RAM Structural System Help

Gravity Forces

As described in the Concrete Analysis Manual - Technical Section, the following gravity forces are calculated for each column:

SettingDescription
Dead Load
  1. Axial Force, M major , M minor and Torsion top.
  2. M major and M minor bottom.
Floor Live Load (if skip loaded)
  1. Maximum Positive M major top, and associated M minor , Torsion and Axial top.
  2. Maximum Positive M major bottom, and associated M minor bottom.
  3. Minimum Negative M major top, and associated M minor , Torsion and Axial top.
  4. Minimum Negative M major bottom, and associated M minor bottom.
  5. Maximum Positive M minor top, and associated M major , Torsion and Axial top.
  6. Maximum Positive M minor bottom, and associated M major bottom.
  7. Minimum Negative M minor top, and associated M major , Torsion and Axial top.
  8. Minimum Negative M minor bottom, and associated M major bottom.

One additional force, the maximum axial force with all beams loaded, is also computed. This additional point is included to ensure that the ACI 318-99, Section 8.8.1 requirement of "Columns shall be designed to resist the axial force from factored loads on all floors or roof…" is met (See Design Forces ).

SettingDescription
Roof Live Load (if it exists)
  1. Axial Force, M major , M minor , and Torsion top.
  2. M major and M minor bottom.

These gravity forces are combined in load combinations as described in Design Forces to generate the design points to be checked against the column's capacity curve.

The user should be aware of a special consideration regarding live load reduction. In RAM Structural System, the portion of the live load acting on a column that is delivered from two-way slabs is not included in the reducible area for the live load reduction calculation. Thus, absent any other action, the live load forces in columns that support two-way slabs will be larger than if all tributary area for the column had been considered in the live load reduction calculation. To overcome this, the user may directly assign a live load reduction factor to a member in RAM Modeler, which will then override the value automatically calculated by Concrete Analysis.

Parent topic: Column Design Forces