Working with RC Beams

Different Type of RC Beam

They are different types of reinforced concrete beam. The icons are accessible from the Modelling tab, RC Beam drop down list.

Foundation Beam

A foundation beam is a reinforced concrete beam modelled in ST0, which is always the foundation level.

Hence, this icon will only be available if ST0 view is made current and active by double clicking on this level in the Structure Tree.

To model a foundation beam :

1. Switch to the foundation storey (St: 0)
2. Click Modeling tab > Beam dropdown > Foundation Beam
3. The beam property window will be opened
4. Create beam as stated in the next section "Defining a New Beam"

The purpose of a foundation beam can be :

1. To insert a Strip Footing

2. Modelled with raft foundation slabs to stiffen or strengthen it.

For further details, read Raft Foundation and Piled Raft Foundation Analysis & Design Example

Tie Beam

Tie beams are often used to connect pile caps or pad footings to prevent relative vertical and lateral movement. Tie Beam can only be created if ST0, i.e. foundation level, is made current & active.

Important!

Foundation Tie Beam design is currently only done to Turkish Seismic Code (TBDY 2018)

To create a tie beam:

1. Switch to the foundation storey (St: 0)
2. Click Modeling tab > Beam dropdown > Tie Beam
3. The beam property window will be opened
4. Create beam between 2 foundation columns, as stated in next section "Defining a New Beam"

The Tie Beams in are designed considering the maximum axial loads in connecting columns.

The axial force considered in the design of tie beam is calculated with this equation :

Normal Beam

A Normal Beam is a reinforced concrete beam created in storey 1 and above (i.e. not foundation level).

To create a tie beam:

1. Switch to Storey 1 (St: 1) or above
2. Click Modeling tab > Beam dropdown > Normal
3. The beam property window will be opened
4. Create beam as stated in the next section "Defining a New Beam"

Wall Coupling Beam

Wall Coupling Beam are used to link shear walls for increased stiffness to resist large lateral loads, i.e. seismic loads. This beam type can only be created in Storey 1 & above, i.e. as a superstructure beam.

Specific checks are performed to validate this system to ACI seismic code.

This consequently decrease overturning effect and improve overall stiffness of a building system.

To create a Wall Coupling Beam:

1. Switch to Storey 1 (St: 1) or above
2. Click Modeling tab > Beam dropdown > Wall Coupling Beam
3. The beam property window will be opened
4. Create beam connecting 2 shearwalls, as stated in the next section "Defining a New Beam"

This beam type enables ProtaStructure to :

Use different cracked section properties as dictated by different seismic codes.
Assess and check the connected wall panels to see if they act as a coupled wall or not.
Currently, there is no special design nor detailing for coupling beam - it will be designed and detailed as a normal beam.
Details are shown in the Post Analysis Checks Report > Wall / Frames Effect Check.

Defining a New Beam

Before inserting a Beam member, its reference axes should be defined.

Beams are defined by two axis intersection points (insertion points) defining the start "I" and end "J" of the member. Hence for beams, 3 axes are needed to create the 2 insertion points.

To define a new Reinforced Concrete Beam member:

Display the storey level in the drawing area which will contain the beam.
Click the Beam Icon from the reinforced concrete category under the Modelling ribbon
Pick the Beam Type as stated in the above section
Edit the fields in the Beam Properties box. For example, users can edit the label of their beams in the Label field (max. 11 characters), modify the section dimensions and its eccentricities.
To insert the beam, locate the insertion points in the plan view drawing area, or the 3D view. Click on two axes intersection points to insert the beam.

Defining a New Beam without Reference Axis

A new beam can also be defined without necessity of predefining the main reference axes that should run along the beam. However, true potential end points or the axes that will potentially generate end points, must be defined first. The following figures illustrate this.

A new beam will be defined between Point 1 and Point 2. These points are true potential end points of the beam (I and J) and they are created by other axes, rather than a non-orthogonal axis that the beam is supposed to defined on.

When the new beam is drawn by picking the Point 1 and Point 2, a new axis will also be generated. This new axis is given a unique name preceded "@" sign. The label of new axis can been seen on Structure Tree.

This feature is very useful but must be used with caution. If it is intended to define a beam by traditional method over an already existing axis, you must be sure to snap to the real intersection point. Program may draw the beam but not on the axis intended. Snapping options can be adjusted via Display Settings > Object Snap > in Display ribbon.

Editing an Existing Beam

In order to edit an existing beam:

Select an existing beam.
Right-click and select Properties.
Modify the fields such as Label, "b", etc. in the Beam Properties box.
Press the "Update" button in the form.

Right-clicking on any one of the "b", "e" "h", or "e-z" fields will load a list of commonly used values that may facilitate data entry.

You can repeat this process to as many members as you wish. One member at a time can be edited by this method.

If you want to update several beams at once, you can use Beam Table in the right-click menu Properties in Beam ribbon.

