Análisis experimental de distintas configuraciones de chapa metálica en el refuerzo a flexión de vigas de concreto armadoRESUMENEl acero de refuerzo estructural externo a través de chapas de acero pegadas con adhesivo epóxico es una opción para incrementar la capacidad de carga de elementos de concreto reforzado. En este estudio se evaluaron vigas de concreto reforzadas con chapas de acero SAE 1020 de diferentes espesores (0.75, 1.50 y 2.25 mm), longitudes (80 and 150 cm) y configuración (en forma de U o plana) con el propósito de revisar y comparar las mejores prácticas con chapas pegadas al refuerzo estructural. Se elaboraron 21 vigas construídas con una sección trasversal de 12 x 20 cm y una longitud de 200 cm, con concreto C25 y armadura de flexión con 2 Ø10 mm. Las vigas fueron sometidas a ensayos de flexión en 4 puntos, lo que permitió analizar las cargas últimas y desplazamientos verticales. Como resultado, se presenta una comparación relativa al desempeño de las vigas.Palabras clave: refuerzo estructural; placas de acero coladas, vigas de concreto reforzado. Experimental analysis of various configurations of metal sheets in the reinforcement of flexion of reinforced concrete beamsABSTRACT The external structural reinforcing steel in the way of steel sheets attached with epoxy adhesive is an option to increase the load capacity of reinforced concrete elements. This study evaluated concrete beams reinforced with steel sheets SAE 1020 of different thicknesses (0.75, 1.50, and 2.25 mm), longitudes (80 and 150 cm), and configurations (U-shape or flat) with the purpose of reviewing and comparing the best practices with sheets adhered to the structural reinforcement. Twenty-one beams were built with a cross-section of 12 x 20 cm and a longitude of 200 cm, with C25 concrete, and flexion frame with 2 Ø10 mm. The beams where subject to a four-point flexural test, which allowed analyzing the optimal loads and vertical displacements. Thus, a comparison relative to the performance of the beams is presented.Keywords: structural reinforcement; cast steel plates; reinforced concrete beams. Análise experimental de distintas configurações de chapa metálica no reforço à flexão em vigas de concreto armadoRESUMO O reforço estrutural externo com chapa metálica colada com adesivo epóxi é uma opção que possibilita aumentar a capacidade de carga em elementos de concreto armado. Este trabalho avaliou experimentalmente vigas de concreto armado com reforço de chapas de aço SAE 1020 de diferentes espessuras (0,75; 1,50 e 2,25 mm), comprimentos (80 e 150 cm) e configurações (perfil U ou simplesmente plana) com intuito de revisar e comparar as melhores práticas de reforço estrutural com chapa colada. Foram fabricadas 21 vigas com seções transversais de 12x20 cm e comprimento de 200 cm, utilizando concreto C25 e armadura de flexão com 2 Ø10 mm. As vigas foram submetidas a ensaios de flexão em 4 pontos, o que permitiu analisar as cargas últimas e deslocamentos verticais. Como resultado, apresenta-se um comparativo de desempenho das vigas.Palavras-chave: Reforço estrutural; chapa de aço colada; vigas de concreto armado.

The use of steel fibers in the concrete is mainly aimed at increasing the post-peak toughness, due to the adhesion of the fibers to the cementitious matrix. However, there are several typologies of steel fibers, and the main differences are in the form (relation between length and diameter), fiber geometry, and the characterization between macrofibers and microfibers, which generally serve to reduce macrocracking and microcracking, respectively. In this context, this work evaluated the use of microfibers (20 kg/m³ or volume equal to 0.26% (Vf) of concrete volume), macrofibers (20 kg/m³ or Vf = 0.26%) and hybridization (10 kg/m³) + macrofibers (10 kg/m³) inserted in a high strength concrete (fc = 80 MPa). Two types of steel fibers were used: macrofibers with a diameter of 0.75 mm and a length of 60 mm (a form factor of 80); and microfibers with a diameter of 200 μm and a length of 13 mm (a form factor of 65). The fibers were used in concrete to act as a reinforcement on the compression face of reinforced beams (12×20×160cm), and the mechanical characteristics of the concretes were analyzed: (i) flexural strength in prismatic specimens (10×10×35 cm), (ii) compressive strength in cylindrical specimens (20×Ø10 cm) and (iii) modulus of elasticity in cylindrical specimens (20×Ø10 cm). Analysis of the results showed that compressive strength increased by approximately 8% for all the compositions with fibers compared with concrete without fibers. Similar behavior was verified for the modulus of elasticity. In the prismatic specimens (10×10×35 cm) an increase in toughness was observed, with the macrofibers performing better. In beams measuring 12×20×160 cm, an increase in bearing capacity was verified regarding cracking time and plastic rotation, with the best result also obtained using macrofibers. Overall, it can be concluded that the application of reinforcement with steel fibers in the compression face of beams was efficient, even though it did not present a significant increase in compressive strength, a fact that could be correlated with the reduced volume of fibers used.