Structural behaviour of welded plate connections to round and elliptical hollow sections under static loading
Final Report Abstract
The object of the research project was to investigate welded plate-to-round hollow section connections. The study concentrated on circular and elliptical HSS (Hollow Structural Section) members under static loading with and without concrete-filling. Round hollow sections are still the most favoured tube profile by architects for architecturally-exposed structural steel (typically as columns and truss members). However, tube-to-tube welded connections are expensive to fabricate and tube profiling especially is costly. As a consequence, plate-to-tube connections are far more commonplace than directly-welded, tube-to-tube connections. Plate-to-tube connections generally have a relatively low connection design capacity, often putting designers in a dilemma. To achieve stronger connections plates are often slotted through the tube, then sometimes the tube is additionally filled with concrete. Unfortunately, so far no design recommendations exist for these typical forms of strengthened connections and “engineering judgement” is needed by a designer to assess the benefits of such stiffening measures. An experimental program has been carried out, consisting of 14 branch plate connections to circular hollow sections and 6 plate-to-elliptical hollow section connections. The connections were subjected to quasi-static axial tension or compression loading applied to the branch plate. The experimental work looked at both regular, unstiffened branch plate connections as well as connections stiffened by through plates or concrete-filling as well as connections with skewed branch plates. The results of the experimental work indicate a correlation between the orientation (longitudinal, transverse) of the branch plate and the stiffness and ultimate strength of the connection governed by a 3% deformation limit. The effectiveness of through plate connections versus regular branch plate connections could be proven. It was also found that, for regular branch plate connections, the existing specifications address one failure mode too conservatively while the other failure mode is not addressed sufficiently. The results of the experimental work also indicate that the connection capacity of regular branch plate connections is largely affected by the loading sense (tension versus compression) while through plate connections do not exhibit this behaviour. Concrete or grout filling of the connections resulted in the highest connection capacities for otherwise similar connections. Finite element models of laboratory experiments have been created using commercially available finite element software, ANSYS, utilizing the non-linear geometric and material properties of the experimental test specimens. The FE models correlate well with the experimental connection results with regard to load-displacement behaviour, overall connection deformation, local stress concentrations, failure modes and initial fracture location. The FE models agree with the experimental test results well enough for confidence in the modelling techniques used, the element mesh arrangement, the element type used and the boundary conditions imposed. The FE models created and validated could now be utilized for a parametric study. More research is recommended to use the verified numerical model to conduct a parametric study. The parametric study can be used to create a large connection database which will allow a statistical evaluation of the connection database and finally allow the modification of existing or the creation of new design equations to describe branch and through plate-to-CHS connection behaviour under branch axial tension and compression loading. Applications of branch plate connections to round hollow sections are generally found in large-scale structures such as bridges or roof structures of arenas.
Publications
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(2005) Branch Plate Connections to Round Hollow Sections. Comité International pour le Développement et l’Étude de la Construction Tubulaire (CIDECT) Interim report 5BS-7/05, 32 pages
Willibald, S., Packer, J.A., Zhao, X. and Voth, A.P.
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(2006) Branch Plate Connections to Round Hollow Sections. Comité International pour le Développement et l’Étude de la Construction Tubulaire (CIDECT) Interim report 5BS-4/06, 19 pages
Willibald, S., Packer, J.A., and Voth, A.P.
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Through-plate joints to elliptical and circular hollow sections, Proceedings of the 11th International Symposium on Tubular Structures, Québec, Canada, September 2006, pp. 221-228, 2006
Willibald, S., Packer, J.A., Voth, A.P. and Zhao, X.
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(2007) Branch Plate Connections to Round Hollow Sections. Comité International pour le Développement et l’Étude de la Construction Tubulaire (CIDECT) Interim report 5BS-5/07, 46 pages
Willibald, S., Packer, J.A., and Voth, A.P.
