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D1.G.5 Design Parameters

The timber design parameters for the AITC codes.

D1.G.5.1 AITC 1994 Parameters

Table 1. AITC 1994 Timber Design Properties
Parameter Name Default Value Description
STAAD AITC 1994 Code
CB Cb 1.0 Bearing Area Factor, Table 4.13
CFB CF 1.0 Size Factor for Allowable Bending Stress, see Table 8.3, 8.4, 8.5, 8.6, 8.7
CFC CF 1.0 Size Factor for Allowable Compression Parallel to Grain, see Table 8.3, 8.4, 8.5, 8.6, 8.7
CFT CF 1.0 Size Factor for Allowable Tension Parallel to Grain, see Table 8.3, 8.4, 8.5, 8.6, 8.7
CFU Cfu 1.0 Flat Use Factor, see Table 4.9
CSS CH 1.0 Shear Stress Factor, Section 4.5.14
CMB CM 1.0 Wet service Factor for Allowable Bending Stress, see Table 4.8
CMC CM 1.0 Wet service Factor for Allowable Compression Parallel to Grain, see Table 4.8
CME CM 1.0 Wet service Factor for Modulus of Elasticity, see Table 4.8
CMP CM 1.0 Wet service Factor for Allowable Compression Perpendicular to Grain, see Table 4.8
CMT CM 1.0 Wet service Factor for Allowable Tension Parallel to Grain, see Table 4.8
CMV CM 1.0 Wet service Factor for Allowable Shear Stress Parallel to Grain, see Table 4.8
CR Cr 1.0 Repetitive Member Factor, see Section 4.5.10
CSF CF 1.0 Form Factor, see Section 4.5.12
CTM Ct 1.0 Temperature Factor, see Table 4.11
CTT CT 1.0 Buckling Stiffness Factor, see Section 4.5.15
KB Kb 1.0 Buckling Length Coefficient to calculate Effective Length
KBD Kbd 1.0 Buckling Length Coefficient for Depth to calculate Effective Length
KBE KbE 0.609 Euler Buckling Coefficient for Beams, see Section 5.4.11
KCE KcE 1.0 Euler Buckling Coefficient for Columns, see Section 5.8.2
KEY Key 1.0 Buckling Length Coefficient in Y Direction
KEZ Kez 1.0 Buckling Length Coefficient in Z Direction
KL Kl 1.0 Load Condition Coefficient, Table 4.10
LZ LZ Member Length Effective shear length in the z direction for Column Stability Check, Le=Ke*L
LY LY Member Length Effective shear length in the y direction for Column Stability Check, Le=Ke*L
LUZ LUZ Member Length Member length in the z direction for Beam Stability Check,  Lu=Kb*l+Kbd*d
LUY LUY Member Length Member length in the y direction for Beam Stability Check,  Lu=Kb*l+Kbd*d
CDT CDT 1.0 Load Duration Factor
CCR CCR 1.0 Curvature factor (Section 4.5.11)
INDEX INDEX 10 Exponent value in the Volume Factor Equation (Section 4.5.6)
CV CV 1.0 Volume Factor (Section 4.5.6)
CC CC 0.8 Variable in Column Stability Factor, Cp (Section 5.8.2, Eqn 5-14)
SRC SRC 1.0 Slenderness ratio of Compression member
SRT SRT 1.0 Slenderness ratio of Tension member
RATIO   1.0 Permissible ratio of actual to allowable stress
BEAM   1.0
  • 0.0 = design at start and end nodes and those locations specified by the SECTION command.
  • 1.0 = design at 13 evenly spaced points (i.e., 1/12th points) along member length, including start and end nodes.
Note: See D1.A.6 Design Parameters.

D1.G.5.2 AITC 1984 Parameters

Table 2. AITC 1985 Timber Design Parameters
Parameter Name Default Value Description
BEAM 1.0
  • 0.0 = design at start and end nodes and those locations specified by the SECTION command.
  • 1.0 = design at 13 evenly spaced points (i.e., 1/12th points) along member length, including start and end nodes.
Note: See D1.A.6 Design Parameters.
CCR 1.0 Curvature factor
CDT 1.0 Duration of load factor
CSF 1.0 Form factor
CTM 1.0 Temp. factor
LAMINATION 1.50 inch Thickness of lamination in inch (1.50 or 1.375)
LUZ 1.92*L Unsupported effective length for beam in z.
LUY 1.92*L Unsupported effective length for beam in y.
LY Member Length Same as above in y-axis.
LZ Member Length Effective length of the column in z-axis.
NSF 1.0 Net section factor for tension members. (both shear and tension stresses are based on sectional area x nsf )
RATIO 1.0 Permissible ratio of actual to allowable stresses.
WET 0.0

0.0 - dry condition

1.0 - wet condition

wet use factors are in-built

Parent topic: D1.G. American Codes - Timber Design per AITC Code