Investigationofductilecement basedcompositesforseismicstrengtheningandretrofit

Traditional civil engineering materials such as reinforced concrete are continually being engi- neered with more specific performance characteristics. Engineered cementitious composite (ECC) materials, which consist of a cement-based matrix reinforced with a low volume fraction of polymeric fibers, represent an example of materials with specific performance characteristics. ECC materials exhibit steady-state crack- ing and pseudo-strain hardening in tension. The use of ECC materials as an infill wall system for seismic ret- rofit of critical facilities is being investigated. Preliminary numerical results indicate that ECC infill panels can increase the strength, stiffness and energy dissipation in steel frames. An improved material model is needed for further analysis of infill panel systems. Therefore laboratory tests on ECC materials under cyclic load are conducted. Results of cyclic testing are presented and key aspects of the response are discussed. 1 INRODUCTION from conventional concrete materials in that they 1.1 Background exhibit pseudo-strain hardening and steady-state cracking in tension. This is in contrast to the largely Engineered cementitious composite (ECC) materials brittle or quasi-brittle nature of traditional concrete represent an innovative fiber reinforced cement- and fiber reinforced concrete materials. The devel- based composite. The materials are comprised of a opment of ECC materials is based on evaluating the Portland cement matrix with a low volume fraction pullout behavior of the fibers from the Portland ce- of fibers such as ultra high molecular weight poly- ment matrix. The majority of the development of ethylene (UHMWPE) fibers. ECC materials are de- ECC materials has been by Li. (Li, 1998). veloped from micro-mechanical analysis of the in- In ECC materials, fibers are used as a traction teraction between the matrix and fibers.