Date of Award
Master of Applied Science (MASc)
K. S. Sivakumaran
Steel structures are commonly used all over the world. Structural cold-formed steel sections can be used as the primary building members, as well as the secondary members with other structural materials. They can be used as joists, truss members, and studs; they can also be used as frame systems, floor systems and wall systems, etc.
It is common to see openings in these plated structures for all kinds of reasons. For example, openings are needed for ancillary systems such as water pipes, plumbing, electric wiring, etc. In cold-formed steel members, openings are often introduced in the web of a joist. The existence of large openings can change the stress distribution around the opening regions, thus changing the buckling and strength characteristics of web panels. The extent to which the openings can affect the plated structures depends on the size, shape, locations and number of the openings in the web. In this study, parametric studies were performed on a total of 42 simply supported plates with centrally located square openings utilizing the finite element modeling. The parameters of interest are the size of the opening (d。/h), the slenderness ratio of the plate (h/t) and the aspect ratio of the plate (a/h). It was observed from the study that, a centrally located square opening can significantly reduce the ultimate shear strength of the plate. The opening size is the primary parameter influencing a plate's ultimate shear strength. The ultimate shear strength of a plate decreases approximately linearly as the size of the opening increases. The ultimate shear strength also decreases as the slenderness of the plate increases and tends to increase as the aspect ratio increases. The aspect ratio is found to be the least significant parameter in the sense of affecting the ultimate shear strength of plates with square openings. This study also compared the ultimate shear strength obtained from finite element modeling with that calculated from the AISI (2007) method. It was shown that the AISI (2007) tends to underestimate the ultimate shear strength of thick to moderate thick plates with square openings, but overestimate the ultimate shear strength of thin plates with square openings. A new equation for estimating the shear reduction factor (qs) is proposed based on the finite element analysis undertaken to better estimate the ultimate shear strength of plates with centralized square openings.
To compensate for the reduction in strength of steel members due to large openings, reinforcements may be used in practice. In this research, simply supported steel plates with an aspect ratio of 3 (a/h=3) and having a 60% reinforced square opening (dc/h =0.6) under pure shear loads were analyzed through the finite element modeling. Four slenderness ratios (h/t), namely h/t=50, 100, 150 and 200 were considered. Three reinforcement schemes, namely the flat-reinforcement, the lip-reinforcement and the angle-reinforcement, are applied on the plates to evaluate the effectiveness of these three reinforcement schemes. It was observed from the research that all three reinforcement schemes were capable of restoring the shear strength of plates with square openings. However, the flat-reinforcement is found to be the most efficient way of the three reinforcement schemes considered.
Chen, Bo, "Shear Behavior of Steel Plates with Reinforced Openings" (2009). Open Access Dissertations and Theses. Paper 4407.
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