Resumo em Inglês:

Abstract Accounting for fluid-solid coupling in saturated underwater soils, the scattering problem of underwater tunnel under plane SV-wave incidence is investigated by using the Fourier-Bessel series expansion method of wave function. Numerical examples analyze the effects of incident wave angle, frequency, tunnel burial depth, and porosity on displacement at the water-soil interface and dynamic stress concentration on the tunnel surface. When η=0.5, increasing the incident angle reduces horizontal displacement by up to 39.3%, increases vertical displacement by up to 96.2%, and raises the Dynamic Stress Concentration Factor (DSCF) on the tunnel surface by 65.6%. Porosity shows minimal impact on stress and displacement. As porosity increases, horizontal displacement decreases by up to 2.1%, vertical displacement increases by approximately 1.23%, and DSCF decreases by 1.2%. As incident frequency increases, displacement and stress distributions become more complex, with more pronounced peaks, and troughs. Maximum horizontal displacement increases by 86.4%, and vertical displacement by 91.2%. Displacement and stress concentration are most pronounced above the tunnel under shallow burial conditions.

Resumo em Inglês:

Abstract This article presents a comparative study of the reliability of reinforced concrete (RC) cross-sections subjected to simple bending, designed at the ultimate limit state and following the recommendations of the 2014 and 2023 versions of the Brazilian code NBR 6118. The analyses are based on reliability theory by implementing the FORM algorithm on three rectangular cross-section configurations, considering three constant values of dimensionless bending moments and five different concrete strength classes between C30 and C90. Although the elements designed by NBR 6118:2023 have shown additions of up to 19% in the total steel cross-section area as a consequence of the implementation of the strength reduction factor (ηc), the results show no significant improvements in reliability compared to the 2014 previous version of NBR 6118.

Resumo em Inglês:

Abstract The objective of this research is to present practical solutions for improving structural performance of thin-walled conic polygonal monopoles. The analysis encompasses computational simulations, analytical evaluation, and structural verification of reinforcements for openings and longitudinal folded stiffeners of flat walls. A benchmarked solution is derived from a design involving a 20-sided cold-formed steel polygonal section employed to support telecommunication antennas at a height of 40 meters. The structural verification is performed under the influence of wind loads, with particular attention to the commonly reported basic gust wind speed in Brazil. The conducted analysis encompasses: (i) wind-induced static equivalent dynamic behavior, (ii) parametric elastic buckling analysis, (iii) non-linear finite element analysis of reinforced openings, and (iv) direct strength method (DSM) performance evaluation of stiffened polygonal cross-sections. The importance of combining tailored numerical tools such as the finite strip and finite element methods, as well as wind-induced behavior, is demonstrated through the structural analysis results. In essence, the study's findings reveal the previously overlooked local-distortional buckling interaction in current design guidelines. Moreover, the research demonstrates that incorporating reinforcements and longitudinal stiffeners significantly enhances the flexural capacity of slender structures. Notably, the adoption of a single 4-fold (trapezoid) stiffener shape, per polygonal wall, emerges as a promising effective solution for enhancing the overall flexural capacity. Further full scale experimental structural tests and computational fluid dynamics should be considered for advanced structural analysis and improved design.

Resumo em Inglês:

Abstract This article investigates the buckling and free vibration behavior of bio-inspired helicoid laminated composite (BiHLC) plates resting on a Pasternak foundation (PF) using the meshfree moving Kriging (MK) method for the first time. In this study, the MK method leverages Reddy's first-order shear deformation theory (FSDT) for analysis of the mechanical behavior of plates. The PF is characterized by two stiffness parameters: spring stiffness k1 and shear stiffness k2. A key advantage of the MK interpolation is its Kronecker's delta property, enabling direct enforcement of boundary conditions (BC). Unlike original MK method, this approach does not require pre-defining the correlation parameter, which can influence approximation accuracy. The governing equations are derived using Hamilton's principle. A thorough analysis is conducted to understand how the helicoidal layup scheme, geometrical parameters, BC, and the foundation's stiffness parameters influence the critical buckling loads and natural frequencies of BiHLC plates.

Resumo em Inglês:

Abstract A numerical investigation is performed in this work to evaluate the influence of controlled spoilers on pressure mitigation over low-rise building roofs. Considering that low-rise buildings are susceptible to severe damages caused by wind action, spoilers are utilized along the roof windward edges to reduce the aerodynamic load, which are controlled using PID control techniques. Numerical simulations are carried out using a semi-implicit Characteristic-based Split algorithm, where linear tetrahedral finite elements are employed for spatial discretization in a standard Galerkin procedure. Turbulence modeling is performed using Large Eddy Simulation and the flow fundamental equations are written considering isothermal and incompressible conditions in arbitrary Lagrangian-Eulerian kinematical description to consider the spoiler angular motion. Two and three-dimensional simulations are carried out using a low-rise building model, where the influence of controlled roof spoilers is evaluated. Wind tunnel predictions are utilized to validate the numerical formulation proposed here.