Abstract The chord length is an essential geometric property that must be defined in the analysis of isolated joints composed of hollow steel sections, as well as the boundary conditions of the test. The analysis of these parameters’ effect on the behavior of joints has been addressed by other studies, mostly with joints between circular hollow sections with compact or semi-compact cross-sections. Recent research about tubular joints has addressed cases with slender sections, where the design of joints containing these sections is still in development. In this context, this study aimed to evaluate the effect of the chord length in the behavior of T-joints between circular hollow section braces and slender rectangular hollow section chords through experimental tests and a numerical study considering the application of axial compression at the braces. The joint behavior was examined through the load-strain and load-deformation curves and the von Mises stress distribution, which allowed the failure mode's determination and the joint resistance value. Chord face failure was observed in the prototypes. It was concluded that a minimum chord length of 0.6m would be the adequate value for the study of the T-joints containing the geometric properties used in this study, which would be equivalent to a chord length five times higher than the width of the cross-section (5b0).

Abstract This article presents a theoretical and numerical study of an innovative joint using cold-formed steel sections. The motivation for the study of this connection is the ease of manufacturing and assembly that it provides. The profiles are made of cold-formed lipped channel sections, which are welded to form closed built-up sections on the columns and open built-up lipped sections to the beams. The beams use endplates connected by bolts (threaded bars) to the columns. The study evaluates the connection’s initial stiffness of 19 models, where the following parameters were varied: the thickness of the profiles and endplates, the height of the column sections and the diameter of the bolts. A theoretical and a numerical study were developed: the numerical study was performed using finite elements through the commercial software ANSYS, whereas the theoretical study was made based on the component method, prescribed by Eurocode 3, that does not include the design of the connection analyzed herein. Thus, aiming to enable the design of joints composed of cold-formed lipped channel sections, the analysis results were compared and an adjustment coefficient, proportional to the slenderness of the column’s plates, was proposed. The coefficient was introduced to the stiffness component that represents the column web in compression in the mechanical model. The ratio between the coefficients’ numerical and theoretical values presented a maximum variation of 11%, which was considered satisfactory.

INTRODUÇÃO: Estudos experimentais de embolia pulmonar (EP) são habitualmente realizados sob ventilação mecânica. A maioria dos pacientes com suspeita de EP adentra os Serviços de Emergência em respiração espontânea e em ar ambiente. Assim, medidas das variáveis hemodinâmicas, gasométricas e capnográficas, nessas condições, em muito contribuiriam para compreensão mais específica das alterações cardiopulmonares e gasométricas na fase aguda da doença. Dessa forma, faltam estudos experimentais que avaliem animais em tais condições. OBJETIVO: O objetivo do presente estudo foi submeter à EP animais sob ventilação espontânea e sem oxigênio suplementar. MÉTODOS: A EP por coágulos autólogos foi induzida em seis porcos e os registros cardiorrespiratórios e gasométricos foram realizados no pré e pós-EP. O valor da pressão média de artéria pulmonar (PMAP) "quase fatal" foi previamente determinada. RESULTADOS: A presença de choque obstrutivo agudo pôde ser evidenciada pelo aumento da PMAP (de 17.8±3.5 para 41.7±3.3 mmHg) (P<0.0001) e pela queda do débito cardíaco (de 4.9±1.0 para 2.7±1.0 L/min) (P<0.003). Consequentemente, a presença de acidose metabólica pode ser constatada (de 2.4±0.6 para 5.7±1.8 mmol/L) (P<0.0001). Observou-se, ainda, hipoxemia (de 73.5±12.7 para 40.3±4.6 mmHg) (P<0.0001), porém, a PaCO2 não variou (de 44.9±4.4 para 48.2±6.0 mmHg) (NS). Houve expressivos aumentos, tanto para P(a-et)CO2 (de 4.8±2.8 para 37.2±5.8 mmHg) quanto para a P(A-a)O2 (de 8.2±8.9 para 37.2±10.3 mmHg) (P<0.0001). Ocorreu, também, significativo aumento do volume minuto alveolar total (de 4.0±0.9 para 10.6±2.9 L/min) (P<0.0001). CONCLUSÕES: Nesse modelo, a PMAP quase fatal foi de 2 a 2,5 vezes a PMAP basal e as variáveis capnográficas, associadas a gasometria arterial e venosa, mostraram-se eficazes em discriminar um quadro obstrutivo agudo.

INTRODUCTION: Experimental studies on pulmonary embolism (PE) are usually performed under mechanical ventilation. Most patients with suspicion of PE enter the Emergency Services in spontaneous breathing and environmental air. Thus, under these conditions, measurements of hemodynamic, gasometric and capnographic variables contribute largely to a more specific comprehension of cardiopulmonary and gasometric alterations in the acute phase of the disease. Studies which evaluated animals under conditions are lacking. OBJECTIVE: This study aimed to submit animals under spontaneous ventilation and without supplemental oxygen to PE. METHODS: PE was induced in six pigs using autologous blood clots, and cardiorespiratory and gasometric records were performed before and after PE. The values of "near fatal" mean pulmonary arterial pressure (MPAP) were previously determined. RESULTS: The presence of obstructive shock could be evidenced by increased MPAP (from 17.8±3.5 to 41.7±3.3 mmHg) (P<0.0001) and decreased cardiac output (from 4.9±1.0 to 2.7±1.0 L/min) (P<0.003). Consequently, metabolic acidosis occurred (Lac art) (from 2.4±0.6 to 5.7±1.8 mmol/L)(P<0.0001). It was observed hypoxemia (from 73.5±12.7 to 40.3±4.6 mmHg) (P<0.0001); however, PaCO2 did not vary (from 44.9±4.4 to 48.2±6.0 mmHg) (NS). There were significant increases in both P(a-et)CO2 (from 4.8±2.8 to 37.2±5.8 mmHg) and P(A-a)O2 (from 8.2±8.9 to 37.2±10.3 mmHg) (both P<0.0001). There was also a significant increase in the total alveolar minute volume (from 4.0±0.9 to 10.6±2.9 L/min) (P<0.0001). CONCLUSIONS: In this model, the near fatal MPAP was from 2 to 2.5 times the basal MPAP; and the capnographic variables, associated with arterial and venous gasometry, showed effective in discriminating an acute obstructive profile.