Each of the Building Codes has provisions for reducing the live loads under certain conditions. When appropriate, the program automatically calculates these reduction factors and reduces the loads accordingly. On the output, these reduction factors are listed as a percent of allowable reduction. For example, if the output lists a reduction of 60%, the unreduced load is multiplied by 0.40 to obtain the reduced load. The program recognizes four types of live loads: Reducible, Storage, Unreducible, and Roof. Additionally, Partition loads can be explicitly specified, in which case they will be treated as Unreducible. If the specified building code does not require that Partition loads be treated as unreducible they can merely be added to the other live loads, where they will be reduced according to the reduction appropriate for the Live Load. The Roof load may be treated as either Reducible or Snow, as specified by the user in the RAM Manager criteria.

It should be noted that live load reduction covered in this section is only applicable for loads on one-way slabs. Regarding two-way slabs, the engineer is provided to use user-specified live load reductions for each member.

Live load reduction factors are a function of the area associated with the loads acting on a member. In calculating the reduction for a given load, the program only uses the area on the member associated with that live load type. For example, if part of the load on a member is Reducible and part is Storage, only the area associated with the Reducible loads will be included in the calculation of the reduction factor on the Reducible loads, and only the area associated with the Storage loads will be included in the calculation of the reduction factor, if permitted, on the Storage loads.

In some Building Codes, the Live Load Reduction is a function of the number of stories carried by a member or is dependent on whether the load is coming from a single level or from more than one level. The user can specify which load types are to be considered in this determination, for the purpose of calculating Live Load Reduction. For example the user can specify that a level carrying Roof Live Load not be included when determining the number of levels that a member supports (this does not mean that the Roof loads are not applied). These options appear in the Determining Number of Stories group box in the Criteria > Live Load Reduction command in the RAM Manager.

Roof Live Loads specified in the International Building Code (IBC), Uniform building Code (UBC), Standard Building Code (SBC), and the BOCA National Building Code (BOCA) are reducible in some cases based on the tributary area and the slope of the roof. The RAM Structural System automatically considers both parameters when calculating the Roof Live Load Reduction. When the Roof loads are specified by the user, the magnitude of the load should be that given as the basic Roof Live Load value, not the reduced value to account for slope or area. For example, in the UBC, SBC and BOCA the Roof Live Load charts list 20 psf as the basic roof load for tributary areas less than 200 square feet and slopes less than 1:3. This is the value that should be specified by the user even if the roof is sloped. The program will calculate the slope and the tributary area and use the corresponding table value. If a value other than 20 psf is specified by the user, the program will use the same Live Load Reduction percentage as calculated for a 20 psf load, but will apply it to the specified value. Columns and girders may be supporting members that support various areas of differing roof slope. In that case the program uses a weighted average slope in the calculation of the Roof Live Load Reduction factor. Likewise, Roof Live Loads in the Hong Kong Building Regulation can be reduced as a function of the slope; hence the magnitude of the roof live loads should be specified as for a flat roof, and the program allowed to make the reduction based on the slope of the framing.

The user may limit the live load reduction on beams by specifying a Use Calculated Value, limited to a Maximum ofwith the Layout > Beams > LL Reduction command in the RAM Modeler. The limit is assigned on a beam-by-beam basis. For example, the user can specify that for purlins the live loads not be reduced, but for girders the live loads get the full allowable reduction. If a limitation is assigned using this command, the program will use the more stringent of the code required value and the user specified value. With this same command the user may also assign an explicit value to use, which will override the calculated value. These assignments have no impact on the design of the beams.

The user may limit the live load reduction on columns by specifying a Use Calculated Value, limited to a Maximum of with the Layout > Columns > LL Reduction command in the RAM Modeler. The limit is assigned on a column-by-column basis. If a limitation is assigned using this command, the program will use the more stringent of the code required value and the user specified value. With this same command the user may also assign an explicit value to use, which will override the calculated value. These assignments have no impact on the design of the beams.

The user may assign an explicit live load reduction value on beams by specifying that value with the Layout > Beams > LL Reduction command in the RAM Modeler. The value is assigned on a beam-by-beam basis. If a value is assigned using this command, the program will use that value even if the code required value is more stringent. This has no impact on the design of the columns.

The user may assign an explicit live load reduction value on columns by specifying that value with the Layout > Columns > LL Reduction command in the RAM Modeler. The value is assigned on a column-by-column basis. If a value is assigned using this command, the program will use that value even if the code required value is more stringent. This has no impact on the design of the beams.

The requirements for live load reduction are different for each Building Code. They are outlined below by Building Code. Particulars on the various live load reduction code implementations can be found in the RAM Steel Beam, RAM Steel Column, or RAM Frame manuals (or in the manuals available from the Help menu in each module).