Precast Concrete Diaphragms Research Articles

Seismic Design Methodology for Precast Concrete Diaphragms Part 1: Design Framework

The Precast/Prestressed Concrete Institute is conducting an area of emphasis: research project on precast concrete diaphragms. The project has been called Diaphragm Seismic Design Methodology (DSDM). The purpose of this paper is to outline the foundation for the research by presenting the underlying design philosophy and resulting design framework that will serve as the basis for the technical papers to follow and the eventual design methodology at the projected conclusion. The objective of the DSDM project is to develop an industry endorsed design methodology for precast/prestressed concrete diaphragms including: the forces, displacements, and deformations for which the diaphragm should be designed; the diaphragm reinforcing details that can provide this performance; and the required stiffness of the diaphragm relative to the primary lateral force resisting system elements.

Seismic Design Recommendations for Precast Concrete Diaphragms in Long Floor Span Construction

The paper Effect of Dimension and Detail on the Capacity of Precast Concrete Parking Structure Diaphragms, published in the September-October 2003 PCI JOURNAL, presented the effect of structural dimension and construction detail on the capacity of precast concrete floor diaphragms, using parking structures as the prototype structure. Parallel research by the authors has established seismic demands for flexible diaphragm structures. In this paper, the findings of these two research steps are interpreted to propose design recommendations for precast concrete diaphragms in long floor span construction. These recommendations include provisions for diaphragm design strength, allowable flexibility, and ductility capacity based on seismic performance requirements. The provisions are incorporated into a design procedure employing performance-based design concepts. Application of the procedure is shown in a design example (Appendix B) for precast parking structure diaphragms. Research on this subject will continue over the next several years, with funding provided by both governmental and industry organizations.

Effect of Dimension and Detail on the Capacity of Precast Concrete Parking Structure Diaphragms

The paper presents a study that focuses on diaphragms in precast parking structures. The analytical study presented represents an examination of precast concrete diaphragm capacity. In this stage, the global stiffness, strength, and ductility capacity of the diaphragm are examined with respect to structural dimensions and diaphragm reinforcing details. Many of the findings can equally be appplied to long-span precast concrete diaphgrams in general. The paper presents conclusions that pertain to internal load paths, service level behavior, and ultimate capacity of precast parking structure diaphgrams. The conclusions are qualitative in nature; the quantitative realizations of these conclusions are presented in a companion paper recommendations.

CFRP Composite Connector for Concrete Members

Steel plate connections are frequently used in tilt-up and precast concrete building construction to tie adjacent wall panels together for shear and overturning effects, and to provide continuous diaphragm chord connections for wind and seismic loading. These welded connectors perform poorly in regions of high seismicity and are vulnerable to corrosion. Until now, retrofit and repair strategies for in-plane shear transfer strengthening were limited to attaching steel sections across panel edges. In the present paper, an experimental program is described that utilizes carbon fiber reinforced plastic (CFRP) composites to develop a viable retrofit scheme for precast concrete shear walls and diaphragms. Nine full-scale precast wall panel assemblies with CFRP composite connectors have been tested. The results show that the CFRP composite connection is an effective solution for the seismic retrofit and repair of precast concrete wall assemblies and other precast concrete elements, such as horizontal diaphragms, that require in-plane shear transfer strengthening.

Untopped Precast Concrete Diaphragms in High-Seismic Applications

This article indicates how code-complying untopped precast concrete diaphragms may be designed for buildings assigned to high Seismic Design Categories (D and above) by the International Building Code or the NFPA 5000 Building Code.

Considerations in the Design and Construction of Precast Concrete Diaphragms for Earthquake Loads

T is a tendency in building design to consider separately the functions of horizontal and vertical structural subsystems. This paper discusses the design of horizontal diaphragms from the viewpoint of their participation in seismic response of a complete, three-dimensional structure. Pointed out are structural parameters which affect the magnitude of seismic loads in a diaphragm; the importance of proper modeling in the prediction of