Fiber-reinforced concrete joints for precast construction in seismic areas.

Abstract

This report presents an investigation on the effectiveness of cast-in-place (CIP) fiber reinforced concrete (FRC) joints in improving the seismic behavior of precast R/C structures. The study was divided in two parts: experimental and analytical. In the first part of the experimental study the characteristics, such as strength and toughness, of various FRC composites were identified. In the second part of the experimental study, six beam specimens were constructed and tested. Each specimen consisted of two precast concrete elements joined together at midspan with a cast-in-place FRC connection. The specimens were subjected to reversed cyclic third-point loading. Compared to the control specimen, larger displacement ductilities, higher load levels, and better energy dissipation values were observed for all the FRC specimens. In the third part of the experimental study four beam-column subassemblages were constructed and tested. The subassemblages consisted of a precast beam and precast column joined together by a cast-in-place FRC connection. Displacement ductilities up to 6.0 were observed for the FRC specimens. Higher load levels were attained for the FRC specimens when compared to the control specimen. The maximum cumulative energy dissipated by one FRC specimen was more than ten times larger than that for the control specimen. The first part of the analytical study involved the modeling of the beam-column subassemblages. This analytical model provided the tool necessary to analyze an entire structure to determine the effectiveness of precast concrete buildings with CIP connections in resisting earthquake loads. The DRAIN-2D program was used in this study. In the second part of the analytical study the adequacy of the fiber reinforced concrete CIP joints was examined through the dynamic analysis of a seven story R/C frame. The frame had two configurations: monolithic and precast with CIP joints one beam depth away from the column face. The frames were subjected to three earthquake records; Miyagi-Ken-Oki, Mexico SCT, and El-Centro. The overall behavior was similar for both frames, although there were increases in base shear and beam rotational ductility demands for the precast frame.