|CUREE-Caltech Woodframe Project
Element 1 - Testing & Analysis
Task 188.8.131.52 Connection Studies
PI: Seb Ficcadenti (Ficcadenti & Waggoner, CSE)
The standard of practice for the lateral analysis and design of light framed timber structures has been changing to more closely consider the effects of wall stiffness in the distribution of forces in a structure. The stiffness on the shear wall system is a function of the anchorage, sheathing and shear transfer connections. While one can find many studies done on sheathing and anchorage, shear transfer studies are notably scarce.
Main Objectives, Methodology, Progress to date
Connection tests were conducted at UC Irvine in 1995 to determine the performance of several diaphragm-to-shear wall connections. These tests showed that significant deformation occurs within the region between the top plates of a wall and the floor or roof diaphragm. Furthermore, the deformation can be quite different depending on the orientation of the floor or roof joists.
Recently, Task 184.108.40.206 tested the connections for 12 diaphragm-wall samples (three connections in two directions with two samples per configuration). The samples included dimensional lumber joists as well as engineered lumber joists. The goal of these connection tests has been to assign stiffness properties, deformation capacity and degradation characteristics to each of the connection configurations. These properties can be used in the analysis models of light framed timber structures and in future engineering procedures and standards. The six separate shear transfer connection tests that have been completed include:
Plywood web joists perpendicular to the wall with cut joist blocking and nailing from the flange directly into the top plate
Plywood web joists parallel to wall with nailing from the flange directly to the top plate
2x12 joists perpendicular to the wall with 2x12 blocking toe nailed into the top plate
2x12 joists perpendicular to the wall with 2x12 blocking and framing clips from the blocking to the top plates
2x12 joists parallel to the wall with toe nails from the joist to the top plate
2x12 joists parallel to the wall with framing clips from the joist to the top plate
Each configuration had an 8 by 20 plywood diaphragm with an 8 shear transfer connection. The tests were conducted by restraining the ends of the diaphragm to a reaction floor and simultaneously loading the shear transfer assembly via the top plate which, in turn, was connected to the 10 by 12 shake table in UC Irvines Structural Engineering Test Hall. The shake table was, in effect, used as large, distributed force actuator in order to provide a computer controlled, pseudo-dynamic displacement input to the realistically proportioned diaphragm-wall connection samples.
The CUREE test protocol required a monotonic load pattern prior to testing the diaphragm assembly to the reversed cyclic load test protocol. Accordingly, monotonic tests for most configurations were conducted to provide the reference displacement needed for the ensuing CUREE test protocol using reversed cyclic loads. Data analysis for all shear transfer connection tests is now underway.