Loads - automation and transparency

 

17.0

One of critical step while modelling a structure is to apply loads on the structure and distribute them properly to load bearing members. SCIA Engineer pays attention primarily to the speed and transparency of this process. First, SCIA Engineer enable the user to run the calculation for just a selection of load cases and/or non-linear combinations, avoiding the unnecessary long calculation time. Second, a new method for transfer of surface load to load bearing elements has been introduced for load panels. This method is based on "Tributary areas". Another enhancement is the option to suppress automatic regeneration of loads from all load panes after geometry modifications (naturally, the loads are always regenerated before the calculations itself), which is useful while handling large projects. Furthermore, the 3D wind load generator has been extended to support parapets and protruding roof (overhangs) in compliance with Eurocode 1 Part 4 (actions on the structure).

Highlights
Ability to run the calculation for a selection of load cases or non linear combinations
Tributary areas method for distribution of surface loads
Climatic load improvements: support of parapets and protruding roofs
Disabled automatic updates of load panels after every change of geometry.

Ability to run calculation for a selection of load cases or non-linear combinations

The user may have a big project with both linear load cases and non-linear combinations. It is obvious that calculation with non-linear combinations requires several iterations and it might lead to a long computational time. To get a preview on the structure response, the engineers may want to calculate first only a critical combination.

In the calculation dialogue the user can select the required load cases or non-linear combinations. By default, all of them are calculated.

The option to run the calculation for just a selection of load cases or non-linear combinations is available within the "v17" environment, which can be activated from the Project data dialogue under the Post-processing section.

Tributary areas for load distribution

Load panels are not load-bearing part of the structure (they can be used to represent e.g. the glass part of a structure or cladding of a steel hall, or they can be used to distribute the 3D wind load). The existing methods for the transfer of loads from load panels have been extended by the "Tributary areas" method. The user is able to visualize on the screen the generated areas and can easily check how the loads are distributed.

Purpose

The tool improves the general workflow with any kind of projects:

  • the user does not need to determinate the size of supported regions per beam and calculate the load intensity for each beam manually
  • there is no need to model flat structural elements like roofs or wall panels, if these are considered not to have a sufficient stiffness to contribute to the load-bearing capacity of the structure.

  • total load is distributed to beams proportionally to the distance of individual beams and supported edges and it is available for:
    • "load panel to edges"
    • "load panel to edges and beams"

Features

  • The load panels are input graphically in the 3D window;
  • The surface load may act in any direction, parallel to any coordinate system that is defined;
  • The shape of the load panels may be rectangular, or a general polygon with straight edge;
  • The user can select which beams located in the loading plane will take up the load and keep other beams without any load;
  • Thanks to the algorithm used, the equilibrium in the structure is achieved in 99% of configurations;
  • Load panels are required for the definition of 3D wind on frame structures (without load bearing walls);
  • Load panels remain editable after the load redistribution. The calculation always reflects the current properties of the load panels.
  • Load panels are available in all project types;
  • Supporting nodes and edges of a panel can be displayed;
  • The strength and stiffness of load panels are not considered in the analysis of the structure.

Application

Load panel with tributary areas can represent:

  • wall and roof sandwich panels with insufficient stiffness or fastener strength;
  • roof or wall windows subjected to wind or snow load;
  • 3D wind and snow loads on framed structures or structures without modelled cladding.

Climatic load improvements: parapets and protruding roofs (overhangs)

The 3D Wind-Load Generator is a complex tool for generation of wind load acting against buildings. The module is available for the following codes: EC-EN (Eurocode) and IBC (International Building Code). The Eurocode module includes the calculation of external pressure coefficients using national annexes for Austria, France, Belgium, Germany, Netherlands, Slovakia and United Kingdom.

The wind load generator creates default zones for all the walls and roof items for each of the defined wind direction.

Parapets

Basic building geometry ( Reference height ze and wall height (h) ): These definitions apply to walls without parapets and the actual parapets. Walls with parapets above them will take their highest point from the parapet. See the diagram below:

Parapets are assessed for return corners and then classified as windward, windward oblique, leeward or leeward oblique depending on q. Based on the classification, parapets have either a single zone, or up to 4 zones. Side parapets have special zero zones, i.e. no nett pressure.

Protruding roofs (known as roof-overhang)

Eurocode 1991-1-4 identifies as protruding roofs the edges of the roof which overhang the face of a wall and, normally, project beyond the side of a building. SCIA Engineer automatically detects protruding roofs and applies correct zones.

Disabling automatic update of load panels

While handling big structures with a large number of load panels SCIA Engineer regenerates load panels during the modelling process in order to check if the changes in the model affect the load panels. This process might interfere with the user workflow and therefore, the user has the option to disable this automatic update of load panels after every change in the model. This can be set in Setup > Geometry/Graphics > Disable automatic update of load panels.

This option disables the automatic regeneration of load panels, and the consequent generation of loads, while modelling. All load panels are properly regenerated once calculation is started.

22/03/2017