Testing of a New Composite Framing System for Vertical Evacuation Structures

Abstract

Communities on the coast of the pacific northwest are vulnerable to earthquakes followed bytsunami. These communities have little to no access to high ground and therefore vertical evaluation structures are needed. Vertical evacuation structures typically take one of two form: a closed structure using shear walls or an open structure using frames. Multipurpose buildings typically utilize shear walls, while single purpose evacuation towers use frame elements. This project investigates a new open frame structure for use in a multipurpose building, where the stories below the inundation depth are sacrificial and detailed with break-away slabs (and break-away walls, although this is beyond the scope of this project). This is the second phase of a two-phase experimental study using the Hinsdale Wave Laboratory at Oregon State University. The first phase studied shear-wall systems (Pyke, 2020). This study investigates a new framing system, using concrete filled steel tube columns and piles. The specimen simulated a single bay by single bay frame. Above the inundation depth, a hat truss provides the stiffness; below that the slabs are detailed with break-away connections. There were three study parameters: (i) wave height, (ii) slab, i.e., no slab, fixed slab and break away slab, and (iii) soil height. Relative to the wall specimen, the CFST frame specimen reduced the forces by 89%. The tests also indicated that the break-away slab can significantly reduce the large fluid pressures within the structure. In contrast, the effects of soil level on the specimen was far smaller, likely due to the relative stiffness of the specimen. However, in a real structure, the stiffness changes resulting from scour and the tsunami could have a more significant impact on the response.