Resumo em Inglês:

Abstract Prestressed concrete structures are widely utilized in civil engineering due to their superior structural efficiency and load-carrying capacity. However, long-term losses in prestressing forces can compromise both structural integrity and service performance. This study develops a finite element model to assess the impact of prestressing force on the natural frequencies of simply supported beams. The model accounts for the combined effects of axial compression and the physical characteristics of the tendon, including variations in eccentricity and geometric profile. Validation against experimental results from the literature demonstrates strong correlation, particularly for the first and second vibration modes, with average discrepancies of 2.48 and 2.68%, respectively. Numerical simulations also reveal that the influence of prestressing is most pronounced during the early stages of loading, with frequency shifts tending to stabilize as the applied load nears critical levels. The proposed framework offers a valuable complementary approach for the indirect estimation of losses in prestressing forces.

Resumo em Inglês:

Abstract In seismic analysis, it is crucial to consider the interaction between the infill walls and the concrete frame in order to prevent local failures in RC columns. To this end, this paper presents a comparative study of the different structural models to determine the additional shear force in reinforced concrete columns due to the interaction between masonry and structure under seismic loading, for design applications. Simplified models using a single equivalent diagonal strut and multiple equivalent diagonal struts for the simulation of masonry infill structures were investigated. The efficiency of such models was evaluated based on two- and three-dimensional modelling using the Finite Element Method by simulating the contact problem between the masonry infill and the concrete frame. These comparisons focus on examples of single and multi-story masonry infilled frames. The results obtained confirm that the classic concentric strut model significantly underestimates the values of the maximum shear forces in the columns and that these values can be better predicted if the model is adapted for the transfer of the axial force of the equivalent diagonal strut along the contact length of the column and wall.

Resumo em Inglês:

Abstract Buckling is a critical failure mode for aircraft composite panels. Therefore, determining the critical buckling load is essential for properly modeling. To optimize composite laminate structures, it is important to know the strength of the laminate, which can be obtained through statistical analyses based on test data. The resultant strength value is known as a design allowable. This paper aims to establish an approach to evaluate two types of statistically determined buckling allowables, A-Basis and B-Basis, for an aircraft composite wing. In this study, a finite element model of a composite semi-wing was used to perform linear buckling simulations. Six input parameters were initially selected as relevant to affect the buckling strength of the semi-wing: four material properties and two geometric parameters. A set of Monte Carlo simulations was conducted varying these parameters of interest, followed by a global sensitivity analysis using Sobol indices to identify the influence of each one, individually (first-order) and in pairs (second-order). A surrogate model based on artificial neural networks was then trained using data from the Monte Carlo simulations. Finally, this surrogate model was used to define the A-Basis and B-Basis allowables for a critical loading case.

Resumo em Inglês:

Abstract The transmitting boundary (TB) is very important for seismic analysis of the structure-foundation. In this paper, the transmitting boundary in the finite element model for seismic analysis of the structure-foundation is studied. First, the modified viscous boundary is developed to address the non-plane wave behavior of the structure-foundation. Then, the seismic analysis of the model for the structure-foundation is formulated, where a potential earthquake is defined by the incoming waves, and the truncated boundary is imposed with the transmitting boundary conditions. Further, the tied boundary model and the transmitting-layer boundary model are set up to address the radiated waves in the model of the structure-foundation. Finally, the transmitting-layer boundary model has been extended for the structure-foundation subject to obliquely and horizontally incoming seismic waves. In comparison with the various schemes of TBs, the proposed transmitting boundaries have advantages of efficiency, convenience and versatility. The research is of great significance for the dynamic response analysis of structural-foundation.

Resumo em Inglês:

Abstract In order to solve the problems related to the prediction of penetration depth of composite materials, a new method combining physical mechanism and data driving is proposed in this paper. This method integrates 53 groups of ballistic experimental data and 278 groups of LS-DYNA simulation data to construct a data set with 23 characteristic parameters. Previous studies have shown that the ratio of the radius of the circular arc of the warhead to the diameter of the projectile (CRH) has a significant influence on the penetration depth of the projectile. This paper uses the hyperbolic tangent function (tanh(2CRH)) to calculate its saturation effect and conduct in-depth analysis. An adaptive noise injection method of concrete type is used in data processing, which can reduce the data distribution difference between C80 and C150 to 42%. At the same time, because of the modified sequential forward selection algorithm, the input dimension of the model is reduced by 56% and its important physical characteristics are retained. Finally, a Bayesian-optimized Bagging integrated model is constructed, which realizes the high accuracy prediction of RMSE (Root mean square error)=0.23 m and R2=0.90 on the test set. The test data show that when the fiber content reaches about 1%, the penetration resistance of the material is obviously improved. This discovery provides a new direction for optimizing protective materials. Compared with the traditional Forrestal theoretical model, this model not only reduces the prediction error by 92%, but also verifies the effectiveness and universality of the "physical mechanism-guided + data-driven correction" hybrid modeling method in complex penetration problems, providing a generalizable research paradigm for similar engineering mechanics problems that are difficult to fully parameterize.

Resumo em Inglês:

Abstract Based on the theory of elastic wave propagation under thermal effects, this study develops a bedrock-saturated soil-unsaturated soil site model under S-wave incidence to investigate its seismic dynamic response. The analytical solution is derived using Helmholtz decomposition with appropriate boundary conditions. Numerical simulations systematically examine how thermal conductivity, saturation, and ground water level affect ground motion characteristics. Results demonstrate significant differences in displacement amplification factors between thermal and isothermal models. The thermal expansion coefficient and kelvin medium temperature substantially influence vertical displacement amplification, whereas thermal conductivity and heat flux phase delay show minimal effects. With increasing incident angle, horizontal displacement amplification decreases progressively while vertical amplification first increases then decreases. Higher ground water levels and saturation reduce horizontal displacement amplification but enhance vertical amplification.