Concept’s elastic analysis leads to an equilibrium load path that requires little ductility.See Designing for Net Axial Forces below for more details. Concept’s design of reinforcement for each design section can include both bending and axial forces.Concept’s analysis and the design section forces are always in equilibrium with the nodal loads, even with coarse meshes.Concept satisfies the above three criteria as follows: In Concept, design sections are used to specify the reinforcing zones. The structure is ductile enough that it can deform without a local failure until the intended equilibrium load path is mobilized.The zone is reinforced adequately to resist all the forces allocated to it.The allocation of structural forces to the reinforcing zones is part of a complete equilibrium load path.Different reinforcing zone decisions by the engineer will result in different designs for the structure.Īny reinforcing zone decision will lead to a safe design if the following is true: The reinforcing zones are also used to verify that code criteria (such as hypothetical stress limits) are met. When designing a continuous concrete structure, engineers must divide the structure into reinforcing zones that are assumed to work as units in resisting the forces in the structure. Moment Plots for Design Strips Including T-Beam Only and Adjacent Slabs Only Moment Plot for Design Strip Including T-beam and Adjacent Slabįigure 3. In this example, the total bending moment in the slab is divided into two parts: half of the bending moment is resisted by local bending (see Figure 2) and the other half is resisted by the force couple due to tension in the web and compression in the flanges (see Figure 3).įigure 1. Axial Force Distribution in a T-beam and Adjacent Slabįigure 2. ![]() The figure below shows a T-beam with plots of axial force (see Figure 1). This behavior is easy to understand in the simple example of a T-beam resisting a positive bending moment the flanges of the beam will be in compression and the web will be in tension even though there is no net axial force in the beam. While some finite element slab analysis programs make the assumption that all of the slab elements have the same centroid elevation, Concept correctly analyzes steps in the slab centroid that are caused by changes in either the surface or the soffit elevation of the floor system.Īt a centroid step, in the real structure, and in the true elastic analysis performed by Concept, bending moments in the floor system will cause axial forces in the floor. How are T-Beams (or L, Z and U Beams) Different? T-Beams and Internal Forces in RAM Concept
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