resumo: A atualização do mapa de isopletas da norma NBR 6123 – Forças devidas ao vento em edificações – é um dos aspectos tratados no âmbito do trabalho da comissão encarregada da revisão da citada norma. Tradicionalmente estes mapas são elaborados por meio de análises de valores extremos das velocidades do vento registradas em estações meteorológicas, da aplicação de métodos estatísticos para caracterização dos dados, e de interpolação matemática para geração do mapa. Entretanto, a distribuição espacial dos fenômenos atmosféricos responsáveis por ventos fortes no Brasil não pode ser desconsiderada. Este trabalho apresenta uma proposta para um novo mapa de isopletas da velocidade básica do vento para a NBR 6123 elaborado com base em uma abordagem climatológica e em recente pesquisa incluindo novos dados de centenas de estações meteorológicas. Inicialmente foi desenvolvido um mapa de regiões climáticas associadas aos fenômenos que produzem ventos fortes, a partir do qual o mapa de isopletas foi traçado. Resultaram isopletas associadas a velocidades de vento variando entre 30 e 48m/s.

abstract: Updating the basic wind speed map of NBR 6123 –-Wind loading on buildings – is one of the duties of the committee responsible for the revision of this code. Traditionally such maps are elaborated by means of extreme value wind speed data collected at meteorological stations, use of statistical methods for data characterization, and application of mathematical regression to elaborate the territorial maps. However, the spatial distribution of the atmospheric phenomena responsible for strong winds cannot be disregarded. This work presents a proposal for a new wind speed map for NBR 6123 combining a climatological approach and wind speed data recently compiled from hundreds of meteorological stations. A climatological wind map was first produced considering the phenomena which cause strong winds, and used as a basis to draw the isopleths of the basic wind speed map, considering the measured wind speed data. The resulting map shows basic wind speeds ranging from 30 to 48m/s.

Abstract Wind-induced loading on buildings may be altered due to presence of upwind structures. These variations are quantified by the interference factors (IFs), which is determined experimentally for each case analyzed, since obtaining this quantification in codes and standards is still impractical due to the complexity of the multi-parameters involved. To understand the influence of some of these parameters on the interference effects, contour plots and power spectra density were presented for IFs corresponding to aerodynamic coefficients of the along-wind and cross-wind force, as well as for torsion. Wind tunnel tests were conducted applying the synchronous pressure measurement technique. Interference arrangements with one and two upstream interfering buildings were investigated for different wind angles, relative positions and terrain roughness. Results indicate that the shielding effect is predominant in most of the studied cases. Nevertheless, the amplification effects are generally present in specific configurations and are usually caused by channeling and buffeting effects, as well as vortex shedding.

Abstract The increasing verticalization of urban environments led to the consideration of loads influenced by horizontal forces arising from the action of the wind. Different neighborhood densities alter the flow behavior and reflect on interference effects. An extensive study developed in the wind tunnel through aerodynamic characterization in the reduced model of the CAARC building, simulated with the insertion of distinct windward neighborhood densities in three configurations, I (one interfering model), II (two models) and III (three models), with different relative positions between the models, D and 2D, where D is the smallest dimension of the model, aiming to understand the interaction relationship between such parameters. Based on the results, both the insertion and number of interfering buildings, and the variation in spacing, influence on the determination of the coefficients. The results indicated that the FV values are mainly given as a function of the proximity and size of buildings directly in the surroundings, most forces on the x-axis have been increased (96.2%), on y-axis, most actions have been reduced (65.4%).

ABSTRACT The objective of this paper is to obtain the form coefficients of a two-equal leg angle section, not reflected in the wind load calculation standards used in Cuba for the construction of triangular-based self-supporting telecommunication towers. An experimental test was carried out in the Joaquim Blessmann wind tunnel, belonging to the Federal University of Rio Grande do Sul, for angles of attack between 0º and 180º with intervals of 15º. The obtained results allow to demonstrate the independence of the form coefficients of the Reynolds number and of the turbulent strenght of the flow. The corrected form coefficients are reported as a result of the blockage effect, obtaining the highest values in the attack angles of 0º and 30º.

RESUMEN El presente trabajo tiene como objetivo obtener los coeficientes de forma de una sección compuesta por dos angulares de alas iguales, no reflejada en las normas de cálculo de carga de viento, utilizada en Cuba para la construcción de torres de telecomunicaciones autosoportadas de base triangular. Para ello fue realizado un ensayo experimental en el túnel de viento Joaquim Blessmann, perteneciente a la Universidad Federal de Rio Grande do Sur, para ángulos de ataque entre 0º y 180º con intervalos de 15º. Los resultados obtenidos permiten demostrar la independencia de los coeficientes de forma del número de Reynolds y del contenido de turbulencia del flujo. Se reportan los coeficientes de forma corregidos producto del efecto de bloqueo, obteniéndose los mayores valores en los ángulos de ataque de 0º y 30º.

Abstract A numerical investigation is performed in this work in order to evaluate the aerodynamic performance of building cross-section configurations by using corner modifications. The CAARC tall building model is utilized here as reference geometry, which is reshaped considering chamfered and recessed corners. The numerical scheme adopted in this work is presented and simulations are carried-out to obtain the wind loads on the building structures by means of aerodynamic coefficients as well as the flow field conditions near the model’s location. The explicit two-step Taylor-Galerkin scheme is employed in the context of the finite element method, where eight-node hexahedral finite elements with one-point quadrature are used for spatial discretization. Turbulence is described using the LES methodology, with a dynamic sub-grid scale model. Predictions obtained here are compared with experimental and numerical investigations performed previously. Results show that the use of corner modifications can reduce significantly the aerodynamic forces on the building structures, improve flow conditions near the building locations and increase the Strouhal number, which may have an important influence on aeroelastic effects.

Abstract This paper presents a series of results with respect to the mean values of shear, base moment and torsion acting in a building obtained through an experimental wind tunnel study using the standard building proposed by the Commonwealth Advisory Aeronautical Research Council (CAARC) as building reference. In the loading determination, the interference of a neighboring building with similar geometric characteristics to the CAARC was simulated, considering variations of positioning and spacing in relation to the reference building. It was concluded that the presence of the neighboring building increased the mean loads in the reference building for a significant number of directions considered. In the case of the considered deviations and the proposed provisions by this study, it was concluded that the vicinity factor that would contemplate the majority of the results obtained in the tests should increase the wind loads by at least 60% in relation to the values obtained for the building reference considered in isolation.