For the openings that may be assigned some definite loadings one should be able to use both the strut and tie method and the elastic analyisis to determine stresses, and from there required rebar. The elastic analyisis is at hand for plates, and then from the stresses we can reinforce, for almost any situation. Maybe some bigger safety factor should be used there. The more stringent cases, such a cut at the end of the beam to make space for support have some specific procedures stated in the books, but normally I think don't include such bigger safety factor.except in using quite limited tensile stress (and strain) for the rebar. RE: Trimmer bars at re-entrant corners of slabs (Structural). I have seen the kind of analysis you refer to in one Concrete International magazine of 2-3 years ago. Have it entrants or not seems not relevant to what that procedure can give, I assume.
In the real world you could not build a part with perfect sharp inside corners unless the part were cracked. A re-entrant corner. Re-entrant corners. Steve VandeWater 1 Why Concrete Cracks By Steve VandeWater Cracks in concrete are extremely common but often misunderstood. When an owner sees. Cracks and re-entrant corners in functionally graded. With re-entrant corners due to the. The classical case of a crack to re-entrant corners.
In any case it looks the rationale of examining if the restrained shrinkage stresses exceed the available tensile strain seems the way to go. The problem I think is that 3D modeling the early concrete and the early tensile strenght on half hardened concrete is not precisely established ground. In reality not even a proper simple 3D criterium of 3D final strength of normal concrete (what would be the equivalent to some Tresca or Von mises for ductile) seems to have gained the general favour, less for non early concrete.
Re-entrant Corner Bars At Doorway
Stress concentrations also may make more difficult to model. RE: Trimmer bars at re-entrant corners of slabs (Structural) 13 Oct 01 08:54. Chris, The rationale is for shrinkage control and I look at it in the same manner as direct tension control, though the actual stress distibution is mostly bi-directional. As an example, consider a block-out box for a column. A majority of shrinkage is perpendicular to each 'flat' side of the box.
This results in a concentration of shearing occurring at the same time in two different directions, resolving to a 45 degree line off the re-entrant corner. The result of this bi-directional loading is a bar that is in bending and shear simulaneously, with no good means of predicting the level of stress! For no good rhyme or reason, when I consider reinforcing across the re-entrant corner, I consider the thickness of the slab (related to mass shrinkage) and use 1 bar perpendicular to the 45 degree line, 3 to 4 inches off corner, assuming a development length of 12 inches on each side of the anticipated crack. Bar is located upper part of thickness, near center.
Re-entrant Corner Cracks In Concrete
For thicker slabs, increase to two bars, parallel, spaced about 12 inches apart. You will not completely stop the cracks, but keep them tight. RE: Trimmer bars at re-entrant corners of slabs.