings, simplified design equations for strength and deflection are proposed to support design optimization and practical implementation.

Resumo em Inglês:

Abstract To support dynamic penetration decision-making, the millisecond-level real-time response requirement of missile attitude control systems requires efficient ballistic limit velocity (BLV) prediction models. This study proposes a deep learning model based on a YOLO–Mamba hybrid architecture, which achieves the adaptive modeling of multiphysical field coupling effects through feature cross-modules and polynomial expansion. The global feature extraction capability of YOLO and the local temporal modeling of Mamba synergistically enhance multiscale feature capture. In experiments, the model’s inference speed is 1.3 times greater than that of traditional methods, and its prediction error on ballistic datasets is reduced by 32.5–47.8% compared to those of SVM/random forests while maintaining a generalization accuracy of over 92% in data-scarce scenarios. The proposed model serves as a high-precision tool for the optimization of protective materials, and the YOLO–Mamba hybrid architecture offers a novel approach to data-driven modeling of complex impact dynamics problems.