America relies on a robust and resilient building stock to minimize harm to its citizens and damage to its economy due to extreme natural hazards such as earthquakes and hurricanes. In the past, structural engineers have focused their attention on creating stronger, more ductile, more reliable lateral-resistance systems that can be used within the walls of buildings to resist the extreme demands associated with these natural hazards. Comparatively little attention has been paid to the role of the floor systems of buildings in resisting these demands. The floor diaphragm acts as a critical element that distributes the demands developed in a building during an extreme event to the lateral-resistance systems and eventually to the building foundation. Steel deck, i.e., thin corrugated steel panels typically with concrete fill, forms one of the most commonly used diaphragm elements in multi-story steel buildings. This project has as its objectives: to develop fundamental understanding of steel deck diaphragms as structural systems integrated within the overall building performance, to develop improved strategies for accurate modeling of floor systems within three-dimensional building models, and to develop new solutions for steel deck diaphragms that enhance the overall structural resilience of buildings.

Current lack of knowledge about floor diaphragm systems impedes a needed evolution for building design approaches from focusing on two-dimensional frame design to enabling creative solutions within three-dimensional building design. The utilization of the diaphragm as an energy dissipating system has not been harnessed nor optimized in buildings. This project will develop a series of building archetypes appropriate to steel deck diaphragms. An integrated experimental program will be conducted at the connection and diaphragm scale, including novel non-contact measurement schemes for revealing damage and deformations during testing, to bridge critical knowledge gaps that currently impede three-dimensional modeling and design of buildings. To explore new solutions for energy-dissipating diaphragms, this project will perform testing of structural fuses and develop prototypes for integrating these fuses into steel diaphragm systems. This project will also complete high fidelity material and geometric nonlinear finite element models to enable detailed investigations of the flow of forces in diaphragms and between the diaphragm and all connected components. A series of lower fidelity, reduced order models will be developed, appropriate for whole building analysis of selected building archetypes. Formal optimization of the role of the diaphragm in building response, including a novel two-level optimization scheme, will be performed. Taken together, these activities will provide a significant advancement in the state-of-the-art for design of building diaphragms. Through a comprehensive outreach effort with industry, the findings will be transferred to engineers and utilized to improve the structural resilience of the nation's buildings.

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