Experimental And Theoretical Research On Shear Capacity Of Broad-limb Special-Shaped Columns

In recent years, there are more and more small high-rise residential withspecial-shaped columns. Due to the increase of weight in frame structure system ofsmall high-rise residential with special-shaped columns, the column axial force isincreasing. It needs to increase limb width of special-shaped column in order to meetthe requirements of axial compression ratio, when the column width to thickness ratiois4-5, it becomes broad-limb special-shaped column. At present, the research ofbroad-limb special-shaped column is rarely, and with no applicable designspecifications, which greatly limits the development of this structural system. In orderto adapt to the development requirements of broad-limb special-shaped columnstructure system, the research has become inevitable. Due to the obvious brittle failurecharacteristics of broad-limb special-shaped column, it has a very importantsignificance to study on its shear performance.It is shown that both shear performance and shear capacity of broad-limbspecial-shaped column are closely related to loading angle and limb width, and limbwidth to thickness ratio has little effect on shear capacity form the results of test studyon shear capacity of24broad-limb special-shaped columns (11L-shaped and13Z-shaped) under the action of low cyclic loading research. In addition, the relevantcurves of shear capacity components of L-shaped and T-shaped section broad-limbspecial-shaped columns along the two directions of major axis is given respectively inthis paper.Through the research on the applicability of shear capacity design formula ofgeneral special-shaped columns in broad-limb special-shaped columns design, it isconsidered that it is partial to safety to calculate broad-limb special-shaped columnsby this formula from this paper, and it can be used for shear capacity design ofbroad-limb special-shaped columns. Through grey correlation degree analysis onshear capacity influence factors of special-shaped columns, it is concluded that thecorrelation degree decreases in the order of axial compression ratio, stirrup ratio, limbwidth to thickness ratio, concrete tensile strength, longitudinal reinforcement ratio,and shear span ratio in the shear capacity influence factors of special-shaped columns.Through multiple linear regression analysis on the shear capacity of broad-limbspecial-shaped columns and treatment of approaching to a lower limit on the regression results, the proposed design formula of shear capacity of broad-limbspecial-shaped column can be concluded.The finite element analysis model on L-shaped and T-shaped broad-limbspecial-shaped columns has been established, the calculation results and experimentalresults are consistent, and calculation models can better simulate shear failureconditions of concrete columns, which will help to further analyze shear capacity ofbroad-limb special-shaped columns.The reliability analysis of bearing capacity calculation formula on special-shapedcolumns considering the combination of seismic effects has been carried out, and thecalculated reliability index can satisfy the requirements of specification. The result ofstudy on influence regularity of various factors on reliability index of shear capacitycalculation formula of special-shaped columns shows that the reliability index ofcalculation formula decreases with the increase of shear span ratio and stirrup ratio,and improves with the increase of concrete strength, cross-section area, and loadingratio etc.