Cyclic Response of Shear Transfer Connections Between Shearwalls and Diaphragms in Woodframe Construction

The stiffness of a shearwall in woodframe construction is a function of its sheathing, the sliding and overturning anchorage at its base, and the shear transfer connection at the top of the wall. While one can find a number of studies conducted on the sheathing and anchorage components of shearwalls in resisting seismic forces, studies conducted on shear transfer components are notably scarce. Recent work on the connections between roof rafters and wall top plates has focused on the resistance to uplift loads induced by wind forces. The experimental program documented in this report focuses specifically on diaphragm to shearwall connections designed to resist seismic forces.

Nine diaphragm to shearwall connection configurations were tested under cyclic loads using the shake table in the Structural Engineering Test Hall at the University of California, Irvine as a large actuator. Using the shake table to load the test specimens allowed the application of the load to be consistent with how it would be applied in an actual earthquake.

Three shear transfer connection types were investigated, each in three different framing configurations. The three connection types were (TN) toe nailing of framing members to top plates, (FC) fastening framing clips to framing members and top plates, and (FN) flange nailing of framing members to top plates. The three framing configuration used with each connection type were (1) unblocked diaphragms supported by joist framing parallel to the shearwall, (2) unblocked diaphragms supported by joist framing perpendicular to the shearwall, and (3) blocked diaphragms supported by joist framing perpendicular to the shearwall. For each set of tests for a given connector type, two test specimens were tested for each unblocked diaphragm configuration and one additional test specimen was tested for the blocked diaphragm configuration. All together cyclic tests were conducted on 15 test specimens.