He, Chen, Eatherton and Shao 2018
The authors evaluated asymmetric angles to see if they could concentrate the damage while having the advantages of easy installation, inspection and removal. They tested this by conducting cyclic tests on full scale sub-assemblies.
System Concept
The asymmetrical moment-resisting connection is designed to consolidate damage from an earthquake in replaceable angles to minimize the disruption and cost of repairs following the earthquake. In order to accomplish this, sub-assemblies were designed having the same beam section dimensions and column section dimensions with differing angles, either reduce section angles or end-reinforced angles. The shape of the angles was designed to focus inelasticity, avoid early cracks and minimize the likelihood of fracture. The main difference in specimens was the angle configuration and the free deformable length of the angles.
Experimental Study, Results and Discussion
Three full scale connection sub-assemblies were subjected to cyclic tests. Specimen P1 had a reduced section angle while Specimens 2 and 3 had end-reinforced angles. Each assembly was test up to a story drift of approximately 0.015-0.02 rad (where damage to the specimen was limited), before the angles were replaced and another test was conducted until the specimens experienced total failure.
In their first tests, all specimens exhibited full and stable hysteric loops, but there were slight deformations. The second test had more pronounced deformations, but the specimens still exhibited stable hysteretic behavior before the final fracture failure.
Overall, the tests confirmed that the proposed connections could concentrate a majority of damage in the angles located at the lower flange, protecting the permeant aspects of the connection and the concrete slab. It was also determined that the specimens exhibited satisfactory performance even after the story drift from the first test.
Reference
He, X., Chen, Y., Eatherton, M. R., and Shao, T. (2018). “Experimental evaluation of replaceable energy dissipation connection for moment-resisting composite steel frames.” Journal of Structural Engineering, 144(6).