Direct Design of Reinforced Concrete Skew Slabs

[摘要] This thesis presents the results of an experimental and theoretical study of reinforced concrete skew slabs designed using the elastic stress fields in conjunction with the yield criterion for reinforced concrete slabs. The elastic stress field is obtained from finite element program using uncracked stiffness and the yield criterion adopted is given by (M*x - Mx + M*a cos2alpha ) (M*alpha sin2alpha - My) - (Mxy + Ma*sinalpha cosalpha)2 = 0 where Mx, My and Mxy are the elastic applied bending and torsion moments normal to the x and y axis at the ultimate load. M*x and M*a are the ultimate flexural moment capacities of the section normal to the x and skew axis respectively and a is the angle of skew between x and a axis. The experimental work was conducted on a "large scale" skew slabs. The models included slabs of uniform thickness and ribbed slabs. The major parameters were the angle of skew and the arrangement of steel in the slab viz orthogonal or skew directions. The theoretical work was done using the nonlinear finite element program based on the isoparametric Mindlin element. In order to allow for the development of cracks through the thickness, the "layer approach" was adopted. Nonlinear effects due to the yielding of steel, cracking and crushing of concrete were included. A nonlinear finite element program was used to study the spread of yielded zones in the slab, the effect of fixing the direction of crack at its first appearance, prediction of the true deflection at working loads from the elastic deflection at working loads and a careful study of the yield criterion itself. The results show that the design procedure adopted is viable but care has to be taken to ensure that punching shear failure does not occur at obtuse corners.

[发布机构] University:University of Glasgow

[关键词] Civil engineering