Nonlinear finite element analysis of non-symmetrical punching shear of rectangular flat slabs supported on square columns. (15th February 2023)

• Record Type: Journal Article
• Authors: Zheng, Bowen; Zheng, Wenzhong; Cao, Bang; Zhang, Yanzhe
• Is Part Of: Engineering structures. Volume 277(2023)
• Publication Date: 2023-02-15
• Subjects: Flat slabs -- Punching shear -- Concrete damaged plasticity -- Finite element method -- Shear span ratio -- Rectangular slabs; BX the short side length of the slab -- BY the long side length of the slab -- h the thickness of the slab -- d the average effective depth in both directions of the slab -- ρX the longitudinal tensile reinforcement ratio along the X-direction -- ρY the longitudinal tensile reinforcement ratio along the Y-direction -- cX the short side length of the column -- cY the long side length of the column -- fcu the standard cube compressive strength of concrete -- fc the standard cylinder compressive strength of concrete -- Ec the elastic modulus of concrete -- Ec1 the secant modulus of concrete -- fy yield strength of the longitudinal tensile reinforcement of the slab -- σs stress of the reinforcement -- εs strain of the reinforcement -- fu ultimate strength of the reinforcement -- εlim maximum strain of the reinforcement -- σt the tensile stress of concrete -- εt the tensile strain of concrete -- εt1 tensile strain of the concrete when -- εt lim, tensile strain of the concrete when -- w the crack width of concrete -- w1 crack width of the concrete when -- wc Crack width of the concrete when -- GF the fracture energy of concrete -- lc the characteristic length of C3D8R element -- ft the uniaxial tensile strength of concrete -- σc the compressive stress of concrete -- εc the compressive strain of concrete -- εc1 the peak compressive strain of concrete -- εc lim, the ultimate compressive strain of concrete -- θ the dilation angle -- μ the viscosity parameter -- rX the distance between the contra-flexure points to column center along X-direction -- rY the distance between the contra-flexure points to column center along Y-direction -- LX distance between the axes of the columns along X-direction in flat slabs -- LY distance between the axes of the columns along Y-direction in flat slabs -- Vu the punching shear capacity of the slab -- ψX rotation in the X-direction -- ψY Rotation in the X-direction -- a the shear span -- λ the shear span ratio -- β the aspect ratio of the slab -- b0 perimeter of the critical section -- λs the size effect factor of the slab thickness in equation of ACI -- βc the aspect ratio of the column -- αs the influence parameter of the column location -- Bl the average length of the slab -- α the ratio of the shear force to the average moment in the region of the shear -- kb the shear gradient enhancement factor -- dg0 the reference aggregate size of concrete -- dg the maximum aggregate size of concrete -- ddg the reference value of the roughness of the critical shear crack -- Vflex the flexure bearing capacity of the slab; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2022.115451
• Languages: English
• ISSNs: 0141-0296

Abstract

Highlights: ABAQUS FEM is developed based on CDP model and calibrated based on tests. The parametric study of the shear span ratio and the slab aspect ratio are carried out. FEA results show slab aspect ratio affects failure mode, ultimate load, and symmetry. Evaluation of four punching shear capacity equations for rectangular flat slabs. Abstract: Different tests and calculation methods for determining the punching shear of flat slabs are based on symmetrical punching shear. However, in practical engineering, most flat slabs are not subjected to symmetrical punching shear due to the differences of two orthogonal directions in load, slabs reinforcement, column section size and slabs plane dimensions. The calibrated nonlinear finite element model (FEM) effectively expands the test database, performs variable parameter analysis, and verifies the calculation method. In this paper, the FEM of isolated slab-column connections is developed using ABAQUS and calibrated based on 14 test results from the literature. The simulation of punching behavior of 49 slab-column connections is carried out, the corresponding effects of the shear span ratio and the slab aspect ratio are evaluated. The results indicate that the shear span ratio and the slab aspect ratio significantly affect the crack development, reinforcement stress, stiffness, and punching shear strength. Furthermore, the slab aspect ratio influences the symmetry of the response. With the increase in the slab aspect ratio, the failure mode changes from symmetrical punching shear failure to non-symmetrical punching shear failure and flexural punching failure. The finite element analysis (FEA) prediction results of the ultimate load are compared with the calculation results of four equations of ACI, EC2, CSCT-simplified, and CSCT ( ψX − ψY ). The results confirm that the prediction using equations of CSCT ( ψX − ψY ) is reasonable, ACI method gives conservative results, whereas the safety factor of EC2 and CSCT-simplified is less than 1.0.