Resumo Obras de arte especiais com elementos estruturais mistos de aço e concreto consistem em uma solução popular, uma vez que tais elementos combinam os benefícios estruturais do aço e do concreto. Em pontes de pequenos e médios vãos, a solução que usualmente garante resultados econômicos interessantes é composta por uma laje de concreto sobre vigamento de aço em perfis I. Outras opções que despontam como alternativas eficientes na construção de obras de arte especiais são o sistema de vigas com conectores de cisalhamento em chapa de aço contínua recortada e o sistema de vigas mistas preflexionadas. Diante disso, o presente trabalho tem por objetivo a realização de um estudo comparativo das diferentes soluções de vigas mistas a fim de delimitar a performance das soluções propostas. Para tanto, o estudo de caso da superestrutura de uma ponte ferroviária de duas vias com vão biapoiado é apresentada em detalhes para definir os indicadores de desempenho das soluções. As soluções de vigas mistas propostas apresentaram vantagens quando comparadas com o sistema tradicional, demonstrando o impacto positivo de seu uso no contexto das obras de arte especiais. popular vãos I preflexionadas disso tanto tradicional

Abstract Steel-concrete composite bridges are a popular solution due to the structural benefits of both steel and concrete. The typical system of a concrete slab and steel I-girders for small and medium-span bridges often displays the most economical results. However, other solutions emerge as innovative alternatives for bridge construction, such as composite beams with composite dowels and pre-cambered composite beams. This paper aims to develop a comparative study of these composite beam solutions to delimitate their efficiency, performance, and economy. Thus, a case study for the superstructure of a two-way simply supported railway bridge is detailed to define the composite beam’s performance indicators. The innovative alternatives presented benefits when compared to the traditional system, demonstrating the positive impact of their use on bridges. Steelconcrete Steel Igirders I girders mediumspan medium span results However construction precambered pre cambered efficiency economy Thus twoway two way s indicators

Abstract Carbon-black nanoparticles (CBN) have been incorporated into cement-based materials for improvement of mechanical or self-sensing properties. There is no previous research focused on the microstructural evaluation of effects of CBN on both parameters. In this work, mortars containing different CBN contents were produced, cured for 28 days, and subjected to electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Tests for determination of compressive strength, modulus of elasticity and piezoresistivity response were developed. SEM indicated that lower CBN contents refined the cementitious matrix, while higher contents increased the volume of voids. XRD and Raman spectroscopy indicated hydration improvements for CBN contents between 0.375% and 3%. The best mechanical improvements were provided by concentrations of CBN up to 3%. CBN contents of 5% and 6% provided the best sensing properties. The optimal concentration was found to be 5% of CBN, since it provided excellent piezoresistivity, without significant mechanical properties loss.