The iMesh applet does not require you to use any particular units, as long as all used units (for length, area, force and stress) are consistent with one another. You can thus for in millimeters [mm], Newton and MegaPascal [MPa] (1 [MPa] = 1 [N/mm2]), in meters [m], MegaNewton [MN] and [MPa] or in in pounds (lbs), inches (in) and pounds per square inch (psi). All this is possible, as long as your units are consistent.
Proposed units: meter, MegaNewton and MegaPascal
If your loads are expressed in MegaNewton and your lengths in meters, then your stresses and moduli of elasticity must be expressed in MegaNewton per square meter, which is a MegaPascal. A MegaNewton is a fairly large force, but it can be used for civil engineering applications (1 [MN] = 1’000 [kN] = 1’000’000 [N]). The weight of small is 10 [kN] which is equal to 0.01 [MN].
The iMesh applet makes by default the hypothesis that you work in meters, MegaPascals and MegaNewtons. The default value for the thickness of the concrete elements (0.3 [m]), the default diameter of the reinforcing bars (0.02 [m], that is 20 [mm]) and the default material properties for concrete (fc = 20 [MPa], Ec = 30’000 [MPa]) and steel (fs = 500 [MPa], Es = 205’000 [MPa]). But you are free to change these values by editing them in the *GEOMETRY and *MATERIAL sections of the iMesh text input file.
