The confinement of concrete columns provided by carbon fibre reinforced plastic (CFRP) sheets can be an efficient technique for their structural strengthening. The principal advantages of this technique are the high strength-to-weight ratio, good fatigue properties, noncorroding characteristics of the CFRP, and the facility of its application.An experimental research program, that included tests on 54 short column specimens, was carried out to investigate the gain in strength and ductility of concrete columns externally confined by CFRP wrapping. The variables studied were the column cross section shape (circular, square and rectangular) and the amount of confinement expressed in the number of CFRP sheet layers applied to the models (one or two layers).On the basis of the obtained results, equations were proposed to calcuhte the confined concrete strength and the ultimate confined concrete strain as a function of the confining lateral stress for each of the cross section geometry used, circular, square and rectangular. The estimations given by these equations and by those from formulas encountered in the literature were compared with the experimental ones and general conclusions were, finally, drawn. RESUME

Este trabalho teve por objetivo apresentar alguns casos de fissuração do concreto em travessa de apoio de pontes em concreto. São comentados seis casos ocorridos em pontes de concreto, onde se relatam os problemas encontrados, as causas da fissuração e as possíveis soluções para estes casos. Há causas de fissuração do concreto relacionadas à corrosão das armaduras internas pela entrada de agentes agressivos no concreto ou pela corrente elétrica de fuga, e ao recalque de apoio das travessas. Verificou-se neste trabalho que a maioria das causas de fissuração se deve a falhas na execução e no projeto, detalhamento e dimensionamento desta travessa de apoio.

This article investigates the shear behavior of reinforced concrete beams without transverse reinforcement. Two types of concrete were produced: a Reference Conventional Concrete (RCC) and a Lightweight Self-Consolidating Concrete (LSCC), all with an average 28-day compressive strength (fc) of approximately 30 MPa and characterized by rheological and mechanical tests. Twelve 15 x 30 x 200 cm beams were manufactured for shear failure during a four-point bending test. Concrete properties, longitudinal reinforcement ratios (0.89%, 1.27% and 1.68%) and shear-span to depth ratio (1.87 to 2.71) were determined. The studied beams were compared in terms of cracking pattern, diagonal cracking load, shear strength, specific concrete and longitudinal reinforcement deformation at failure. The strength values obtained experimentally were compared with ABNT NBR 6118 (2014), ACI 318 (2019) and CEN EC-2 (2004). The tested beams of LSCC showed less shear strength when compared to beams of RCC.

Many advances have been made on driven piles bearing capacity tests, such as the static and dynamic load tests. However, the cost and the time necessary to prepare these kinds of tests usually restrict their application to a small percentage of the piles. Consequently, the simple and low-cost ways to estimate the bearing capacity of driven piles, for instance, through the final set and the elastic rebound, can be used to control the majority of the piles, and then the results can be compared with more complex and accurate tests executed in fewer elements. This paper describes the development of an in situ tool to measure the elastic rebound and the final set without any direct contact with the pile. Afterwards, these values can be used to evaluate the bearing capacity based on the dynamic formulas proposed by many authors. The apparatus was tested in three different sites, with the results very close to those obtained with the conventional elastic rebound and the final set measuring method.

Este trabalho tem por objetivo apresentar um método teórico de previsão do momento fletor e da flecha de ruptura de vigas de concreto armado reforçadas à flexão com o uso da técnica da inserção de barras no cobrimento do concreto. Esta técnica é conhecida como a técnica NSM (Near Surface Mounted). No presente trabalho foram utilizadas barras de polímero reforçado com fibras (FRP). Os resultados teóricos foram comparados com os resultados experimentais disponíveis na literatura. Todas as vigas de concreto armado foram submetidas à flexão em quatro pontos. Os parâmetros considerados no método proposto foram as dimensões e taxas de armaduras internas das vigas, a resistência do concreto à compressão, a taxa e o tipo da armadura de reforço, o tipo de cola e o comprimento colado da barra de FRP. Foram analisadas vigas armadas com barras de CFRP, GFRP e aço. Os resultados teóricos obtidos apresentam uma boa aproximação com os resultados experimentais, indicando que a teoria da flexão simples pode ser utilizada para obtenção de valores razoáveis e a favor da segurança de momento fletor e flecha de ruptura de vigas retangulares reforçadas à flexão pela técnica NSM.