| Among many types of reinforced concrete buildings, reinforced concreteslab-column structure is very popular and has been widely used at home and abroad inrecent years due to the concise form, less total building height, convenientconstruction, and good comprehensive economic benefit. In addition to vertical shearforce, slab-column connections also have to transfer unbalanced moment due tocombined vertical and lateral forces as a result of wind effect or earthquake action.Slab-column connections usually tend to occur brittle punching shear failure, whichcontrols the ultimate bearing capacity of slab-column structures. However, theinterpretation of the punching shear failure mechanism is still not clear enough for theeccentric loading case. The current seismic code, code for design of concretestructures and other technical standards in China only have the method of calculatingpunching shear resistance of slab-column connections, but there is no analysis anddesign method for the unbalanced moment case, which has brought certain difficultiesfor the engineering design. The mechanical performance and failure mechanism ofslab-column connections under shear and unbalanced moment is very complex, and atpresent researchers both at home and abroad have not reached a unified understandingon this issue.In order to more deeply understand the inner mechanism and ultimate bearingcapacity of slab-column connections occurring punching shear failure under theeccentric loading, in this thesis, a total of8slabs with stub were designed based onthe three variables of concrete intensity, the punching span ratio and longitudinalreinforcement ratio, and tested under the combined concentric and eccentric loading.During the test process, the corresponding point deflection, strain of steel bar andconcrete, and ultimate bearing capacity were recorded and collected. The crackdistribution characteristics on the slab bottom were outlined. In addition, theload-deflection curve and the load-strain curve of steel bar and concrete were givenaccording to the observed phenomena and collected data. Meanwhile, the influence ofunbalanced moment, concrete intensity(C30,C50), the punching span ratio(5,7) andlongitudinal reinforcement ratio(0.86%,1.28%) on the punching shear capacity andfailure pattern of slab-column connections were expounded and analysed. Finally, theauthor discussed the calculation of punching shear capacity of interior slab-column connections for the unbalanced moment case and verified the accuracy of relevantcalculation models using the experimental results. |
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