Barkley flexibility

The new Lake Barkley Crossing in Kentucky has been equipped with particularly flexible mageba modular expansion joints

The unparalleled flexibility offered by the TENSA®MODULAR expansion joint has been demonstrated on numerous bridges around the world – most recently at the new Lake Barkley crossing in Kentucky, whose 20 million dollar main archway is bounded by joints of this type. The bridge, which will provide access to the famous Land Between The Lakes National Recreation Area following completion of construction this year, has been fitted with 7-gap TENSA®MODULAR expansion joints that will accommodate 21” (530 mm) of longitudinal movement (SLS).

The ability to accommodate such longitudinal movements (and much larger) is standard for mageba modular joints – indeed, 25-gap TENSA®MODULAR joints have been providing excellent service at the Tsing Ma Bridge in Hong Kong since installed in 1996, and larger joints of this type have been supplied since then.

And thanks to the especially elastic design of the TENSA®MODULAR joint, significant transverse and vertical movements, and substantial rotations about every axis, are generally possible. But where large transverse movements are required, this joint type can be readily designed to accommodate them – as in the case of the 7-gap joints for the Lake Barkley Bridge. The bridge’s design required the joints to accommodate transverse movements of +/- 9” (+/- 230 mm), and this was achieved by designing the joints with trapezoidal, rather than straight, support bar boxes (“joist boxes”).

The primary function of these boxes is to allow the joint’s support bars (“joist beams”, which support the surface beams above) to move into and out of the superstructure at one side of the joint as the bridge gap closes and opens. By enabling the support bars to pivot about a vertical axis at the point where they enter the superstructure, thanks largely to their trapezoidal shape, the boxes enable the joint to facilitate large lateral movements. The functioning of the TENSA®MODULAR joint is succinctly explained by its promotional video, and the pivoting movement (and exceptional general flexibility of the joint type) can be seen in a short video showing seismic testing of a 7-gap joint.

The supply contract for Lake Barkley Bridge also included cover plates for the bridge’s multi-use path for pedestrians and cyclists, and articulating barrier cover plates. Of course, these also had to be designed to accommodate the same longitudinal and transverse movements as the modular joints; in the case of the barrier cover plates, for instance, transverse movements were facilitated by designing them with a vertical pin at each end about which the barrier cover plate will be able to rotate as it expands and contracts.

With these highly flexible and very reliable TENSA®MODULAR joints and cover plates installed on the bridge, visitors to the Land Between The Lakes can expect their journey across the bridge to be unimpeded by avoidable expansion joint repair and replacement work.

Picture of the new bridge, taken immediately after the demolition of adjacent old bridge in April 2018

Loading of two TENSA®MODULAR joints on a truck for transport to the bridge

Lifting of a joint into position on site

Recess as prepared for an expansion joint, following positioning of a similar joint at the far end of the recess

The bridge is being constructed by PCL Civil Constructors, Inc. of Denver, Colorado

A TENSA®MODULAR joint as installed, showing the trapezoidal support bar boxes, or “joist boxes”, that enable the support bars that span the bridge gap to rotate about a vertical axis

An articulating barrier cover plate, designed to be installed with a vertical steel pin at each end, enabling it to rotate and thus to accommodate transverse deck movements

The barrier cover plates are also designed to resist traffic impacts, with ROBO®SLIDE-like sliding pads between the internal and external steel profiles facilitating sliding movements as the barrier expands and contracts during superstructure movements