Beam Properties

Beam Properties will be loaded when the Beam option in the Modelling ribbon is selected. A new beam can be defined by arranging the fields in the form and then by picking two axes intersections in the plan view window.

The Beam Properties form can also be accessed after selecting an existing beam an then by right-clicking and choosing Properties in the shortcut menu.

When the Beam Properties form is open, right clicking a new beam member and selecting Select and Load Properties option in shortcut menu will also load the properties of the new member in the same window.

The Beam Properties form comprises two pages named as Gen and 3D.

Gen tab

Label

The beam member label. The label is limited to 11 characters. Repeating member label is not allowed.

Beam Section

"b" is the section width of the beam
"e" is eccentricity of the beam along its section width which measured the distance between the insertion axis and the beam centreline. The "e" value cannot be greater than b/2 or less than -b/2.
"h" is the section depth of the beam.
"e-z" is the eccentricity of the beam along its section depth which measured the distance between top of the beam and the slab top reference level. Generally, all beams are inserted to stay below the slab reference level, having "e-z = 0". If you need to define beams spanning above the slab top edge, then e-z will be a non-zero value.

The "e-z" value cannot be greater than "h" or less than "-h".
"e-z" value affects only the elevation of beam in physical model, i.e. it only affects the 3D rendering display and beam elevation drawings.
It does not affect the elevation in the actual Analytical Model.
In contrast, the Delz value affects both analytical & physical elevation level of the beam.

Beam Section Manager

This is a shortcut to the same dialog as Edit Section/ Material which is found in the beam ribbon when a beam is selected.

This is covered below : Beam Section Manager

Generate Properties to Other Storeys

To copy the properties of this beam to other storey :

1. Activate this icon
2. Change properties of the beam
3. Update > Dialog will appear as below

4. Multiple select storey by holding down CTRL key
5. Click OK

Beam Insertion Options Button

Eccentricity Option Button

Choosing one of the options provided by Eccentricity Option Button when clicking it will automatically redefine the "e" field in the Beam Properties form. Update button must be clicked to update the selected beam with new eccentricity value.

Alternatively, "e" value also can be controlled by using direction keys of keyboard :

Select a beam.
Press up/down (horizontal beam) or left/right (vertical beam).
The "e" value will be modified and beam will be displaced.

The eccentricity step value can be set using Member Section Eccentricity Step value in Settings Center > ProtaStructure Environment > General.

The eccentricity of the beam defined here will not modified the location of the actual analytical frame member used in analysis model. The frame member will be located on the insertion point of beam

Beam Anchor Point Button

Beam anchor point button is provided to anchor a specific point on its section. After anchored a point on beam section, when section size is changed, the member is automatically resized with reference to the anchor point.

To assign Anchor point via Beam Properties:

Select a beam, right-click > Properties.
Click on Beam Anchor Point button and choose the desired anchor point.

To assign Anchor point via shortcut menu:

Select a beam > Right-click
Beam Section Anchor Point > Choose the desired anchor point.

Insertion Axes

All structural members are inserted based on axes intersections as insertion reference. At least two axes of different direction code (namely 1 and 2) must intersect at every insertion point.

When an axis intersection is picked in the drawing area, the name of the intersecting axes will appear in the Axes fields in the form. If there are more than two axes in the intersection, then the first direction-1 axis and the first direction-2 axis found will be selected.

Following rules apply to insertion of Beams:

Insertion points can be selected in any preferred direction along the insertion axis. The defined of "I" and "J" points will be swapped automatically when necessary with lower left point priority.
At least one common axis must exist among the axes found in the two intersections. This common axis is termed as "Intersection Axis" of the beam.
At every axis intersection at least a direction-1 and direction-2 axis must be found.

Beam End Releases Condition

Beam ends are fixed by default. The End Releases enables users to release the internal forces of a beam with respect to the I-end and J-end. This is done by clicking at beam end condition icon

N releases the internal axial force
V2 releases the minor shear, in the floor plane
V3 releases the major shear, out of floor plane
M2 releases the major moment, out of floor plane
M3 releases the minor moment, in the floor plane

Beam end conditions also can be assigned through shortcut menu. Select a beam or multiple beams, right-click > Update Beam End Condition > select your preference.

3D tab

Plane (Top) & (Bot)

This field will be state the plane number that is attached to this beam. The start & end node will automatically follow that of the attached plane.

To detach it from the plane you can click the icon

For information on plane, refer : Working with Planes

DelZ - I an DelZ - J

The Delz property controls both analytical & physical elevation level of I & J end of the beam.

For detail explanation on physical & analytical model, refer to : Analytical Model

In 3D view, press F11 or CTRL+D repeatedly until "Linear" display is shown - which will show the analytical wireframe of the beam.

In contrast, e-z value only affects the physical model elevation of the beam.

When a beam is modeled, it is by default created horizontally with top of the beam aligned with the top of the active storey, i.e. the DelZ is set to zero for both ends I & J.

