STRUCTURAL COMPONENTS AND SYSTEMS

XTTM Cross Tie

XT glulam-to-glulam diaphragm cross tie.

XT purlin wall tie

The XT Cross Tie is a connection device that was designed and developed as a highly improved alternate to holdown type connection devices for use in wall and diaphragm continuity tie installations in tilt-up, concrete block, and RWFD buildings. XT Cross Tie features include the following:

• Paired Installations. The XT Cross Tie was specifically designed to be installed in paired configurations in order to provide for concentric connections.


• Integrated Drill Guide. For paired installations the XT Cross Tie is designed to be installed with an integrated drill guide that attaches to the XT Cross Tie during installation. This allows the for the bolt holes to be accurately drilled, thus eliminating, or highly minimizing the potential for oversized and/or back-drilled bolt holes, and maximizing the load deformation performance of the overall connection. All of the standard XT Cross Ties are designed to be installed with one universal Drill Guide. In addition, the use of a drill guide typically allows for faster installations, which generally allows for reduced installation costs.


• Bi-directional Load Capacity. The XT Cross Tie was specifically designed to resist loading bi-directionally. This allows connections to be designed to resist both tension and compression loads (through use of the rod as a tension and compression element).


• COLA Load Deformation Capacity Criteria. The load capacity of the XT Cross Tie is not limited by the COLA Load Deformation Capacity Criteria (load required to produce an 1/8" of device deflection on a steel test jig divided by three).


• Bolt length-to-diameter (l/d) ratio > 4.5 for Ductile Bolt Failure Mode. The standard XT Cross Tie is designed to be installed with only 3/4" bolts in 2, 4, 6, or 8 bolt configurations (and with rod sizes of 3/4", 1", and 1-1/8"). This allows the standard XT Cross Tie to be used in 4x timber elements (or larger) and still provide for a ductile bolt failure mode (l/d > 4.5), while minimizing the number of bolts that might be required in a connection. For paired installations, it should be noted that the difficulty associated with aligning all of the bolt holes with each other increases substantially with each additional bolt hole that must be drilled (Sum[N-1], N = number of bolts), and thus it is important to minimize the number of bolts in a connection in order to simplify installation. It should also be noted that this problem can be greatly mitigated with the use of Drill Guides.


• Rod Offset Distance. The XT Cross Tie was designed with a standard rod offset distance of ROD = 2.33". This rod offset distance allows for much easier installations by providing the clearance required in order avoid the interference problems that can occur between the rod element and most any purlin hanger that might be encountered during purlin-to-wall and purlin-to-purlin diaphragm cross tie installations (in buildings with panelized roof framing systems). In general, a minimum rod offset distance of ROD = 2" is typically required in order to allow for sufficient clearance between the rod element and most purlin hangers that might be encountered during such installations. For connection devices with a ROD of less than 2", 1/2" to 3/4" plywood padding is generally required to be installed in order to increase the rod offset distance to 2", or greater. This padding can be a costly addition, as it must be structurally attached or bonded to the timber element in order for the installation to be considered a standard installation (and bolt capacity calculated per the NDS provisions), otherwise the plywood padding must be considered a gap or air space, which must be taken into account when evaluating the bolt capacity. Please note that XT Cross Ties can be fabricated with rod offset distances other than 2.33" by simply modifying the depth of the gusset and end bearing plates. The drill guides are simply modified by changing out the alignment guide pins with modified alignment guide pins sized in length for the modified rod offset distance.