Study On Shake Table Test Of Damaged Single-span Frame Structure Strengthened By Steel Braces And Angle Steel

After the Wenchuan Earthquake, it is urgently demanded in the newly revisedcodes that the single-span RC frame structure should not be used in the school buildingswhich are classified as the category B building, and the available single-span RC frameschool buildings must be appraised and strengthened. The existing single-span RCframe teaching buildings must be damaged in different degrees in use or afterearthquakes, which should be appraised and strengthened more urgently. Strengtheningmethods to the damaged single-span RC frame school building and it’s shake table testwere studied in this paper inorder to provide the reference and basis for the seismicreinforcement of the primary and secondary school buildings.As the object of study in this paper a1:5large scale single-span four-story RCframe structure model was selected, which had been damaged in the shake table test inthe Reference [34]. By comparing the existing common strengthening methods andconsidering characteristics of the damaged single-span RC frame structure, a singlestrengthening method is not enough to the seismic strengthened requirement of thisstructure. By the steel braces and angle steel composite reinforcement method, thecapacity and ductility of the structurecould be improved and the seismic defense andredundancy of the building could be also increased. The seismic requirement would besatisfied for the damaged single-span RC frame structure.To study the seismic capability of the damaged single-span RC frame structurestrengthened with steel braces and angle steel, finite element analysis and shake tabletest were conducted in this paper. By the three-dimensional elastic anlaysis of thedamaged single-span RC frame structure with the software SAP2000, the strengtheningeffect of the building was studied,considering different models before and afterstrengthening, different steel braces and different sections of steel brace. By comparingthe results of the models, the approviate scheme to the strengthening method of thedamaged single-span RC frame structure was obtained for the shake table test model.After the seismic appraisal, it was found that the damaged single-span RC framestructure must be strengthened. First, structural adhesive was primed into cracks of thedamaged structure in low pressure to repair cracks; second, steel angles and steel braceswere welded to the columns of the structure; last, the maintenance of the structure andpreparation to the shake table test were made. For comparing the results with wing wallstrengthening model and no-strengthening model in Reference [34], the same ground motions in Reference [34] were used during the shake table test in this paper, whichabout20seismic loading conditions in the single-span direction (Y) were conducted. Byanalyzing the test phenomenon and the test results, it was found that the distribution ofstiffness of the model with steel braces and angle steel was more reasonable,the damagemechanics of structurewas changed which the ductility of the structure was improvedgreatly and the seismic capacity of the strengthened structure was stronger. The relatedrequirement in current code was satisfied. By reinforcement to the columns and joints ofthe first and second floor, the collapsing of the structure could be taken toprevent,especially progressive callape of the first floor.In the meantime, the beamsdamaged earlier than the columns, which the seismic design ideas of ‘strong columnand weak beam’were achieved.