Live load reduction

 

17.1

Version 17.1 of SCIA Engineer brings an important extension for projects calculated in the IBC environment of the software. Live loads are now automatically reduced according to the rules given in the ASCE 07-16. In addition, the program makes a distinction between regular, heavy, and roof live loads and makes sure that these are reduced (or not) independently from each other.

The newly-provided solution is accurate, safe, and offers a great deal of automation. Built-in intelligence allows users to achieve economic building design in full compliance with the ASCE 07 norm.

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Live load reduction is directly applied in the IBC steel and composite checks and requires no extra action from the user other than enabling it at a project level. SCIA Engineer also gives the user great flexibility to decide how live load reduction is applied. This is important in situations when customisation is important and the engineer needs to diverge from a general case.

Highlights
Reduction of regular, heavy and roof live loads in full accordance with ASCE 07-16.
Automatic recognition of tributary and influence areas, also considering openings in slabs and areas with no applied load.
Robust and customisable handling of columns that support multiple floors, even when the columns are not exactly aligned at each floor.
Versatile output possibilities for live load reduction factors and intermediate calculation parameters such as tributary and influence areas, graphical visualization and error / warning / note reporting.

Principle

Live load reduction factors are calculated per member, per Load Group. The user may combine different categories of floor loads (e.g., office, corridors, stairs) within one Load Group. Tributary and influence areas are then determined from the geometry of the 3D model and all live loads present in that Load Group. Discontinuities (like openings in slabs) are also taken into account in the determination of reduction factors.

Live load reduction on the level of Load Groups is straightforward, yet offers great flexibility: the user can easily influence which loads are to be considered together when reducing the load.

Regular live loads, heavy live loads, and roof live loads are always considered separately.

Safe Solution

One of the main advantages of how SCIA Engineer applies live load reduction is that the software always checks what portion of the floor is actually loaded. Areas not subjected to any load are subtracted from the influence areas, thus ensuring that the final result is always safe and no unjustified reductions are taking place.

In addition, the derivation of tributary and influence areas is very robust: ed edirregular slabs, non-parallel beams and openings in slabs are taken into account.

Over different floor levels

In the design of multi-storey buildings, the engineer can benefit from the increased influence areas of columns that support multiple floors: when the total influence area increases, more reduction is allowed. SCIA Engineer makes it possible to reduce live loads acting on multiple floors, even when the columns are not exactly aligned at each floor. ee pos

The user can choose how live load is reduced for columns that support more than one floor. The following three possibilities exist:

  • Any column continuity between floors is disregarded. In this case, only the influence area on the floor directly supported by the column is counted in the calculation of live load reduction factors. This solution is the most conservative: it allows the user to be on the safe side and assume that the live loads on each floor are probabilistically independent.
  • Only perfectly aligned columns are considered as continuous. In this case, the influence areas on multiple floors will only be counted together if the columns above are exactly in-line (i.e., share a node) with the columns below.
  • Live load reduction rules are accommodated even when eccentricities exist between columns on different floors. The influence area on multiple floors will, in this case, be counted if the columns above are located within a specific area. This area is defined as a fraction of the tributary areas of the columns below. The user determines himself what tolerance to use for the eccentricity.

Output

The results and intermediate parameters of the live load reduction calculation can be reviewed and checked visually (graphically) and in a tabular form.

Users can control, both visually and in tabular form, the results and intermediate parameters of the live load reduction calculation.

Tributary areas and influence areas are visualised directly on the 3D model, allowing the user to scrutinise all relationships between the different members in the structure.

Reduction factors and KLL factors are shown on the structure. This is important primarily in the reporting phase.

All factors and areas are reported also in a tabular form; Table Results allows the user to link the tabular results to the graphical scene of SCIA Engineer: selecting rows in Table Results also selects and highlights the relevant columns and beams in the 3D model.

If any issue arises during the calculation, the notification system informs the user. The notifications (errors, warning, or notes) are also displayed in the 3D window as small labels attached to the beams or columns; hovering on a label shows a tool-tip with a detailed description of the problem.

If the user is does not agree a with any of the calculated intermediate parameters or final result, he can overwrite these with manually-defined values.

28/11/2017