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Frequently Asked Questions
What does a girder tiedown do?
It holds a girder down onto its support against uplift.
Gravity is not always the dominant force on a beam.
Wind suction over a roof can generate net upward force.
A girder resting with nothing holding it down can lift and shift.
Once it moves off its bearing, the load path no longer exists.
The tiedown prevents that from happening.
How is it different from a post cap?
A cap transfers downward load; a tiedown resists upward load.
They solve opposite problems at the same joint.
Confusing them is a frequent error.
Some connectors do both jobs.
Where they do, both capacities are published separately.
Reading one figure and assuming it covers both cases is a mistake.
Does it work on its own?
No - it is one link in a continuous chain to the foundation.
A girder tied to its support achieves nothing if the support is not tied below.
Uplift finds the weakest link in the chain.
The chain has to run unbroken from roof to foundation.
A single missing connection makes the others ineffective.
That is why uplift connectors are specified as a system rather than individually.
When is one required?
When the uplift loading for the site calls for it.
That varies enormously between locations.
High-wind and cyclone-prone regions have substantially heavier requirements.
In sheltered low-wind areas it may not be required at all.
The local code governs and no general rule substitutes.
On engineered buildings the engineer specifies the connector and its capacity.
When should it be fitted?
As part of the erection sequence rather than afterwards.
Access becomes awkward once the girder is placed.
Fasteners on the underside can be very difficult to reach.
The schedule still has to be fully satisfied.
Planning the sequence before lifting makes it achievable.
Retrofitting is possible but consistently more expensive and more awkward.
Does it also resist sideways movement?
Some patterns do, and the capacities are published separately.
Lateral restraint is a different requirement from uplift.
A connector strong in uplift may offer little laterally.
Seismic design in particular demands lateral capacity.
The published table gives each figure individually.
Where both are needed, both have to be satisfied rather than assumed from one value.
Does the fastener schedule apply here too?
On both sides of the connection, fully.
Girder side and support side each have their own count.
Filling one side and not the other gives the weaker side's value.
Fastener type is specified as well as quantity.
Substituting screws for tested nails invalidates the figure.
The schedule is part of the product rather than a fixing suggestion.