In a research project under way at PEER, a jacket is being used in combination with steel encasement plates to strengthen the beam outside the jacket. The encasement plates on the top and bottom of the beam are attached to the concrete by prestressed bolts and welded to the jacket. The encasement plates strengthen the beam away from the joint with minimal disruption to the floor slab. The jacket can also be used in combination with other retrofit procedures including (1) diagonal, prestressed cross bracing; (2) supplemental energy-dissipation devices; (3) fiber wrapping outside the joint region (column); and (4) base isolation. The segmental plates greatly facilitate postearthquake evaluation because they can easily be removed for inspection of the concrete.
Analytical studies are in progress to verify the applicability of the proposed rehabilitation approach to an older existing prototypical RC building that can be expected to experience ground motions varying from impulsive to harmonic.
The studies take into account various combinations of steel jackets and encasement plates to indicate the strength and deformation demands placed on an upgraded structure.
Future work will include cyclic load tests on large-scale specimens representing the nonductile components of older RC frame buildings needing retrofit. Under the umbrella of performance-based engineering, this project will be coordinated with a multifaceted, innovative system for the upgrading of existing RC buildings having nonductile moment frames.