Design Checks/Forces

The Criteria > Design Check/Forces tab is used to select sections of the code that the user may want to include or ignore during the design process, and the origin of gravity forces on lateral members.

Setting	Description
Design Checks	Include Torsional Capacity code check per ACI 318-99/02 Sec 11.6.1 - When selected the section of the code is checked and if the requirements are not met a Design Warning is generated. Include Max Column Axial Load Limit code check per ACI 318-99 Sec 21.4.1 (SMF) and Sec 21.10.2 (IMF) and ACI 318-02 Sec 21.4.1 (SMF) and Sec 21.12.2 (IMF)- When selected the columns are check to see if they have enough axial load to be designed as columns and if the requirements are not met a Design Warning is generated.
Gravity Forces for Lateral Columns	In some circumstances it may be advantageous to use the gravity forces that are produced in RAM Frame rather than those produced in RAM Concrete Analysis, for the design of lateral concrete columns. As described in the RAM Concrete manual (Concrete Analysis Technical Section) and visible through the Finite Element Model the concrete analysis is performed on a single story at a time. As such any column forces that would result due to 'r;frame' building behavior are not captured in the concrete analysis model. Frame behavior refers to the forces that result from the entire 3D building deformation (when subject to gravity loads) as opposed to the forces that occur from the single isolated story model. Regardless of the selected source of the gravity forces, the program will always combine the factored gravity forces with the factored lateral forces (from RAM Frame) for all combinations with lateral load cases. In general the gravity forces from RAM Frame should be of similar magnitude to those in RAM Concrete Analysis. If a comparison shows that the gravity forces are significantly different between the two programs the user should decide which of the two most accurately represent the building behavior and select the appropriate option. The following points should be considered when deciding which option to select for the source of the gravity forces on lateral members. Use RAM Concrete Analysis Forces - When selected, the program will use the gravity forces calculated from RAM Concrete Analysis for lateral columns. These gravity forces consider all the skip load conditions that would provide a bounding condition for gravity live loads on the column. The finite element model used to generate these forces assumes that only the current story members and loads will have a measurable impact on the design forces, and considers columns and walls restrained at the levels above and below the story being analyzed. For structures that experience little or no frame action (lateral translation or rotation) when subject to gravity loads, RAM Concrete will produce the most accurate and comprehensive gravity column forces for design. Use RAM Frame Analysis Forces - When selected, the program will use the gravity forces calculated from RAM Frame Analysis for lateral columns. Forces calculated in RAM Frame consider the behavior of the full 3D structure when subject to the applied gravity loads. If this option is selected and no analysis results are currently available from RAM Frame (i.e. the model has not been analyzed in RAM Frame, or results have been invalidated) all column lines will be colored light blue and cannot be designed. The gravity forces that are calculated in RAM Frame do not consider the live load skipping and as such a single pair of column forces (one each top and bottom of column is generated for each gravity load case. For structures that experience significant lateral translation or rotation when subject to gravity loads, RAM Frame will produce the most accurate gravity forces for design.

Setting

Description

Design Checks

Include Torsional Capacity code check per ACI 318-99/02 Sec 11.6.1 - When selected the section of the code is checked and if the requirements are not met a Design Warning is generated.
Include Max Column Axial Load Limit code check per ACI 318-99 Sec 21.4.1 (SMF) and Sec 21.10.2 (IMF) and ACI 318-02 Sec 21.4.1 (SMF) and Sec 21.12.2 (IMF)- When selected the columns are check to see if they have enough axial load to be designed as columns and if the requirements are not met a Design Warning is generated.

Gravity Forces for Lateral Columns

In some circumstances it may be advantageous to use the gravity forces that are produced in RAM Frame rather than those produced in RAM Concrete Analysis, for the design of lateral concrete columns. As described in the RAM Concrete manual (Concrete Analysis Technical Section) and visible through the Finite Element Model the concrete analysis is performed on a single story at a time. As such any column forces that would result due to 'r;frame' building behavior are not captured in the concrete analysis model. Frame behavior refers to the forces that result from the entire 3D building deformation (when subject to gravity loads) as opposed to the forces that occur from the single isolated story model. Regardless of the selected source of the gravity forces, the program will always combine the factored gravity forces with the factored lateral forces (from RAM Frame) for all combinations with lateral load cases.

In general the gravity forces from RAM Frame should be of similar magnitude to those in RAM Concrete Analysis. If a comparison shows that the gravity forces are significantly different between the two programs the user should decide which of the two most accurately represent the building behavior and select the appropriate option.

The following points should be considered when deciding which option to select for the source of the gravity forces on lateral members.

Use RAM Concrete Analysis Forces - When selected, the program will use the gravity forces calculated from RAM Concrete Analysis for lateral columns. These gravity forces consider all the skip load conditions that would provide a bounding condition for gravity live loads on the column. The finite element model used to generate these forces assumes that only the current story members and loads will have a measurable impact on the design forces, and considers columns and walls restrained at the levels above and below the story being analyzed. For structures that experience little or no frame action (lateral translation or rotation) when subject to gravity loads, RAM Concrete will produce the most accurate and comprehensive gravity column forces for design.
Use RAM Frame Analysis Forces - When selected, the program will use the gravity forces calculated from RAM Frame Analysis for lateral columns. Forces calculated in RAM Frame consider the behavior of the full 3D structure when subject to the applied gravity loads. If this option is selected and no analysis results are currently available from RAM Frame (i.e. the model has not been analyzed in RAM Frame, or results have been invalidated) all column lines will be colored light blue and cannot be designed. The gravity forces that are calculated in RAM Frame do not consider the live load skipping and as such a single pair of column forces (one each top and bottom of column is generated for each gravity load case. For structures that experience significant lateral translation or rotation when subject to gravity loads, RAM Frame will produce the most accurate gravity forces for design.