So far, we had to calculate the beam using a linear elastic analysis, because an important component is missing in our input: reinforcing bars. In concrete structures, reinforcing bars have the function to carry tensile forces that concrete, which is a brittle material in tension, with a very small tensile strength, cannot carry. The basic principle of reinforced concrete is a clear separation of the functions: concrete mostly carries compression and provides stiffness to the system, and reinforcing steel bars offer their tensile strength.
In fact, Figure 1 is incomplete, because the needed reinforcement is not shown. Please consider now Figure 16 which now includes some of the reinforcing bars. There is no need, however, to again take that picture and use it as a background image, as the three reinforcing bars that it includes can be approximately located with enough precision to sole this example.
Figure 16: Geometry and loading of the beam with steel reinforcing bars
The definition of reinforcing bars is made graphically using the
button. The drawing works exactly as for areas: clicking on the screen will create a node, right clicking will terminate the input. It is better to deactivate the display of the Finite Element mesh during that operation (button
again). You will notice a “strange” behaviour as you will move your mouse close to an existing area: it will highlight and, if you click, no node will be added. Rather, the area will be selected. This is intentional, and needed to facilitate the selection of these elements. If you want to START a line on an existing line (area, but also reinforcing bar), you will need to press the Shift key when clicking. This is only needed for the input of the first node. After that, the program will know that you are working on the creation of a reinforcing bar, and this will not be needed. After defining all three steel bars, your screen should look as shown in Figure 17.
Figure 17: Input after the definition of the reinforcing bars
button. The drawing works exactly as for areas: clicking on the screen will create a node, right clicking will terminate the input. It is better to deactivate the display of the Finite Element mesh during that operation (button
again). You will notice a “strange” behaviour as you will move your mouse close to an existing area: it will highlight and, if you click, no node will be added. Rather, the area will be selected. This is intentional, and needed to facilitate the selection of these elements. If you want to START a line on an existing line (area, but also reinforcing bar), you will need to press the Shift key when clicking. This is only needed for the input of the first node. After that, the program will know that you are working on the creation of a reinforcing bar, and this will not be needed. After defining all three steel bars, your screen should look as shown in Figure 17.