There is a bit of disinformation [in “Connecting Girders to Deck Ledgers,” April 2015] as related to the behavior of a ledger board. As described in the article, the ledger behavior is the same as that of the rim joist and its point loads; however, reality is very different since a ledger’s dynamics are a universe away from the rim joist’s. When one factors in the fastener schedule of lag bolts that tie the ledger uniformly to the main structure and the cumulative effect of the decking on the framing, the illustrated properties associated with the described load and moment around the girder/ledger are virtually nullified. In fact, with a standard schedule of lags factored into the mix, the forces required to promote the effect illustrated would substantially exceed the holding capabilities of the hanger holding the girder in place, thus causing a catastrophic failure at the girder/ledger point load, not a situation that is likely in the real world for reasonable structures—possible but not wholly likely.
Anonymous reader comment (online, 4/30/15)