This paper presents the experimental data of the behavior of reinforced concrete beams strengthened to shear with carbon fiber composites. The tests were composed of eight T beams, b w =15 cm, h=40 cm, flange width 40 cm, flange height 8 cm, and length 300 cm, divided into two series with the same longitudinal steel reinforcement and a reference beam without strengthening in each series. The beams had two types of arrangement of internal steel stirrups. The test variables were the internal and external geometric ratio of the transverse reinforcement and the mechanical ratio of carbon fiber composites stirrups. All the beams were loaded at two points. The strengthened beams were submitted to a preloading and the strengthening was applied to the cracked beam. All the beams were designed in order to guarantee shear failure, and the ultimate load of the strengthened beams was 36% to 54% greater than the reference beams. The Cracking Sliding Model applied to the strengthened beams was evaluated and showed good agreement with the experimental results.Keywords: shear strengthening; reinforced concrete; external strengthening; carbon fiber composites.Este artigo apresenta os dados de ensaios de vigas de concreto armado reforçadas à força cortante com compósito de fibras de carbono. Os ensaios de oito vigas T, b w =15 cm, h=40 cm, largura da mesa igual a 40 cm, altura da mesa 8 cm, comprimento de 300 cm, divididos em duas séries com a mesma armadura longitudinal e uma viga de referência sem reforço externo para cada série. As vigas tinham dois tipos de arranjos de estribos internos de aço. As variáveis dos ensaios foram as taxas geométricas das armaduras transversais internas e externas, e a taxa mecânica da armadura em estribos de compósito de fibras de carbono. Todas as vigas foram carregadas em dois pontos. As vigas reforçadas foram submetidas a um carregamento prévio e reforçadas após a fissuração. Todas as vigas foram projetadas para garantir a ruptura por força cortante, e as forças últimas das vigas reforçadas foram de 36% a 54% superiores às das vigas de referência. O Modelo da Fissura Deslizante foi avaliado e mostrou boa concordância com os resultados experimentais.Palavras-chave: reforço à força cortante; concreto armado; reforço externo; compósito de fibras de carbono. RC T beams strengthened to shear with carbon

A few international standards regulate the use of the high strength concrete, which may not be adopted generally without consideration of the differences that can be among the materials in different countries. This paper presents the results of an experimental study consisting of pull out tests of Brazilian steel, with five different concrete strengths, 20, 40, 60, 80 and 100 MPa, and three different steel bar diameters, 16.0, 20.0 and 25.0 mm. The experimental results for the bond stress vs. slipping relationship were compared with the provisions of the CEB and with some theoretical formulations found in literature. One statistical analysis is made and equations for predicting the bond stress were derived.

The geometric characterization and evaluation of structural integrity are challenges for the preservation of historical buildings. The challenges are associated to the lack of constructive records, material diversity, access and contact restrictions, and sample extraction. Non-destructive tests are indicated in these cases. The objective of this paper is to evaluate the Ground Penetrating Radar (GPR) technique with 1.2 GHz antenna in the study of the determination of material thickness and discontinuities in the masonry shells of the Theatro Municipal do Rio de Janeiro, a heritage built in early 20th century, with high historical and cultural value. With paintings by renowned artists on their intrados, the domes and vault of brick masonry were at risk of collapse in the 1970s due to differential settlements in the supports and moisture, compromising their paintings. A strengthening intervention was carried out in 1976. Considering the masonry of bricks the main component, the electromagnetic wave propagation velocity was determined as 0,15 m/ns in one of the support walls, allowing to estimate the thicknesses of the elements ranging between 20 and 31 cm. Materials incorporated into the structure were identified: reinforcement, metal inserts and bricks. However, the frequency of the antenna did not allow the detection of damages. The application of the GPR to the characterization of materials and investigation of the integrity of the domes of the Theatro Municipal highlights the potential of this technology to study heritage and other constructions.