If multiple connectors are used, are their capacities additive?

If you are asking about mechanical connectors, that is a question for the connector manufacturer. For multiple fasteners and/or fastener types, there are specific design requirements (see NDS 10.1.4 and 10.2.2). In general, capacities of different fastener types cannot be directly summed.

The following FAQ is based on the presentation of STD312 - Part 3 of the 2012 WFCM Webinar Series: Connections.