The aim of this work was to determine the soil Bray P critical level (CL) and to develop phosphate fertilization guidelines for alfalfa in Argiudolls soils. Results from four years' dry matter production (DM) and P response were re-analyzed. The relationship between DM relative yield (RY) and Bray P was evaluated with logarithmic, quadratic, linear-plateau, quadratic-plateau and arcsine-logarithm models (modified ALCC). The modified ALCC model fulfilled the assumption of homogeneity of variance and explained the greater percentage of variation between RY and P Bray (R²= 0.87). The CL (18.1 mg kg-1, confidence interval between 15.8 and 20.1 mg kg-1) coincides with those determined in other environments. Seven Bray P categories were calibrated and guidelines were designed for fertilization and refertilization according to the sufficiency, reconstruction and maintenance criteria. For 5 mg kg-1 Bray P, the recommended superphosphate rate was 118 kg ha-1 according to the sufficiency criterion. According to the reconstruction and maintenance criteria, the recommended P rate ranged from 160 to 248 kg ha-1, for target production of 8 to 15 Mg MS ha-1, respectively. This information will allow a more rational use of phosphate fertilizers in alfalfa pastures.

Se planteó determinar el nivel crítico (NC) de P Bray en suelo y confeccionar guías de fertilización fosfatada para alfalfa en suelos Argiudoles. Se reanalizaron resultados de producción de materia seca (MS) y respuesta a P de cuatro años. Se evaluó la relación entre el rendimiento relativo (RR) de MS y P Bray con modelos logarítmico, cuadrático, lineal-plateau, cuadrático-plateau y arco-seno-logaritmo (ALCC modificado). El ALCC modificado cumplió el supuesto de homogeneidad de varianza y explicó el mayor porcentaje de variación entre el RR y el P Bray (R²= 0,87). La estimación del NC (18,1 mg kg-1, intervalo de confianza 15,8 y 20,1 mg kg-1) coincide con el determinado en otros ambientes. Se calibraron siete categorías de P Bray y se confeccionaron guías para la fertilización y refertilización según el criterio de suficiencia, y de reconstrucción y mantenimiento. Para 5 mg kg-1 de P Bray la dosis de superfosfato según el criterio de suficiencia fue de 118 kg ha-1, para el criterio de reconstrucción y mantenimiento las dosis variaron de 160 a 248 kg ha-1 con producciones objetivo de 8 a 15 Mg MS ha-1, respectivamente. Esta información permitirá un uso más racional de los fertilizantes en pasturas de alfalfa.

A utilização de estruturas mistas está cada vez mais presente nas obras de Engenharia Civil. As vigas mistas, em particular, são estruturas compostas por dois materiais, um perfil metálico, situado em região predominantemente tracionada, e uma seção de concreto, situada em região predominantemente comprimida, ligados entre si através de dispositivos metálicos denominados de conectores de cisalhamento. As funções prin- cipais dos conectores são: permitir o trabalho solidário da laje-viga, restringir o escorregamento longitudinal e o deslocamento vertical na interface dos elementos e, absorver forças de cisalhamento. Nesse contexto, apresentam-se neste trabalho, modelos numéricos tridimensionais de vigas mistas aço-concreto, com a finalidade de simular o seu comportamento estrutural, enfatizando a interface laje-viga. As simulações foram feitas através do software ANSYS versão 10.0, que tem como base o Método de Elementos Finitos. Os resultados obtidos foram comparados com os previstos por norma e com referências encontradas na revisão bibliográfica, verificando-se que a modelagem numérica é uma ferramenta válida para a análise de vigas mistas aço-concreto.

The use of composite structures is increasingly present in the constructions of Civil Engineering. Steel-concrete composite beams, in particular, are structures consisting of two materials, a profile metal, located in predominantly region of tension, and a section of concrete, located predomi- nantly in compressed region, connected by metallic devices called shear connectors. The main functions of the connectors are: allow the joint work of slab-beam, restrict the longitudinal slipping and uplifting at the interface of the elements, and absorb shear forces. In this context, this work presents three-dimensional numerical models of composite steel-concrete beams, in order to simulate their structural behavior, with emphasis at the slab-beam interface. Simulations had been carried out by means of the ANSYS software, version 10.0, based on Finite Element Method. Results were compared with those provided by Standard Codes and with references found in the literature. Reported results demonstrate that the numerical approach is a valid tool to analyze the behavior of steel-concrete composite beams.