Self-Weight dialog

Opens when either:

the Self-Weight tool is selected
Criteria > Self Weight is selected

Setting	Description
Member Dead Loads	Automatic consideration of beam, column, wall and slab self-weight is an option. Except as noted below, this eliminates the need for the user to include an approximate value for member self-weights in surface load and line loads. Self-weight of Steel Joists is not automatically included. In order for the design to consider the self-weight for these members, it must be applied by the user as part of the surface load or as a series of separate line loads. This is necessary because only the self-weight of Standard steel joists is known (although even that can vary with the actual span). The actual self-weight of Girders and Special joists is not known. So for consistency, no self-weight is automatically considered for any Steel Joists. Self-weight of Braces is not automatically included. Warning: Column self-weight is not included in the column load applied to transfer girders. If significant, the user should specify a Point load at that location to approximate and account for the self-weight of the supported column. This is necessitated by the fact that if self-weight was to be automatically included in this case, the columns would need to be designed before the beams in order to get the column self-weight applied to the transfer girder, but the beams need to be designed first in order to get the beam self-weights applied to the columns. Thus it would require an iterative design process, alternating between the beam design and the column design until no sizes changed. For simplicity it was decided to not automatically apply the column self-weight to transfer girders. When the top of a wall slopes, the wall self-weight is applied as a trapezoidal load rather than a uniform load, based on the wall thickness, unit weight and height of the wall at each end. You can select if wall member loads are applied along the top of the wall or distributed evenly throughout the wall mesh. For columns, the calculated self-weight is applied as a point load at the top of the column. Note: Self-weights are based on the center-to-center of supports and floor-to-floor heights of beams and columns respectively. This means that there is a duplication of self-weight at the joints. The program does not make any attempt to reduce this. The self-weight of a Composite Floor system is calculated using the Unit Weight value for the concrete and the area of concrete on the deck for the slab thickness and deck type selected, plus the self-weight of the steel deck itself, as specified by the user in the Modeler. The self-weight of a non-composite system is as specified by the user in the Modeler. The self-weight of a Concrete Slab system is calculated using the Unit Weight for Self-Weight and the Concrete Slab Thickness specified by the user in the Modeler.
Story Masses	Similar to the ability to determine the self-weight of members for the member loads, the program has the ability to determine the self-mass of members, used in RAM Frame for the calculation of P-delta, periods and modes, seismic forces, etc. This includes the self-mass of beams, columns, walls and decks/slabs. The options for self-mass can be selected independently of the options for self-weight for member loads. The engineer has the option to have RAM Frame automatically consider the self-mass of walls. If considered the engineer can choose to have the wall mass added up to the mass of the story above; or to split the mass of the wall between the two adjacent levels, half up and half down. Wall mass is based on the actual wall height (for a sloped wall the mass is based on the average height). The same is true for columns where the mass can be lumped at the level above or split between two levels that the column spans between. Beam self weight is added to the story self weight at the level they are located at. Note that all members (gravity and lateral) are considered in this self weight calculation. The self weight is therefore dependant on sizes being available on all members (gravity and lateral), if the sizes change and the self mass option is selected then the analysis in RAM Frame will need to be rerun to obtain current results.

Setting

Description

Member Dead Loads

Automatic consideration of beam, column, wall and slab self-weight is an option. Except as noted below, this eliminates the need for the user to include an approximate value for member self-weights in surface load and line loads.

Self-weight of Steel Joists is not automatically included. In order for the design to consider the self-weight for these members, it must be applied by the user as part of the surface load or as a series of separate line loads. This is necessary because only the self-weight of Standard steel joists is known (although even that can vary with the actual span). The actual self-weight of Girders and Special joists is not known. So for consistency, no self-weight is automatically considered for any Steel Joists.

Self-weight of Braces is not automatically included.

Warning: Column self-weight is not included in the column load applied to transfer girders. If significant, the user should specify a Point load at that location to approximate and account for the self-weight of the supported column. This is necessitated by the fact that if self-weight was to be automatically included in this case, the columns would need to be designed before the beams in order to get the column self-weight applied to the transfer girder, but the beams need to be designed first in order to get the beam self-weights applied to the columns. Thus it would require an iterative design process, alternating between the beam design and the column design until no sizes changed. For simplicity it was decided to not automatically apply the column self-weight to transfer girders.

When the top of a wall slopes, the wall self-weight is applied as a trapezoidal load rather than a uniform load, based on the wall thickness, unit weight and height of the wall at each end.

You can select if wall member loads are applied along the top of the wall or distributed evenly throughout the wall mesh.

For columns, the calculated self-weight is applied as a point load at the top of the column.

Note: Self-weights are based on the center-to-center of supports and floor-to-floor heights of beams and columns respectively. This means that there is a duplication of self-weight at the joints. The program does not make any attempt to reduce this.

The self-weight of a Composite Floor system is calculated using the Unit Weight value for the concrete and the area of concrete on the deck for the slab thickness and deck type selected, plus the self-weight of the steel deck itself, as specified by the user in the Modeler.

The self-weight of a non-composite system is as specified by the user in the Modeler.

The self-weight of a Concrete Slab system is calculated using the Unit Weight for Self-Weight and the Concrete Slab Thickness specified by the user in the Modeler.

Story Masses

Similar to the ability to determine the self-weight of members for the member loads, the program has the ability to determine the self-mass of members, used in RAM Frame for the calculation of P-delta, periods and modes, seismic forces, etc. This includes the self-mass of beams, columns, walls and decks/slabs. The options for self-mass can be selected independently of the options for self-weight for member loads.

The engineer has the option to have RAM Frame automatically consider the self-mass of walls. If considered the engineer can choose to have the wall mass added up to the mass of the story above; or to split the mass of the wall between the two adjacent levels, half up and half down. Wall mass is based on the actual wall height (for a sloped wall the mass is based on the average height). The same is true for columns where the mass can be lumped at the level above or split between two levels that the column spans between. Beam self weight is added to the story self weight at the level they are located at.

Note that all members (gravity and lateral) are considered in this self weight calculation. The self weight is therefore dependant on sizes being available on all members (gravity and lateral), if the sizes change and the self mass option is selected then the analysis in RAM Frame will need to be rerun to obtain current results.