How do I specify lateral loads?

There are two kinds of lateral loads possible in RAM Structural System. The most common are Program Generated Diaphragm forces. The program can generate Wind and Seismic loads, including Dynamic Response Spectrum Analysis cases for most codes. This is done through RAM Frame - Analysis mode using Loads - Load Cases. 

The generated diaphragm forces are only applicable to models with rigid, semi rigid or pseudo-flexible diaphragms. In structure with no diaphragms, only lateral Nodal loads can be applied. Nodal loads are defined and applied in Ram Modeler, in the Elevation View.

Details for all analyzed load cases is available through Reports - Loads and Applied Forces.

Process - Results - Applied Story Forces can be used to visualize static diaphragm forces.

Note, if nodal loads are merged with story forces only the resulting merged load case will be listed for analysis and reporting.

Why are some load cases grayed out?

Gravity loads and Nodal loads that are defined in Ram Modeler are listed here in gray as RAMUSER loads. These can only be edited in Ram Modeler, though the Ram Frame user can include or exclude them when performing the analysis.

What do the abbreviations in the load type stand for?

The program uses a shorthand to identify each type of loading, code, direction and commentary so that there is a unique label for every load case.

type label = [type]_[code]_[subgroup]_[direction]_[commentary]

Below is a summary of the most common abbreviations used in load case names and reports, refer to the RAM Frame manual, Section 3.3.5 Load Case Type Labels for compete details.

Type

• D - Dead load (may include self-weight)
• L - Live floor loads
• Rf - Roof live load
• S - Snow load
• Wind (W) - Wind
• Eq (E) - Seismic (Static ELF type)
• Dyn - Dynamic Response Spectrum analysis case
• NL - Notional (a lateral force derived from gravity totals). On reports ND is for Notional Dead, NL for Notional Live and NR for Notional Roof
• O - Other (user defined story forces, e.g. for earth pressure)
• Virtual (V) - Virtual Work load case used in Drift mode for performing energy analysis of member participation.

Additionally Eigen Solution, Center of Rigidity types can be included.

Code

Codes are generally abbreviated with the code acronym and year.

Subgroup

Larger collections of loads are grouped into subgroups. For example IBC wind loads are grouped as follows:

1. the non- eccentric cases
2. eccentric cases
3. angled cases
4. maximum torsion cases

Direction

• X - positive X direction (plan west to east)
• Y - positive Y direction (plan south to north)
• -X - negative X direction (plan east to west) only used when tension-only members considered
• -Y - negative Y direction (plan north to south) only used when tension-only members considered
• X+Y - combinations of +X and +Y loads to create an angled case, e.g. ~45 degrees
• X-Y -  combinations of +X and -Y loads to create an angled case, e.g. ~315 degrees
• 0.3 - when seismic loads are generated using the Orthogonal Effects (100%/30%) this is used to distinguish which direction is acting at 30%

Commentary

• +E - with positive eccentricity. For an X+E case the load is in the positive X direction with positive Y eccentricity, in other words the load is shifted slightly to the north. (Wind, Eq, Dyn)
• -E - with negative eccentricity (Wind, Eq, Dyn)
• CW - multi-directional load with eccentricity to induce greatest clockwise rotation (Wind)
• CCW - multi-directional load with eccentricity to induce greatest counter-clockwise rotation (Wind)
• F - provisions for member forces (Eq)
• Drft - provisions for drift (Eq)
• CQC - Complete Quadratic Combination method (Dyn)
• SRSS - Square Root Sum of Squares combination method (Dyn)

See Also

RAM Frame - Building and Frame Story Shear

RAM Frame - Wind Loads [FAQ]

RAM Frame - Seismic Loads [FAQ]

RAM Frame Semirigid Diaphragms

RAM Frame Pseudo Flexible Diaphragms FAQ