What are Flexible Connections?

Flexible Connections will be the most common type likely to be encountered by the detailer, they will make up just about all beam-to-beam connections and for braced frames, will be found to make up the beam-to-column connections as well. So, what is a Flexible Connection?

When a vertical load is applied to a horizontal beam it is immediately subjected to bending, this bending creates a rotational moment at the beam end, and to prevent this moment being transmitted to the supporting beam or column, it’s designed to be flexible. Likewise, if the structure is subject to lateral displacement, due mostly to wind or seismic activity, the flexible connection will not offer significant resistance to the resulting moment. This flexibility is determined by the Rotational Capacity of the connection - which is largely governed by the deformation capacity of the connection components and the ‘slip’ between the connected parts. Therefore, the components of a flexible connection should be as thin as reasonably possible and the bolt-hole cross-centres should be wide enough to prevent the build-up of restraining moments.

Flexible connections may connect beams-to-beams or beams-to-columns


Notes on Flexible Connections

In this initial introductory series of articles we'll examine the parameters for selecting the appropriate connection for the particular application, in addition we'll look at some of the more common pitfalls.

To assist the structural detailer in selecting the connection, we've prepared a quick Selection Guide to highlight the material advantages and disadvantages of the various connection types. these include:

We also examine the detailers responsibility with regards to Connection Selection as far as it relates to the difference between design and selection.

In addition, we'll look at some of the common problems associated with Shared Bolts and Interferences which only manifest on site during erection.

Finally, we have provided information on nominal Beam End Clearances, Notching or Coping a beam fitting between the flanges of the supporting beam or column and Standard Bolt / Hole Diameters

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