The elevation of the beam can be changed by :

Select an existing beam, Right-click > Properties.
Click on 3D tab > Input the relative elevation from storey level in "Del-Z (I)" and "Del-Z (J)".

Negative values will lower the beam end with respect to storey level while positive value will elevate it.

Press Update.

Read these articles for illustration with example on usage of DelZ :

How to model slanting / inclined beam

How to raise or drop a beam in elevation

Cantilever Mark

All cantilever beams should be correctly marked, to ensure correct design & detailing :

I End Free : Marks I End as Cantilever
J End Fee : Marks J End as Cantilever

This is discussed in more detail below : Mark Free End of Cantilever Beam

Vertical-Only Member

Enables users to design the beam to vertical load combinations only, as selected in the Vertical Loads Combination in the Load Combinations Editor :

As an example, when this option is checked. the beam will be designed considering only gravity load combinations.
Lateral load combinations such as notional, wind and seismic load combinations are excluded in accordance with their respective design practice.

Beam Shortcut Menu

You can access all the command related to beam members by selecting a beam and all the command will be shown in the top Beam ribbon. Alternatively, you can also right-click to expose the same shortcut menu. The most commonly use functions are discussed below.

Beam Sections Manager

Beam section properties and materials can be defined in Edit Section/ Material which is accessible under the Beam Ribbon tab after selecting a beam.

After selecting the Edit Section/ Material, the RC Beam dialog window will be loaded.

The dialog window comprised of “General” tab, “Properties” tab selection.

• The section name, display color & grade of concrete can be changed in “General” tab.
• The moment of inertia, section area and shear areas, etc can be reviewed in the “Properties” tab.

Split Beam Member

Split existing member into two by select a beam member, followed by right-click, select "Split Beam Member" then click an intersection point.

Merge Beam Members

Merge existing two beam members into one member by select two beam members, followed by right-click, select "Merge Beam Members".

Mark Free End of Cantilever Beam

A cantilever beam can be mark and defined using "Mark Free End of Cantilever Beam" command.

After selecting a beam or group of beams > Right-click > choose "Mark Free End of Cantilever Beam".

Three options show below :

Both Ends Supported - Both LHS (Left hand side) of member and RHS (Right hand side) of member supported.

I End Free - Only LHS of member supported
J End Free - Only RHS of member supported

The "Red Arrow"

indicate the cantilever side and will always pointing towards the support side.

Please take note that all 3 options of cantilever are meant for design and detailing of cantilever beams and have nothing to do with analysis. For more information, refer to Mark Free End of Cantilever Beam and its Impact on the Analysis & Design of Cantilever Beam

Set Section Angle to Selected Member

To rotate a beam, input the preference angle value in section angle (Beam Properties > Genenal tab).

Alternatively, select the beam and right-click > "Set Section Angle to Selected Member" > then click on another member that you wish to align to.

Beam Table

Following methods can be used to load the Beam Table :

If no selection is made, all beams in the current storey or in the whole system can be listed by using right-click menu list > Member Tables > Beam Table.
If a mixed selection is made involving beams, only selected beams can be listed using "Beam Table" option in shortcut menu. If some of the beams are selected, only the selected beams will be listed using "Properties" option in the shortcut menu.
If "All Storeys" option is checked in "Beam Table", other beams defined in the Graphic Editor are displayed even they do not belong to current storey.

Using "Beam Table" will allow you to modify more than one existing beam. All cells in the table are editable and you can use cursor keys or mouse to select a cell and edit the contents.

Refer to this article for more details : Display and Edit Member Properties

Defining Curved Beam Members

The method for defining Curved Beam Members is as follows:-

Press the "Beam" button located in "Modelling" ribbon.
Right-click and select "Properties". When the "Beam Properties" form is loaded.
Select "Curved Beam Insertion" from the insertion method .
Pick the first and second points. The first and second points defined in this way will be the "I" and "J" points of beam respectively.
Press "F2" on keyboard to enter the chord offset (h) of the curved beam or you can simple define the chord offset (h) of the curved beam by picking a point on the graphical editor plan view.

Defining Beams out of Columns Insertion Points

"I" and "J" ends of beams in ProtaStructure Model must actually be defined at the same insertion point with column or wall insertion point. This assures the continuity of analytical model. However, due to grid system complexities, architectural limitations or possible user errors, end points of the beam may not coincide with column that is supposed to support it.

If the beam end (I or J) is defined on another point within the physical borders of the column section, a rigid link is automatically created by the analysis engine and the continuity is granted for.

This feature helps to prevent user errors or to work around some geometrical necessities. In normal conditions do not create your models relying on rigid links. Always work with “node-to-node” concept in mind.

To illustrate this, below is an example where the column insertion point is different from the beam insertion point. in this case, the beam is defined near the column border.

The analytical assumption is as shown below. A rigid link is automatically created to "catch" the beam.

For more detail discussion, refer to: Rigid links automatically created inside columns to support offset beams

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