A.2.1: Basic Properties of Materials

Material Stiffness

The stiffness i.e. resistance of a material against deformation is characterized by its Young’s Modulus or modulus of elasticity “E”. The higher its value the stiffer the material.

If one stretches a piece of material it not only gets longer but also thinner: it contracts laterally. In case of steel for example lateral strain amounts to 30% of the longitudinal strain. In case of beams with a large ratio of cross section height to span this effect influences the displacement response.

In common beam structures however this effect is of minor importance. The shear modulus “G” describes material behavior in this respect.

Specific Weight

Table A.2.1.1 gives specific weights of a number of typical building materials. The weight of materials only takes effect if gravity is added to a load case (see section 3.2.1).

Theoretical Background of Stiffness, Stress and Strain

Hooke’s law expresses the fact that the more you deform something the more force you have to apply.

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