SPLITTING OF REINFORCED-CONCRETE PANELS UNDER CONCENTRATED LOADS

It is well understood that concentrated forces applied in the plane of a beam or panel (such as a wall or slab) lead to splitting forces dev eloping within a disturbed region forming beyond the bearing zone. In a linearly elastic material the length of the disturbed region is appr oximately equal to the depth of the member. In concrete structures, ho wever, the length of the disturbed region is a function of the orthotr opic properties of the concrete-steel composite. In the detailing of s teel reinforcement within the disturbed regions two limit states must be satisfied; strength and serviceability (in this case the serviceabi lity requirement being acceptable crack widths). If the design require s large redistribution of stresses, the member may perform poorly at s ervice and/or overload. In this paper the results of a plane stress fi nite element investigation of concentrated loads on reinforced concret e panels are presented. Two cases are examined (i) panels loaded conce ntrically, and (ii) panels loaded eccentrically. The numerical investi gation suggests that the bursting force distribution is substantially different from that calculated using elastic design methods currently used in some codes of practice. The optimum solution for a uniformly r einforced bursting region was found to be with the reinforcement distr ibuted from approximately 0.2 times the effective depth of the member (0.2D(e)) to between 1.2D(e) and 1.6D(e). Strut and tie models based o n the finite element analyses are proposed herein.