Engineered Cementitious Composites for Ductile R/C Columns

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Serious damages in buildings were reported in the disastrous earthquake which occurred in Kobe, Japan on January 17, 1995. Those damages has raised concern on the design of columns. Specifically, the adequacy of the current design code in preventing brittle failure of columns is called into question. This problem is not limited to the Japanese building code (AIJ 1989) but also extends to the US code (ACI 1995). Both codes are constructed on similar fundamental concept, in which structural collapse is prevented by ensuring ductility in structures under excessive seismic load by means of closely arranged transverse reinforcement. However, structural damage observed in Kobe revealed that transverse reinforcement does not necessarily provide the elements with sufficient ductility, and that further design consideration is necessary to enhance seismic safety. The Advanced Material Research Laboratory at the University of Michigan has developed super ductile cementitious composites with ultimate tensile strain capacity over 5%. These engineered cementitious composites (ECC) have been applied to shear beams and beam-column joints. The initial experimental investigations demonstrated that ECCs contribute extensively to enhancing structural performance especially in terms of ductility. It is reasonable to expect that the application of ECCs could lead to substantial improvement in ductility of columns synergistic with transverse reinforcement, resulting in the reduction of seismic risks. This project is aimed at establishing the proper design of a ECC material specifically for use in weak columns. The research involves analytic components on seismic design of structures with ECC columns, as well as experimental verification of ECC and ECC column response. Applications of ductile cementitious composite and its design procedure to other critical structural elements for improved seismic safety of buildings and civil infrastructures will be investigated. This is a project supported under the second year program of NSF initiative or `Composite and Hybrid Structures`, NSF-94-154.