Specifies a tied single expansion joint that is capable only of transverse (lateral) movement. Pressure thrust is restrained internally by the tie-bars. This is a good, dependable expansion joint to use for several reasons:
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You do not have to design for pressure thrust.
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Tie rods provide stability to the overall joint. This makes working with it in the field easier.
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There is a single displacement mode (lateral). You can compare this mode directly to the rated lateral movement in the catalog without the need for the relatively complicated geometric calculations in the Expansion Joint Rating.
The disadvantages to the single tied expansion joint are:
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They are fairly stiff in practice. This joint often does not provide the needed flexibility to sufficiently reduce the loads on sensitive equipment.
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The tie-bar assembly does provide some nonlinear restraining effect on flexibility that is unaccounted for in the analysis. This may be appreciable when the bellows displacement becomes large, such as when it is most critical that it perform as predicted.