Timber column stacks and lifts

Timber columns are automatically split into stacks at construction levels provided at least one member or slab connects to the column at that level.

Where a change in cross section is required between stacks you should indicate a splice in the stack properties before initiating the column design.

Each splice insertion introduces a new column lift above the splice position.

A lift can either comprise of a single stack, or multiple stacks, depending on the defined splice locations.

Design of a single stack lift

The Tedds calculation for a single stack lift is based on the stack length. The forces used in the design will depend on the command selected as follows:

Design using Tekla Tedds > Group
uses the GROUP forces in each direction within the stack length.
Design using Tekla Tedds > Member
uses the MEMBER forces in each direction within the stack length.

Design of a multi-stack lift

Design of a multi-stack lift is performed using a single Tedds calculation for the whole lift. The major and minor axis unbraced lengths are taken from the longest stack in the lift.

The following sets of forces are established for use in the design:

Stack MEMBER forces - maximum forces in each direction in the stack.
LIFT forces - maximum forces in each direction in the lift.
GROUP forces - maximum forces in each direction in the lift from all members in the group.

The design process adopted will depend on whether column grouping is enabled and also on the command selected for the design as follows:

Ungrouped design

Design using Tekla Tedds > Member (with an individual stack selected)
1. The lift containing the selected stack is designed for its LIFT forces.
2. All stacks in the lift are then checked for their individual stack MEMBER forces.
Design using Tekla Tedds > Member (with an entire column selected)
1. All lifts in the column are designed for their LIFT forces.
2. All stacks in all lifts are then checked for their individual stack MEMBER forces.
Design performed from Review Data > Design Summary (by clicking the Results.. button adjacent to a stack)
1. The lift containing the selected stack is designed for its LIFT forces.
2. All stacks in the lift are then checked for their individual stack MEMBER forces

Grouped design

Design using Tekla Tedds > Group
1. All lifts are designed for the respective lift GROUP forces.
2. All stacks of all lifts in the group are then checked for their individual stack MEMBER forces.
Design using Tekla Tedds > Member (with an individual stack selected)
1. The lift containing the selected stack is designed for its LIFT forces.
2. All stacks of this lift in the group are then checked for their individual stack MEMBER forces.
3. The designed lift is also checked for the lift GROUP forces so as to be available for export of group to Tedds.
Design using Tekla Tedds > Member (with an entire column selected)
1. All lifts in the column are designed for their LIFT forces.
2. All stacks in all lifts in the group are then checked for their individual stack MEMBER forces.
3. The designed lift is also checked for the lift GROUP forces so as to be available for export of group to Tedds.
Design performed from Review Data > Design Summary (by clicking the Results.. button adjacent to a stack)
1. The lift containing the selected stack is designed for its LIFT forces.
2. All stacks of this lift in the group are then checked for their individual stack MEMBER forces.
3. The designed lift is also checked for the lift GROUP forces so as to be available for export of group to Tedds.


Example: Column with 2 lifts and 4 stacks
	MEMBER unbraced lengths unbraced_length_{stack_1} unbraced_length_{stack_2} unbraced_length_{stack_3} unbraced_length_{stack_4}
MEMBER forces: Stack 1 bending_major_{stack_1} bending_minor_{stack_1} shear_major_{stack_1} shear_minor_{stack_1} axial_{stack_1}	MEMBER forces: Stack 2 bending_major_{stack_2} bending_minor_{stack_2} shear_major_{stack_2} shear_minor_{stack_2} axial_{stack_2}
MEMBER forces: Stack 3 bending_major_{stack_3} bending_minor_{stack_3} shear_major_{stack_3} shear_minor_{stack_3} axial_{stack_3}	MEMBER forces: Stack 4 bending_major_{stack_4} bending_minor_{stack_4} shear_major_{stack_4} shear_minor_{stack_4} axial_{stack_4}
LIFT forces: Lift 1 bending_major_{lift_1} = max (bending_major_{stack_1}, bending_major_{stack_2}) bending_minor_{lift_1} = max (bending_minor_{stack_1}, bending_minor_{stack_2}) shear_major_{lift_1} = max (shear_major_{stack_1}, shear_major_{stack_2}) shear_minor_{lift_1} = max (shear_minor_{stack_1}, shear_minor_{stack_2}) axial_{lift_1} = max (axial_{stack_1}, axial_{stack_2})
LIFT unbraced lengths: Lift 1 unbraced_length_{lift_1} = max (unbraced_length_{stack_1}, unbraced_length_{stack_2})
LIFT forces: Lift 2 bending_major_{lift_2} = max (bending_major_{stack_3}, bending_major_{stack_4}) bending_minor_{lift_2} = max (bending_minor_{stack_3}, bending_minor_{stack_4}) shear_major_{lift_2} = max (shear_major_{stack_3}, shear_major_{stack_4}) shear_minor_{lift_2} = max (shear_minor_{stack_3}, shear_minor_{stack_4}) axial_{lift_2} = max (axial_{stack_3}, axial_stack4)
LIFT unbraced lengths: Lift 2 unbraced_length_{lift_2} = max (unbraced_length_{stack_3}, unbraced_length_{stack_4})
GROUP forces: Lift 1 bending_major_{lift_1_group} = max of bending_major_{lift_1} for all columns in the group bending_minor_{lift_1_group} = max of bending_minor_{lift_1} for all columns in the group shear_major_{lift_1_group} = max of shear_major_{lift_1} for all columns in the group shear_minor_{lift_1_group} = max of shear_minor_{lift_1} for all columns in the group axial_{lift_1} = max of axial_{lift_1} for all columns in the group
GROUP forces: Lift 2 bending_major_{lift_2_group} = max of bending_major_{lift_2} for all columns in the group bending_minor_{lift_2_group} = max of bending_minor_{lift_2} for all columns in the group shear_major_{lift_2_group} = max of shear_major_{lift_2} for all columns in the group shear_minor_{lift_2_group} = max of shear_minor_{lift_2} for all columns in the group axial_{lift_2} = max of axial_{lift_2} for all columns in the group