Element 1 - Testing & Analysis
Task 18.104.22.168 Inter-Story Shear Transfer in Woodframe Buildings
PI: Kenneth J. Fridley (Washington State University)
One area of construction that has seen little engineering consideration is the mechanism that transfers shear between stories. Often considered a problem area, shear transfer between stories is one area where detailing and earthquake design methodologies will have a significant impact. Shear transfer between story levels is one area in wood construction that has historically been a prescriptive design technique (conventional construction) rather than an engineered one. That is, under certain determined conditions the nailing schedule and blocking requirements, for example, are specified based on past performance rather than engineering theory. As a result, common trends (e.g., prescriptive vs. engineered design) in structural engineering need to be addressed if woodframe buildings are to resist structural damage in earthquake loads such as occurred at Northridge.
The research conducted in Task 22.214.171.124 will experimentally evaluate the inter-story shear transfer mechanism in wood-frame buildings. For example, considering a two story wood-frame building, the shear force at the base of the upper (second story) shear wall must be transmitted through the floor diaphragm and, along with the diaphragm force, transferred into the top of the lower (first story) shear wall. Currently, there is no recognized design procedure for this shear transfer due to a lack of understanding how this force is resisted in conventional construction.phragm
Testing includes the analysis of eight different scenarios. The first scenario is set as the "baseline" scenario since all others are a variation on this scenario. Each scenario will include a total of four tests, one monotonic and three cyclic.
Description of Results
To date, testing has been successful and the failure of scenario number one followed a pattern that we predicted prior to testing. Currently, we are analyzing our data from the first set of tests and hope to see results consistent with our predictions. We are also looking at the relationship of our data with data already analyzed in the other tasks performed for CUREE.