private void columnRadioButton_CheckedChanged(object sender, EventArgs e)
{
if (columnRadioButton.Checked)
currentSection.ConcreteProperties = new ConcreteColumnSectionProps();
else if (beamRadioButton.Checked)
currentSection.ConcreteProperties = new ConcreteBeamSectionProps();
else
currentSection.ConcreteProperties = new ConcreteSectionProps();
}