D1.G.4 Naming Conventions for Sections
The following conventions are used to describe timber sections in STAAD.Pro
D1.G.4.1 Dimensional Lumber sections
As can be seen from Tables 8.3 through 8.6 of the AITC 1994 manual, one or more of the following attributes have to be considered while choosing a section :
Nominal size of the section
Grading rules agency
STAAD.Pro uses a naming convention that incorporates all of the above. Shown below is the name of a section that has characteristics as shown. It may be found on page 8-637 of the AITC 1994 manual.
Timber naming conventions
- Species: Douglas Fir Larch
- Commercial Grade: Dense Select Structural
- Size Classification: Beams
- Nominal size: 5"x 5"
- Grading Rules Agency: WCLIB
D1.G.4.2 Implementation of Glulam Properties
For glulam sections, each glulam designation has an associated value of modulus of elasticity and a set of allowable stresses. However, these values are not dependent on the size of the cross section. For example, a 3-1/8"x 6" 24F-V8 DF/DF beam and a 6-3/4" x 30" 24F-V8 DF/DF beam both have an E of 1,600 ksi and an allowable bending stress in the tension zone, Fbx, of 2,400 psi.
Therefore, in STAAD.Pro’s glulam database, the section sizes are not linked to the glulam type. Users may specify any cross-section size they choose and pick the desired glulam type. The Modulus of Elasticity and allowable stresses associated with that glulam are assigned to the member. The material properties for the glulam database are taken from Table 1 of AITC 117-93 – Design Standard Specifications for Structural Glued Laminated Timber of Softwood Species. This publication has been reproduced in the AITC 1994 manual starting from page 8-843.
Example for Dimensional Timber
UNIT FEET KIP DEFINE MATERIAL START ISOTROPIC DFLN_SS_4X4 E 273600 POISSON 0.15 DENSITY 0.025 ALPHA 5.5e-006 END DEFINE MATERIAL MEMBER PROPERTY AITC 3 4 7 8 TABLE ST DFLN_SS_4X4 CONSTANTS MATERIAL DFLN_SS_4X4 MEMB 3 4 7 8
D1.G.4.3 Glulam Sections
The STAAD.Pro name for glulam sections incorporates
- Combination Symbol
- Species-Outer Laminations/Core Laminations
Shown here is a typical section listed in page 8-854 of the AITC manual.
Implementation of Material Constants
As explained in the previous paragraphs, for sawn lumber as well as glulam sections, E is built into the database and gets automatically assigned to the member along with the section dimensions. Density, Poisson’s ratio and Alpha (coefficient of thermal expansion) have to be assigned separately. If they are not assigned, the analysis engine will use default values for those.