Development of Seismic Strengthening and Retrofit Strategies for Critical Facilities Using Engineered Cementitious Composite Materials

This research describes the development of a seismic retrofit system for critical facilities that uses steel reinforced engineered cementitious composite (ECC) materials. An infill panel system was developed that utilizes the pseudo-strain hardening properties of the ECC materials. A combination of laboratory and numerical studies were employed. The infill panel system, which consists of precast ECC panels with bolted connections, was developed for use as a retrofit strategy in critical facilities. Based upon finite-element simulations, a beam-type infill system was found to be effective in increasing the strength, stiffness, and energy dissipation of a steel frame without yielding of the bare frame at drift levels up to 0.75%. Structural-scale lab tests were used to test the strength of the proposed bolted connections between panel members and to evaluate response of ECC infill panels made with various ECC materials, reinforcements, and panel geometries. Connection test results showed the viability of the pretensioned bolted connections. The panel test results indicated the different levels of panel strength, stiffness, and energy dissipation that can be attained. These results serve as benchmark studies for further development of the infill system. To examine the infill panel concept further, additional simulations were performed using a material model for the ECC developed from reversed cyclic tests. The simulations demonstrate the ability of the proposed ECC infill system to strengthen, stiffen, and increase energy dissipation of steel frames, without causing frame damage.