# General Information

Section Builder (Builder) enables you to create arbitrary compound sections from rolled steel profiles and plates, and calculate their geometric properties required for structural analysis. Builder operates in the MS Windows environment and does not require any special computer configuration. User interface elements do not differ from the majority of other programs operating in the Windows environment.

The following values are determined for the designed section:

• cross-sectional area A;
• values of the moments of inertia Iy and Iz about centroidal axes parallel to the coordinate axes of the right-handed Cartesian coordinate system Y and Z;
• torsional moment of inertia It;
• coordinates of the center of mass;
• value of the angle of the principal axes of inertia (angle α between U and Y axes);
• maximum Iu and minimum Iv moments of inertia;
• maximum iu and minimum iv radii of gyration;
• maximum Wu+ and minimum Wu- section moduli about the U-axis;
• maximum Wv+ and minimum Wv- section moduli about the V-axis;
• core size from U-axis along the positive au+ and negative au- directions of V-axis;
• core size from V-axis along the positive av+ and negative av- directions of U-axis;

The calculations are performed according to the rules of strength of materials, the torsional moment of inertia is approximately determined as the sum of the torsional moments of inertia of profiles comprising the section.

The geometric properties are always calculated considering the section as continuous, neglecting the ductility of connecting grates and/or plates.

It should be noted that in case of a section with equal moments of inertia (Iy = Iz) the angle α is undefined. The axes shown on the screen are to some extent accidental, since in the considered case the ellipse of inertia degenerates into a circle of inertia (iy = iz = iu = iv), so any orthogonal couple of the central axes can be considered as the principal one.

The calculation of geometric properties is not the end in itself. It is assumed, that the calculation results will be used during the further analysis of the stress-strained state, in particular, when specifying the initial data in any program of the structural calculation. Moreover, the program can be used to calculate the stiffness properties of buildings and structures and their elements. Section Builder enables to obtain the fields of normal stresses if the internal forces in the section have been specified.