Sections

The properties of a beam (or related) element are determined by the section shape and material. These are defined through a section definition and separate material definitions. In the most general case a section can be comprise of several component parts and may vary in along the length of the element. The variation along the length can be either a variation of the section dimensions, or in the case of a concrete section a variation in the reinforcement.

At present GSA does not support multiple components but does allow for varying section dimensions along the length of the section.

The material associated with a section component is defined in two parts: a material type and a material grade, with an optional analysis material. Choosing a material type give the options of selecting a suitable material grade. So for a steel material type the steel grades are offered, and for a concrete material type the grades appropriate to the current design code are offered. For other material type various grade are also offered but mainly as a means of initialising an analysis material.

If a material type and grade are chosen the relevant properties are copied into the GSA data structure. A subsequent change to the design code will not update or delete these definitions. If updated properties are required a new grade should be chosen after changing the design code.

In the case where a material type and material grade have been selected the material properties for analysis can be inferred from the grade, so the analysis material can be set to 'from Grade' to use grade derived values. The properties picked up from the grade are:

• $E$ – elastic modulus
• $\nu$ – Poisson's ratio
• $G$ – shear modulus
• $\rho$ – density
• $\alpha$ – thermal expansivity

For many analyses these properties are sufficient, but if the analysis properties need to be modified, for example an elasto-plastic material, a separate analysis material can be defined.

The shape and dimensions of a section are defined with a section profile. For steel sections additional design parameters can be specified.

Sections can have associated environmental parameters, such as embodied energy and CO2. These can either be read from the environmental database or alternatively entered directly for the section. If no values are defined for the section the material values are used.