The present research was dedicated to investigation into the strength of timber structures under fire conditions. Two kinds of timber specimens including oak and pine were used. The carried out investigation covered static tests on tensile strength, compressive strength along the grain, compressive strength perpendicular to the grain and flexural strength. The specimens were tested under the temperatures of 50°C, 100°C, 150°C, 200°C and 230°C. The obtained results show that pine specimens have better properties over the entire temperature range in case of tests on tensile and flexural strength. Also, as for these types of strength, oak specimens show a higher strength reduction rate than those of pine specimens, whereas oak specimens have better properties over the entire temperature ranges in case of compressive strength perpendicular to the grain. Based on statistical analysis, a linear expression of the strength reduction coefficient was proposed.
This article provides a behaviour analysis of moment resisting joints with curved endplates. This is a new type of connection that can be used for joining steel beams to the circular hollow section (CHS) columns by means of bolts. Some researchers apply the Eurocode model without considering the differences in calculation schemes and assumptions, such as by using the general model of an equivalent T-stub in tension. Consequently, many of the existing behaviour studies are somewhat misleading, thus there is a need for further research. Apart from the absence of analytical methods that are devoted to predicting the initial stiffness and strength of the curved T-stub, other technical difficulties were encountered, such as gaps between the endplate and the column, as well as the initial pre-loading force of the bolts. In the previous studies, endplates were manufactured by rolling flat plates to the precise curvature which resulted in firm contact. In contrast, in this study, endplates were manufactured from a standard CHS tube, which led to significant initial gaps. Meanwhile, in terms of preloading force, it was found that it affected the moment resistance of the joint. This paper discusses problems associated with ongoing researches and presents experimental tests of the two connections. The obtained results were further used in the parametric finite element analysis (FEA) to determine the effect of the gaps and preloading force of the bolts on the moment resistance and initial rotational stiffness of the joint. The results indicate that the behaviour of curved plated connections is exceedingly complex and that the preloading force is the key factor, therefore, it should be controlled.
The article investigates analytical models for calculation of tension capacity of axially-loaded RHS end-plate joints bolted along two and four sides of the tube in order to investigate the phenomena of prying. Design of such joints is impeded by lack of rules in EN 1993-1-8 and it raises the question whether the Eurocode 3 equivalent T-stub in the tension component should contain integrated assumptions from the AISC/CIDECT/CISC design guides. This paper considers the effect of the bolt hole on the length of the plastic hinge and compares different T-stub models with various assumptions. The behaviour and collapse mechanism of joints with non-preloaded and preloaded bolts was tested during an experiment. The statistical analysis of the test results of 47 joints found in the literature in conjunction with 7 tests determined that it was preferable to use a common approach for connections bolted along two and four sides. Additionally, a limitation of a minimum flange thickness is specified. The performed research has disclosed the benefits and shortcomings of the T-stub models and justified recommendations for their improvement.
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