Title: Seismic Retrofit of Beam-to-Column Joints with Grouted Steel Tubes
Author(s): T. E. Hoffschild, H. G. L. Prion, and S. Chery
Publication: Symposium Paper
Appears on pages(s): 397-426
Keywords: beam-column frame; composite materials; grout; hysteresis; earthquake-resistant structures; joints (junctions); reinforced concrete; frames; shear properties; Structural Research
Presents the findings of an experimental study to evaluate a method of retrofit which addresses a particular weakness that is often found in reinforced concrete structures, especially older structures, namely the lack of sufficient reinforcement in and around beam-to-column joints. Many of these structures lack the required confining reinforcement within the joints and in adjoining beams and columns. The result is a reinforced concrete frame that is weak in the joint areas and lacks sufficient ductility during a seismic event. The proposed retrofit method consists of encasing the reinforced concrete joint with a grouted steel jacket that provides confinement to the joint area and imparts ductility to the frame. In this study, two styles of retrofit jacket were tested: a circular steel tube and a rectangular casing. The circular steel jacket provided direct confinement as well as a ductile force transfer mechanism through the jacket itself, but it was more difficult and expensive to fabricate than the rectangular casing. Although the rectangular jacket did not provide the same amount of concrete core confinement, it seemed to be sufficient to prevent damage in the joint area. The load transfer mechanism of the rectangular jacket was found to be adequate in withstanding the loads and deflections typical for seismic events. In the paper, the two jacket styles are evaluated for strength, stiffness, and ductility and their relative merits are discussed.