Building Stories

When the building model is activated, the Navigator - Data lists building stories; slabs; walls and wall-like beams.

The 'Building stories' dialog box consists of two tabs.

Base

In the Base tab, you can define the story heights and specify boundary conditions for modeling. A 'story' comprises all model objects within a certain height section, i.e., slabs, walls, and columns.

Dialog Box "Building Stories"

List

The individual building stories are listed on the left in the list. As usual in RFEM, the information in the other dialog sections refers to the entry you have selected in this list.

You can create new stories using the buttons at the bottom of the list. They have the following functions:

Button	Label	Effect
	New topmost story	Creates a new topmost story at the first position in the list
	New higher story	Creates a new story above the current floor
	New lower story	Creates a new story below the current floor
	New lowest story	Creates a new lowest story at the last position in the list
	Story generator	Creates stories based on the existing model geometry
	Delete story	Deletes the story or stories selected in the list

Story Dimension

Specify the story height via the 'Elevation' of the coordinates Z_top and Z_bottom. You can also define the story height graphically using the button by selecting two nodes in the model.

The 'Height' of the coordinate ΔZ describes the floor height relative to the story below. The values are linked to the absolute coordinate specifications. The height ΔZ₀ represents the clear height between floors. This value is only relevant if you specify a slab thickness; otherwise, the height difference refers to the center axes of the slabs.

The input field for the 'Thickness' d is accessible if you defined the story height via the Clear height option in the 'Global Settings' tab. Here, you can specify the slab thickness of the upper story surface, which is then considered in the clear height ΔZ₀.

In the Navigator - Display of RFEM, you can specify whether and how the dimensions of the stories are to be displayed on the model.

Displaying Dimensions of Stories on Model

Modeling

For each story, additional specifications are possible, which you can adjust in this section.

Once the stories are defined, it is possible to model the building in the so-called flight mode. Walls, slabs, and columns can be created easily and conveniently in the 2D plan view. This applies to all selected stories.

Story Modeling

The upper slab plane of a story can be modeled using four options.

Modeling Plane for Story

• None | Original stiffness: With the standard specification, the model is analyzed in a global 3D calculation. No partial calculations with local 2D analyses for slabs and walls take place. However, specific output tables are generated for dynamic analyses.

• Semi-rigid: This approach corresponds to the concept of the rigid plane, but the FE nodes are not rigidly coupled with the center of mass. This allows the elasticity of a slab to be considered as well.
• Rigid: At each FE node of the plane, Rigid Couplings are applied to the center of mass of the story slab, and the horizontal displacements are coupled in this way.

Rigid Diaphragms with Couplings to Center of Gravity

• Without stiffness | Flexible | Only load transfer: The story slab has no influence on the stiffness in and out of plane. This element type merely "collects" the loads on the slab and transfers them to the supporting elements of the 3D model. This allows you to model secondary components such as gratings and load distribution elements without further effects on the 3D model.

Depending on the story modeling, the stiffnesses of the slabs and walls are considered differently. The following table schematically compares the options.

Schema for Story Modeling

This table is described in more detail in the chapter Overview.

Nodal Support Modeling / Line Support Modeling

For a rigid or semi-rigid plane, you can influence the support of the slabs for the local 2D model. Various options are available for selection in the lists.

Modeling Nodal and Line Supports of Story

For a 'Support with fixed hinge', a support is applied in all directions; no rotation about the vertical axis is possible either. With the other options, you can assign an elastic support to both the nodes and the lines of a story. The parameters correspond to the options for determining the stiffness by means of a fictitious column or fictitious wall described in the chapters Nodal Supports and Line Supports of the RFEM manual. The program determines the spring constants automatically from the boundary conditions of materials, cross-sections, thicknesses, and geometry.

Information | Analytical & Mesh

In this section, you can find specific information about the current story (selected in the 'List'). The analytical information about the story is listed in the first value column; the information calculated on the basis of the generated FE mesh is listed in the second column.

Graphics

The right part of the dialog box shows either a static sketch of the story height or a dynamic image of the current story in a 3D view. You can switch between the two display options using the button. The usual RFEM options for controlling the graphics are available in the 3D view.

Members contained in slabs No. | Local 2D calculation describes a possibility to transfer horizontal members, e.g., ribs or downstand beams, from the calculation of walls into the local calculation of slabs.

For downstand beams that are usually intended to support the slabs, this is the desired effect.

Global Settings

In the Global Settings tab, you make basic specifications for story modeling, which also affect the Base tab.

Tab "Global Settings"

Ground Floor

Define the coordinate Z₀ of the lowest point of the ground floor. You can graphically select a node of this plane in the work window using the button.

Modification of Story Height

The list offers several options for controlling the story height for modifications.

Story Height Modification

• --: Changes to the story height have no effect on the RFEM model.
• Fixed on top: When changing the height, all other nodes retain their absolute position relative to the upper plane.
• Fixed on bottom: When changing the height, all other nodes retain their absolute position relative to the lower plane.
• Proportional: When changing the height, all other nodes retain their relative position in the modified floor relative to the upper and lower elevation.

The options for modifying the story height only affect inner nodes of the respective story. For example, if you increase the story height from 3 m to 4 m (see following image), an inner node of a divided member or an opening retains its distance to the topmost point of the story with the 'Fixed on top' option. The distance to the lower plane of the story increases by 1 m.

Story Height Modification – Floor 0 Fixed to Top

Definition of Story Height

The list offers two selection options:

• Effective height: The story height refers to the center axes of the slab surfaces.
• Clear height: You can specify the thickness of the upper slab surface user-defined in the 'Base' tab. This option is also helpful for reading the net height (clear height ΔZ₀) of a story.

Display Warning for Neglected Openings

For openings in wall panels, you can use the check box to control whether the opening surfaces are neglected in the building model calculation. The limit value Δ represents the maximum ratio of opening area to surface or surface cell size. If this value is exceeded, a corresponding warning appears.

You can find further notes on modeling openings in the chapter Recommendations.

Vertical Result Line

If the check box is selected, RFEM creates a vertical section for the result diagrams. After the calculation, you can read the values in the individual stories on this vertical result line.

Vertical Result Lines with Forces in Walls

The position of the result line is defined by the distances ΔX and ΔY. The percentage refers to the center of mass and the directions of the global positive axes.

You can change the input mode using the button and specify the distances as absolute values. These refer to the origin of the axis system.