'REPAIR AND RETROFITTING'SEISMIC EVALUATION AND STRENGTHENING OFURM EMERGENCY GENERATOR BUILDING AT ANUCLEAR POWER PLANT IN EASTERN EUROPE

摘要

1. Statement of the Problem and Its SignificanceA seismic evaluation of an existing URM emergency generator building was performed to developstructural strengthening to allow the building to remain operational after a major earthquake. TheEmergency Generator Station/Building, constructed circa 1970, is a two-story unreinforced brickmasonry (URM) shear wall building above grade with a one-story reinforced concrete shear wallbasement below grade. The emergency generator foundations are supported on large reinforcedconcrete pads supported on soil at the basement level approximately 3.85m below the first floor whichis at grade. The lateral force-resisting system consists of a flexible metal deck diaphragm and steeldiagonal bracing at the roof and rigid concrete slab diaphragms at the second floor/mezzanine and firstfloor, which transfer their forces to interior and exterior load-bearing URM walls.The seismic evaluation was based on the "Seismic Qualification and Design Procedure - Part A: CivilStructures" issued by Konsortium Rekon Framatome ANP, Vuje. A three-dimensional dynamiccomputer model of the structure was developed using SAP 90, a general structural analysis computerprogram appropriate for three-dimensional finite element analysis. The results of this analysis (thedemand imposed on the elements) are presented graphically as In-plane shear stress Iso-Contour plotsfor the walls and member forces for the elements and are compared to the results of in-place masonryshear tests for the walls (the capacity of the in-situ elements), and calculated element capacities.2. Proposed SolutionIn-plane testing of the emergency generation station building determined that the shear capacity of theexisting unreinforced brick masonry (URM) walls were adequate to resist the required seismic demandwhen combined with new steel bracing.3. Sample Results and ApplicationRequired structural strengthening for in-plane forces consist of revised and additional vertical steelframing and connections located on the north elevation stiffening of horizontal roof bracing, andstrengthened steel connections between the roof and supporting walls. Out-of-plane forces require theaddition of vertical steel strongback members attached to the URM walls with large openings and/orexcessive height to thickness ratios.