In structural engineering, a diaphragm is a horizontal element such as a floor or a roof that transfers loads to the bracing elements. They are critical elements of the load path in a steel building’s lateral force resisting system. Concrete-filled steel deck diaphragms, due to their strength, stiffness, and hysteretic characteristics, have demonstrated that they can influence the seismic performance of steel buildings. However, minimal testing has been conducted on the concrete-filled steel deck floor assemblies that are typical of contemporary steel buildings.
To fill the gaps in the body of knowledge, researchers R. E. Avellaneda-Ramirez, M. R. Eatherton, W. S. Easterling, B. W. Schafer, and J. F. Hajjar, conducted an experimental program as part of the Steel Diaphragm Innovation Initiative. Their research, “Experimental Program on Behavior of Concrete-Filled Steel Deck Composite Diaphragms,” included eight cantilever diaphragm specimens using a concrete-filled steel deck connected to steel beams which were subjected to a cyclic in-plane shear displacement history. The authors used variations in the diaphragm specimens, and presented the progression of failure and assessed ductility, residual strength, and dissipated energy. This testing evaluated proposed prediction equations for both initial stiffness and shear strength associated with the diagonal tension cracking limit state. Learn more about this research in the Journal of Structural Engineering at https://doi.org/10.1061/JSENDH.STENG-12556. The abstract is below.
Abstract
A limited amount of data exists on the cyclic behavior of concrete-filled steel deck diaphragms, and the few historical testing programs that have been conducted used specimens that may not be representative of modern floor assemblies typical in North America. As part of a larger research project, the Steel Diaphragm Innovation Initiative, an experimental program was conducted to fill critical knowledge gaps related to the behavior and design of concrete-filled steel deck diaphragms leading to a better understanding of the seismic performance of steel buildings utilizing these types of diaphragms. The experimental program included eight diaphragm specimens that were approximately 4 m by 5 m, tested in a cantilever test setup wherein one edge is restrained against translation while the opposing edge is subjected to an in-plane cyclic displacement history. Parameters that were varied included deck height (51 mm and 76 mm), concrete cover over the deck (51 mm to 115 mm), concrete type (normal weight and lightweight), configuration of perimeter headed shear studs, and the presence and amount of reinforcing steel. Specimen behavior was quantified including initial stiffness, peak shear strength, ductility, and energy dissipation and qualitatively connected to observed cracking and deformations. The results of this experimental program, combined with tests from the literature were used to develop proposed expressions for peak shear strength and initial stiffness. The proposed expressions reasonably capture the experimental results and are suitable for design.
How could these results influence your use of concrete-filled steel deck diaphragms? Find out in the ASCE Library: https://doi.org/10.1061/JSENDH.STENG-12556.
