A crescente demanda por conhecimento sobre a ação de altas temperaturas nas estruturas vem impulsionando pesquisas em todo o mundo. Este artigo tem por objetivo apresentar resultados experimentais de pilares mistos curtos de aço e concreto submetidos a altas temperaturas em fornos, com e sem ação de carregamento de compressão centrada, assim como analisar numericamente a distribuição da temperatura nesses pilares, nos tempos de 30 e 60 minutos e compará-los aos resultados experimentais. Os modelos adotados são tubos preenchidos com concreto, com três espessuras e dois diâmetros diferentes para os tubos, e o concreto de preenchimento com propriedades convencionais que se mantiveram constantes para todos os modelos. O comportamento força - deformação dos pilares mistos foi alterado após exposição à altas temperaturas em relação aos mesmos pilares em temperatura ambiente, sendo mais evidente nos ensaios de 60 minutos, os quais atingiram temperaturas mais elevadas. Na análise numérica adotaram-se curvas de elevação de temperatura que foram obtidas experimentalmente.

The growing demand for knowledge about the effect of high temperatures on structures has stimulated increasing research worldwide. This article presents experimental results for short composite steel and concrete columns subjected to high temperatures in ovens with or without an axial compression load, numerically analyzes the temperature distribution in these columns after 30 and 60 minutes and compares them with experimental results. The models consist of concrete-filled tubes of three different thicknesses and two different diameters, and the concrete fill has conventional properties that remained constant for all of the models. The stress-strain behavior of the composite columns was altered after exposure to high temperatures relative to the same columns at room temperature, which was most evident in the 60-minute tests due to the higher temperatures reached. The computational analysis adopted temperature rise curves that were obtained experimentally.

This paper presents an analysis on the effect of support springs in an ends circular hollow sections welded into a YT joint. The overall behavior and failure of the joint were characterized under axial compression of the lap brace. Two joint failure modes were identified: chord wall plastification (Mode A) and cross-sectional chord buckling (Mode F) in the region below the lap brace. The system was modeled with and without support springs using the numerical finite element program Ansys. Model results were compared with experimental data in terms of principal stress in the joint intersection. The finite element model without support springs proved to be more accurate than that with support springs.