No abstract
Composite steel-concrete columns utilise the advantages of both materials, by combining high strength and ductility of steel with the compressive strength of the concrete. But the wide adaptation of composite structures is limited, mainly because of the lack of cheap and easy to construct connections, as many of which require costly and timeconsuming on-site welding, when circular concrete filled steel tubes (CFST) are adopted. New connections, like those incorporating the use of blind bolts and curved end-plates, may represent a valuable alternative. Such joints can be adapted to circular CFST to eliminate on-site welding, but they require the creation of new curved T-stub components. This paper proposes an analytical model for the evaluation of bolt forces in the curved T-stubs within the elastic range. The model is then validated against experimental results of joints between circular CFST columns and steel beams, with both preloaded and snug tightened bolts. Analytical model shows good agreement with experimental data, but needs further development to take into account the prying forces.
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.
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.
Composite steel-concrete columns of circular cross-section have high strength and stiffness, which theoretically could help to reduce the cost of construction, but their advantages are still widely unexploited. In comparison with other constructions, composite columns account for a diminutive market share. One of the many reasons for this, is the complexity of connections that may require on-site welding, which not only slows down the construction, but also makes it more expensive. With the recent extensive development of blind bolts, new design options for the tube columns emerged. Such bolted joints would eliminate onsite welding and speed up installation. In this review a particular attention is paid to the circular columns, because these columns have the least studied connections. This article reviews the most recent stage in the development of the connections between steel-concrete composite columns and steel beams, as well as provides provisions for using such connections and outlines the directions for further research.
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